Preparation Of Rice Polypeptide And Detection Of Its Antioxidant Activity

Rice polypeptide exists in abundant rice materials,except for the early rice,broken rice,old rice,rice dregs are also a good resource of rice polypeptide.Rice polypeptide has been confirmed to have good amino acid composition,higher bioactivity,lower irritability and potential functions for health protection,which has got a lot of attention,while there are limited reports of it's antioxidant activities.Therefore,based on rice dregs and broken rice,this paper optimized the process route of protein extraction and polypeptide preparation,emphatically explored the antioxidant effect of rice polypeptide,hereby to provide basis for its industrial application.(1)Rice dregs as materials,protein purity and extraction rate as indicators,the optimal alkali extraction conditions are:p H12.0,temperature 45?,extraction time 5.0h,solid-liquid ratio 1:8;under these conditions,the protein purity was 67.31%,the extraction rate was 50.44%.The degree of hydrolysis as criterion,the optimum hydrolysis conditions are:substrate concentration 3%,p H7.5,temperature45?,time5.0 h,the amount of neutral protease 500 U/g;under these conditions,the degree of hydrolysis of polypeptide solution was 21.4%,with a concentration of 1.0%,the scavenging rate of polypeptide agianst rice hydroxyl radicals,superoxide radicals radical were 52.54%,47.72%,respectively.And the rice polypeptide are effective in inhibiting lipid peroxidation.(2)Physical and chemical qualities and antioxidant activities as indicators,polypeptide powder was prepared by spray drying,the optimal spray-drying conditions were:inlet temperature of 105?,atomization pressure 0.15 Mpa,the injection rate of0.30 L/h,the amount of wind 0.45 m³/min;under these conditions,the obtained polypeptide was beige,with a water content of 9.20%,PDI of 87.65%;with the concentration of 1%,the highest scavenging capacity of rice polypeptide power against·OH and O₂^-·had 92.87%and 95.63%of that before spry drying.(3)Rice residue was form sugar refineries,for the liquefaction and saccharification process,the protein denatured,making its internal protein solubility descend,protein extraction rate is not high by direct alkali extraction.To take full advantage of protein resources,improve the protein utilizable efficiency,rice residue was degraded by neutral protease before alkaline extraction.With protein purity and extraction rate as indicators,response surface methodology was used to optimize pre-hydrolysis process,the result are as follows:neutral protease content of 456.18 U/g,p H7.52,hydrolysis time 4.69 h;based on which,further conducted the alkali extraction,the protein purity was 72.86%,protein extraction rate was 78.27%,the DH of the enzymolysis liquid was 17.7%;and the extracts exhibited some antioxidant activities.(4)Based on the optimal preparation process of rice polypeptide,broken rice was used to prepare rice polypeptide,alkali extraction time was adjusted to 2.5 h,under which,the protein purity was 90.76%,the extraction rate was 71.01%,further conducted the enzymolysis,the DH of the rice polypeptide was 21.6%.With a concentration of 1.0%,the scavenging rate of hydroxyl radicals,superoxide radicals radical were 68.67%,57.64%,respectively,which also exhibited an equal level of anti-lipid peroxidation with VE,and the polypeptide was white.(5)To determine the relationship between anti-oxidative activity of rice polypeptide and its molecular weight(MW),the molecular weight distribution of rice polypeptide was tested by HPLC.The wavelength of maximum absorption of rice polypeptide was218.3 nm,the distribution of different molecular weight rice polypeptide:10?14 KD,5?10 KD,3?5 KD,<3 KD accounted for 74.76%,21.52%,2.60%,1.12%,respectively.HPLC repeatability and precision experiments showed that the method were accurate and reliable,hence it can provide research basis for the quality evaluation and control for the industrial production of rice polypeptide,which has practical values.