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Understanding the influence of processing operations such as drying/dehydration, canning, extrusion, high hydrostatic pressure, pulsed electric field, and ohmic heating on the phytochemicals of fruits, vegetables, and grains is important in retaining the health benefiting properties of these antioxidative compounds in processed food products. Most of the previous investigations in the literature on the antioxidants of fruits, vegetables, and grains have shown that food-processing operations reduced the antioxidants of the processed foods, which is also the usual consumer perception. However, in the last decade some articles in the literature reported that the evaluation of nutritional quality of processed fruits and vegetables not only depend on the quantity of vitamin C but should include analyses of other antioxidant phytochemicals and antioxidant activity. Thermal processing increased the total antioxidant activity of tomato and sweet corn. Most importantly, analysis also depends on the condition, type, and mechanism of antioxidant assays used. This review aims to provide concise information on the influence of various thermal and nonthermal food-processing operations on the stability and kinetics of health beneficial phenolic antioxidants of fruits, vegetables, and grains. [ABSTRACT FROM AUTHOR]

Mactra veneriformishas been used as seafood and traditional Chinese medicine for thousands of years in China. In the present study, hydrolysate was prepared from waste proteins ofM. veneriformisby trypsin treatment. The protective effect of hydrolysate on the defense system against oxidative stress was investigated by estimating the superoxide dismutase (SOD) activity and malondialdehyde (MDA) level in normal mice. The antioxidant activity of hydrolysate was investigated in D-galactose-induced aging mice by estimating the SOD and glutathione peroxidases (GSH-px) activity and MDA level. Amino acid composition and molecular weight distribution were also determined. These investigations suggest that hydrolysate derived from by-products ofM. veneriformispossess antioxidant activity and may be attributed to elevation of the activity of antioxidase and enhanced antioxidant defenses. [ABSTRACT FROM PUBLISHER]