A FSA spokesperson told FoodManufacture.com that the agency first became aware of the problem in 2009 and has subsequently received up to 500 complaints.
“Although the condition is not dangerous, we want to gather more information about it,” said the spokeswoman. “We have asked local trading standards officers to investigate complaints about bitter tasting nuts.”
Studies show that 99% of the problem pine nuts concern the species Pinus Armandii which are imported from China.
The Chinese authorities had pledged to produce a list of approved pine nut exporters by last month. But the FSA spokesperson confirmed that the list had yet to arrive at its offices.
Meanwhile, the agency has contacted the Poisons Centre in Belgium, which investigated the problem nuts as long ago as 2001. Affected batches showed no chemical differences from normal batches, or contamination, and no reason for the bitter taste has been found.
Pine nuts are usually eaten in salads, as a snack or in a pesto sauce.
Problem nuts can be reported to the FSA online at toxicology@foodstandards.gsi.gov.uk.