Changes Of Flavor Substances In Traditional Solid State Fermentation Of Millet Rice Vinegar And Technological Improvement

In this paper,millet vinegar was brewed by solid state fermentation process.First,in order to provide theoretical data for the traditional brewing process of millet vinegar,we researched the changes of physical and chemical indexes and flavor substances in the traditional brewing process.Second,in order to select the optimal fermentation process,find out the relationship between the specific microorganism and its corresponding millet vinegar quality,improve the quality of millet vinegar as well as the fermentation efficiency,we altered the traditional brewing technology of millet vinegar through artificial inoculation of microorganism.The main research contents and results are as follows:1.Use the traditional solid-state fermentation technology of Qingshuihe area in Inner Mongolia to brew millet vinegar.It was found that oxalic acid,tartaric acid,malic acid,citric acid and succinic acid increased in saccharification and alcohol fermentation.In the fermentation stage of acetic acid,the content of acetic acid increased significantly,while the content of lactic acid decreased,and the other organic acids increased first and then slightly decreased.After acetic acid fermentation(lactic acid acetate)/ total organic acid value was 84.9,and the content of pyroglutamic acid did not change significantly.The change of the content of amino acid displayed that the total content of amino acids in saccharification and alcohol fermentation increased from 26.88 mg/100 g to mg/100 g.781.96 Leucine(Leu),glutamic acid(Glu),arginine(Arg),proline(Pro),alanine(Ala)and phenylalanine(Phe)are the main amino acids in wine mash;The total amino acid content increased to mg/100 g,1112.13 in d 18 At the end of acetic acid fermentation,The total amino acid content declined.The contents of free amino acids in vinegar are leucine(Leu),glutamate(Glu),alanine(Ala)and phenylalanine(Phe).With the help of electronic nose,alcohol fermentation stage and acetic acid fermentation in W2S(alcohols,aldehydes and ketones)the most prominent changes in response values.the response values of sensors W3C(ammonia,aromatic components),sensors W6S(hydrides),sensors W5C(olefins,polar molecules,aromatic components),sensors W1W(inorganic sulfides)did not change significantly throughout the fermentation period,but still had better response values,indicating that all kinds of volatile substances were stable throughout the fermentation process.2.Brewing millet vinegar by artificial inoculation microorganism method.The volatile aroma components of millet vinegar were analyzed by solid phase microextraction and GC-MS.The results showed that the content of higher alcohols decreased with the increase of lipid content and species in saccharification and alcohol fermentation.In the fermentation stage of acetic acid,with the extension of time,the types of flavor substances increased obviously,in which the contents of lipids and acids increased,while the contents of alcohols and aldehydes decreased.The relative contents of furan compounds,benzene-containing compounds,amines and other compounds were lower,and the contribution to flavor was less.The type and content of acid substances increased obviously through aging;although the ester substances decreased,the relative content of ester substances still accounted for a high proportion,which contributed greatly to the flavor of millet vinegar;the content of aldehydes and ketones increased obviously after 2 months of aging.The flavor and sensory of aged millet vinegar were obviously improved,and the aging method of fermented grains was more beneficial to the improvement of flavor substances of millet vinegar.The sensory score of millet vinegar produced by artificial inoculation was lower.3.Millet vinegar was brewed by traditional brewing combined with artificial microorganism.By comparing,it was found that the efficiency of alcohol fermentation was improved,the yield of alcohol was elevated.In the acetic acid fermentation stage,the acetic acid fermentation efficiency was improved and the total acid content increased rapidly.The total amount of amino acids in the modified process 2 after inoculation with ester-producing yeast and acetic acid bacteria was 169.42 mg/100 m L,of which the essential amino acids were 66.15 mg/100 m L,and the non-essential amino acids 103.28mg/100 m L,were higher than those in the traditional process and the modified process 1 sample.The acetic acid and lactic acid were the main organic acids in millet vinegar,which accounted for over 85% of the total organic acids.The maximum content of organic acids in millet vinegar produced by modified process 2 was up to 4825.21 mg/100,and except herbicidal acid and succinic acid,the other organic acids were higher than the other two groups.According to the results of sensory evaluation,the aroma,taste and total score of millet vinegar brewed by modified process 2 were higher than that of traditional brewing process.To sum up,the fermentation efficiency of millet vinegar and the formation and accumulation of flavor substances can be effectively boosted by combining the traditional brewing technology with the modified technology of inoculation functional microorganisms,so as to replace the traditional brewing process for industrial production.