tag:theconversation.com,2011:/global/topics/ice-cream-14139/articlesIce cream – The Conversation2023-08-07T12:01:08Ztag:theconversation.com,2011:article/2105112023-08-07T12:01:08Z2023-08-07T12:01:08ZThe strange history of ice cream flavours – from brown bread to Parmesan and paté<figure><img src="https://images.theconversation.com/files/539568/original/file-20230726-15-q9sqyp.png?ixlib=rb-1.1.0&rect=0%2C7%2C1276%2C926&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Noblewomen eating ice cream in a French caricature, (1801).</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Les_Glaces.jpg">Gallica</a></span></figcaption></figure><p>English Heritage is now selling what it calls “the best thing since sliced bread” at 13 of its sites – <a href="https://www.english-heritage.org.uk/about-us/search-news/the-best-thing-since-sliced-bread--english-heritage-re-creates-georgian-brown-bread-ice-cream-this-summer/">brown bread ice cream</a>, inspired by a Georgian recipe. The announcement of the flavour mentions <a href="https://www.youtube.com/watch?v=6z-pIgKG27M">several more outlandish Georgian flavours</a> trialled by English Heritage before it landed on brown bread, such as Parmesan and cucumber.</p>
<p>English Heritage is not alone in its efforts to beguile visitors with historical treats. In Edinburgh, the National Trust for Scotland’s <a href="https://www.nts.org.uk/visit/places/gladstones-land/history-of-food-and-drink">Gladstone’s Land</a> features an ice cream parlour linked to the dairy which stood there in 1904. The property sells elderflower and lemon curd ice cream based on a recipe from 1770, and visitors can go on several <a href="https://www.nts.org.uk/visit/places/gladstones-land/highlights/tours">food-themed tours</a>. </p>
<p>While brown bread ice cream, praised for its caramel nuttiness, may be a more familiar flavour to contemporary eaters than other historical offerings, the iced delights eaten in Britain in previous centuries took a huge variety of flavours and forms. </p>
<p><a href="https://www.canalmuseum.org.uk/ice/marshall.htm">Agnes Marshall</a>, the authority on ice cream during the late 19th century, published two cookbooks specifically about “ices” (1885) and “<a href="https://www.canalmuseum.org.uk/ice/marshall.htm">fancy ices</a>” (1894). They included flavours from an elaborately moulded and coloured <a href="https://archive.org/details/b21528068/page/42/mode/2up?q=spinach">iced spinach à la crème</a>, to <a href="https://archive.org/details/b29314501/page/130/mode/2up">little devilled ices in cups</a>. </p>
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<a href="https://images.theconversation.com/files/539569/original/file-20230726-17-y7r11f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Illustrations of ice cream in the shape of pineapples and doves." src="https://images.theconversation.com/files/539569/original/file-20230726-17-y7r11f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/539569/original/file-20230726-17-y7r11f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=964&fit=crop&dpr=1 600w, https://images.theconversation.com/files/539569/original/file-20230726-17-y7r11f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=964&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/539569/original/file-20230726-17-y7r11f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=964&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/539569/original/file-20230726-17-y7r11f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1211&fit=crop&dpr=1 754w, https://images.theconversation.com/files/539569/original/file-20230726-17-y7r11f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1211&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/539569/original/file-20230726-17-y7r11f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1211&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Some of the different ice cream designs made by Agnes B. Marshall.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Fancy_Ices_ice_cream_illustration.jpg">Dominic Winter Auctioneers</a></span>
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<p>The latter consisted of a chicken pâté spiked with curry powder and Worcestershire sauce, egg yolks and anchovies, which was then mixed with gravy, gelatine and whipped cream, before being frozen in decorative cups and served “for a luncheon or second-course dish”.</p>
<p>Earlier texts contain even more outlandish flavours alongside the typical, sweet offerings. </p>
<p>French foodie <a href="https://www.bbc.co.uk/programmes/articles/5cSf963VtsNDsr3qj0qCVNV/8-scoops-on-the-history-of-ice-cream">Monsieur Emy</a>’s <a href="https://sotherans.co.uk/products/emy-m-lart-de-bien-faire-les-glaces-doffice-ou-les-vrais-principes-pour-congeler-tous-les-raffrichemens-la-manier"><em>L’Art de Bien Faire les Glaces d’Office</em></a> (1768) has recipes for truffle, saffron and various cheese-flavoured ice creams.</p>
<h2>The history of ice cream</h2>
<p>By the time Marshall was publishing, ice cream was far more accessible to the public than in earlier centuries. Prior to the 1800s, ice was collected from frozen waterways and stored in underground ice houses, largely restricted to large estates with the necessary land, wealth and resources. </p>
<p>From the 1820s, however, ice was imported to Britain from Europe and then the US and stored in ice wells and warehouses. The importation of larger stocks of ice reduced costs, while simultaneously, innovators were designing apparatus for mechanical freezing. </p>
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<a href="https://images.theconversation.com/files/539570/original/file-20230726-27-srlzvl.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A black and white advert for. round turn handle ice cream maker." src="https://images.theconversation.com/files/539570/original/file-20230726-27-srlzvl.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/539570/original/file-20230726-27-srlzvl.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=954&fit=crop&dpr=1 600w, https://images.theconversation.com/files/539570/original/file-20230726-27-srlzvl.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=954&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/539570/original/file-20230726-27-srlzvl.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=954&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/539570/original/file-20230726-27-srlzvl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1199&fit=crop&dpr=1 754w, https://images.theconversation.com/files/539570/original/file-20230726-27-srlzvl.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1199&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/539570/original/file-20230726-27-srlzvl.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1199&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An advertisement for Marshall’s patent freezer from 1885.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Marshall%27s_patent_freezer.png">Robin Weir</a></span>
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<p>It would be a long time until ice was easily produced within the home, but cheaper ice made ice cream more readily available and implements were devised so it could be made at home. Both Emy and Marshall’s cookbooks depicting ice cream makers and Marshall’s patent freezer enlisted the same freezing technique as Emy’s <a href="https://www.vam.ac.uk/blog/creating-new-europe-1600-1800-galleries/can-i-have-a-taste-of-your-ice-cream"><em>Sarbotiere et son Seau</em></a> (<a href="https://research.colonialwilliamsburg.org/Foundation/journal/Spring10/icecream.cfm">pot freezer</a> and bucket). </p>
<p>Ice and salt were placed around a bucket, within which a custard or water mixture was stirred or rotated until it froze. Marshall’s innovation was the shallow pan, which gave an increased surface area for faster freezing. Equipped with such a freezer (and perhaps <a href="https://archive.org/details/b29314501/page/246/mode/2up">Marshall’s patent Ice Cave</a>, for storing the ices), middle-class housewives could produce ice cream in their own kitchens.</p>
<h2>Ice cream and leisure</h2>
<p>Ice cream is well suited for engaging visitors at heritage properties today, not because of the history of how it was produced within the home but because of its holiday connotations. Whether it is a “99”, an “oyster” enjoyed at the beach, or the nearing jingle of an ice cream truck, ice cream has clear cultural and emotional links to recreation and enjoyment. This was also true in the past. </p>
<p>In 19th century Britain, street vendors (many of them Italian immigrants) began selling <a href="https://scarboroughmuseumsandgalleries.org.uk/object/penny-lick-glasses/">penny licks</a>, or “hokey-pokey” from stalls or carts in the streets. In contrast to the immaculately-moulded delicacies in Marshall’s cookbook – which required the purchase of several pieces of equipment – this ice cream was to be enjoyed while out and about. It was also cheap, as implied by “penny” in the title. </p>
<p>Customers would purchase their ice upon a glass “lick”, eat it and then return the lick to the vendor for reuse. With growing numbers of <a href="https://www.bbc.co.uk/history/british/victorians/seaside_01.shtml#:%7E:text=Most%20of%20our,%27traditional%27%20summer%20holiday.">seaside resorts</a> and the rise of the leisure industry over the 19th century, ices were enjoyed while on holiday or daily excursions and at public events like exhibitions or fairs. </p>
<figure class="align-center ">
