Analysis Of The Microbial Community Structure And The Correlation With Flavor Substances During Koumiss Fermentation

In this study,the fresh mare's milk and koumiss during ferm entation(13in total)fermented by the Abaga Horse of Xilin Gol League as the research object.Using gas chromatograph y-mass spect rometr y(GC-MS)and liquid chromatograph y t echniques to explore t he changing laws of ke y fl avor compounds,and using hi gh-throughput sequencing t echnology to study the dynamic succession of mi croorganisms.On this basis,the relationship between microbial communit y structure and flavor composition was explored.The conclusions are as follows :(1)Stud y on the variation of volatile flavor substances.A total of 52 volatile flavor subst ances were det ect ed,including 19 acids,17 esters,7alcohols and so on.Based on aroma vitalit y value(OAV)anal ysis,there were16 aroma components contributing to koumiss,including et hyl capr yl ate,eth yl caprat e,lauri c acid and so on.The tot al acid content increased graduall y,and the total alcohol content increased aft er decreasing.Most aroma components were concentrated in the lat er fermentation peri od,and eth yl octanoate was the most important arom a component contributi ng to koumiss flavor in the l ater fermentation period.(2)Stud y on the vari ation of non-volatile flavor substances.A t otal of 17 kinds of free amino acids and 4 kinds of organic acids were det ected.The four t ypes of t asted amino acids showed an overall upward t rend,am ong which the glutami c acid content was the largest.M ost of the tasted ami no acids were enriched in the lat er stage of ferm entat ion.Lactic acid,acetic acid,and propionic acid showed a si gnifi cant increase trend,and the content of citric acid decreased si gni ficantl y with the ferm entation until it disappeared.Free amino acids and organic acids enri ch the taste of koumiss and improve the qualit y.(3)D ynami c changes of microbi al communit y structure.Bacterial sequences belonged t o 9 phyla and 73 genera.The dominant bacteri a in fresh mare's milk and koumiss at the earl y ferment ation stage belonged to Enteroba cter of the Proteobacteri a,and the dom inant bacteri a in 9 h ferm entation belonged to Lactococcus.After 12 hours of fermentation,Lactobacillus of Firmicutes was the onl y dominant genus,and the relative abundance graduall y increased as the fermentation progressed.The fungal sequence belonged to 7 phyla and 172 genera.The Rhodotorula in Basidiom ycet es was the dominant fungus genus in fresh mare's milk,while Dek ker a in Ascom ycetes became the onl y dominant fungus genus after ferm entation,and the rel ative abundance increased with the deepening of ferm entation.(4)Correlation anal ysis of microbi al com munit y and fl avor substances.Lactobacillus and De kker a were rel ated to the s ynthesis of 32 and 29 fl avor substances,respect ivel y,followed by Enterobacter,Enterococcus,Rhodotorula,and G uehom yc es.These are the microorganisms that have important contributi ons to the formation of koumiss flavor,which ma y becom e the direction of precise screening of koumiss-flavored functional bacteria.