Pine nuts are those crunchy, delectable seeds we scatter over summer salads, use to make pesto and that form the base of some favourite desserts, such as pignoli and baklava. They usually have a sweet, buttery, resinous flavor. But some people can find them distasteful.
Some consumers complain of a bitter metallic taste in their mouth (metallogeusia) that begins one to three days after eating pine nuts and may persist up to two weeks before resolving. This phenomenon has become known as “pine mouth” and is being increasingly reported across the world.
Over the past three years, the United States Food and Drug Administration has received more than four hundred complaints of taste disturbances following the consumption of pine nuts. In France, more than three thousand cases have been reported to poison centres in the same period.
Eating pine nuts is not a new thing. They have been a staple of Indigenous cuisine since Palaeolithic times, from Asia and Europe, to the Americas. For their size, pine nuts are rich in calories, most of which comes from their high content of mono-unsaturated fatty acids (MUFA).
A Mediterranean diet, which is rich in foods containing MUFAs, is thought to prevent heart disease by improving blood cholesterol levels and reducing inflammation. Pine nuts are also rich in dietary fibre, vitamins and minerals essential for good health.
But why now, after centuries of salade landaise, are we finding pine nuts so disagreeable?
Jamie Oliver and rise of culinary experimentation are partly to blame. Over the last few years, more and more consumers have tried new ingredients and combinations to spruce up their food. And thanks to Gordon Ramsey, savvy patrons are also demanding more from their restaurant experience. Both have meant more pine nuts are being devoured than ever before. And the more you use, the greater the chance you’ll come across a dodgy nut.
Pine nuts are actually the edible seeds of pines trees. The seeds sit between the scales of the pine cone and are released as the fertilised cone matures. Pine nuts are usually collected by harvesting and drying the pine cone, and then shaking the seeds free.
The Korean Pine (Pinus koraiensis) from China represents the major source of pine nuts found in Australian supermarkets. These pine nuts are typically plump, teardrop-shaped seeds. By contrast, seeds of the European stone pine (P. pinea), which are the staple of European cooking, are longer and look more torpedo-shaped than Chinese nuts.
Almost all of the people experiencing pine mouth had eaten pine nuts many times before, without problems. Often all those sharing the same product were affected. This points to a potential problem with quality control – increasing demand for pine nuts means shaking many more trees of varying quality.
Another theory for pine mouth is that someone, somewhere, picked up the wrong pine cone. Not all pine nuts are edible. Because a premium is paid for a good bag of nuts, it’s widely believed that unscrupulous vendors have been passing off nuts not suitable for human consumption. Two small studies – published last year in the Journal of Toxicology and the Journal of Agricultural Food Chemistry – found that all their collected victims of “pine mouth” had inadvertently eaten at least some seeds of P. Armandii. This pine tree is normally only used for building material, and its seeds are not considered to be edible.
Finally, because of their high fat content, pine nuts are best eaten fresh. They don’t store well. Once removed from their shell and exposed to light and air, their fats progressively become oxidised and the nut goes rancid. If you want to store them, they are best kept in the freezer, vacuum-packed, or in a dark, cool, dry container. Never use those old nuts from the back of the pantry.
Given increasing demand and consumption, “pine mouth” is a rapidly growing problem; a bad taste that will not simply go away.
Have you experienced “pine mouth”? Leave your comments below.