Study On Extraction And Purification Of Protein From Carya Cathayensis Cake

Pecan(Carya cathyensis Sarg.)is a tree nut with high nutritional value,has been cultivated for a long time in China,and its kernels are rich in unsaturated fatty acids and amino acids with reasonable proportion.Nowadays,our country pecan acreage and yield in the constantly expanding,pecan processing way in addition to the direct drying fry make nuts food,part used in the production of pecan oil,pecan cake after removing oil contains high quality protein resource,and the present stage of cake protein resources development and utilization of the research,In order to make the pecan cake protein more reasonable use of resources,improve pecans,value-added products rich pecan products,this study with cold pressed pecan pie pulp as raw material,to explore the extraction and purification of protein in the cake,craft,and pecan protein functional properties,so as to enhance the utilization value of cold pressed pecan cake,broaden the pecan industry chain,To promote the development of intensive processing of pecan industry in China.The main results are as follows:Using cold pressed pecan cake as raw material,the main nutritional components were determined,and the process of extracting protein from cold pressed pecan cake by enzyme-assisted alkali method was studied.The content of protein,fat,moisture,ash and carbohydrate in pecan cake was 12.26%,33.21%,5.25%,2.77% and 46.51% respectively.Single factor experiment was used to explore the influence of five factors on protein extraction rate: p H of extraction solution,adding amount of alkaline protease,solid-liquid ratio,extraction time and extraction temperature.Combined with orthogonal experiment,the optimal process conditions of enzyme-assisted alkaline method were as follows: Under the conditions of p H 10.0,alkaline protease dosage 1 000 U/g,solid-liquid ratio 1:16(g/m L),extraction time 1.5 h and extraction temperature 60 °C,the protein extraction rate could reach 84.83%.During the extraction process,the protein extraction rate could be increased to 89.72% by constant p H 10.0.The optimal p H of protein acid precipitation was 3.7.The lipid content of crude extract of cake decreased from 27.38% to 5.02% with the addition of alkaline protease.The purification process of crude extract was studied.The process flow was as follows: firstly,the inner seed coat and woody fruit shell in cake were partially removed by grading and screening to improve the quality of raw materials,and then the crude extract was purified by enzymatic method combined with alcohol washing to remove impurities to improve the protein content of crude extract.The protein content of raw material was increased from 12.26% to 14.80% by sieving method.A variety of purified enzymes were screened with the crude protein content as the index,and the optimal enzyme was identified as glycosylase.On this basis,the optimal conditions of glycosylase purification process were determined by single factor test: enzyme dosage of 100 U/g,enzymatic hydrolysis time of 2.5 h.By single factor combined with orthogonal test,the optimal process of alcohol washing was determined as follows: ethanol concentration of 80%(V/V),solid-liquid ratio of 1:12(g/m L),elution temperature of 50 °C,elution time of 45 min.The protein content of crude extract of cake was increased from 22.14%to 40.93% by purification process,and high purity pecan protein was obtained by purification of crude extract.The functional characteristics and amino acid composition of pecan protein were determined.The results showed that the solubility of pecan protein was the lowest when p H 4.0 was close to the isoelectric point(p H 3.7),which was only 4.5%.The solubility of pecan protein increased when p H10.0 was deviated from the isoelectric point,and reached 86.0%.The emulsifying properties,emulsifying stability and foaming properties of pecan protein showed the same trend as solubility,which were 3.8%,16.7% and 5% at p H 4.0.However,its foam stability is the highest at p H 4.0,which is 50.0%.A total of 17 amino acids were detected in pecan protein(tryptophan was destroyed by acid hydrolysis),including 7 essential amino acids,which accounted for 29.64%.The contents of glutamate and arginine in pecan protein were much higher than those in pecan meal,which were 27.33 g/100 g N and 23.53 g/100 g N,respectively.The contents of other amino acids were almost the same as those of the protein in the meal.The AAS and CS scores showed that the first limiting amino acid of both pecan protein and pecan meal protein was methionine.SDS-PAGE analysis shows that: Pecan pie proteins and enzymes in the pulp alkali mention protein subunits are mainly distributed in 45 ～ 55 ku,the protein and nuts in the area of relative molecular mass significantly reduced the number of subunits,the alkaline protease can improve the reason of protein extraction rate is not easy to dissolve in the pecan cake into relative molecular mass of smaller polypeptide protein enzyme solution,increased its solubility in the water.