The Research Of Extracting Protein From Subcritical Peanut Meal By The Mixed Solvent And Preparing ACE Inhibitory Peptides

Peanut meal was one of the main by-product in the peanut oil producing process, due to poor current processing technology, the-utilization rate of peanut meal in China is low. In order to promote the comprehensive utilization of peanut meal resources and the development of deep processing of peanut protein, these study used by the peanut meal originating from subcritical extraction as raw material, and researched the method of mixed solvent extraction of peanut protein technology, by the end obtain the best extraction process. Compared this kind peanut protein with those obtained by the traditional method, it has differences in the functional and structural aspect. Explored the use of mixed solvent extraction of peanut protein hydrolyzate prepared by ACE inhibitory peptides analyzed the impact of the condition, and the peanut ACE inhibitory peptides were purified and identified its composition. The main results were as followings:Existing oil process, the presence of high temperature and high-pressure processing, peanut protein occurred denaturation to some extent, and it limits the extraction and subsequent use of peanut protein. Alkali-soluble and acid precipitation, although able to obtain protein of high purity products, it would damage the protein and caused pollution. Therefore, subcritical peanut meal as raw material for the mixed solvent extraction protein to protein purity as an index of four two-level factors, univariate and mixing experiment, the optimum conditions: the best ratio of the mixed solvent components: n-hexyl hexane: ethanol: water = 0.25: 0.49: 0.26, liquid ratio of 16: 1, the temperature is 40 ℃, extraction time 30 min, under this condition once the ethanol wash protein purity 62.62%(dry basis), the extraction rate 97.05%. Compared ethanol-washing process for many times, this experiment optimization of an ethanol washing process had a cost savings, the advantages of simplified process, and suitable for industrialization promotion.PPEW(peanut protein prepared by ethanol washing), NPP(natural peanut protein) and HTPP(high temperature peanut protein) compare results in their functionality: PPEW had strong water and oil absorption, and emulsifying properties. SDS-PAGE electrophoresis analyzed of three samples showed: PPEW and NPP had no obvious difference in their composition and distribution; HTPP and NPP have obvious difference, the high temperature caused by the degradation of the high molecular weight 70 k Da subunits, low molecular weight subunit com, 15 k Da subunit following no significant bands, which would affect their properties and application range. The results of this three amino acid content analysis showed that: The total amount of essential amino acid PPEW were the highest, they were 29.15%, the total content of essential amino acid of the HTPP was the lowest. Which PPEW and NPP the content of methionine, isoleucine, leucine, and lysine was higher than of HTPP content. The results of Fourier transform infrared spectroscopy analysis showed that: PPEW and NPP in the amide III bands of the absorption peak was at 1241cm-1, and HTPP in the amide III bands of the absorption peak was at 1235cm-1. Through the above research, found that due to the different raw material sources, the peanut protein structure differences, which affected the functional and nutritional properties. The level of Subcritical meal extraction of peanut protein structure damage degree was low, highly nutritious and functional, more suitable for food as raw material.PPEW as substrates, was chosen from a variety of protease 2709 alkaline protease hydrolysis PPEW preparation of ACE inhibitory peptides, the best process conditions: p H 9.3, enzymolysis’ temperature 50 ℃, time of 150 min, enzyme dosage for 3000 u/g, substrate concentration of 4%, short peptide generation rate of 77.89%, 17.87% degree of hydrolysis and ACE inhibition rate of 76.26%. It was found out that SDS-PAGE electrophoresis analysis digestion process: with the increase of digestion time, polymer peanut protein subunits decreased, when it was under 15 k Da it increased, indicating that 2709 alkaline protease hydrolysis of peanut protein, to produce the enzyme solution of low molecular weight products. From 75 min, after more than 30 k Da was disappeared; peanut protein was hydrolyzed into peptides. When analyzing the relationship between peptide generation rate, degree of hydrolysis, and ACE inhibition rate was found that, extend the hydrolysis time, although it would increase the degree of hydrolysis, but excessive hydrolysis would lead to lower short peptide production rate and the rate of ACE inhibition.By 30 k Da, 10 k Da, 5 k Da three ultrafiltration enzyme solutions were separated and concentrated. Three stage of ultrafiltration results showed that, through the liquid half inhibitory concentration of 10 k Da(IC50) for a minimum of 1.32 mg/ml. Using Sephadex G-15 10 k Da to the permeate of desalting and grouping, the results showed that: the desalination rate reached 94.50%, the recovery rate of 78.23% of the peanut peptide. Isolated peak 4 IC50 minimum was 0.634 mg/ml, illustrated the effect of the ACE inhibitory activity peak 4 best. The component peak 4 was detected by LC-MS molecular weight of the main 1193.5, 1512.6, 1530, 1608.9, 1777.6.