Preparation Of Peptides From Sacha Inchi Protein And Their Antioxidant Activities

Plukenetia volubilis L is one of the valuable plant protein resources. The protein content of the seeds is up to 30% and the composition profile of amino acid is balanced. In this paper the Plukenetia volubilis L protein isolate was hydrolyzed by Alcalase and the bioactive properties of the peptides from hydrolysates were studied. The purpose of the research was to provide some theoretical reference for further exploitation and utilization of Plukenetia volubilis L.Plukenetia volubilis L protein isolate was hydrolysed by Alcalase 2.4 L. The effects of substrate concentration, the ratio of enzyme and substrate, pH, temperature and hydrolysis time on DPPH? scavenging activity of the hydrolysates were studied. Based on the results of single factor experiments and DPPH? scavenging activity as antioxidative index, the preparation process of Plukenetia volubilis L peptide was optimized by Response Surface Methodology. The optimum hydrolysis conditions were: substrate concentration4.32%, ratio of enzyme and substrate 3.29%, at pH 8.52, temperature 57.0℃ and the hydrolysis time 3.0h. Under this condition, the DPPH? scavenging activity was 34.61%. The preparation process of soybean protein peptides was optimized by the same analysis method and the DPPH? scavenging activity of soybean peptides was measured and compared with the peptide from Plukenetia volubilis L proteins. It revealed that the DPPH? scavenging activity of Plukenetia volubilis L peptides was lower than that from soybeans.By mesuring peptide solubility, water-holding properties, oil absorption, emulsifying properties and foam properties, functional properties of peptides were studied. The experimental results showed that solubility,foam properties and emulsifying properties decresed with increasing pH 2 to 4. Water-holding properties of peptides reached the maximum at pH 10; oil-holding properties of peptides reached the maximum at 40℃.Plukenetia volubilis L peptides were further separated by ultrafiltration membrane with the molecular cut-off with 10 kD, 5kD, 3kD and 1kD. The effects of the fluid concentration, operating pressure, pH, temperature and operating time on membrane flux were evaluated. The optimum ultrafiltration conditions were: concentration 6%, pH6.0; operating pressure 0.18 MPa with time 80 min for 10 kD and 5kD ultrafiltration membranes; pressure 0.20MPa with time 100 min for 3kDa and1 kD membranes. Under these conditions, the higher separation efficiency was obtained. After ultrafiltration, the four fractions were obtained and then their reducing capacities were measured, including DPPH?scavenging capacity, hydroxyl radical scavenging capacity and superoxide anion radical scavenging capacity. The conclusion was that the smaller the molecular weight of the Plukenetia volubilis L peptide, the higher the antioxidant activity. The antioxidant activity of whose molecular weight less than 1kD is highest. In other words, the molecular weight of the peptides with the best antioxidant activity is mainly less than 1kD.In vitro experiments was conducted with different digestion time and the Plukenetia volubilis L peptides which molecular weight less than 1kD showed the best antioxidant activity.