The antioxidant mechanisms of whey proteins in a Tween 20-stabilized salmon oil-in-water emulsion were investigated. The antioxidant activity of the high molecular weight (HMW) fraction of whey from pasteurized milk was found to increase with concentration, as determined by its ability to inhibit TBARS and lipid peroxide formation. The ability of sulfhydryl-blocked whey to inhibit TBARS formation was reduced 60% compared to the HMW fraction alone at 7 days of storage. HMW fraction was able to scavenge peroxyl radicals, with scavenging decreasing approximately 20% when sulfhydryls were blocked. HMW fraction was able to chelate iron away from the surface of negatively charged BSA-stabilized emulsion droplets, indicating that the whey proteins were able to chelate iron. A better understanding of the mechanisms by which whey proteins inhibit lipid oxidation could increase the use of whey proteins as food antioxidants.

The antioxidant capabilities of whey in a Tween 20 TM -stabilized salmon emulsion were investigated. Whey fractions inhibited formation of thiobarbituric acid reactive substances (TBARS) and lipid peroxides in a 10 % salmon oil emulsion in the order of whey > high-molecular-weight (HMW) fraction > low-molecular-weight fraction. Heating the HMW fraction exposed sulfhydryls, with optimum exposure at 80°C. Heating the HMW fraction above 80°C increased antioxidant activity. The HMW fraction of whey (80°C) alone, ␣ ␣ ␣ ␣ ␣-tocopherol (40 ppm) alone, and their combination inhibited TBARS 59, 19 and 86%, respectively, at 21 d of storage. Sulfhydryls oxidized before ␣ ␣ ␣ ␣ ␣-tocopherol, suggesting that sulfhydryls are the primary antioxidant. Results indicate that whey proteins could be useful antioxidants in food emulsions.

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The antioxidant potential of chum salmon spermary tissue was evaluated using a sardine triacylglycerol emulsion system. Intact and high-molecular weight water-soluble fractions of spermary tissue were found to accelerate both autoxidation and iron/ascorbate-catalyzed oxidation. The low-molecular weight (LMW) fraction inhibited autoxidation and oxidation catalyzed by iron/ascorbate and 2,2‘-azobis(2-amidinopropane) dihydrochloride (AAPH). Inhibition of iron/ascorbate-catalyzed oxidation by the LMW fraction decreased with decreasing pH until no activity was observed at pH ≤6.4. Activity of the LMW fraction was not strongly influenced by pH (5.0−7.0) in the presence of AAPH. Antioxidants in the LMW fraction, including spermine, putrescine, hypoxanthine, xanthine, and glutathione, both alone and in combination, exhibited less antioxidant activity than the LMW fraction, indicating that other unidentified antioxidants were present. Keywords: Antioxidants; lipid oxidation; polyamines; fish oil; seafood