Storage stability of paralytic shellfish poisoning toxins

Variations in C toxins (C1- 2), GTX (gonyautoxin) 1-4, STX (saxitoxin) and NEO (neosaxitoxin) in scallop digestive glands and a mixture of purified paralytic shellfish poisoning (PSP) toxins were studied during storage at −35, 5 and 25°C and at different pH levels. Heated and unheated samples of homogenates and purified toxin mixtures were stored for 1 year and 4 months, respectively, and analyzed at different times by HPLC. C toxin levels decreased rapidly during storage at 25°C with a significant decrease after the first 2 months. GTX 2/3 in the unheated samples did not change initially at pH 3–4, but decreased at pH 6–7 with the fastest rate at 25°C followed by 5°C. There was no significant change in any toxin type stored at −35°C regardless of pH. GTX 1/4 decreased significantly after 4 months at 25°C. NEO and STX remained unchanged at all temperatures at low pH (pH 3), whereas NEO levels continued to decrease at higher pH (pH 6–7) at 25°C. All toxins were stable at low pH (pH 3–4) and −35°C.