Optimization Of Rrice Protein Enzymolysis Technology And The Identification Of Antioxidant Peptides From Rice Hydrolysates

China is known as a great producer of rice, with a production of more than 180 million tons every year, which is about 42% of the world’s total production. The rice dreg is byproduct of sugar industry, whose protein content as high as 60%(dry basis),but it can’t be fully utilized at present. While the peptides’ properties and functionality are significantly higher than the rice protein, the rice peptides being a new protein resource showed antioxidant capacity, antihypertensive properties, immune enhancing ability. So the rice protein can be used to develop high value-added products. This topic mainly use rice dreg as a medium of highly active peptides of enzymatic hydrolysis, decolorizing with powdered activated carbon, purification and identification of antioxidant peptide from rice hydrolysate. The main results are as follows:(1) Optimization of enzymatic hydrolysis: we used rice dreg as raw material, enzyme hydrolysis with the enzyme K. The optimum hydrolysis conditions were as follows: the ratio of material to water 1:7(g: mL), enzyme dose 6000 U/g,, hydrolysis time 6 h, hydrolysis temperature 60℃, pH 8. Under these conditions, the conversion rate of peptides reached 39.67%, the conversion rate of amino acids was 4.31%, and enzymatic hydrolysis was peptides mixture which mainly composed of 3~8 amino acid residues.(2) Decolorizing with powdered activated carbon: powder activated carbon was applied to decolorizing rice protease hydrolysate, according the decolorizing rate and the loss rate of peptides to determine the optimization conditions. And the conditions were as follows: decolorizing temperature 55℃, pH 3.0, the addition quantity of activated carbon 0.5%, decolorizing time 3h. Under these conditions, decolorizing rate reached 76.14% and the loss rate of peptides was 3.32%.(3) The pilot experiments and desalination experiments: the pilot experiments showed that the conversion rate of peptides reached 42.24%, the conversion rate of amino acids was 5.97%. Thus, it should be possible for amplification production. After NF process, acid soluble protein content reached 80.28% with the ash mass fraction being only 3.64%.(4) Separation and identification: the physiological analysis experiment showed that the rice peptides had strong antioxidant activity. Especially the ultrafiltration with molecular weight less than 3 KD had the strongest DPPH radical scavenging rate, when the concentration of ultrafiltration was 40 mg/mL, the DPPH radical scavenging rate was 96%. We separated and identification rice peptides with the methods of GFC and RP-HPLC. Then RP-HPLC-ESI-MS analysis,indicated that the amino acid sequence was L-Q-P-Y(519.27 Da).And the DPPH free radical scavenging rate of 1 mg/m L synthetic fragments L-Q-P-Y reached 85.84%.