The Study On Aroma Characteristics Of Aroma-producing Yeast Fermentation And Its Application In Vegetarian Meat Products

Soybean protein,pea protein and other plant proteins are used as the main raw materials in vegetarian meat products,and their sensory characteristics such as taste and flavor are different from animal meat products.Especially the special smell of plant protein such as beany smell that is not easy to cover up or remove distinguish the flavor of vegetarian meat products from animal meat products.The purpose of this study is to isolate,screen and identify a yeast strain with strong aroma-producing ability,and use it to ferment soybean protein to improve the flavor of soybean protein;to improve the recipe of vegetarian sausage by soybean protein fermentation to provide theoretical guidance for further improvement of the flavor of vegetarian meat products.The main findings are as follows:1.An aroma-producing yeast strain 13-1 was isolated from fermented foods of different regions.The strain can produce 2.15 g/L total esters and was identified as Saccharomyces cerevisiae through morphological observation,physiological and biochemical identification,molecular identification and phylogenetic tree analysis.2.The cultural characteristics and environmental tolerance of the isolated strains were observed,and the types and contents of volatile flavor compounds in the fermentation broth were analyzed.The optimum culture conditions were: glucose as carbon source,yeast extract as nitrogen source,28 °C,initial p H 5;the maximum tolerance concentrations of ethanol,acetic acid and Na Cl were 12 %,0.4 % and 6 %,respectively.A total of 54 volatile flavor compounds were detected in the fermentation broth,and the fermentation broth had floral and fruity characteristics.Compared with the blank control group,the types and contents of alcohols,esters and other substances have increased significantly.Among them,rose flavor 2-phenethyl alcohol was the dominant flavor in the fermentation broth,and the aroma activity value was as high as 5754.44.3.The effects of aroma-producing yeast strains on the flavor of soybean protein,pea protein,wheat protein and peanut protein were observed.The results showed that after the fermentation of aroma-producing yeast strains,the negative flavor attributes of the four plant proteins were weakened,and good flavor attributes such as fruit flavor and sweet flavor were produced.With the increase of glucose addition(or the extension of fermentation time,or the increase of inoculation amount),the acceptance of soybean protein fermentation products increased at first and then decreased.The analysis showed that the flavor attributes of fruity and sweet flavor gradually became evident in soybean protein fermentation;the concentration of ethyl caproate and phenylethyl alcohol gradually increased,and that of beany flavor substances such as hexanal gradually decreased until disappeared,which promoted the sensory acceptance of soybean protein fermentation products.The increase in the content of alcohols such as isoamyl alcohol and acids had a negative impact on acceptance.As the soybean protein addition increased,the flavor of astringent and oil taste gradually became apparent,and the substances producing beany flavor such as 1-octen-3-ol and trans-2-octenal gradually increased.The changes of isoamyl alcohol and other alcohols in different soybean protein addition groups were not obvious,and the acceptance of soybean protein fermentation products increased first and then decreased.4.The recipe of fermented soy protein sausage was improved by the PB test,steepest ascent test and BBD response surface design test.With the sensory score as the evaluation index,the optimal recipe of the vegetarian sausage was: 239.9 g(17.70 %)of fermented soybean protein powder,75.8 g(5.59 %)of modified starch and 12.8 g(0.94 %)of edible salt.Compared with the control group,there was no significant difference in texture characteristics(p > 0.05),and the extrusion loss was significantly reduced(p < 0.05).The types and contents of volatile flavor substances were higher than those of the control group,and the flavor substances were more abundant.The odor activity values of beany flavor substances decreased,and the pyrazine substances with barbecue flavor and 2-phenethyl alcohol components with rose flavor were increased.Therefore,it can be concluded that the isolated aroma-producing yeast plays a significant role in reducing the beany flavor in fermented soybean sausage and improving the overall flavor of the sausage.