Antioxidant activity of soy protein fractions in a liposome model system

Abstract:

The antioxidant activity of soy protein and soy protein hydrolysates has been demonstrated in model and food systems. However, their capacity to increase lipid stability is not as effective as synthetic antioxidants, probably due to the ability of some of the protein fractions to act as pro-oxidants. Therefore, the objective of this study was to fractionate soy protein hydrolysates by peptide size and to measure the ability of different fractions to decrease liposome oxidation. A pre-heated (90 C for 5 min) soy protein isolate solution (SPI) was hydrolyzed with flavourzyme®(HSF) or chymotrypsin (HSC) to achieve a 9% and 5% degree of hydrolysis, respectively. Hydrolysates were fractionated by ultrafiltration using different membrane pore sizes (50, 10, and 3 kDa). The ability, of each isolated fraction, to decrease the formation of TBA-reactive substances (TBARS) was measured in a liposome oxidizing system (15mM FeCl3, 0.1 mM ascorbate, pH 7.0). SDS-PAGE was run to identify the molecular weight (MW) of peptides in each SPI hydrolysate fraction. TBARS assay detected antioxidant activity in all SPI fractions; although their ability depend significantly (p< 0.05) on their molecular weight. Fractions from HSF with a MW lower than 10 kDa were more effective (p< 0.05) to inhibit TBARS production (> 49% inhibition) than SPI (non-hydrolyzed, 15.2% inhibition) and non-fractionated sample (20.4% inhibition). Similar results were obtained with HSC fractions with a MW lower than 3 kDa. Fractions with the highest ability to decrease liposome oxidation (p< 0.05) in HSF and HSC (80.4 and 84%, respectively) had a MW< 3 kDa. By ultrafiltration we were able to …

Año de publicación:

2004

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Fuente:

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