| Shaoxing JIUYAO,as an important starter of local traditional handmade Huangjiu,can not only introduce an important source of microorganisms into the brewing process of Huangjiu,but also guarantee the quality and stabilize the flavor of Huangjiu.However,at present,there are often unqualified products in the production process of JIUYAO,and there is no suitable quality evaluation method.At present,it only relies on manual production experience to judge,which causes difficulties in quality control and affects the quality of Huangjiu.At the same time,we do not know the role of JIUYAO in the fermentation of Huangjiu.The traditional preservation method has great loss,which greatly limits the application of JIUYAO in the production of Huangjiu.In this paper,Shaoxing JIUYAO was taken as the object.Based on the comparison of the main components,enzyme activity and microbial community structure of normal and defective JIUYAO,the influence of JIUYAO on various indexes of Lin-fan liquor was analyzed.Then,the key indexes for evaluating the quality of JIUYAO were selected through correlation analysis.Furthermore,the quality changes of traditional storage conditions and different atmospheres and temperatures after one year were discussed,and the suitable conditions for storage of JIUYAO were obtained,which provided a certain theoretical basis for quality control and preservation of JIUYAO.The main results of this study are as follows:(1)The differences in sensory,physicochemical,enzyme activity,volatile substances and microbial community structure between normal and defective type I and II JIUYAO were analyzed.The results showed that the water content of normal liquor was 9.85～10.08 g/100 g.The liquefaction power was 0.27～0.44 U/g,saccharification power was 240.99～276.57 U/g,acid protease activity was192.00～208.15 U/g,fermentation power was 0.43～0.72 g/g·72 h,total free amino acid content was 68.59～122.75 mg/100 g.The abundance of Pediococcus was3.96%～10.77%,Saccharomycopsis 61.54%～77.97%,Rhizopus 21.96%～38.37%.The water content,reducing sugar content,starch content,free amino acid content,acid protease activity and esterification power of typeⅠdefective JIUYAO were significantly lower than those of normal JIUYAOr(p<0.05),protein content,liquefaction power,glycosylation power and neutral protease activity were significantly higher than those of normal JIUYAO(p<0.05).The contents of starch and free amino acid in type II defective JIUYAO were significantly higher than those in normal group,but the other indexes were significantly lower than those in normal group(p<0.05).A total of 39 volatile substances were detected,and 2-amylfuran,phenylethyl acetate and ethyl butyrate were missing from the defective group,which may affect the odor of JIUYAO.Compared with normal JIUYAO,the defective JIUYAO typeⅠcontained higher abundance of aerobic pediococcus and Marivita.Type II defective JIUYAO contains high abundance of anaerobic types such as Mucor and Staphylococcus.Correlation analysis showed that the quality of liquor was most affected by the content of water in JIUYAO.The variation of the abundance of aerobic bacteria and anaerobes in JIUYAO suggests that oxygen may also be an important parameter affecting the quality of JIUYAO.(2)Analyzed the Lin-fan liquor prepared with normal JIUYAO,and explored the influence of JIUYAO on the production of Lin-fan liquor and the formation of flavor.Physical and chemical indicators show that The alcohol content(14.70%vol～15.60%vol)and the number of yeast(5.72～5.88×10~8/m L)of high quality Lin-fan liquor were significantly higher than that of ordinary Lin-fan liquor(8.1%vol～12.30%vol)and yeast count(1.38～3.42×10~8/m L)(p<0.05).The total contents of organic acids(4.08～4.92 g/L),free amino acids(754.23～813.44 mg/L)and volatile aroma substances(2.75～2.86 mg/kg)of high quality Lin-fan liquor were analyzed.The total contents of organic acids(2.89～2.99 g/L),free amino acids(627.36～668.09 mg/L)and volatile aroma substances(2.09～2.14 mg/kg)were significantly higher than those of defective JIUYAO(p<0.05).(3)By establishing partial least squares regression(PLSR)model,the correlation between JIUYAO and Lin-fan liquor index was analyzed.A total of 17 indexes were selected to evaluate the quality of JIUYAO,including water content,reducing sugar content,alcohol content,acid protease activity,esterification power,the abundance of Pediococcus,Rhizopus and Saccharomycopsis.The 17 key indexes were used for fuzzy comprehensive evaluation of JIUYAO samples,each index was quantified,and a more accurate evaluation method for JIUYAO quality was obtained.(4)The changes of normal JIUYAO in traditional storage conditions and packaging methods of different temperatures and atmospheres over a year were analyzed.The results showed that the indexes of JIUYAO changed significantly after one year of storage under traditional storage conditions(p<0.05),while the surface of JIUYAO was yellow,borers were easily produced.The moisture content increased by about 4.0%,the reducing sugar content decreased by about 72.16%,the free amino acid content increased by about 427.69%,the liquefaction power decreased by about30.68%,the saccharification power decreased by about 4.54%,the fermentation power decreased by about 17.83%,and the esterification power decreased by about23.08%.However,there was almost no significant change in alcohol indexes under nitrogen and vacuum packaging(p>0.05),and the nitrogen package is better.After changing the temperature,the indexes of JIUYAO stored at 4℃changed the least,followed by 15℃,which proved that low temperature environment may be conducive to JIUYAO storage.In summary,the water and oxygen content in the process of making JIUYAO have a significant impact on the quality of JIUYAO,and the activity of acid protease and the content of 2-amylfuran can significantly affect the use of Lin-fan liquor quality.Therefore,a JIUYAO quality evaluation system was established.After a year of storage by lowering the temperature and filling with nitrogen,the composition of the microbial community remained more stable and the loss of enzyme activity was significantly reduced compared with traditional methods. |
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