Proteins were isolated from defatted flaxseed cake and hydrolysed with pancreatin. The hydrolysis process was conducted at a stable temperature of 50°C and pH 7.5, and monitored with the pH-stat method. The obtained hydrolysates with a degree of hydrolysis (DH) of 5, 10, 15, 20, 25% were investigated in terms of antioxidant properties. The radical scavenging activity was assayed against DPPH· and ABTS·+, the reducing ability - with FRAP assay, and the capability to bind Fe(II) - by reaction with ferrozine. SE-HPLC analysis was used to determine molecular weight distribution of hydrolysis products.
The antiradical activity of pancreatin hydrolysates of flaxseed proteins was increasing along with an increasing DH and for the hydrolysate with DH 25% the EC50 value determined with the DPPH assay accounted for 0.083 mg/assay, and the ABTS·+ scavenging activity - for 0.218 mmol Trolox/g. This hydrolysate was constituted mainly by peptides with low molecular weights (MW) of 0.238-0.556 kDa. In turn, the Fe(II) binding capability increased from 44.5% to 64.9% in the case of hydrolysates with DH 5-20% and decreased in the case of the hydrolysate with DH 25%. A similar de-pendency was observed in the ability of pancreatin hydrolysates of flaxseed proteins to reduce Fe(III). The maximum value of reducing ability reached 0.25 mmol Fe(II)/g for the hydrolysate with DH 20% that was predominated by polypeptides and peptides with MW of 0.238-1.046 Da.