| Flax cake meal contains a large amount of protein,dietary fiber,amino acids and other organic substances,has great research potential.At present,its use is mainly limited to animal feed and fertilizer,which is an important source for developing high-quality protein.Plant protein active peptides have a lot of special physiological functions,the use of enzyme bacteria synergistic fermentation technology to process plant protein prepared bioactive peptides,can be applied to food,medicine,cosmetics and other fields in the flax cake meal industry has some practical significance.Based on this,the following work has been carried out:(1)Analysis of the nutritional composition of linseed cake meal: protein content of32.31%,hydrolyzed essential amino acids of 7.16%,hydrolyzed non-essential amino acids of 11.30%,total hydrolyzed amino acids reached 18.46%,crude fat content of 6.84%,free fatty acid content of 1.2%,crude fiber content of 30%,ash content of 5.20%,total sugar content of 14.24%,and 4.9 mg/g of polyphenols.(2)The alkaline protease was selected as the most suitable enzyme for flaxseed cake meal from eight proteases by single-factor experiments using peptide yield and hydrolysis degree as indicators.The alkaline protease was optimized by single-factor and response surface analysis for the preparation of flaxseed cake meal.The results showed that the optimal process optimization conditions were 4059.7 U/g of alkaline protease enzyme addition,enzymatic p H 10.0,enzymatic temperature 50.0 ℃,enzymatic time 5.2 h,and material-liquid ratio 1:20 g/m L.The yield of enzymatic peptides prepared under these conditions was 67.24% and the degree of hydrolysis reached 22.43%.(3)Lactobacillus and Saccharomyces as the starting strains,with biosafety and protein decomposition ability as the primary screening principle,and effective protein decomposition,fast growth rate and high fermentation peptide yield of flax cake meal,high biofunctional activity and no odor as the re-screening principle,from which four strains were screened,namely Lactobacillus plantarum BYBC4.20070(Lactobacillus plantarum).(4)Single-factor and response surface were used to optimize the process parameters of protein fermentation in flax cake meal by Lactobacillus plantarum(BYBC4.20070).The results showed that the optimal fermentation conditions were 2.1% inoculum,38.0℃fermentation temperature,23.2 h fermentation time,210 r/min speed and 1:20 g/m L feed to liquid ratio,and the yield of flaxseed peptide was 15.27% and the degree of hydrolysis reached 19.57% under these conditions.(5)The flaxseed peptides were further optimized by treating flaxseed cake meal in different ways of enzyme-bacteria synergy and bacteriophage synergy.The results showed that the suitable preparation route of flaxseed protein peptide was the enzyme-bacteria synergistic method of enzymatic digestion and then fermentation: the best enzyme-bacteria synergistic treatment conditions were alkaline protease enzyme addition 4059.7 U/g,enzymatic p H 10.0,enzymatic digestion temperature 50.0℃,enzymatic digestion time 5.2h,material-liquid ratio 1:20 g/m L;after enzymatic digestion,Lactobacillus plantarum BYBC4.20070 was used for fermentation.The conditions were 2.1% inoculum,38.0 ℃fermentation temperature,23.2 h fermentation time and 210 r/min.The total yield of flaxseed peptide was 78.18% and the degree of hydrolysis was 28.27% under these conditions.(6)The physiological functions related to flaxseed plant protein peptides prepared by bioprocessing were investigated by in vitro biofunctional activity assay.The results showed that: the enzyme-bacteria co-treatment method had higher ABTS+ radical scavenging rate than the mycobacteria-enzyme co-treatment method;the hydroxyl radical scavenging rate of the mycobacteria-enzyme co-treatment method was higher than that of the enzyme-bacteria co-treatment method,and the antioxidant activity was better;when the enzyme-bacteria co-fermentation was carried out for 18 h,the α-glucosidase and α-amylase inhibition rates were 77.60% and 58.43%,respectively;in the evaluation of in vitro bile salt inhibition activity In the evaluation of in vitro cholate inhibitory activity,the adsorption capacity of the enzyme-bacteria synergistic treatment was stronger than that of the enzyme-bacteria synergistic treatment,and the adsorption rate of glycocholate was close to80% and that of sodium taurocholate was higher than 70%.In the in vitro xanthine oxidase inhibitory activity evaluation,the enzyme-bacteria synergistic treatment method showed better xanthine oxidase inhibitory activity of 58.24%.(7)The preliminary investigation of protein structure by circular bispectroscopy showed that: 2.1% of α-helical structure in enzyme-bacterial synergistic preparation of flaxseed plant protein;44.7% and 17.5% of β-fold and β-turn angle content,respectively,and 35.8% of irregular curl;59.5% and 18.0% of β-fold and β-turn angle content in enzyme-bacterial synergistic preparation of flaxseed plant protein,respectively,and irregular The β-fold and β-turn content of flaxseed plant protein was 59.5% and 18.0%,respectively,and the irregular curl was 22.5%,while there was no α-helical structure.Theα-helix content of flaxseed plant protein is less,while the β-fold and β-turn and irregular curl content is more.(8)The results of amino acid analysis showed that the total amino acids in the peptide free amino acids prepared by enzyme-bacteria synergistic method and bacteriophage synergistic method were 0.16% and 0.37%,the total essential amino acids were 0.097%and 0.20%,the ratio of non-essential amino acids were 0.061% and 0.17%,and the essential amino acids accounted for 61.52% and 54.86% of the total amino acids.The total amino acids in the peptide hydrolyzed amino acids prepared by enzyme-bacteria synergistic method and bacteriophage synergistic method were 1.19% and 1.23%,the total essential amino acids were 0.34% and 0.43%,the ratio of non-essential amino acids were 0.85% and0.80%,and the essential amino acids accounted for 28.57% and 35.20% of the total amino acids. |
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