Abstract:

We investigated the enzymatic hydrolysis of buckwheat albumin to produce antioxidant peptides. In order to obtain the highest degree of hydrolysis (DH) and O2· scavenging activity of buckwheat albumin hydrolysates, an optimal enzyme was screened from alkaline protease, trypsin and papain, and the parameters of hydrolysis catalyzed by screened enzyme were optimized by single-factor method and orthogonal array design. Subsequently, the buckwheat albumin hydrolysates were separated by Sephadex G-25 column chromatography, and fractions obtained were analyzed for their molecular weight and O2·, ·OH and DPPH· scavenging activities. Higher DH and O2· scavenging activity of buckwheat albumin hydrolysate were achieved using alkaline protease in comparison with other two enzymes. The optimal parameters for improved hydrolysis of buckwheat albumin by alkaline protease were determined as follows: temperature 50 ℃, pH 10, substrate concentration 20 g/L, enzyme concentration 10% and hydrolysis time 2 h, and the DH reached 17.57% and the O2· scavenging ratio was 37.06% under these conditions. Two fractions, namely fractions Ⅰ and Ⅱ, were obtained from the hydrolysates, whose molecular weights were 20.89 – 204.2 kD and 219 – 691 D, respectively. The O2·, ·OH and DPPH· scavenging activities of fractionsⅠand Ⅱwere all higher than those of the hydrolysates and higher activities of scavenging the three free radicals were found in fraction Ⅱ when compared with fraction Ⅰ. The radical scavenging efficiency of fractionⅡ decreased in the following order of O2·＞·OH ＞ DPPH· and the IC50s were 0.072, 0.19 and 0.32 mg/ml, respectively.

Key words: buckwheat, albumin, biologically active peptides, enzyme, antioxidation, free radical