| As a by-product of starch processing,wheat gluten is a protein resource with a wide range of sources,low prices,and safe consumption.The poor solubility of wheat gluten in food processing has led to the development of fewer high value-added products with it as the mainstay.At present,the research on the deep processing and comprehensive utilization of wheat gluten is still in the initial stage,and improving its functional properties to develop more new food products has become a key objective of the current research.The enzymatic modification can not only improve the nutritional value of wheat gluten,but also effectively regulate its various physicochemical properties and physiological activities,and the preparation of various active peptides as functional additives by enzymatic modification technology meets the development requirements of modern food industry.However,the enzymatic of proteins will expose the hydrophobic group,and produce the bitter taste in the taste buds which is unacceptable to consumers.How to efficiently reduce,mask or remove the bitter taste of hydrolysates is a technical problem for many food companies.This project adopts stepwise enzymatic to prepare low bitterness wheat protein peptide powder,and deeply analyzes the mechanism of stepwise enzymatic to reduce the bitterness of wheat gluten hydrolysates,and applies the hydrolysates to the development of functional beverage,which is important to regulate the quality of wheat gluten peptide powder and broaden its application in food industry.In this study,the enzyme-wheat gluten system was used as the research object.Firstly,Neutrase,Papain and Pepsin were selected to modify the raw material by restrictive enzymatic hydrolysis,and then Flavourzyme was added to remove bitterness,and the bitterness intensity of the enzymatic hydrolysates was determined by sensory evaluation,and the effects of bitter peptide content,amino acid composition,molecular weight distribution,surface hydrophobicity and amino acid sequence on the sensory characteristics of the enzymatic hydrolysates were analyzed.The effects of bitter peptide content,amino acid composition,molecular weight distribution,surface hydrophobicity and amino acid sequence on sensory characteristics were analyzed.The results showed that the decrease of bitterness of wheat gluten hydrolysates after bitterness removal by Flavourzyme was more caused by the change of bitterness threshold,and the decrease of hydrophobic amino acid ratio and the increase of free amino acid content were the most important factors influencing the increase of bitterness peptide threshold,and the proportion of peptides with molecular weight of500-3000 Da and surface hydrophobicity were the second most influential factors.The most significant effect of bitterness removal was observed for the Neutrase hydrolysates after 4 h of Flavourzyme action,with the bitterness decreasing from 3.35 to 1.46,the proportion of total hydrophobicity of bitter peptides in the products decreasing from 41.98% to 37.64%,and the proportion of fractions with molecular weight less than 180 Da increasing from9.35% to 21.18%.The primary structural sequence of the bitter peptide in the low limit enzymatic modification product was identified,and it was found that the relative molecular mass of the bitter peptide decreased from 887.426-1640.877 Da to 729.360-1503.770 Da after debittering,and the proportion of peptide fractions with average hydrophobicity greater than 5.86 decreased from 73.17% to 58.82%.The decrease in the content of hydrophobic amino acids at the end of the bitter peptide and proline in the center of the peptide chain was intrinsically responsible for the increase in the bitterness threshold.Based on the preliminary understanding of the effect of Flavourzyme on the bitterness characteristics of wheat gluten modified by low limit enzymatic,the peptide powder was prepared by deep enzymatic of wheat gluten with Alcalase,Trypsin and Protamex,and the bitterness was removed by Flavourzyme,and the changes of bitterness and bitterness peptide characteristics of wheat protein peptide powder before and after the removal of bitterness were systematically studied.The results showed that the bittering effect of Flavourzyme was mainly achieved by degrading the bitter peptides with high hydrophobicity into peptides with low hydrophobicity and free amino acids.The changes of bitterness values of wheat gluten protein deep enzymatic hydrolysates were most influenced by the hydrophobicity of bitter peptide,and the bitter peptide content and amino acid composition also had significant effects on the bitterness intensity of enzymatic hydrolysates,while the molecular weight distribution had a weaker degree of influence.The most significant effect of bitterness removal was found in the Alcalase enzymatic hydrolysates,in which the surface hydrophobicity value of the bitter peptide decreased from 475.05 to 271.39 and the bitterness value decreased from 4.08 to 2.28.The best solution was found in the enzymatic hydrolysates of the Protamex and Flavourzyme fractions,in which the bitterness value of the hydrolysates was only 1.51.Most of the bitter peptides identified in the deep enzymatic hydrolysates were short peptides consisting of about 7 amino acids,and the relative molecular masses were concentrated in the range of 504.282-1194.590 Da,and the peptides with Q values greater than 5.86 k J/mol accounted for more than 60%.The number of peptides,relative molecular masses and surface hydrophobicity of the bitter peptides decreased to different degrees after bitterness removal,and the decrease of the ratio of hydrophobic amino acids at the C-terminus and basic amino acids at the N-terminus of the peptide chains mainly contributed to the increase of the bitterness threshold.The results of mass spectrometry identification were consistent with the results of bitter peptide content,amino acid fraction,molecular weight distribution,and surface hydrophobicity.Wheat gluten powder with low bitterness was used as the main raw material,supplemented with common food additives to develop a wheat protein peptide functional beverage,and single-factor and orthogonal tests were used to optimize the process parameters of wheat protein peptide beverage.The optimal formulation of the beverage was determined as 0.9% wheat protein peptide powder,0.8% β-cyclic dextrin,8% stevioside,0.1% citric acid and 0.2% sodium alginate,using sensory evaluation as the standard.The sensory,physicochemical and microbiological indices of the finished beverage were measured to ensure that all the indices of the product met the national standards for plant protein beverages.In summary,this paper explored the optimal protease combination scheme for the preparation of low bitterness wheat protein peptide powder,i.e.,Protamex and Flavourzyme.The mechanism of wheat gluten hydrolysates by Stepwise enzymatic hydrolysis and the influencing factors that mainly contribute to the bitterness removal were elucidated.Finally,a wheat protein peptide functional beverage with better flavor and stability was developed,which provides the theoretical basis for the industrial development of wheat protein active peptide and the development of new peptide beverage. |
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