EFFECT OF COOKING ON THE CONCENTRATION OF TOXINS ASSOCIATED WITH PARALYTIC SHELLFISH POISON IN LOBSTER HEPATOPANCREAS

The hepatopancreases from lobsters (Homarus americanus) obtained from two locations in eastern Canada (Gaspe and Bay of Fundy) were analysed for paralytic shellfish poisons (PSP) before and after the shellfish were cooked by boiling or steaming. Forty-five lobsters from each location were divided into three groups of 15. Two of the groups were boiled or steamed while the third was uncooked for comparison purposes. The hepatopancreases of all lobsters were individually analysed for total PSP toxicity using the standard mouse bioassay procedure. Individual toxins were determined in each sample using a high-performance liquid chromatographic procedure employing pre-chromatographic oxidation of the toxins to form fluorescent derivatives. The results demonstrated that boiling or steaming reduced total toxicity (measured as saxitoxin equivalents per hepatopancreas) by approximately 65% compared to values obtained from raw lobsters. Of the individual toxins studied, saxitoxin decreased by about 60% with both the cooking treatments while gonyautoxins 2 and 3 (combined) decreased by almost 100% in the Gaspe samples and by about 90% in the Fundy samples with the same cooking treatments. Trace amounts of saxitoxin or gonyautoxins 2 and 3 were detected in some samples of tail or claw meat before or after cooking. In vitro boiling of raw hepatopancreas for up to 30 min led to no change in total or individual PSP concentration, indicating that the toxins in cooked lobster are not removed through chemical decomposition but are leached out during the loss of water.