49B-7 |
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H. PETTY and H. G. Kristinsson. Dept. of Food Science & Human Nutrition, Univ. of Florida, 130-B Aquatic Foods Pilot Plant, PO Box 110370, Gainesville, FL 32611-0370 Protein isolates can be produced from underutilized fish species with acid and alkali processing. One drawback of acid processing is rapid development of lipid oxidation. The addition of antioxidants could provide stabilization to oxidation and ultimately result in higher quality protein isolates. Our objective was to investigate the addition of antioxidants to mackerel homogenates and their effect on lipid oxidation at high and low pH’s compared to post-mortem pH. Spanish mackerel fillets were ground and homogenized in 4°C deionized water (1:9 w/w). Antioxidants were added (weight per weight homogenate) in the following concentrations: ascorbic acid (0.1% & 0.2%), tocopherol (0.1% & 0.2%), and in combinations of 0.1% + 0.1% and 0.2% + 0.2%. Fish homogenates were adjusted to different low (2.5-3.5) and high (10.5-11.5) pH and samples taken at 0, 2, 4, 8, and 12 hours and analyzed for primary and secondary oxidation products. Without antioxidants oxidation developed rapidly at low pH while oxidation was retarded at high pH, compared to the pH 6.5 control. An increased level of preformed oxidation products in the starting material led to a significant increase in oxidation development at low pH. All antioxidant treatments were highly effective in inhibiting oxidation at low pH, particularly the incorporation of both lipid and water soluble antioxidants. The antioxidant capabilities of ascorbic acid and tocopherol were concentration and pH dependent. Both antioxidants were more effective at higher concentrations and at lower pH. Both antioxidants, ascorbic acid in particular, served as significant pro-oxidants at pH 6.5. Addition of antioxidants at high pH had little effect since oxidation did not develop in their absence. The results show that alkali-processing is preferred over acid processing if lipid oxidation is to be minimized during extraction of muscle proteins, unless proper incorporation of antioxidants is employed.
Session 49B, Aquatic Food Products: General
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