New study of pine nuts leaves mystery of 'pine mouth' unsolved

A new study of the composition of pine nuts, including those associated with "pine mouth," leaves unsolved the decade-old mystery of why thousands of people around the world have experienced disturbances in taste after eating pine nuts. The report on pine nuts or pignolia — delicious edible nuts from pine trees enjoyed plain or added to foods ranging from pasta to cookies — appears in ACS' Journal of Agricultural & Food Chemistry.

Ali Reza Fardin-Kia, Sara M. Handy and Jeanne I. Rader note that more than 20,000 tons of pine nuts are produced each year worldwide. "Pine mouth," first reported in Belgium in 2000, is a bitter metallic taste that develops within one to two days of eating pine nuts and can last from one to two weeks. In 2009, the French Food Safety Administration reported a possible link between "pine mouth" and consumption of nuts of Pinus armandii, a pine species whose nuts are not traditionally eaten by humans. Researchers have identified certain fatty acids whose levels vary among pine species, making them a potentially useful tool for telling different species apart. To determine the source of pine nuts sold in the U.S., the first such effort, they measured the ratio of these compounds to the overall amount of fatty acids in the nuts.

Using fatty acid composition and a fatty acid diagnostic index (DI) along with DNA analysis, they found that most pine nuts sold in the U.S. are mixtures of nuts from different pine species, including Pinus armandii. They report that combining the fatty acid DI and DNA analysis is a useful way to determine which samples of pine nuts are mixtures of nuts from several species, but that this information itself may not definitively predict which pine nuts may cause "pine mouth." Its cause remains a mystery.

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