Alteration of functional properties of peanut (Arachis hypogaea L) protein fractions by chemical and enzymatic modifications

Major protein fractions of peanut namely, arachin, conarachin II and conarachin I, were isolated, from defatted flour to homogeneity, and succinylated to 84, 83 and 85% levels, respectively. The protein fractions were also hydrolyzed with alpha-chymotrypsin, Succinylated peanut proteins exhibited minimum solubility in the pH range 3.0 - 4.0, away from the range for unmodified proteins. Enzyme treatment improved the solubility, except in the pH range 2.0 - 3.0 and above pH 8.0. Succinylation improved the water and fat absorption capacities of all the protein fractions. The emulsifying capacity and activity of succinylated peanut protein fractions were higher than the unmodified fractions. The emulsifying capacity of enzyme-hydrolyzed fractions increased by 30-50%. The emulsifying activity also increased, after hydrolysis with alpha-chymotrypsin. Foam stabilities of succinylated peanut protein fractions were found to be improved, except for conarachin II. After hydrolysis with alpha-chymotrypsin, the foam capacity and stability of peanut protein fractions improved in every instance. Maximum improvement of functional properties occurred after chemical and enzymatic modifications of arachin, the major fraction. Thus, either chemical or enzymatic modification improves the functional attributes of peanut protein fractions.