| Four experiments were conducted to develop, characterize, and validate antioxidative protein hydrolysates (HPPs) from potato protein. In experiment 1, HPPs were prepared by alcalase hydrolysis (up to 6 h). All HPPs, comprised mostly of short peptides (< 6 kDa), exhibited increased radical scavenging activity (up to 13-fold), reducing power (up to 28-fold), and copper chelation activity (up to 43%) when compared with a control. Addition of 4% HPP1h inhibited the production of peroxides and thiobarbituric acid-reactive substances in cooked beef patties (4°C, 7 days) by 74.5% and 50.3% when compared with control patties. In experiment 2, HPP1h was subjected to gel filtration, HPLC, and membrane ultracentrifugation to separate HPP into fractions. The antioxidant activity was found to be concentrated mostly in low molecular weight fractions. In experiment 3 and experiment 4, the effect of antioxidative HPPs on inhibiting oxidative changes in physicochemical properties and functionality of pork myofibrillar protein (MPI) was investigated. MPI suspensions (30 mg/mL) mixed with 0, 1, 2.5 and 5% (MPI basis) of HPP1h were incubated at 4°C for 24 h with iron-catalyzed (IOS) and H2O2-activated metmyoglobin (MOS) oxidizing systems. Oxidation altered myosin Ca- and K-ATPase activities and increased the production of protein carbonyl (by 24% in IOS and 220% in MOS). The presence of HPP1h markedly reduced the extent of MPI oxidation. Oxidized MPI was prone to thermal aggregation when compared with non-oxidized MPI, but this was partially inhibited by HPP1h. Oxidation with IOS, and more so with MOS, promoted MPI network formation (storage modulus, G') during thermal gelation, and the oxidized MPI gels appeared to be less fibrous but more grainy in texture. Incorporation of HPP1h partially diminished the oxidation-induced gelling characteristics. Oxidation did not affect the emulsifying activity of MPI, but significantly lowered the emulsion stability in both oxidizing systems; these changes were reduced by HPP1h treatments.; Overall, alcalase-hydrolyzed potato protein exhibits strong antioxidant activity in model systems, and shows promise in minimizing oxidative changes in ground meat. The effectiveness in maintaining functional properties of myofibrillar proteins under oxidative meat processing conditions makes HPP a potential antioxidant for formulated muscle foods.; Keywords: Potato protein, Hydrolysis, Antioxidant, Myofibrillar protein, Protein oxidation. |
