Properties of Different Fish Processing By-products from Pollock, Cod and Salmon

Individual fish processing waste stream components can be used to make feed ingredients or other products. Waste stream components obtained from commercial fish processing plants included heads, viscera, frames, and skins from Alaska pollock (Theragra chalcogramma) and Pacijic cod (Gadus macrocephalus); and heads, and viscera from pink salmon (Oncorhynchus gorbuscha). The protein content of heads from all three species ranged from 13.9 to 16.4%; and the fat content rangedfrom 0.9 to 10.9%. Viscera protein content rangedfrom 13.0 to 15.3% and the fat content from 2.0 to 19.1%. After heating to 85C the percent soluble protein in salmon heads was digerent (P < 0.0s) frompollock or cod heads. Percent soluble protein ofpollock and cod skin increased 8 fold (P < 0.05) ajier the 8SC heat treatment. Connective tissue content was calculated from chemical determination of hydroxyproline content, and large differences in percent connective tissue content were found (1 % for pollock viscera to 46% for skin). Estimated rat PER values ranged from a low of 2.1 for skin to a high of 3.1 for viscera and fillet samples (P<O.OS).