Effects of Thawing Methods on Chemical, Biochemical, and Microbial Quality of Frozen Whole Rainbow Trout (Oncorhynchus mykiss)

This study investigated the effects of different thawing methods (i.e., refrigerator, water, air ambient temperature, and microwave oven) on chemical [thiobarbituric acid, (TBA), peroxide value (PV), total volatile basic nitrogen (TVB-N), free fatty acid (FFA) values, proximate analysis, fatty acids profiles], biochemical [thawing loss, liquid loss (LL), pH], and microbiological (total viable, coliform, psychrotrophic, yeast, and mold counts) analyses of frozen whole rainbow trout carcasses. The results showed that the levels of ash, protein, and pH values and microbial count of thawed samples decreased significantly. Meanwhile, TBA, PV, FFA, LL, TVB-N, and fat increased, compared to the fresh fish (unfrozen) as control. Coliform counts in the fresh and thawed samples were < 3-log CFU g1. After the freezing-thawing process, the polyunsaturated fatty acids (PUFA) and n-3 contents decreased significantly (p < 0.05) compared to the fresh sample. The results suggested that thawing in water was the best method for freezing of the whole trout carcass.