<img alt="Colourful postcard showing colourised picture of children surrounding an ice cream man." src="https://images.theconversation.com/files/539571/original/file-20230726-21-gq406w.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/539571/original/file-20230726-21-gq406w.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=381&fit=crop&dpr=1 600w, https://images.theconversation.com/files/539571/original/file-20230726-21-gq406w.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=381&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/539571/original/file-20230726-21-gq406w.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=381&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/539571/original/file-20230726-21-gq406w.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=479&fit=crop&dpr=1 754w, https://images.theconversation.com/files/539571/original/file-20230726-21-gq406w.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=479&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/539571/original/file-20230726-21-gq406w.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=479&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Children surround an ice cream vendor in 1909.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Children_in_the_Ghetto_and_the_Ice-Cream_Man._Chicago_Ill._(FRONT).jpeg">Wiki Commons</a></span>
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<p>It is the portability of ice cream, as well as its culinary appeal, that has led to its lasting place in our leisure time – a delicious treat that can be enjoyed, one-handed, as part of a larger experience. The act of eating ice cream prepared from a Georgian or Victorian recipe therefore connects today’s visitors to a long tradition of enjoying ices recreationally.</p>
<p>While heritage properties are unlikely to embrace the more unsanitary ways ice cream used to be eaten, serving up historical recipes gives visitors a chance to savour a new sensory layer of the past. That taste can be linked into larger histories. From ice cream, we can learn about technological developments, changing attitudes towards sanitation, global travel, the availability of ingredients throughout time, trends, fashion and leisure habits. </p>
<p>Delving into the history of food – from the tins in our cupboards, to a cup of tea, or an ice cream at the beach – can bring new perspective to both the past and the present.</p>
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<img alt="" src="https://images.theconversation.com/files/536131/original/file-20230706-17-460x2d.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/536131/original/file-20230706-17-460x2d.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536131/original/file-20230706-17-460x2d.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536131/original/file-20230706-17-460x2d.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536131/original/file-20230706-17-460x2d.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536131/original/file-20230706-17-460x2d.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536131/original/file-20230706-17-460x2d.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p class="fine-print"><em><span>Lindsay Middleton's research was previously funded by the Arts and Humanities Research Council.</span></em></p>Chicken pâté was mixed with gravy, gelatine and whipped cream, before being frozen in decorative cups.Lindsay Middleton, Food Historian and Knowledge Exchange Associate, University of GlasgowLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2050382023-07-24T04:17:13Z2023-07-24T04:17:13ZHow does ice cream work? A chemist explains why you can’t just freeze cream and expect results<figure><img src="https://images.theconversation.com/files/538876/original/file-20230724-79526-ui0tqq.jpg?ixlib=rb-1.1.0&rect=181%2C623%2C6237%2C3842&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/homemade-neopolitan-ice-cream-vanilla-chocolate-1093782722">Shutterstock</a></span></figcaption></figure><p>Ice cream seems like a simple concept. Take some dairy, add some sugar and flavours, and freeze.</p>
<p>But to get a perfectly creamy, smoothly textured frozen treat, we need more than just a low temperature – it takes a careful interplay of chemistry and three states of matter: solid, liquid and gas.</p>
<h2>What’s in the box?</h2>
<p>Commercial ice cream includes many ingredients: air, water, milk fat, so-called milk solids (mainly milk proteins and lactose), sweeteners, stabilisers, emulsifiers and flavours. The ingredients are mixed and <a href="https://theconversation.com/e-coli-in-milk-wont-necessarily-make-you-sick-but-it-signals-risks-from-other-bacteria-119229">pasteurised for food safety</a>.</p>
<p>Homemade ice creams tend to use milk, heavy cream, sugar and flavourings, such as fruit, berries, or chocolate. The exact quantities vary with the recipe, but the processing steps are similar.</p>
<p><a href="https://www.hsph.harvard.edu/nutritionsource/milk/">Milk is composed</a> of everything a young cow needs to grow and develop – water, fats, carbohydrates, proteins, minerals and vitamins. These components respond in different ways when they are frozen.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/crying-over-plant-based-milk-neither-science-nor-history-favours-a-dairy-monopoly-123852">Crying over plant-based milk: neither science nor history favours a dairy monopoly</a>
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<h2>First, the crystals</h2>
<p>As the mixture of ice cream ingredients is cooled down, small clusters of water molecules assemble to form <a href="https://theconversation.com/how-do-snowflakes-form-is-each-snowflake-really-unique-why-is-some-snow-light-and-fluffy-or-heavy-the-amazing-science-of-snow-196269">tiny ice crystals</a>. The size of the ice crystals is responsible for the mouth feel of the ice cream – the <a href="https://ift.onlinelibrary.wiley.com/doi/full/10.1111/j.1541-4337.2009.00101.x">smaller the crystals, the smoother the feel</a>.</p>
<p>If the crystallisation is not well controlled, these crystals can get very large. Ice cream makers (commercial or for home use) ensure small ice crystals by agitating or beating the liquid as it freezes. This keeps the water molecules moving and prevents the crystals from growing larger.</p>
<p>The mixing process also incorporates air, which is the secret ingredient to give ice cream a lighter texture.</p>
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<a href="https://images.theconversation.com/files/526974/original/file-20230518-23-jkyrps.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Close up of ivory coloured ice cream being churned in a stainless steel container" src="https://images.theconversation.com/files/526974/original/file-20230518-23-jkyrps.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/526974/original/file-20230518-23-jkyrps.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/526974/original/file-20230518-23-jkyrps.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/526974/original/file-20230518-23-jkyrps.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/526974/original/file-20230518-23-jkyrps.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/526974/original/file-20230518-23-jkyrps.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/526974/original/file-20230518-23-jkyrps.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Without mixing during the freezing process, the ice crystals in the milk or cream will be too large to yield the texture that defines ice cream.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-on-industrial-ice-cream-mixing-1584957778">Shutterstock</a></span>
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<h2>Next, the fat</h2>
<p>The fat in the milk exists as globules surrounded by proteins. These proteins bridge the fat and the water, helping to keep the fats suspended. (Milk looks white because light scatters off these fat globules.)</p>
<p>These dairy fat molecules have different properties at different temperatures. At room temperature they are semi-solids (like butter), and are about two-thirds solid when at 0°C. </p>
<p>The fat globules can stick together – that’s why you get a layer of cream on top of unprocessed milk. A process called <a href="https://iufost.org/iufostold/wp-content/uploads/2020/05/98-Milk-Homogenization.pdf">homogenisation</a> forces the milk through a small opening under very high pressure, breaking large fat globules down into smaller ones. This process makes many small fat globules – as many as a trillion per litre. Homogenised milk ensures the mixture will freeze evenly, and separated fats won’t get stuck to the mixing machinery.</p>
<p>Freezing the fat globules makes them clump together, with the surrounding proteins acting as bridges to other fat molecules and to the ice crystals. These fats melt in your mouth, giving a creamy feel and taste.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/slip-slop-slurp-the-surprising-science-of-sunscreen-sand-and-ice-cream-169155">Slip, slop, slurp! The surprising science of sunscreen, sand and ice cream</a>
</strong>
</em>
</p>
<hr>
<h2>Then, the sugar</h2>
<p>The sugar and other dissolved ingredients in milk are also essential to the final texture of ice cream. The presence of sugars in the water lowers the mixture’s freezing temperature to below 0°C. </p>
<p>Here’s why that’s important. As ice crystals start to form, the concentration of sugars and other dissolved materials in the <a href="https://www.tandfonline.com/doi/full/10.1081/FRI-100100289">unfrozen liquid increases</a>, which further <a href="https://theconversation.com/salt-doesnt-melt-ice-heres-how-it-actually-makes-winter-streets-safe-110870">lowers its freezing point</a>. By the time the majority of the ice crystals have formed, the resulting liquid is very concentrated in sugars. </p>
<p>This concentrated liquid, known as the “serum”, bridges <em>between</em> the ice crystals, solid fat globules and air bubbles. The serum remains a liquid well below 0°C and adds enough flexibility to the mixture so the ice cream can still be scooped or shaped.</p>
<p>In this way, the unique chemical properties of water, fats, proteins and sugars come together with air to give the solid, liquid and gas mixture we know and love.</p>
<h2>Not everything is ‘ice cream’</h2>
<p>What’s called “ice cream” is actually governed by a <a href="https://www.legislation.gov.au/Series/F2015L00424">food standards code</a>. That’s why not all frozen desserts can be legally called ice cream, because they don’t contain enough milk fat.</p>
