The Distribution Of Oat Milk Components In The Centrifugal Field And The Aqueous Extraction Of The Oat Protein

As a grain with green property and high nutritional value,oat is favored by modern people.With development of oat deep processing,oat protein product with high nutritional value has attracted people’s attention gradually.Because oat has higher lipid content than other grain,it is common to use organic solvent to remove lipid before preparing oat protein product with high protein content.The aqueous extraction method is a plant protein extraction process with green concept because it doesn’t use organic solvent.The study focuses on future trend,under the condition of oat pretreatment and the distribution of components in oat milk,the oat protein with high protein content(90%)preparation process that no organic solvent、enzyme and meets the green product standard is studied.This study will provide a basis for further development of oat deep processing.The main findings are as follows:Firstly,the influence of the raw material pretreat method on extraction of oat protein was investigated.The results showed that:under the condition of dry pulverization,the moisture content has an important effect on separation of protein and lipid;the content of oat protein obtained by isoelectric point precipitation is only 55.16%,and the extraction rate is 75.56%.The protein content of the product obtained by oat grinding and isoelectric point precipitation can reach 61.38%,the extraction rate of oat milk can reach 82.56%.Therefore,oat milk is prepared by grinding pretreatment.Secondly,the influence of conditions such as the ratio of material to water,pH and temperature on extraction of protein were studied and the routing was optimized.The results showed that under the conditions of material to water ratio 1:12,extraction pH 8.5,temperature25°C,centrifugal force 4000 r/min、15 min,the extraction rate of protein in oat milk was89.52%,and the protein content after isoelectric point precipitation was 69.15%.Subsequently,the effect of different factors on the distribution of protein and lipid in oat milk was studied,and the mechanism of protein-lipid interaction in oat milk was explored by the method of sucrose density centrifugation.It was found that the higher the salt concentration in oat milk,the easier it is to form insoluble protein-lipid complex;the ratio of protein/lipid content in the insoluble phase of oat milk at freeze-thaw treatmeat is 22.97,much higher than the ratio of 70℃ treatment(7.01).After ultracentrifugation,the oat milk can be divided into four parts:oil phase,low-density soluble phase,high-density soluble phase and insoluble phase.After the oat milk is frozen,the proportion of lipid in the oil phase increased from 68.12%to75.41%,and it tends to transfer from the high-density soluble and insoluble phases to the low-density soluble and oil phases,while protein transfer in the opposite direction,the protein content in the insoluble phase increased from 47.83%to 63.84%,indicating that freeze-thaw treatment facilitates the separation of protein and lipid.On this basis,the method of fractional precipitation and enrichment of oat protein was studied.It was found that after freeze-thaw treatment,the pH was adjusted to 7.20,at temperature of 50°C,then centrifuge to obtain a precipitate with protein content of 92.46%.After drying,oat protein isolate(OPI)was obtained,and the extraction rate is 42.46%.Adjust the pH of supernatant to 5.20,and centrifuge to obtain precipitate with protein content of65.14%.After dilution、neutralization and drying,oat protein concentrate(OPC)with extraction rate of 44.75%was obtained.Finally,the protein composition,functional properties and flavor characteristics of OPI and OPC were characterized,the comprehensive utilization of the by-products of oat protein extraction was also studied.The results showed that OPI is mainly composed of globulin,including 12S,7S and 3S components,of which 12S is formed by A peptide chain with relative molecular mass of 32000～37000 and B peptide chain with 19000～25000 respectively.OPC is richer in other types protein except globulin.The contents of total essential amino acids in OPI and OPC are 33.40%and 34.42%respectively,which are equivalent to the average value of animal protein and meet the recommended requirements of WHO/FAO.The emulsifying activity of OPI under the condition of pH 7.00 is better,reaching 33.56 m~2/g,which is higher than OPC.The overall flavor of OPI and OPC is relatively mild,showing a weak hay and nut flavor,and the main volatile components are aldehydes and alcohols.Oat starch andβ-glucan can be obtained simultaneously from the by-products of oat protein extraction.The extraction rate of oat starch is 90.72%,and the starch content is 95.75%,which has good functional properties;the extraction rate ofβ-glucan is 88.21%,and the purity ofβ-glucan is 68.72%.