Survival of Anisakis simplex in microwave-processed arrowtooth flounder (Atheresthes stomias)

The purpose of this study was to define the relationship between survival a nd temperature of nematodes of the species Anisakis simplex in microwave-pr ocessed arrowtooth flounder (Atheresthes stomias). Ten fillets (each 126 to 467 g, 0.5 to 1.75 cm thick), with an average of five larvae of Anisakis s implex per fillet, were processed to target temperatures on high (100%) pow er using a commercial 700-W microwave oven. Fillets were neither covered no r rotated and had a temperature probe inserted to two-thirds depth into the thickest portion. After the fillet was digested using a 1% pepsin solution , the viability of nematodes was determined by viewing them under a dissect ing microscope. Survival rates were 31% at 140 degrees F (60 degrees C), 11 % at 150 degrees F (65 degrees C), 2% at 160 degrees F (71 degrees C), 3% a t 165 degrees F (74 degrees C), and 0% at 170 degrees F (77 degrees C). Mic rowave processing of standardized fillet "sandwiches," 14 cm long, 4.5 cm w ide, and approximately 1.75 cm high, each of which was preinoculated with 1 0 live nematodes, resulted in no survival at either 160 degrees F or 170 de grees F. Using ultraviolet light to detect both viable and nonviable nemato des in fillet sandwiches as an alternative method to pepsin digestion resul ted in survival rates of 1% at 140 degrees F (60 degrees C), 3% at 145 degr ees F (63 degrees C), and 0% at 150 degrees F (65 degrees C). Smaller fille t sandwiches, which most likely had fewer cold spots during microwave proce ssing, required 150 degrees F (65 degrees C), whereas larger whole fillets required 170 degrees F (77 degrees C) to kill larvae of Anisakis simplex. T he parasites were most likely inactivated by a thermal mechanism of microwa ve treatment. Damage to the nematodes was often evident from ruptured cutic les that were no longer resistant to digestive enzymes. The high hydrostati c pressure and low chloride content of the pseudocoelomic fluid probably co ntributed greatly to the damage incurred by the larvae.