Abstract
A model of fish meats was prepared by combining several defatted freeze-dried tissues of sardine with ethyl eicosapentaenoate (EPA). The effects of fish tissues on EPA oxidation were compared quantitatively with those of casein and defatted soybean meal by oxygen uptake, conjugated diene formation, composition of oxidation products and reactions with proteins and other constituents, i.e. browning and fluorescence formation. Furthermore, to observe the involvement of enzymes in the oxidation, raw fish tissue preparations were also incubated with ethyl EPA.
The prooxidant activity of skin, among various sardine tissues was the strongest. The prooxidants in the skin were assumed to be enzymes labile to heat. Hydroperoxide determination (peroxide value) is less reliable as a quantitative measure of oxidation in fish and fishery products because of the instability of hydroperoxides in fish model systems. Thus, the determination of relatively stable secondary products or termination products such as polymers, fluorescent materials and browning matter are thought to be more reliable in evaluating oxidative deterioration in fish and fishery products.