<p>There are lots of variations on the standard ice cream recipe. Gelato uses more sugar, incorporates less air, and typically has less fats and other solids. Sorbets do away with the dairy and typically contain more sugar, but have historically used egg or gelatin as a protein source. </p>
<p>Regardless of the exact recipe, the fundamental ice crystal formation, fat solidification, and serum phase separation steps are the same.</p>
<p>Product names like “soft serve”, “dairy dessert”, or “ice confection” are often an indication the ingredient list includes vegetable fats rather than more expensive milk fats. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/526980/original/file-20230518-2311-9i1j4h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A hand holding a waffle cone under the nozzle of a machine dispensing pink and white soft serve" src="https://images.theconversation.com/files/526980/original/file-20230518-2311-9i1j4h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/526980/original/file-20230518-2311-9i1j4h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/526980/original/file-20230518-2311-9i1j4h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/526980/original/file-20230518-2311-9i1j4h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/526980/original/file-20230518-2311-9i1j4h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/526980/original/file-20230518-2311-9i1j4h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/526980/original/file-20230518-2311-9i1j4h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Technically, soft serve isn’t ice cream.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/soft-ice-cream-machine-1312164440">Shutterstock</a></span>
</figcaption>
</figure>
<p>Soft serve products are also formed by agitation as the mixture freezes, but tend to contain less air than ice cream you’d buy in a tub, due to the constant agitation inside the dispensing machine.</p>
<p>Icy poles, ice blocks, freezies, or freeze pops (depending on <a href="https://theconversation.com/togs-or-swimmers-why-australians-use-different-words-to-describe-the-same-things-52007">your local phraseology</a>) and other “water ices” are frozen inside a mould or plastic tubing. The shape of the mould limits the ability to stir the mixture, so the freezing process is typically done “quiescently”, meaning at rest. The crystallisation of the ice is not well controlled, and you may have experienced large crystals that have grown (technically “seeded”) from the popsicle stick.</p>
<p>Humanity has enjoyed ice cream for centuries. It’s a marvellously versatile food with endless variations of flavours, additives, and toppings coupled with memories of happiness, comfort, indulgence and nostalgia. And plenty of chemistry, too.</p><img src="https://counter.theconversation.com/content/205038/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Kilah does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It might seem like a simple concept, but to get ice cream right, you need three states of matter and a delicate interplay of chemistry.Nathan Kilah, Senior Lecturer in Chemistry, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2039902023-04-20T11:04:45Z2023-04-20T11:04:45ZIs ice cream really healthy? Here’s what the evidence says<figure><img src="https://images.theconversation.com/files/522062/original/file-20230420-28-7etqgx.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C7348%2C4912&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A little bit every now and again probably won't hurt.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/womans-hands-holding-melting-ice-cream-505106287">Johnstocker Production/Shutterstock</a></span></figcaption></figure><p>Ice cream lovers worldwide were probably rejoicing when a recent article suggested that indulging in your favourite flavour might <a href="https://www.theatlantic.com/magazine/archive/2023/05/ice-cream-bad-for-you-health-study/673487/">be healthy</a>. The article drew upon a 2018 doctoral thesis, which suggested that people with type 2 diabetes who consumed more ice cream had <a href="https://dash.harvard.edu/bitstream/handle/1/37925665/ARDISSONKORAT-DISSERTATION-2018.pdf?sequence=3">lower risks</a> of heart disease. But as exciting as this sounds for those of us who sometimes enjoy indulging in a bowl of raspberry ripple, when we actually examine the study, it’s likely this link comes down to variety of other factors.</p>
<p>The 2018 research the article drew upon looked at data from the <a href="https://www.hsph.harvard.edu/nutritionsource/nurses-health-study/">Nurses’ Health Study I</a> and the <a href="https://www.hsph.harvard.edu/hpfs/">Health Professionals Follow-Up Study</a>. These were two large observational studies conducted by researchers at Harvard University which began in 1976 and 1986 and went on for around 20 years. The purpose of these studies was to track the health of participants over a long period of time, and uncover whether there were links between certain diseases and lifestyle factors (such as diet).</p>
<p>To conduct their analysis, the researchers only included data from participants of these two studies who reported having type 2 diabetes when the studies began – so around 16,000 people total. The participants with diabetes had also provided information about which foods they typically ate over the previous year. They were not instructed to eat or avoid ice cream at any point.</p>
<p>The researchers found that those who ate ice cream no more than twice a week appeared to be 12% less likely to develop cardiovascular disease, compared to those who didn’t eat ice cream. </p>
<p>But it’s important to note that this link between ice cream and heart disease only became apparent when other aspects of a person’s health, including how healthily they ate, were taken into account. This suggests that eating an overall healthy diet is perhaps more important in reducing cardiovascular disease risk in people with type 2 diabetes, than eating ice cream.</p>
<p>It could also be the case that participants who reported eating ice cream before joining the study could have stopped eating ice cream altogether just after joining the study – possible because they may have been made aware they were at greater risk of cardiovascular disease. This would then make it appear that eating ice cream was linked with lower risk of cardiovascular disease, when the reverse was true.</p>
<p>It’s also important to make clear that this was an observational study – meaning that it can only show an association between eating ice cream and lower risk of heart disease. It can’t actually prove eating ice cream in and of itself is directly responsible for decreasing risk of cardiovascular disease in people with type 2 diabetes.</p>
<p>To be able to test if ice cream has an effect on cardiovascular disease risk, it would probably need to go through a clinical trial, where one group ate ice cream as part of their diet and the other group ate a placebo for ice cream. This would be practically difficult to do, and given the potential costs is unlikely to ever happen without significant funding from the food industry.</p>
<h2>Can ice cream be healthy?</h2>
<p>Surprisingly, there have not been a lot of studies that have looked at the specific effect of ice cream on health. Studies that have done typically only had participants consume quite a small amount (around <a href="https://academic.oup.com/ajcn/article/111/5/1018/5698396">less than a quarter</a> of a serving per day) – meaning it was not enough to develop any meaningful conclusions about its effect.</p>
<figure class="align-center ">
<img alt="A bowl of plain yoghurt with raspberries on top." src="https://images.theconversation.com/files/522064/original/file-20230420-26-m60zxr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/522064/original/file-20230420-26-m60zxr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/522064/original/file-20230420-26-m60zxr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/522064/original/file-20230420-26-m60zxr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/522064/original/file-20230420-26-m60zxr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/522064/original/file-20230420-26-m60zxr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/522064/original/file-20230420-26-m60zxr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Other types of dairy have more convincing evidence of their health benefits.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/fresh-white-yoghurt-raw-forest-fruits-1031184493">Krasula/ Shutterstock</a></span>
</figcaption>
</figure>
<p>But one Italian study suggested that consuming more ice cream may be linked to a <a href="https://www.mdpi.com/2072-6643/11/11/2744">higher risk</a> of non-alcoholic fatty liver (a risk factor for type 2 diabetes and heart disease). However, the researchers also found that this link existed for other foods, such as red meat – suggesting that the quality of a person’s overall diet may matter more for health than a specific food.</p>
<p>Ice cream is also considered an <a href="https://www.fao.org/3/ca5644en/ca5644en.pdf">ultra-processed food</a> – meaning that because of the processing methods used to create it, it’s typically very high in calories, fat and sugar. Ultra-processed foods have been linked to a range of health issues, including increased risk of developing both <a href="https://pubmed.ncbi.nlm.nih.gov/31841598/">type 2 diabetes</a> and <a href="https://www.bmj.com/content/365/bmj.l1451">cardiovascular disease</a>. Nutrition guidelines also encourage us to <a href="https://www.gov.uk/government/publications/the-nutrient-profiling-model">limit our intake</a> of sugar and fat because of this. This makes it pretty likely that too much ice cream may have a negative effect on health.</p>
