'Metallic' pine nuts?

Have you experienced a metallic taste in your mouth that lingers for several days? It may be from those pine nuts in your pesto or salad.

Scores of people recently have been reporting "an awful, bitter taste" in their mouths after eating pine nuts, sometimes lasting as long as two weeks.

Reports of an unpleasant taste following consumption of pine nuts circulated in Belgium in 2001, prompting the Poisons Centre there to conduct a comparison of affected and unaffected nut batches. Although they concluded there was no safety threat, no chemical differences were found among the batches.

In recent months, however, the problem has arisen again around the United States and in Britain, and most of the reported incidents involve nuts imported from Asia or Russia. The unexplained phenomenon could have an impact on ingredient sourcing and screening by food manufacturers – although it is unlikely that they will be able to take measures to ensure product quality is not affected until the underlying reason is found.

Even more curiously, the metallic taste is reported to affect only some people who have eaten nuts from an affected batch, and not others.

A blogger on Babyccino, Monica, posted on Feb. 26, 2009:

This is caused by the way the pine nuts was made. I was born and brought up in China. Pine nuts were always bitter. They were sold as sugar covered candies. ... After I came to US, I was surprised to find out that pine nuts is actually a little sweet. We need to help them to improve the process in China by our technology. The bitter taste we feel may not be an issue over there.

The UK’s Food Standards Agency has confirmed that it is taking on the matter – although it emphasised that it is not a food safety issue. “As far as the Agency is aware, no adverse health effects have been associated with these symptoms,” a representative said, but the FSA is inviting people who have experienced the problem to email toxicology@foodstandards.gsi.gov.uk with details of the pine nuts consumed and how long the metallic taste lasted.