Study On The Differences Of Compounds In Chixiang Aroma Type Traditional Bingqu And Mechanical-making Moldy Bran (Fuqu)

Chixiang aroma type traditional bingqu is a representative type of Xiaoqu.The quality of Qu could influence the character and yield of liquor.Non-volatile compounds in Qu determine the growth of microorganism,and there are also important precusors of flavor compounds.But the specific composition of these substances in Chixiang aroma type is still unclear.At present,it has been found that the quality of Chixiang aroma type mechanical-making moldy bran?fuqu?is still not as good as that of traditional techniques,and the differences between them are not clear at present.Therefore,it is necessary to understand the composition and changes of metabolites in the process of Qu-making further so as to control it accordingly.In this research,we studied the volatile and non-volatile compounds in traditional and mechanized Chixiang aroma type Qu by headspace solid-phase microextraction and derivatization combined with gas chromatography-mass spectrometry?GC-MS?analysis,in order to give a preliminary understanding of the differences between these two kinds of Qu.Furthermore,providing guidance for improving the quality of traditional bingqu and mechanical-making moldy bran?fuqu?.The main results of this thesis are as follows:?1?Derivatization combined with GC-MS analysis was applied to research the non-volatile compounds in traditional bingqu and mechanical-making moldy bran?fuqu?,a total of 79 non-volatile compounds were detected,of which 63 kinds of compounds were accurately identified and 16 were temporarily identified.These compounds include 12 kinds of saccharides,among which gentiobiose and 2-phenyl-?-D-glucopyranoside were detected for the first time in bingqu;9 kinds of sugar alcohols and glycerol,among them L-threitol,meso-erythritol,D-pinitol,and galactitol were first detected in bingqu;26 kinds of organic acids and 11 kinds of amino acids,3-hydroxybutyric acid,2-hydroxy-3-methylbutyric acid,and 3-hydroxypropionic acid,glyceric acid,tartaric acid were first detected in bingqu;20aromatic compounds,among them 4-hydroxybenzoic acid,gallic acid,protocatechuic acid,gentisic acid,syringic acid,and caffeic acid were first detected in bingqu.Head space-solid phase microextraction?HS-SPME?and GC-MS were used to analyze the volatile compounds in these two kinds of samples.A total of 32 volatile components were detected,including 8esters,3 volatile organic acids,9 alcohols,11 aromatic compounds and tetramethylpyrazine.?2?The compositional characteristics of the Chixiang aroma type traditional bingqu and mechanical-making moldy bran?fuqu?:The kind of aromatic compounds?31?was the most abundant.The concentration level of carbohydrates and sugar alcohols was the highest(35.13-36.30 g?kg^-1?DW?).The highest concentration of aromatic compounds was benzyl alcohol,accounting for 38.29%-40.68%of the total aromatic compounds.D-glucose was the highest concentration level in carbohydrates,accounting for 47.00%-60.62%of total concentration.The concentration of monosaccharide was the highest and the kind of sugar alcohols was the most abundant?9 kinds of sugar alcohols?.The concentration of lactic acid(2.67-3.07 g?kg^-1?DW?)was the highest among all hydroxy acids;linoleic acid was the most abundant long-chain fatty acid(6.84-7.94 g?kg^-1?DW?);3-methylbutyric acid was the highest concentration short-chain fatty acid in traditional bingqu,but it was hexanoic acid in fuqu.?3?The change trend of most carbohydrates,organic acids and amino acids of traditional bingqu and fuqu in the process of fermentation was firstly increased and then decreased.The0-4^th day of the fermentation was the cumulative process,and it was the consumption process from the fourth day.Trehalose accumulated during the first three days of fermentation,and consumed quikly during the third and fourth days.The concentration of lactic acid and long-chain fatty acids increased on day 0-2^th,decreased after the second day,but D-glucose declined first(day 0-3^th)then increased(day 3^th-6^th).During the storage period,the concentration of trehalose gradually decreased while D-glucose increased.The concentration of other compounds did not change significantly.The change trend of non-volatile compounds in fuqu was similar.The concentration of Carbohydrates peaked at the 48^th hour,hydroxy acids had the highest concentration at the 32^nd hour of fermentation,long-chain fatty acids peaked at the 56^th hour,and the non-volatile group at the storage stage.Fractions were all based on their respective concentration,there is no obvious accumulation and consumption.The change process of trehalose in these two kinds of sample was quite different,it was opposite to that of glucose in bingqu,and the change of trehalose concentration was relatively rapid.Trehalose accumulated slowly in fuqu.?4?2-Phenylethanol is an aromatic compound with the largest difference in the average concentration of bingqu and fuqu,and it decreased 2.97 mg?kg^-1?DW?in fuqu.The difference in D-glucose concentration among all carbohytrates was greatest,and it increased by 5.27 g?kg^-1?DW?in fuqu.The concentration of lactic acid was the largest different among hydroxy acids,and the concentration in fuqu reduced by 405.76 mg?kg^-1?DW?.L-Proline was the most variable of all amino acids decreased by 104.97 mg?kg^-1?DW?in fuqu.A total of 14 of 18 kinds of volatile alcohols,esters and pyrazines appeared different degrees of decline.