<p>But it may not all be bad news if you’re someone who enjoys dairy products in general. Evidence for the potential benefits of dairy fat has been growing over the past 20 years, with research showing <a href="https://www.sciencedirect.com/science/article/pii/S1756464620302838">fermented dairy products</a> – such as some types of yoghurt – and cheese in particular may reduce risk of <a href="https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003763#sec025">heart disease</a> and <a href="https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1002670">type 2 diabetes</a>. However, more research will be needed to see whether ice cream may be associated with similar benefits because of it’s dairy fat content.</p>
<p>Research also shows that diets containing calcium-rich foods are associated with a decreased risk of <a href="https://www.nature.com/articles/s41598-022-05144-8">type 2 diabetes</a> and <a href="https://www.tandfonline.com/doi/full/10.1080/07315724.2019.1649219">heart disease</a>. But there are many other foods – including dairy, pulses and nuts – which are also sources of calcium. These also have other nutritional benefits without the negative high sugar content of ice cream.</p>
<p>While it can be exciting to see headlines claiming our favourite foods may have <a href="https://onlinelibrary.wiley.com/doi/10.1111/jhn.13155">unexpected health benefits</a>, it’s important to analyse the research. Often, the effects of one food can be exaggerated by research method errors or other factors – such as the participant’s diet or lifestyle.</p>
<p>At the moment, we simply don’t have enough good quality evidence to suggest that ice cream definitely has any health benefits. But a couple of small portions a week – paired with an otherwise healthy diet and exercise regime – is unlikely to do much harm.</p><img src="https://counter.theconversation.com/content/203990/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Duane Mellor is a member of the British Dietetic Association</span></em></p>Any benefit of eating ice cream can likely be explained by other factors – such as eating a healthy diet or exercising.Duane Mellor, Lead for Evidence-Based Medicine and Nutrition, Aston Medical School, Aston UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1879052022-08-19T12:42:26Z2022-08-19T12:42:26ZWhat is listeria? A microbiologist explains the bacterium behind recent deadly food poisoning outbreaks<figure><img src="https://images.theconversation.com/files/479719/original/file-20220817-21-a18luh.jpg?ixlib=rb-1.1.0&rect=132%2C0%2C3875%2C2951&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Investigators in Florida traced a listeria outbreak to ice cream.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/ice-cream-jar-with-4-flavors-strawberry-vanilla-royalty-free-image/1279372828?adppopup=true">Graiki/Moment via Getty Images</a></span></figcaption></figure><p>Bacteria do, and will, end up in food. Everyone eats – intentionally or unintentionally – <a href="https://doi.org/10.7717/peerj.659">millions to billions</a> of live microbes every day. </p>
<p>Most are completely harmless, but some can cause serious illnesses in humans. Because of these potential pathogens, there is a long <a href="https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/pregnancy-nutrition/art-20043844">list of foods to avoid</a>, including uncooked eggs, raw fish and unwashed fruits and vegetables, particularly for pregnant women. The foods themselves are not bad, but the same cannot be said for certain bacterial passengers, such as <em>Listeria monocytogenes</em>, or listeria for short. </p>
<p>This particular pathogen has found ways to indiscriminately get into our foods. While deli and dairy foods like cold cuts, cheese, milk and eggs are frequently culprits for causing listeriosis – the general name for listeria-caused infections – fresh vegetables and fruits have also been implicated.</p>
<p>The variety of foods responsible for <a href="https://www.cdc.gov/listeria/outbreaks/index.html">U.S. listeria outbreaks in the past decade</a> shows just how easily these bacteria get around. Listeria has turned up in <a href="https://www.cdc.gov/listeria/outbreaks/eggs-12-19/index.html">hard-boiled eggs</a>, <a href="https://www.cdc.gov/listeria/outbreaks/enoki-mushrooms-03-20/index.html">enoki mushrooms</a>, <a href="https://www.cdc.gov/listeria/outbreaks/precooked-chicken-07-21/index.html">cooked chicken</a> and, <a href="https://www.cdc.gov/listeria/outbreaks/packaged-salad-12-21-b/index.html">in 2021, packaged salad</a> – <a href="https://www.cdc.gov/listeria/outbreaks/packaged-salad-mix-12-21/index.html">twice</a>.</p>
<p>Even the frozen aisle is not spared from listeria contamination. Contaminated ice cream in Florida was behind this year’s listeria outbreak, with 25 reported cases spanning 11 states since January 2021, according to <a href="https://www.cdc.gov/listeria/outbreaks/monocytogenes-06-22/details.html">an early August 2022 report</a> from the Centers for Disease Control and Prevention. Those who fell ill ranged in age from less than 1 to 92 years old, and 24 of the cases have involved hospitalizations.</p>
<p>How can such a tiny organism bypass extensive disinfection efforts and wreak such havoc? <a href="https://scholar.google.com/citations?user=G_tH2rUAAAAJ&hl=en">As a microbiologist</a> who has been working with listeria and trying to solve these mysteries, I’d like to share some insider secrets about this unique little pathogen and its strategies of survival inside and outside our bodies.</p>
<h2>Farm to table</h2>
<p>To prevent consumer exposure to listeria, the food industries follow <a href="https://www.fda.gov/files/food/published/Draft-Guidance-for-Industry--Control-of-Listeria-monocytogenes-in-Ready-To-Eat-Foods-%28PDF%29.pdf">stringent disinfection and surveillance guidelines</a> from the Food and Drug Administration and the U.S. Department of Agriculture. Any detection of listeria triggers a recall of potentially contaminated food products. </p>
<p>Since 2017, there have been <a href="https://www.fsis.usda.gov/recalls">over 270 listeria-related food recalls</a>. These are incredibly costly and can sometimes lead to fears in consumers <a href="https://www.npr.org/sections/thetwo-way/2018/01/29/581531318/panera-bread-recalls-cream-cheese-across-u-s-over-listeria-fears">as well as nationwide disruptions in food services</a>. However, the recalls represent one of the few tools that the food industry has to protect consumers from foodborne infections. </p>
<p>Not all listeria strains are created equal. <a href="https://doi.org/10.1016/j.ijmm.2010.05.002">Genetic variations</a> in listeria make a big difference in whether the pathogen ends up being involved in multistate outbreaks or simply hitching a ride harmlessly through our digestive tract. Essentially, based on the <a href="https://doi.org/10.1093/jaoac/85.2.524">different methods used</a>, listeria can be subtyped into different lineages, with some associated with outbreaks more frequently than others.</p>
<p>Researchers are investigating ways to tell these listeria strains apart, distinguishing the less harmful ones from those that are particularly dangerous, or hypervirulent. Being able to accurately identify them can help policymakers assess risks and make economically feasible decisions to improve food safety.</p>
<figure class="align-center ">
<img alt="Illustration of red-orange rod-shaped Listeria bacteria." src="https://images.theconversation.com/files/477025/original/file-20220801-70681-jygdr6.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6000%2C3979&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/477025/original/file-20220801-70681-jygdr6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/477025/original/file-20220801-70681-jygdr6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/477025/original/file-20220801-70681-jygdr6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/477025/original/file-20220801-70681-jygdr6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/477025/original/file-20220801-70681-jygdr6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/477025/original/file-20220801-70681-jygdr6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Listeria is an intracellular pathogen. Inside the body, it can grow inside a cell and spread to neighboring cells.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/listeria-monocytogenes-illustration-royalty-free-illustration/685023881">Kateryna Kon/Science Photo Library via Getty Images</a></span>
</figcaption>
</figure>
<h2>Listeria is tough</h2>
<p>Listeria can live in any place where food is grown, packaged, stored, transported, prepared or served. Our research team has even found listeria in <a href="https://doi.org/10.3390/pathogens7030060">organic lettuce harvested from a backyard garden</a>. </p>
<p>Listeria can survive and grow in temperatures as cold as <a href="https://ask.usda.gov/s/article/Can-Listeria-grow-at-refrigerator-temperatures">24 degrees Fahrenheit</a> (-4.4 Celsius) because it has <a href="https://doi.org/10.1080/10408390701856272">adapted to cold temperatures</a> and developed <a href="https://doi.org/10.4315/0362-028X-69.6.1473">tricks for overcoming cold stress</a>. Considering the average refrigerator maintains a temperature range of 35 F to 38 F (1.7 C to 3.3 C), even when the food is stored properly at refrigeration temperatures, a harmless few listeria can grow to dangerous levels of contamination over time.</p>
<p>Listeria is also extremely versatile in adapting to and surviving all kinds of disinfection processes. When it grows on surfaces, listeria protects itself with <a href="https://doi.org/10.3390%2Fpathogens6030041">a biofilm structure</a>, a kind of coating that forms a physical and chemical barrier and prevents disinfectants from reaching the bacteria within.</p>
<p>Surviving the harsh conditions outside our body is only the first part of the story. Before even beginning to cause infections, listeria needs to get to the intestines without getting caught and destroyed by the body’s defenses.</p>
