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Master of Science (M.S.)
Year Degree Awarded
Month Degree Awarded
Lipid oxidation is a major problem in foods resulting in alteration of texture, appearance, off flavors, aroma and decreased nutritional quality. The ability of compounds to inhibit lipid oxidation in foods is dependent on both physical and chemical properties. The effects of heating (50-90°C), ethylenediaminetetraacetic acid (EDTA), and calcium on the oxidative and physical stability of salmon oil-in-water emlusions were investigated in the first study. Oil-in-water emulsions were prepared with 2% salmon oil, stabilized by 0.2% Brij 35 at pH 7. Above 2.5 μM, EDTA dramatically decreased lipid oxidation in all samples. Addition of calcium to emulsions containing 7.5 μM EDTA significantly increased both thiobarbituric acid reactive substances (TBARS) and hydroperoxide formation when calcium concentrations were 2-fold greater than EDTA concentrations. These results indicate that heat processed salmon oil-in-water emulsions with high physical and oxidative stability could be produced in the presence of EDTA. The objective of the second study was to compare how the free radical scavenging activity of various compounds relates to their ability to inhibit lipid oxidation in cooked ground beef and oil-in-water emulsion. The order of free radical scavenging activity of the polar compounds was: ferulic acid > coumaric acid > propyl gallate > gallic acid > ascorbic acid as determined by oxygen radical absorbance capacity (ORAC). The free radical scavenging activity of the nonpolar compounds was rosmarinic acid > BHT ≥ TBHQ > α-tocopherol as determined by 2, 2-diphenyl-1-picrylhydrazyl (DPPH•). Of these compounds only propyl gallate and TBHQ were found to inhibit the formation of TBARS in cooked ground beef while propyl gallate, TBHQ, gallic acid and rosmarinic acid were able to decrease lipid hydroperoxides and hexanal in the oil-in-water emulsion. These data indicate that a compound’s free radical scavenging activity did not directly correlate with their ability to inhibit lipid oxidation in cooked ground beef and emulsion suggesting that free radical scavenging assays have limited value in predicting the ability of a compound to act as an antioxidant in complex foods.
Eric A Decker