الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
Growing interest in the replacement of synthetic food antioxidants by natural ones has fostered research on vegetable sources and screening of raw materials to identify new antioxidants. The food-processing industry generates substantial quantities of phenolic-rich by-products that could be valuable natural sources of antioxidants. In this study the antioxidant properties and total phenolic, flavonoid, and flavonol contents of three industrial by-products; potato peels, sugar beet pulp, and sesame cake, extracted with various solvents were examined. Since the antioxidant compounds have different mechanisms of action, several methods were used to assess the antioxidant efficacy of extracts. Among the six solvents tested, methanol gave the highest extract yield of potato peels and sugar beet pulp, while diethyl ether gave the highest extract yield of sesame cake. Methanol exhibited the highest extraction ability for phenolic compound, with total phenolics amounting to 2.91, 1.79, and 0.81 mg gallic acid equivalent g-1 dry weight in potato peels, sugar beet pulp, and sesame cake extracts respectively, and also showed the strongest antioxidant capacity in the three assays used. All three methods proved that potato peels extract had the highest antioxidant activity owing to its high content of phenolic compounds and flavonoids. The bioactive materials which extracted with methanol and ethanol were further examined for their antioxidant activity in comparison with synthetic antioxidants under accelerated oxidation conditions using sunflower and soybean oils as oxidation substrates at different concentrations for 72 h at 70 °C. Inverse relationships were noted between peroxide values and oxidative stabilities and also between secondary oxidation products, measured by p-anisidine value and stabilities at termination of the storage. Absorptivity at 232 nm and 270 nm increased gradually with the increase in time, due to the formation of conjugated dienes and polyenes. The order of oxidative stability was as follow: TBHQ > potato peels > BHT = sugar beet pulp > BHA > sesame cake. The HPLC analysis of potato peels, sugar beet pulp, and sesame cake extracts revealed the presence of phenolic compounds. On the basis of the results obtained, potato peels, sugar beet pulp, and sesame cake extracts could serve as natural antioxidants, owing to their significant antioxidant activity, that might be explored to prevent oxidation of vegetable oils. Therefore they could be used as preservative ingredients in the food and/or pharmaceutical industries.