Study On Aggregates In The Process Of Enzymatic Preparation Of Soy Flavor Condiment

With the improvement of living standards,people pay more attention to the safety and nutrition of condiments.Therefore,the use of natural protein resources to prepare flavor condiment is the current hot trend of condiments.Soy protein isolate has high nutritional value,unique flavor and wide sources,it has become a high-quality protein raw material for preparing fancy flavor condiment.Compared with acid hydrolysis and alkali hydrolysis,biological enzymatic hydrolysis is currently a common method for preparing flavor condiments due to its mild reaction,less nutrient loss,and high safety.In the process of protein enzymolysis,more and more small molecule peptides and amino acids were released.Due to their difference in hydrophilicity and hydrophobicity,aggregates might generated in the enzymatic hydrolysis system.These aggregates will not only hindered the enzymatic hydrolysis process,but also affected the flavor quality of the final flavor condiment,limiting its promotion and application in the market.Based on the premise of preparing high-quality soybean flavor condiment,this paper systematically studied the formation of aggregated substances,and discussed how to improve the aggregation plan,in order to develop a soybean flavor condiment with outstanding umami taste and better flavor quality.This article used soy protein isolate as raw material,based on the sensory evaluation index of umami taste,comprehensive consideration of amino acid composition,peptide molecular weight distribution,protein recovery rate,degree of hydrolysis and other indicators.The enzymatic hydrolysis process conditions of the soybean flavor condiment was optimized,and the soybean flavor condiment with high freshness and good nutrition was obtained.The experimental results showed that the optimal enzymatic hydrolysis conditions of soybean flavor condiment was: After high pressure heat treatment(121 ℃,0.1 MPa,2 h),0.50% trypsin,0.50% compound protease and 1.00% flavor protease were added to the soy protein isolate solution with a material-to-liquid ratio of 1:10 and a p H of 7,and enzymatically hydrolyzed at 55°C for 12 h,and the enzyme was quenched and the solution was cooled,then added 0.50% aminopeptidase and enzymatically hydrolyze at 55℃ for 12 h.After the enzyme was inactivated and cooled,the supernatant was collected by centrifugation and concentrated in vacuo to a solid concentration of 50%.Soybean flavor condiment with outstanding umami taste was obtained,and its electronic tongue umami taste score was 5.81±0.29.Analyzing the aggregates appearing in the concentrated enzymatic hydrolysate,it was found that the substance had an adverse effect on the flavor and nutritional quality of the concentrated enzymatic hydrolysate.Through in-depth discussion on the formation of aggregates,it was showed that the content of nitrogenous substances in the aggregates was as high as 92.1±0.51%,of which tyrosine accounted for the highest proportion,72.98%.Subsequently,the influence of temperature,p H,ionic strength,and solid concentration on the precipitation of aggregates in the flavor condiment during the concentration process was systematically studied.Studies have shown that aggregates were thermally unstable,and the precipitation rate of aggregates reached a peak(1.40%)at 65°C;Compared with acidic conditions,the precipitation rate of aggregates under alkaline conditions was higher,reaching a peak value(1.94%)at p H 9,some aggregates wouldn’t depolymerize until p H > 10;When the ionic strength was 1.00 M,the precipitation rate of aggregates reached the peak(1.16%),but under high ionic strength conditions(ionic strength ≥ 2.00 M),the aggregates dominated by electrostatic interactions depolymerized;While the solid content of the flavor condiment was less than 25.0%,there was no aggregation phenomenon.As the solids concentration increased,the precipitation rate of aggregates continued to increase,and reached the highest(1.37%)when the solids concentration was 70%.Subsequently,experiments such as Zeta potential,hydrophobicity,sulfhydryl group,particle size and infrared spectroscopy confirmed the hydrophobic interaction force plays a leading role in the aggregates;Finally,the influence of different denaturants on the microscopic morphology of aggregates was studied,and it was found that SDS depolymerization had the best effect.Among them,the absorbance of the aggregate solution after 2.00 M SDS treatment decreased from 2.41±0.42 to 0.88±0.27,and the aggregate particle size decreased 1222.80 nm to 97.90 nm,which reached the colloidal range.By exploring the influence of different adsorbents(activated carbon,perlite,diatomaceous earth)on the aggregates in the flavor condiment.It was found that activated carbon removed aggregates by adsorbing them,but it also caused a higher protein loss rate(34.80%).It showed that the adsorbent was difficult to be used in the removal of soy flavor condiment aggregates.Studies had found that different polysaccharide coagulants(guar gum,sodium alginate,chitosan)could inhibit the formation of soy flavor condiment aggregates.Among them,it was found that guar gum had the best effect,which reduced the precipitation rate of aggregates to0.49%;and the combined use of guar gum and arabinose further improved the accumulation of flavor condiment.When the ratio of the two was 1:40(0.05%:2.00%,w/w),the effect of inhibiting the precipitation of aggregates was the best(0.26%).Compared with untreated,the precipitation rate of aggregates was reduced by 77.39%.