<p>Traveling and surviving passage through a <a href="https://doi.org/10.3389%2Ffcimb.2014.00009">human digestive tract is not easy</a> for bacteria. Saliva enzymes can degrade bacterial cell walls. So can stomach acids and bile salts. Antibodies in our digestive tract can recognize and target bacteria for degradation. Moreover, <a href="https://doi.org/10.1084%2Fjem.20170495">resident gut microbes</a> are strong competitors for the limited amount of space and nutrients in our intestines.</p>
<p>After digestion, the body’s intestinal movement sends traffic one way – out of the body. In order to stick around and cause infections, bacteria have to attach themselves and hang on against the bowel movement while competing for nutrients. Successful pathogens can establish these survival and attachment tasks while undermining our immune defenses. </p>
<p>Listeria that manage to stick around in our intestines can trigger an immune response. In healthy people, that might manifest as <a href="https://www.cdc.gov/listeria/symptoms.html">minor diarrhea or vomiting that goes away without medical attention</a>. </p>
<p>However, those with compromised immune systems or immune systems temporarily weakened as a result of medication or <a href="https://doi.org/10.3389/fimmu.2020.575197">pregnancy</a> can be more susceptible to severe infections. In the absence of an effective immune system, listeria can invade other tissues and organs by creating an efficient niche for growth.</p>
<h2>Listeria in stealth mode</h2>
<p>Listeria is what we microbiologists call an intracellular pathogen. In an infected individual, listeria can grow inside a cell and <a href="https://doi.org/10.1083%2Fjcb.146.6.1333">spread to neighboring cells</a>. Hiding inside our cells this way, listeria avoids detection by antibodies or other immune defenses that are designed to detect and destroy threats that exist outside of our cells.</p>
<p>Once in stealth mode, listeria can move into and infect different organs. Wherever it goes, inflammation follows as the body’s immune system tries to go after the bacteria. The inflammation eventually results in collateral damage in nearby tissues. </p>
<p>In fact, deaths from listeria infections are often associated with the more invasive forms of the disease in which the microbes have breached the intestinal barriers and moved to other body parts. <a href="https://www.cdc.gov/listeria/symptoms.html">Life-threatening illnesses</a> that can result from listeria include meningitis – inflammation around the brain and spinal cord that can occur when these microbes infect the brain – or <a href="https://doi.org/10.1016/j.ijantimicag.2017.12.032">endocarditis</a>, infection of the heart’s inner lining. And in pregnant individuals, if the pathogen reaches the placenta, it can spread to the fetus and cause stillbirth or miscarriage.</p>
<p>As such, invasive listeria cases often have an alarmingly high <a href="https://www.fda.gov/animal-veterinary/animal-health-literacy/get-facts-about-listeria#">hospitalization rate of more than 90% and a fatality rate that can reach 30%</a>. </p>
<p>The scary statistics argue for a proactive and effective infection control to protect vulnerable populations, such as elderly or pregnant individuals, from listeria exposure. </p>
<h2>Think, cook and eat</h2>
<p>If you have risk factors and want to take extra precautions, maybe turn that unpasteurized cider into a hot, mulled cider to kill the bacteria with boiling and simmering. Eat soft cheeses on foods that get cooked, such as pizzas or grilled sandwiches, instead of eating them cold, straight from the refrigerator. Essentially, use heat to bring out the delicious flavors and eliminate potential listeria contamination in your food. </p>
<p>Ultimately, it’s nearly impossible to live in a completely sterile environment, eating food devoid of all living microorganisms. So enjoy your favorites, but <a href="https://www.fsis.usda.gov/food-safety">stay up to date with ongoing recalls</a> and follow the expiration guidelines, especially for ready-to-eat food.</p><img src="https://counter.theconversation.com/content/187905/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Yvonne Sun does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Listeria causes serious illness and food recalls nearly every year.Yvonne Sun, Assistant Professor of Microbiology, University of DaytonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1691552021-12-26T20:27:14Z2021-12-26T20:27:14ZSlip, slop, slurp! The surprising science of sunscreen, sand and ice cream<figure><img src="https://images.theconversation.com/files/435198/original/file-20211202-25-12jv98a.jpg?ixlib=rb-1.1.0&rect=20%2C8%2C1976%2C1320&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Ahh, summer at the beach! The sun on your face, sand between your toes, an ice cream in your hand. </p>
<p>For scientists young and old, a trip to the beach is also a perfect opportunity to explore the peculiar properties of some fascinating fluids. </p>
<h2>Through thick and thin</h2>
<p>Take sunscreen. When you first squeeze sunscreen from the bottle, it spreads easily over your skin, providing an even protective layer against the Sun’s rays. But once on your skin, sunscreen gains a thicker consistency – it has higher <em>viscosity</em> – preventing it from dripping off. </p>
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Read more:
<a href="https://theconversation.com/explainer-how-does-sunscreen-work-what-is-spf-and-can-i-still-tan-with-it-on-88869">Explainer: how does sunscreen work, what is SPF and can I still tan with it on?</a>
</strong>
</em>
</p>
<hr>
<p>Viscosity is the ability of a fluid to keep its shape when a force is applied. Sunscreen is what’s called a <em>shear-thinning fluid</em>, which means rubbing it makes its viscosity decrease so it flows more freely.</p>
<p>This effect typically occurs in fluids containing chain-like molecules called polymers. At rest, the polymers are tangled up in an irregular pattern; but when they are pushed around, they rearrange themselves into layers that slide past each other more easily. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/435199/original/file-20211202-23-klmz1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435199/original/file-20211202-23-klmz1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435199/original/file-20211202-23-klmz1g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435199/original/file-20211202-23-klmz1g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435199/original/file-20211202-23-klmz1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435199/original/file-20211202-23-klmz1g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435199/original/file-20211202-23-klmz1g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sunscreen is a ‘shear-thinning fluid’, which means it flows more easily under pressure.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Shear-thinning fluids are quite common. Ketchup is a classic example: it has high viscosity at rest, making it stick to the sides of the bottle until you shake it so its viscosity decreases and it flows out the nozzle. </p>
<p>When the ketchup lands on your plate, its viscosity increases again so it forms a satisfying dollop. (If this is starting to make your mouth water, you’ll be interested to know that saliva is also a shear-thinning fluid.)</p>
<h2>Footprints in the sand</h2>
<p>The opposite of a shear-thinning fluid is a <em>shear-thickening fluid</em>, a material whose viscosity increases with applied force. </p>
<p>A familiar example is very wet sand: if you pick up a handful, it will flow between your fingers like grainy custard. When you squeeze it, however, the sand becomes firm and, counter-intuitively, appears dry. </p>
<p>This behaviour, called the <em>wet-sand effect</em>, occurs because the compressive force of your hand pushes apart tiny grains of sand, creating space that lets water drain away from the surface. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/435201/original/file-20211202-19-wox09w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435201/original/file-20211202-19-wox09w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=551&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435201/original/file-20211202-19-wox09w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=551&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435201/original/file-20211202-19-wox09w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=551&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435201/original/file-20211202-19-wox09w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=692&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435201/original/file-20211202-19-wox09w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=692&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435201/original/file-20211202-19-wox09w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=692&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Wet sand is a ‘shear-thickening fluid’: under pressure (like from a footstep) it becomes firmer and less runny.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>The same effect allows you to run on wet sand, producing firm and dry patches where your feet land. But if you stand still and gently wiggle your toes, the wet sand reverts to a liquid state, allowing your feet to sink in – and make a pleasing slurp when you pull them out. </p>
<h2>Newton on the beach</h2>
<p>Simpler fluids, such as water, have a more or less constant viscosity. These are called <em>Newtonian fluids</em>, after Isaac Newton, who first wrote down the mathematical law to describe them in his famous 1687 book Principia. </p>
<p>To understand viscosity, imagine drinking water through a straw. When you suck, you create lower pressure at the top of the straw than the bottom, drawing water upwards.</p>
<p>The fluid near the walls of the straw experiences friction, so it flows more slowly than fluid near the centre. Newton reasoned the fluid separates into thin layers that slide over each other with a relative speed that depends on the applied force. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/kitchen-science-the-many-wonders-of-humble-flour-59310">Kitchen Science: the many wonders of humble flour</a>
