51A-35

F. M. DONG¹, M. N. Ton¹, A. M. Adams², A. P. MacKenzie¹, and M. M. WEKELL². (1) School of Fisheries, University of Washington, 3707 Brooklyn Ave., NE, Seattle, WA 98105-6715, (2) Seafood Products Research Center, U.S. Food and Drug Administration, P.O. Box 3012, 22201 23rd Drive S.E., Bothell, WA 98041-3012

Anisakiasis is one of the most important parasitic problems encountered by individuals who consume raw or undercooked marine fish. If an infected fish is consumed by humans, the larvae can penetrate into the gastrointestinal tract and cause severe abdominal pain, vomiting, and diarrhea. Guidelines in the U.S. state that fish should be frozen at or below –20°C (–4°F) in a freezer for 7 days, or –35°C (–31°F) for 15h in a blast freezer to kill Anisakis simplex. The purpose of this study was to clarify and define holding times at different freezer temperatures required to kill anisakid nematodes in Arrowtooth flounder. Fish in the round were manually filleted, measured for weight and thickness, individually placed into plastic bags, and put in single layers in either a –15°C, a -20°C, a –30°C, or a –40°C (non-blast) freezer. Batches of 10 fillets were removed from each freezer at specific times and thawed for 1-2h in cold running water (18°C). Nematodes were isolated from fillets by a pepsin digestion method, counted, and assessed for viability under a dissecting microscope. Data were analyzed by linear regression and by single factor analysis of variance. All larvae in the fillets were killed by 96h at –15°C, by 60h at –20°C, by 12h at –30°C, and by 9h at –40°C. Average percentage of live larvae per fillet at the next shortest holding time was: 72h at –15°C, 0-3%; 48h at –20°C, 11-30%; 9h at –30°C, 5%; and 6h at –40°C, 0-3%. Fillet thickness and weight were significantly and positively correlated with percent survival in the –30°C treatment. In conclusion, the freezing temperature affected the length of holding time necessary to kill the nematodes. This information will be valuable to companies who freeze-process at temperatures other than at –20°C or –35°C.