Antioxidant stability and functional properties of Pinctada martensii protein hydrolysates

Antioxidant peptides crude product was prepared from Pinctada martensii protein's enzymatic hydrolysis.To investigate their stability and their functional properties, the scavenging capacities against DPPH, hydroxy free radicals and superoxide anions served as the indexes. The chemical stability in different temperature, the storage concentration, pH values, drying method and their functional properties of emulsifying capacity, water absorbing capacity and oil absorbing capacity were explored for providing a theory basis for their industrialized development.The digestion mode on the enzymatic product was simulated to figure out their tolerance to pepsin and trypsinase.The results showed that the enzymatic product was pH- dependent, but had low heat resistance.However, it was unstable in basic solutions and degraded completely at 8h in solution at pH 12.It was stable in freezing conditions at 10 to 50mg /mL but degraded at low and high concentrations after cold storage.Furthermore, its antioxidant activity held steady in vacuum freeze drying among different drying methods. Moreover, it also revealed excellent emulsifying properties, water absorbing capacity and oil absorbing capacity.But the enzymatic product can't keep high activity in vitro digestive system, especially in estine system after 4h.So it may be suitable for cosmetic industries not for oral administration.