| As one of the twelve flavor types,Moutai-flavor liquor has the longest brewing cycle,the most complicated technology,the most participating microorganisms and the most abundant flavor substances,and is deeply loved by consumers because of its unique sensory quality.The formation of its unique style is inseparable from its complicated "12987" process.This paper traces the whole production cycle of Daqu Maotai-flavor liquor in Maotai area,and analyzes the round fermentation process of Maotai-flavor liquor by means of physicochemical analysis,flavor omics technology,microbiology technology and other omics technologies,and analyzes the correlation among physicochemical,microbial and flavor substances.The main results are as follows:(1)The physical and chemical indexes(moisture,acidity,reducing sugar,starch)of fermented grains of Daqu Moutai-flavor liquor in Maotai area were analyzed by T/CBJ 004-2018 General Analysis Method of Solid-state Fermented Grains.The results show that the moisture content,acidity,and starch of fermented grains of each round in the whole production cycle.However,the starch content showed a decreasing trend with the increase of rounds,and the decreasing range gradually decreased.Further analysis of the correlation between physical and chemical indexes by Spearman index shows that water is negatively correlated with reducing sugar and starch(P<0.05),and positively correlated with acidity(P<0.05),while reducing sugar is positively correlated with starch(P<0.01).(2)High-throughput sequencing technology was used to analyze the changes of microbial structure in fermented grains before stacking and in cellar.The results show that 12 kinds of bacteria phylum,6 kinds of fungi phylum,71 kinds of bacteria genus and 43 kinds of fungi genus were detected in fermented grains before stacking and in cellar for 7 rounds.Among them,the dominant bacteria phylum in fermented grains before stacking and in cellar was Firmicutes.At the genus level,the dominant bacteria in fermented grains are lactobacillus,Bacillus,Unidentified Mitochondria,etc.Among them,lactobacillus is the dominant bacteria in the first round of fermented grains before stacking.Unidentified Mitochondria is the dominant bacteria genus in the second,fifth,sixth and seventh rounds.For fermented grains entering pits,lactobacillus is the dominant bacteria genus in the first round,Bacillus is the dominant bacteria genus in the third round and Unidentified Mitochondria is the dominant bacteria genus in the seventh round.The dominant fungi are Issatchenkia,Pichia,Saccharomyces,etc.Among them,for fermented grains before stacking,Issatchenkia first decreased and then increased with the turn,reaching the lowest relative abundance value(0%)in the third round,and the relative abundance ratio in the first,sixth and seventh rounds was 91.3%,96.3% and91.1% respectively.The dominant bacteria in the third and fifth rounds were Pichia(61% and 64.4%),while the dominant bacteria in the fourth round the dominant bacteria in the fourth round was Zygosaccharomyces(57.4%).Issatchenkia’s changing trend of fermented grains in cellar is similar to that of fermented grains before stacking,and it also reaches the lowest relative abundance value in three rounds,and it is the dominant strain in the first,fifth,sixth and seventh rounds,especially in the fifth,sixth and seventh rounds,the relative abundance ratio is over 90%.The dominant bacteria in the second and third rounds were Pichia(72.8% and 48.1%);In the fourth round,the relative abundance of Zygosaccharomyces and Pichia reached 51.3% and 32.4% respectively.(3)GC-FID and IC chromatographic instruments were used to analyze the composition and changes of flavor compounds in rounds of Maotai-flavor liquor.The results showed that the total content of flavor compounds in rounds of liquor decreased first and then increased slightly in 5-7 rounds with the increase of rounds.The top,middle and bottom liquor all reached the highest values in the first round,which were28,364.16 mg/L,22,060.27 mg/L and 4,000 mg/L respectively.In the sixth round,the fifth round and the seventh round,it reached the lowest values,which were 10487.52 mg/L,9748.60 mg/L and 10124.86 mg/L,respectively.Among them,the change trend of the ester flavor compounds content in the round wine first increased and then slowly decreased from the IV econdd round,and the top,middle and bottom wines were all in the second round.Alcoholic flavor compounds showed a decreasing trend with the increase of rounds,reaching the highest value in the first round,which was 20,747.40 mg/L,18,504.66 mg/L and 27,822.12mg/L in the upper,middle and lower liquor respectively,and reaching the lowest value in the seventh round,which was 8,517.03 mg/L,8,000 mg/L,4931.12 mg/L respectively.(4)Based on multivariate statistical techniques,the correlation among physicochemical properties,microorganisms and flavor substances in the round fermentation of Maotai-flavor liquor was analyzed.The results showed that starch and reducing sugar belonged to the same area as Pichia,Acetobacter,Thermoascus,Candida,Aspergillus,Kroppenstedtia and Trichocladium,which indicated that starch and reducing sugar were closely related to these microorganisms.The microorganism most closely related to flavor substances is Pseudomonas,which is significantly related to ethyl octanoate,ethyl oleate,ethyl stearate,ethyl linoleate,phenylethyl alcohol,isobutyraldehyde,butanediol right,isovaleraldehyde,ethyl valerate and ethyl acetate,and significantly related to isoamyl acetate,ethyl palmitate,n-amyl alcohol,hexanol,propylene glycol,acetaldehyde,ethyl laurate,acetone and ethyl phenylacetate.Pediococcus is another microorganism closely related to flavor substances,which is significantly related to ethyl oleate,ethyl stearate,ethyl linoleate and ethyl valerate,and is significantly related to isoamyl acetate,ethyl octoate,ethyl palmitate,propylene glycol,phenylethanol,acetaldehyde,propionaldehyde,isobutyraldehyde,2,3-butanediol(meso),ethyl phenylacetate and ethyl acetate. |
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