| Daqu brewing is the most important technological feature of Chinese liquor.Daqu is a saccharification and fermentation agent for Baijiu brewing.It is an indispensable raw material for Chinese Baijiu brewing,and it is also a key core for maintaining the unique characteristics of Chinese liquor.Daqu has a history of thousands of years and has rich experience.In fact,production,storage and evaluation of Daqu is still based on sensory experience and lacks the necessary scientific basis.This has slowed down the research and brewing mechanism of liquor,and has brought enormous difficulties to the stable production and further improvement of liquor quality.Daqu's production is open fermentation,which involves a large number of microorganisms in the raw materials,natural environment and tools.Due to the large number of microorganisms involved,the strains that actually produce glycosylation are not clear.Liquor production cycle is very long,Daqu fermentation for 28 to 40 days,the end of the fermentation Daqu still need to be stored for 3 to 6 months,the scientific basis for the storage period and the storage period is not clear.Daqu is the main raw material for Baijiu brewing.Daqu quality evaluation is mainly based on sensory evaluation.In recent years,the industry has gradually added some biochemical indicators,such as saccharifying power,liquor-producing power,etc.Due to the solid-state fermentation of Daqu,there are differences in the same batch of Daqu and even in different parts of each Daqu,resulting in a large amount of samples for the detection.This research has done research on the actual problems related to Daqu encountered in liquor production.The results are as follows:1.In order to understand the changes in the storage process of Daqu and determine the optimal storage period of Daqu.In this study,a fragrant low-temperature Daqu was used as the material,and its main indicators were analyzed at different storage periods.The results showed that: During the storage of Daqu,the moisture content and acidity remain basically unchanged.The pH value increased slightly after storage for 3 months,the main acid-producing bacteria were not reduced after analysis.It may be that the acid and alcohol synthesize ethyl acetate.The ethyl acetate content was increased as the storage period extend of Daqu.The saccharifying power of samples HX and HH did not change much during the storage period,sample QC fluctuates during the first 3 months of the storage period and then begins to decline.The liquefying power fluctuates slightly during storage but is not obvious.The ?-diversity analysis showed that the microorganisms fluctuate greatly during the first 3 months of the storage period,Simpson and Shannon indexes trend are very similar,the bacterial is the lowest in 3 months(HH sample),the fungal are the lowest in 3 months(QC,HX and HH samples),and then the diversity increases.From the viewpoint of the ?-diversity of microorganisms,the samples in the same storage period have obvious similarities.At the time of storage for 3 months,the distances between the three Daqus are relatively close,indicating that the microbial composition is similar,but the distance at 5 months is slightly increased.From multi-angle analysis,it was found that the storage time of Daqu was more suitable for 3 months.2.Saccharification is an important biochemical indicator of Daqu.Although it is not yet a necessary indicator of Daqu's quality evaluation,almost all wine companies track the glycosylation ability of Daqu.In order to meet the need for the detection of saccharifying power,a rapid method for the detection of saccharifying power was developed in this study.Through optimization three main processes,the preparation of crude enzyme,the sediment of glucoamylase and the detection of its activity,a method for rapid determination saccharifying power of Daqu was obtained.Results showed that 5 g Daqu sample was dissolved with 150 mL distilled water,and the crude enzyme obtained was sedimented by ammonium sulfate with 60% saturation at 20 ? for 20 min.The sediment was resolved with water in order to avoid the effect of reducing sugar.After the substrate starch was added to react for 10 min,then added with Benedict's reagent and boiled for 3 min.Samples with different saccharifying power presented different colors.The variation trend of colure of Daqu sampled with saccharifying power from 300~1000 U were from light blue,blue-green,dark green,brown,reddish brown and to brick red,respectively.3.In order to apply the saccharifying enzyme functional bacteria to the Baijiu brewing process,a lab-made Daqu model was constructed in this experiment.The results showed that: the water was added at 40% and Muqu was added at 0.5%.The time and temperature were 35 °C 72 h;33 °C 48 h;45 °C 96 h;35 °C 168 h;33 °C 96 h.The saccharifying power of Daqu is 1075 U,the liquefying power is 0.68 U,the content of amino nitrogen is 2.31 g/kg,the acid protease is 1.31 U/g,and the neutral protease is 2.19 U/g.Ethyl acetate,ethyl lactate,ethyl butyrate and 2,3-butanediol(internal raceme)are the main components of distilled liquor chromatography.The content is 69.16 mg/L,36.89 mg/L,2.01 mg/L and 86.29 mg/L respectively.4.In the fermentation process,Aspergillus oryzae MQ-1 solid medium and Rhizopus oryzae MG-1 solid medium were used for the fermentation test,and the alcoholic flavor and flavor precursors(ethyl acetate,ethyl lactate,2,3-butanediol,etc.)are higher than the control group in the content of flavor components and flavor precursors of Baijiu,and the addition of R.oryzae MG-1 solid medium is more than the addition of Aspergillus oryzae MQ-1 solid medium,because its quality of the Baijiu is better.The results showed that: The best condition for producing glucoamylase from Aspergillus oryzae MQ-1 was 250 mL beakerflask with 30 g,initial moisture content of 40%,initial pH value of 6,and culture temperature of 30 °C.Under these condition,the saccharifying power of Aspergillus oryzae MQ-1 reached 1552 U.The best conditions for producing glucoamylase from Rhizopus oryzae MG-1 were 250 mL beakerflask with 20 g,initial moisture content of 40%,initial pH value of 5,incubation temperature of 25 °C,under these condition,the saccharifying power of Aspergillus oryzae MQ-1 reached 1145.6 U.Qualitative and quantitative analysis of glucoamylase production by Aspergillus oryzae MQ-1 and Rhizopus oryzae MG-1 revealed that content of flavor components and flavor precursors produced by Rhizopus oryzae MG-1(ethyl acetate,lactate B)Ester,2,3-butanediol,etc.)produced more than M.oryzae MQ-1.The content of ethyl acetate,ethyl lactate,2,3-butanediol(left-hand),2,3-butanediol(meso)of Rhizopus oryzae MG-1 higher than CKQ's content were 9.19 mg/L,5.96 mg/L,7.85 mg/L,6.86 mg/L,respectively;and Aspergillus oryzae MQ-1 of ethyl acetate,ethyl lactate,2,3-butanediol(left-hand)content higher than CKQ content were 21.84 mg/L,21.84 mg/L,4.15 mg/L,respectively.From the perspective of the chromatographic composition of the liquor,the optimum amount of 0.6 g of Aspergillus oryzae MQ-1 in the liquor brewing process was the best,and the content of ester compounds and the rate of alcohol production was significantly improved;The optimum amount of 0.2 g of Rhizopus oryzae MG-1 was the best,the content of flavor substances and the rate of liquer production have also been significantly improved. |
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