</strong>
</em>
</p>
<hr>
<p>The viscosity measures the amount of friction between these different layers. The greater the viscosity (think of a milkshake), the more force you must apply to suck the fluid up the straw. </p>
<p>Newton’s law of viscosity, as it is known, is a mathematical ideal. No real fluid behaves exactly this way, but common fluids like water, alcohol, and vegetable oil come pretty close. </p>
<p>By contrast, <em>non-Newtonian fluids</em> — including shear-thinning and shear-thickening fluids — do not obey Newton’s law of viscosity: their viscosity changes depending on how much force is applied to them. </p>
<h2>The scoop on ice cream</h2>
<p>Time for some ice cream. Ice cream is a frozen mixture of cream, milk, sugar, and flavourings, but it is the unique behaviour of cream that is responsible for the dribbly joy of really good ice cream. </p>
<p>Cream is peculiar stuff. It is the fat-enriched portion of milk, separated from its watery base. </p>
<p>The resulting <em>emulsion</em> of fat globules and a small amount of liquid gives cream its silkiness. When cream is whisked, the applied force breaks the membranes of the fat globules, which glom together around trapped air, producing a suspension of bubbles and cream: whipped cream. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/435202/original/file-20211202-15-7eey1l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435202/original/file-20211202-15-7eey1l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435202/original/file-20211202-15-7eey1l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435202/original/file-20211202-15-7eey1l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435202/original/file-20211202-15-7eey1l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435202/original/file-20211202-15-7eey1l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435202/original/file-20211202-15-7eey1l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The light, silky texture of ice cream is all due to tiny air bubbles trapped inside little globules of cream.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Whipped cream is a type of non-Newtonian fluid called a <em>Bingham plastic</em>: at rest, it is semi-solid, forming stiff peaks that are perfect for spooning onto strawberries or scones. But under sufficient force, it can flow like a liquid: through the nozzle of a can of instant whipped cream, for example. </p>
<p>As anyone who has made whipped cream by hand knows, the key ingredient is <em>time</em>. The transformation from liquid to semi-solid is caused by applying force over a period of time.</p>
<p>Air bubbles trapped in the cream give ice cream its pillowy softness. In fact, air can make up to 50% of the total volume of ice cream, which explains why it is less dense than water – and why you can use it to make an ice cream float. </p>
<h2>Fantastic fluids</h2>
<p>Non-Newtonian fluids are found in all sorts of useful substances from biofuels to body armour to blood plasma, and there is still much about them to discover. As Isaac Newton said: </p>
<blockquote>
<p>To myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.</p>
</blockquote>
<p>What better way to spend a summer day? </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-story-of-a-wave-from-wind-blown-ripples-to-breaking-on-the-beach-128458">The story of a wave: from wind-blown ripples to breaking on the beach</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/169155/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shane Keating does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A trip to the beach is a perfect opportunity to explore the peculiar properties of some fascinating fluids.Shane Keating, Senior Lecturer in Mathematics and Oceanography, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1351662020-04-23T12:12:09Z2020-04-23T12:12:09ZWhat is a brain freeze?<figure><img src="https://images.theconversation.com/files/329186/original/file-20200420-152581-pm3o7v.jpg?ixlib=rb-1.1.0&rect=74%2C27%2C4456%2C3029&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cold and sweet in the heat.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/children-enjoy-icecream-during-the-hot-afternoon-on-june-7-news-photo/450223408?adppopup=true">Raj K Raj/Hindustan Times via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>What is a brain freeze?</strong></p>
</blockquote>
<hr>
<p>Has this ever happened to you? You’re eating a delicious ice cream cone or frozen lemonade, so cold and sweet and suddenly, bam, brain freeze! What happened?</p>
<p>A brain freeze is a short, intense pain behind the forehead and temples that occurs after eating something cold too fast. If you get one, don’t worry – your brain isn’t actually freezing. The sensation feels like it’s happening inside your skull, but it really has to do with what’s going on in your mouth.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/327044/original/file-20200409-38906-1b1qvqf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/327044/original/file-20200409-38906-1b1qvqf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=439&fit=crop&dpr=1 600w, https://images.theconversation.com/files/327044/original/file-20200409-38906-1b1qvqf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=439&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/327044/original/file-20200409-38906-1b1qvqf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=439&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/327044/original/file-20200409-38906-1b1qvqf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=552&fit=crop&dpr=1 754w, https://images.theconversation.com/files/327044/original/file-20200409-38906-1b1qvqf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=552&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/327044/original/file-20200409-38906-1b1qvqf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=552&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Mmmmmm. Brrrrrrrr. Ouch!</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/DEU-BW-Wetter-Speiseeis/135fdca280524c04a0a4e9a65078965f/211/0">AP Photo/Daniel Maurer</a></span>
</figcaption>
</figure>
<p>Brain freeze isn’t as common as you might expect. Many studies report that less than half of their participants get them. Scientists still don’t understand why.</p>
<h2>What makes a brain freeze hurt?</h2>
<p>There’s a lot we know about how a brain freeze works. There’s also a lot we don’t know.</p>
<p>Just beneath the skin on your face is a network of blood vessels that supply the face and brain with blood. Blood contains many nutrients <a href="https://kidshealth.org/en/kids/blood.html">like oxygen</a>, which is essential for your brain to function. Tangled up in this network of vessels are tiny nerve endings connected to one another and the brain through the <a href="https://www.healthline.com/human-body-maps/trigeminal-nerve">trigeminal nerve</a>. This nerve makes it possible for you to feel sensations in your face, including pain.</p>
<p>Scientists believe the blood vessels in the throat and mouth and the trigeminal nerve are central to what makes a brain freeze hurt. But they don’t quite agree on which is more responsible for causing the pain.</p>
<p>Most agree that eating or drinking something cold, too quickly, rapidly <a href="https://www.sciencedaily.com/releases/2013/05/130522095335.htm">lowers the temperature</a> at the back of your throat and roof of your mouth. Many also agree this causes the tiny blood vessels in these areas to shrink, allowing less blood to pass through them. This reduces their ability to supply your brain with necessary oxygen in the blood. What happens next is a little blurry.</p>
<h2>Pain in the brain means stop!</h2>
<p>Some scientists believe the trigeminal nerve responds to these events in your throat and mouth by sending a pain signal to the front of your brain. Whether the nerve is specifically responding to the cold or a sudden reduction of blood and oxygen supply to the brain – or both – is unclear. </p>
<p>Other scientists believe the pain is caused by a rush of blood to the front of your head. Shortly after the vessels in your throat and mouth shrink from the cold, these same vessels immediately expand. By expanding, additional blood and oxygen <a href="https://www.medicalnewstoday.com/articles/244458">flood these areas</a>. Although this blood rush might provide your brain with desperately needed blood and oxygen, it also might increase the amount of pressure in your head, causing pain.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/X3bn6pmpLEw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The mystery of a brain freeze.</span></figcaption>
</figure>
<h2>Is a brain freeze dangerous?</h2>
<p>A brain freeze may seem like a bad thing at first, but the pain could actually be good. By forcing you to stop eating that delicious but cold treat, the pain from a brain freeze may protect your brain from losing its continuous supply of blood and oxygen.</p>
<p>If you’re worried about a brain freeze, try slowing down. It may be hard with something as delicious as a Bomb Pop on a hot summer day, but at least it will last longer.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/135166/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tyler Daniel Anderson-Sieg does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Have you ever felt a piercing pain in your head when you eat something cold?Tyler Daniel Anderson-Sieg, Doctoral Student in Biomedical Sciences, University of South CarolinaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1226822019-09-06T11:15:09Z2019-09-06T11:15:09Z‘I’ll have what she’s having’ – how and why we copy the choices of others<figure><img src="https://images.theconversation.com/files/291155/original/file-20190905-175691-5wvcll.gif?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The choice of flavor may be up to you, but the number of scoops will depend on what your companion gets.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/various-ice-cream-on-pink-pastel-674512801">Zamurovic Photography/Shutterstock.com</a></span></figcaption></figure><p>Imagine you’re dining out at a casual restaurant with some friends. After looking over the menu, you decide to order the steak. But then, after a dinner companion orders a salad for their main course, you declare: “I’ll have the salad too.” </p>
