Study On Fermentation Technology And Key Aroma Of Oat Laozao By Bacteria Isolation From Pastoral Area Laozao

Laozao in pastoral area has some problems,such as low technology level,uncertain parameters,low modernization degree,unstable product quality and so on.In this study,the main contents are as follows: microbial isolation and identification in the traditional Laozao in pastoral area,the fermentation technology of oat Laozao by inoculating isolated bacteria,analyzing the dynamic changes,key aroma and the relationship with microorganisms and amino acids in the fermentation process of oat laozao.The results of this study can provide process parameters for large-scale production of Oat Laozao and a theoretical basis for the control of the key aroma of Oat Laozao.The main results are as follows:1.Six Bacillus were isolated from Laozao of pastoral area,all of them can grow at high temperature.LZ4#,LZ3#,LZ6# could grow in the culture condition with 10% salt.Six strains had different utilization of nitrogen sources,carbon sources and other components.l Z1#,LZ2# and LZ5# are Brevibacterium Casei,LZ3#,LZ4# and LZ6# are Bacillus Subtilis.Lz1#,lz3#,LZ5# can produce amylase and six strains can produce protease and lipase.2.The fermentation technology parameters of Oat Laozao were 30% oat flour,10%corn malt flour,65? liquefaction temperature and 10 min liquefaction time;the ratio of yeast to bacillus isolated from Laozao of pastoral area is 1:3.The best fermentation conditions were the inoculum amount was 10%,the fermentation temperature was 30? for24 h,and the fermentation temperature was 50? for 48 h.3.The changes of volatile components during oat Laozao fermentation were the contents of esters increased at first and then decreased,and the contents of alcohols increased at first and then decreased and then increased,the contents of acids increased,the contents of aldehydes and ketones decreased first and then increased,the contents of heterocyclic compounds increased first and then decreased,and the contents of hydrocarbons decreased first and then increased;the ratio of sugar to acid and p H decreased,the content of total acid increased slowly,the ammonia nitrogen increased first and then decreased,the total amino acids increased first and then decreased;the number of yeast and bacteria firstly increased and then decreased.4.Comparative analysis results of natural fermentation and inoculation fermentation showed that after fermentation,the p H and sugar-acid ratio of the oat Laozao in inoculation fermentation group were lower than the natural fermentation group,while the total acid content and sensory score were higher than those of the traditional group.No yeast was involved and the bacteria had little change in the fermentation process of traditional natural fermentation;while the yeast did not survive after 48 hours of fermentation and the colony number of bacteria first increased and then decreased with the extension of fermentation time in inoculation fermentation group.The volatile aroma components of oat Laozao in traditional group and inoculation group were 62 and 65,respectively.And the relative contents of Ester,Alcohol,Heterocyclic and Hydrocarbons in inoculation group were higher than those in natural group,while the content of acids was significantly lower than that of the natural group.At the same time,PCA revealed that components of esters(0.965),heterocyclic compounds(0.990),hydrocarbons(0.996)and alcohols(0.984)were highly positive correlated with the volatile aroma of oat Laozao in both fermenting ways.5.29 key aroma components were determined in oat Laozao,including 9 esters,7acids,7 alcohols,4 carbonyl compounds and 2 heterocyclic compounds.The key aroma components were Ethyl butyrate,caproic acid,valeric acid,nonolactone.Principal component analysis showed that 29 key aroma components could be distinguished by 4principal components in different fermentation stages of oat Laozao,and the cumulative variance contribution was 87.026%.6.In the fermentation process,the correlations between different key aroma components of oat Laozao and microorganisms and amino acids were different.Ethyl Acetate,ethyl nonate and ethyl octanoate were positively correlated with yeast(P<0.05),and ethanol was positively correlated with yeast(P<0.01);Ethyl nonanoate,ethyl butyrate,ethyl heptanoate,ethyl octanoate were positively correlated with bacteria(P<0.05),and trans-2-octenonal was positively correlated with bacteria(P<0.05);Caprylic acid and hexanal were positively correlated with amino acids(P<0.05).