Screening Of Kiwifruit Wine Strains,Optimization Conditions Of Mixed Fermentation And Study On Kinetics

At present,the fermentation of kiwifruit wine has the problems of high methanol content,high alcohol content and no prominent fruity.In order to solve these problems,in this study,the kiwifruit peel and the kiwi wine fermentation tank were used as the source of the strain and find the yeast that is suitable for ferment kiwifruit wine by scribing separation,gas production test,tolerance test,fermentation force determination,physicochemical index of kiwifruit wine,volatile flavor substances and Sensory evaluation.The special yeast was used to ferment the kiwifruit wine with other yeast.The inoculation order of mixed fermentation was screened and the fermentation conditions were optimized of mixed fermentation.Finally,the fermentation kinetics was studied and the fermentation kinetics model was established.The research results were as follows:(1)127strains were isolated from the kiwifruit peel and wine feet.Five strains with superior performance,named Q3,J33,F4,Q2,Q1,were selected by gas production test,tolerance test and fermentation force.The five strains could fill the entire Duchenne tube in24h.The alcohol volume fraction of strains Q1,Q2,and J33 was 14%,the F4 and Q3 was16%.The tolerate SO₂mass concentration of five strains was 300.00mg/L.It was found that the five strains have typical yeast characteristics by colony morphology and cell morphology.Q1,Q2 and Q3 belong to Pichia guilliermondii,and J33 and F4 belong to Wickerhamomyces anomalus,according to molecular biology identification.(2)The kiwifruit wine was fermented by selected strains,and the kiwifruit wine fermented by commercial yeast KD and EC1118 as controls.The strain F4 was found to be the most ideal strain of the five strains by comparing physicochemical index,volatile flavor substances and sensory evaluation of kiwifruit wine.The alcoholicity,the V_Ccontent,methanol and higher alcohol contents of the kiwi fruit wine fermented by F4 was 10.77%vol,375.54 mg/L,254.65 and 213.43 mg/L,respectively.32 kinds of volatile flavor substa--nces were detected,and there were 9 kinds of substances with aroma activity value(OAV)greater than 1.The sensory score of kiwifruit wine fermented by KD was highest,but the kiwi wine fermented by KD had higher methanol and higher alcohol content of 339.97 and297.45 mg/L,respectively.Therefore,the strains F4 and KD were used to fermented wine by mixing,it is hoped that the advantages of strain F4 and KD could be retained,thereby improving the quality of kiwi wine.(3)F4 and KD simultaneously inoculated was the best inoculated method to ferment kiwifruit wine.The alcohol content,V_Ccontent,methanol contend of kiwi wine fermented by this inoculation method was 248.41 mg/L,391.78 mg/L,256.86 mg/L,these indicators are better than kiwi wine fermented by KD.In terms of sensory,the sensory score of mixed-fermented wine was higher than those of F4 and KD single-fermented wines.(4)Fermentation temperature,inoculum and inoculation ratio of F4 and KD of mixed-fermented kiwifruit wine were 18?,4%and 70:30.The winemaking verification experiment was carried out under the optimal fermentation conditions It was found that the kiwi wine fermented at optimal conditions was better than that before optimization.The results showed that the total acid content of kiwifruit wine was reduced by 4.02%,the retention rate of V_Cwas increased by 10.01%,the methanol content was decreased by3.83%and the content of higher alcohols was decreased by 44.11%comparing with non-optimized.Meanwhile,the content of methanol and higher alcohols decreased by27.32%and 53.57%comparing with fermented by KD.The sensory quality of kiwifruit wine was also improved.(5)Dynamics models of cell growth,ethanol and higher alcohols production and substrate consumption were established during the mixed fermentation.Analysis the dyna--mics models,ethanol and higher alcohol in the fermentation system were closely related to the growth of yeast,the production of these substances occurred in the logarithmic growth phase of mixed fermentation.Meanwhile,the production of isobutanol and isoamyl alcohol lagged cell growth for 11.968 and 12.515 h in the mixed bacteria system,respectively.