<p>This kind of situation – making choices that you probably otherwise wouldn’t make <a href="https://doi.org/10.1093/jcr/ucv012">were you alone</a> – probably happens more often than you think in a wide variety of settings, from eating out to shopping and even donating to charity. And it’s not just a matter of you suddenly realizing the salad sounds more appetizing. </p>
<p><a href="https://explorable.com/chameleon-effect">Prior research has shown</a> people have a tendency to mimic the choices and behaviors of others. But other work suggests people also want to do the exact opposite to <a href="https://doi.org/10.1086/317585">signal their uniqueness</a> in a group by making a different choice from others.</p>
<p>As scholars who examine consumer behavior, <a href="https://doi.org/10.1177/0022243719853221">we wanted</a> to resolve this discrepancy: What makes people more likely to copy others’ behavior, and what leads them to do their own thing? </p>
<h2>A social signal</h2>
<p>We developed a theory that how and why people match or mimic others’ choices depends a lot on the attributes of the thing being selected. </p>
<p>Choices have what we call “ordinal” attributes that can be ranked objectively – such as size or price – as well as “nominal” attributes that are not as easily ranked – such as flavor or shape. We hypothesized that ordinal attributes have more social influence, alerting others to <a href="https://doi.org/10.1016/j.obhdp.2013.08.007">what may be seen as “appropriate”</a> in a given context. </p>
<p>Nominal attributes, on the other hand, would seem to be understood as a reflection of one’s personal preferences. </p>
<p>So we performed 11 studies to test our theory. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/290592/original/file-20190902-175678-sn1350.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/290592/original/file-20190902-175678-sn1350.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=373&fit=crop&dpr=1 600w, https://images.theconversation.com/files/290592/original/file-20190902-175678-sn1350.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=373&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/290592/original/file-20190902-175678-sn1350.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=373&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/290592/original/file-20190902-175678-sn1350.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=468&fit=crop&dpr=1 754w, https://images.theconversation.com/files/290592/original/file-20190902-175678-sn1350.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=468&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/290592/original/file-20190902-175678-sn1350.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=468&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Size may be social, but flavor remains a personal choice.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Breast-Milk-Ice-Cream/8d3828c71ff542c193c3a4a1c2920310/239/0">AP Photo/Toby Talbot</a></span>
</figcaption>
</figure>
<h2>One scoop or two</h2>
<p>In one study conducted with 190 undergraduate students, we told participants that they were on their way to an ice cream parlor with a friend to get a cone. We then told our would-be ice cream consumers that their companion was getting either one scoop of vanilla, one scoop of chocolate, two scoops of vanilla or two scoops of chocolate. We then asked participants what they wanted to order. </p>
<p>We found that people were much more likely to order the same size as their companion but not the same flavor.</p>
<p>The participants seemed to interpret the number of scoops the companion ordered as an indication of what’s appropriate. For example, ordering two scoops might signal “permission” to indulge or seem the <a href="https://doi.org/10.1509/jm.11.0261">more financially savvy</a> – if less healthy – choice, since it usually costs only marginally more than one. Or a single scoop might suggest “let’s enjoy some ice cream – but not too much.”</p>
<p>The choice of chocolate or vanilla, on the other hand, is readily understood as a personal preference and thus signals nothing about which is better or more appropriate. I like vanilla, you like chocolate – everyone’s happy.</p>
<p>We also asked participants to rate how important avoiding social discomfort was in their decision. Those who ordered the same number of scoops as their companion rated it as more important than those who picked a different amount. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/290769/original/file-20190903-175668-122r5rq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/290769/original/file-20190903-175668-122r5rq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/290769/original/file-20190903-175668-122r5rq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/290769/original/file-20190903-175668-122r5rq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/290769/original/file-20190903-175668-122r5rq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/290769/original/file-20190903-175668-122r5rq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/290769/original/file-20190903-175668-122r5rq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Study participants gave the same amounts to charities as their peers, but they weren’t swayed on whether to give to elephants or polar bears.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/chiang-rai-thailand-january-8-2017-1252190155?src=-1-10">LunaseeStudios/Shutterstock.com</a></span>
</figcaption>
</figure>
<h2>Examining other contexts</h2>
<p>In the other studies, we replicated our results using different products, in various settings and with a variety of ordinal and nominal attributes.</p>
<p>For example, in another experiment, we gave participants US$1 to buy one of four granola bars from a mock store we set up inside the University of Pittsburgh’s Katz/CBA Business Research Center. As the ordinal attribute, we used <a href="https://doi.org/10.1509/jmkg.65.1.71.18132">brand prestige</a>: They could pick either a more expensive well-known national brand or a cheaper one sold by a grocery store under its own label. Our nominal attribute was chocolate or peanut butter. </p>
<p>Before making the choice, a “store employee” stationed behind the checkout register told participants she or he had tested out a granola bar, randomly specifying one of the four – without saying anything about how it tasted. We rotated which granola bar the employee mentioned every hour during the five-day experiment. </p>
<p>Similar to the ice cream study, participants tended to choose the brand that the employee said he or she had chosen – whether it was the cheaper or pricier one – but ignored the suggested flavor.</p>
<p>Moving away from food, we also examined influences on charitable donations. In this study, we recruited online participants who were paid for their time. In addition, we gave each participant 50 cents to either keep or donate to charity. </p>
<p>If they chose to donate the money, they could give all of it or half to a charity focused on saving either <a href="https://www.savetheelephants.org">elephants</a> or <a href="https://polarbearsinternational.org/">polar bears</a>. Before they made their choice, we told them what another participant had supposedly decided to do with their money – randomly based on one of the four possibilities.</p>
<p>[ <em>Like what you’ve read? Want more?</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=likethis">Sign up for The Conversation’s daily newsletter</a>.] </p>
<p>The results were the same as in all our other studies, including ones we conducted involving different brands and shapes of pasta and varieties and taste profiles of wine. People matched the ordinal attribute – in this case the amount – but paid little heed to the nominal attribute – the chosen charity – which remained a personal preference. </p>
<p>These kinds of social cues regarding others’ choices are everywhere, from face-to-face interactions with friends to online tweets or Instagram posts, making it difficult to escape the influence of what others do on our own consumption choices.</p>
<p>And if we believe we’re making our companions feel more comfortable while still choosing something we like, what’s the harm in that?</p><img src="https://counter.theconversation.com/content/122682/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brent McFerran receives funding from the Social Sciences and Humanities Research Council of Canada. </span></em></p><p class="fine-print"><em><span>Kelly L. Haws and Peggy Liu do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New research on consumer behavior shows that we tend to match some types of choices the people around us make, but not others.Kelly L. Haws, Professor of Marketing, Vanderbilt UniversityBrent McFerran, W. J. Van Duse Associate Professor, Marketing, Simon Fraser UniversityPeggy Liu, Assistant Professor of Business Administration and Ben L. Fryrear Faculty Fellow, University of PittsburghLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/696212017-01-01T18:33:53Z2017-01-01T18:33:53ZHealth Check: does my brain really freeze when I eat ice cream?<figure><img src="https://images.theconversation.com/files/148830/original/image-20161206-25746-95rx47.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Little does this woman know what happens to her brain when she licks the ice cream.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/435069991?src=up5tXtzXv9_SlCpFnzUswg-3-17&id=435069991&size=medium_jpg">from www.shutterstock.com</a></span></figcaption></figure><p>It’s a long, hot summer’s day and you’re looking forward to an ice cream. But within seconds of your first bite, you feel a headache coming on: a brain freeze.
