Study On Extraction And Properties Of Effective Components From Low-temperature Defatted Soybean Meal

Soybean oil processing produces a large number of by-products-low-temperature defatted soybean meal,which is mostly used for feed at present,with low added value,resulting in waste of resources.In fact,low-temperature defatted soybean meal contains45-50%protein,and also contains functional components beneficial to human health,such as insoluble dietary fiber,isoflavones,saponins,oligosaccharides,etc.According to China’s energy-saving and emission-reduction policies,this study designed and developed three kinds of products,namely compound functional factors,proteolytic peptides and insoluble dietary fiber,to realize the comprehensive utilization of low-temperature defatted soybean meal.(1)compound functional factorsThe compound functional factors in low-temperature defatted soybean meal were extracted with 60%ethanol,which contained isoflavones,saponins,oligosaccharides and a small amount of soluble protein.The components were further separated by gradient elution of different concentrations of ethanol with macroporous adsorption resin,and the oligosaccharide and soluble protein were first eluted with 60%ethanol.The yield of oligosaccharide was 538.71 mg/g by HPLC and 41.31 mg/g by Kjeldahl method.Then,the isoflavones and saponins were eluted with 95%ethanol,and the isoflavones and saponins were separated by the poor water solubility of isoflavones at50℃.The yield of isoflavones and saponins was 4.16 mg/g and 6.73 mg/g,respectively,by spectrophotometry.(2)proteolytic peptidesThe yield of soluble protein extracted from the composite functional factors is only41.31 mg/g,and there is still a large amount of protein in the remaining filter residue.In order to obtain high degree of hydrolysis peptide,the protein in the filter residue was hydrolyzed by alkaline protease as the index.The optimum enzymolysis parameters obtained by single factor combined with orthogonal test are:The hydrolysis degree of protein was(94.68±0.31)%.when the ratio of liquid to material was 10:1,p H 7.5,enzyme dosage was 8000 U/g,hydrolysis temperature was 50℃and hydrolysis time was 4 h..The content of insoluble dietary fiber was(80.54±0.27)%in the filter residue after enzymatic hydrolysis.The antioxidant capacity of the prepared proteolytic peptides was measured,including the ability to scavenge DPPH free radical,hydroxyl free radical and ABTS~+free radical.Among them,the highest scavenging capacity of proteolytic peptides on DPPH free radical,hydroxyl free radical and ABTS~+free radical is 35.12%,76.57%and 96.79%,respectively.(3)Insoluble dietary fiberIn order to obtain high content of insoluble dietary fiber,alkaline protease was also used to hydrolyze the filter residue with composite functional factors.With the content of insoluble dietary fiber as the index,the optimum enzymolysis process parameters were optimized by single factor combined with response surface methodology:enzymolysis p H 8.5,enzyme dosage 7500 U/g,enzymolysis temperature 50℃and enzymolysis time 3 h,at which time the content of insoluble dietary fiber was(90.43±0.38)%.The analysis of basic components showed that The content of cellulose,hemicellulose,lignin and other substances was(7.03±0.85)%,(78.12±0.39)%,(8.05±0.33)%and(5.31±0.43)%respectively.The physical properties of insoluble dietary fiber are as follows:water holding capacity was 14.05%,oil holding capacity was7.25%,swelling capacity was 12.71 m L/g,the adsorption capacity of unsaturated and saturated oils was 4.68%and 6.32%respectively,and the glucose adsorption value was99.54 mmol/g.Infrared spectrum shows that the insoluble dietary fiber of soybean meal has the characteristic absorption peaks of sugar and cellulose.