| Honey peach wines made with peaches greatly extends the market supply period,but also perfectly combines the nutritional value of peaches with the health-care functions of the wine.However,currently there were very few yeasts suitable for making peach wines so that honey peach wines produced was often difficult to meet the needs of consumers due to insufficient flavor.This study was based on the spontaneous fermented mash of the peach used as the raw material for screening of the brewing strain,a special yeast strain PY01 which can quickly brew honey peach wines within 5 days was obtained by the primary screening and the third-stage re-screening.Based on single-factor experiments,response surface optimization was performed to determine the optimal fermentation parameters for honey peach wines fermented by PY01 strain.The quality index and aroma characteristics of honey peach wines produced by honey peaches with different maturity levels were systematically studied to ensure the best harvest time of honey peaches.The main research contents and results are as follows:(1)10 strains of yeast were isolated from the spontaneous fermented mash of the peach.Preliminary screening of strains by TTC colorimetric and Duchenne tubule method was conducted.Third-stage re-screening of strains through alcohol tolerance,comparison of fermentation speed and wine production capacity,flavor analysis of fermentation liquor and sensory evaluation was also carried out and perform morphological identification and molecular biological identification.The results showed that PY01 strain can quickly produce peach wines within 5 days,and has strong alcohol tolerance,good fermentation performance,and the best evaluation results of sensory and flavor.It can be used as a special yeast for brewing peach wine.The molecular biological identification results confirmed that PY01 was Saccharomyces cerevisiae.(2)Based on the growth curve analysis,PY01 yeast cultured at 28? and 150 rpm for 18 hours was selected as seed culture and inoculated into honey peach juice to make honey peach wines.The initial pH value,main fermentation temperature and yeast inoculation amount were ensured as the influencing factors for the response surface analysis,and the alcohol content was used as the response value.The results showed that the optimum fermentation parameters for PY01 strain fermented honey peach wines were determined as follows.The initial pH 3.9,the fermentation temperature 26? and the yeast inoculum 6.2%,respectively.Under the optimized process conditions,alcohol yield of the honey peach wine was 12.78 % vol,the total sugar content was 8.17g/L.This was a semi-dry honey peach wine with a pure flavor and a mellow taste.This study provides references for strain selection and processing optimization for industrial production of the honey peach wines.(3)This work documented the differences among the honey peach wines produced from different mature peaches by investigating the physico-chemical properties,total phenolic and flavonoid contents,color and transmittance,volatile flavor component,electronic nose detection analyse and sensory acceptability.Tannin and dry extract content in honey peach wines made from a range of 90%-100% mature peaches(9-10 MW)showed a moderate level to let the full-bodied and no astringent.The volatile compounds were also the most abundant,especially the contents of ethyl caprate,ethyl laurate,ethyl caprylate,phenethyl alcohol and ?-unsecalactone were higher,and the comprehensive sensory score reached the highest value.The results of electronic nose detection combined with PCA and LDA analysis were consistent with Gas Chromatography-Mass Spectrometer(GC-MS).9-10 MW increased the main fermentation time compared with honey peach wines made from a range of over-mature peaches(OMW).The total phenolics and flavonoids content were slightly lower than honey peach wines made from a range of 60% mature peaches(6MW).Conclusion: honey peaches at 90%-100% maturity stage is suitable for fermenting of honey peach wines. |
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