What’s going on?</p>
<p>Your brain isn’t literally freezing, or even sensing cold. It can’t sense cold or pain because it lacks its own internal sensory receptors. In fact, surgeons usually perform brain surgery on conscious, sedated patients with the only pain coming from the scalp, skull and underlying tissues, not from the brain itself.</p>
<p>An <a href="http://cep.sagepub.com/content/33/9/629.full">international team of neurologists</a> classifies brain freeze or ice cream headache as a:</p>
<blockquote>
<p>headache attributed to ingestion or inhalation of a cold stimulus. </p>
</blockquote>
<p>Anything cold (solid, liquid or gas) that passes over the roof of the mouth (the hard palate) and/or the back of the throat (posterior pharyngeal wall) can trigger a brain freeze headache.</p>
<p>Pain can be to the front of the head or the temples and while short lasting, can be intense, though not debilitating. People who have these headaches <a href="http://onlinelibrary.wiley.com/doi/10.1111/head.12688/abstract">usually do not seek treatment</a>, so there has been very little research into how brain freeze occurs.</p>
<p>The transient nature of these headaches means common “treatments”, <a href="http://www.wikihow.com/Stop-Brain-Freeze">like putting your tongue on the roof of your mouth</a>, are unlikely to have any major effect.</p>
<p>People most likely to have brain freeze also tend to suffer from migraines, suggesting a common underlying mechanism for both.</p>
<p><a href="http://cep.sagepub.com/content/24/4/293.abstract">One study</a> compared how common brain freeze was in people with migraine alongside those with tension type headaches. When an ice cube was placed on the hard palate of their mouths for 90 seconds, 74% of migraine sufferers reported pain along their temples versus 32% of those with a history of primary headache disorders (headaches that do not have an underlying or identifiable cause). </p>
<p><a href="http://cep.sagepub.com/content/early/2016/05/19/0333102416650704.abstract">Only 12%</a> of volunteers without a history of primary headache disorder experienced brain freeze headache with the same stimulus. These observations are robust and have been <a href="http://cep.sagepub.com/content/32/15/1123.abstract">replicated</a>.</p>
<h2>What causes brain freeze?</h2>
<p>An old fashioned idea about the cause of migraine suggested excessive blood flow through the blood vessels that supply blood to the brain caused the pain. However, this vascular hypothesis for migraine, <a href="https://en.wikipedia.org/wiki/Migraine">although still popular</a>, is now largely <a href="http://www.annualreviews.org/doi/abs/10.1146/annurev-physiol-030212-183717">discredited</a>.</p>
<p>Just like migraines, brain freeze headaches are accompanied by <a href="http://www.fasebj.org/content/26/1_Supplement/685.4.abstract">changes in blood flow</a> through <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2127417/">the arteries of the brain</a>. The link between pain associated with altered brain artery blood flow has <a href="http://www.wakehealth.edu/News-Releases/2013/Brrrrrrrrr!_It_s_Brain_Freeze_Season.htm">led some to speculate</a> the blood flow changes may actually <a href="http://cep.sagepub.com/content/early/2016/05/19/0333102416650704.abstract">cause the pain</a>. But an association between blood flow and pain doesn’t necessarily mean one causes the other.</p>
<p><a href="http://www.nature.com/scientificamerican/journal/v299/n2/full/scientificamerican0808-56.html">Another theory</a> about what causes migraine relates to altered excitability of neuronal pathways that detect and transmit the sensation and pain in the head via the <a href="http://emedicine.medscape.com/article/1873373-overview">trigeminal system</a>, the major nerve that transmits sensory information from the head to the central nervous system.</p>
<p>Ordinarily the cold sensation is not painful. However, if the trigeminal system is prone to over-excitability in people with migraine, pain kicks in at lower level (a lower threshold). If an over-excitable trigeminal system also applies to people with brain freeze, then the threshold may be low enough to activate pain after only a brief exposure to ice cream.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/150029/original/image-20161214-18882-uz447v.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/150029/original/image-20161214-18882-uz447v.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/150029/original/image-20161214-18882-uz447v.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1171&fit=crop&dpr=1 600w, https://images.theconversation.com/files/150029/original/image-20161214-18882-uz447v.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1171&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/150029/original/image-20161214-18882-uz447v.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1171&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/150029/original/image-20161214-18882-uz447v.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/150029/original/image-20161214-18882-uz447v.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/150029/original/image-20161214-18882-uz447v.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Zenobia Ahmed / The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Researchers are studying what causes hyper-excitability of the trigeminal system. The effects of a specific chemical signalling molecule CGRP (calcitonin gene-related peptide) released by trigeminal neurons are a <a href="http://www.nature.com/scientificamerican/journal/v299/n2/full/scientificamerican0808-56.html">necessary component of migraine pain</a>.</p>
<p>In genetically inherited migraine, the cellular processes that result in the release of CGRP from trigeminal neurons <a href="http://www.annualreviews.org/doi/abs/10.1146/annurev-physiol-030212-183717">has been altered</a>. These same mechanisms may explain the hypersensitivity to cold stimulus in ice cream headaches.</p>
<p>It seems likely that all headaches are the result of changes in activity in the trigeminal system, although why we perceive them in the front of the head and at the temples in particular is a mystery.</p>
<h2>Is there anything I can do to stop brain freeze?</h2>
<p>While we do not know exactly what causes brain freeze, there may be a simple way to reduce your chances of having one this summer.</p>
<p>Research shows how long brain freeze headaches last relates to the <a href="http://cep.sagepub.com/content/early/2016/05/19/0333102416650704.abstract">surface area</a> of the mouth that comes into contact with the cold stimulus. So, if you want to reduce your chance of a brain freeze, you may want to avoid gulping down your ice cream all at once. Take small nibbles instead.</p><img src="https://counter.theconversation.com/content/69621/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It’s a long, hot summer’s day and you’re looking forward to an ice cream. But within seconds of your first bite, you feel a headache coming on: a brain freeze. What’s going on?Yossi Rathner, Lecturer in Human Physiology, Swinburne University of TechnologyMark Schier, Senior Lecturer in Physiology, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/344922015-01-04T19:12:41Z2015-01-04T19:12:41ZHealth Check: do ice cream and cold drinks cool us down?<figure><img src="https://images.theconversation.com/files/67749/original/image-20141219-31049-ze9ewz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An ice cream on a summer's day may hit the spot, but it won't help you beat the heat.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/manc/4272986324">Mark Crossfield/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>All over the world summer is synonymous with water activities, cold beverages and, of course, ice cream. While most of us agree ice cream and cold beverages are refreshing summer treats, do they actually help cool us down? </p>
<p>To test whether they do, we need to know a bit more about how the body controls temperature in different environments. The process of maintaining an optimal body temperature is called <a href="http://www.ncbi.nlm.nih.gov/pubmed/19137807">thermoregulation</a>, which involves a delicate balance between producing and losing heat. </p>
<p>Humans are warm-blooded or endotherms, which are scientific ways of saying we can control our body temperature independent of the environment. We can do this because our bodies are constantly producing heat as a by-product of internal chemical processes (metabolism). </p>
<h2>How it all works</h2>
<p>Metabolism is necessary to keep our bodies functioning correctly. It includes digestive processes involved in breaking down nutrients in food, the absorption and transportation of those nutrients to the cells, and their conversion into building blocks or energy necessary for physical activity. </p>
<p>The heat this generates is beneficial when it’s cold, but when outside temperatures rise, we need to avoid overheating. While it may seem logical that introducing something cold, like ice cream, into the stomach should help reduce temperature, its initial cooling effect is rapidly replaced by heat generated by digestive processes needed to break down the nutrients in ice cream. Digesting calorie-rich food leads to an increase in body temperature. </p>
<p>So ice cream is not the best option for cooling down, but what about cold beverages? The heat transfer between a cold beverage and the digestive system can directly <a href="http://www.ncbi.nlm.nih.gov/pubmed/24060271">influence temperature</a>. But, this is only momentary and depends on the quantity and caloric content of the ingested liquid. </p>
<p>A small amount of liquid will lose its cooling effect quite quickly as it gets warmed up by the surrounding organs. And large amounts of cold liquids will cause blood flow to slow, making heat transport less effective. </p>
<p>As you can imagine, beverages with a high caloric content, such as soft drinks, will have a similar effect as ice cream and kick start our metabolism shortly after ingestion. </p>
<h2>But I feel cooler…</h2>
<p>The cooling effects of cold liquids are more likely explained by their <a href="http://www.ncbi.nlm.nih.gov/pubmed/24060271">rehydration</a> effects. If heat does build up, the body will attempt to lose excess heat by transporting it away from the vital organs to the skin surface where it is transferred directly to our environment through convection and radiation. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/67755/original/image-20141219-31563-q2r6bf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=498&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The cooling effects of cold liquids are more likely explained by their rehydration effects.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/joshlowensohn/4718411987/in/photostream/">Josh Lowensohn/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>For this to occur, the ambient temperature needs to be lower than our own temperature, or the opposite happens and heat will transfer into our body. Just like the heat radiated from the sun on a hot summer day. </p>
<p>Sweating is the most effective way our bodies lose heat. Sweating occurs when an increase in core body temperature is detected by the brain, which responds by stimulating the sweat glands distributed all over the body to produce sweat. </p>
<p>Sweat on the skin surface evaporates, causing the skin to cool down (also called evaporative cooling). Blood that’s flowing close to the surface of the skin gets cooled in the process and helps reduce core temperature. </p>
<p>On average, an adult can lose up to half or one litre of sweat every day, but in hot environments this can increase to almost a litre and a half an hour. That’s why it’s essential to keep the body hydrated during hot weather. </p>
<h2>A different approach</h2>
<p>What about alcoholic beverages? Many people reach for a cold beer on a hot summer day in an attempt to cool down. But alcohol is a diuretic, which means that it will make your body lose water and so reduce your ability to lose heat through sweating. </p>
<p>Surprisingly, warm beverages might be a good way to keep you cool. Although counter intuitive, drinking a warm beverage causes receptors in your mouth and throat to trigger a sweat response, allowing your body to cool down without having to ingest a large amount of the warm liquid.<br>
Active ingredients in <a href="http://www.ncbi.nlm.nih.gov/pubmed/2876434">spicy foods</a> have the same effect; they too trigger a sweat response that allows the body to cool down. That’s why these types of foods are popular in warm climates. </p>
<p>So while cold treats can be satisfying and are certainly refreshing, a better way of cooling down is to spice things up, get your sweat on and, most importantly, rehydrate!</p><img src="https://counter.theconversation.com/content/34492/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Poortvliet does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>While most of us agree ice cream and cold beverages are refreshing summer treats, do they actually help cool us down?Peter Poortvliet, Post-doctoral Research Fellow in Neuroscience, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.