| Ponkan?Citrus Reticulata Blanco cv.Ponkan?is a functional fruit with high nutritional value,which is widely grown in various regions of southern China.At present,the research of Ponkan mainly focuses on breeds improvement,growth environment and physical and chemical characteristics analysis,etc.The extended products of Ponkan mainly include extracting essential oil from pericarp,fermenting feed from pomace and processing pulp into canned fruit,fruit juice,fruit wine,fruit vinegar and candied fruit,etc.The survey found that the majority of Ponkan are used for fresh food or simply processed into canned foods and juices,but less for Ponkan fruit wines or fruit vinegar production,and the process is poor.The development and utilization of Ponkan resources are not enough,which leads to the low added value of products in the whole industry.Therefore,the research and development of Ponkan fruit wine has great practical value.In the experiment,Ponkan as the raw material,from Xiangxi,Hunan,the fermentation process,aging process,clarification process,dynamic changes of aroma and establishment of shelf-life model of Ponkan fruit wine were studied.The main results are as follows:1.Taking alcohol yeasts and flavor-producing yeasts as the test strains,the ethanol fermentation process of Ponkan fruit wine was optimized by single factor and Box-Behnken Design?BBD?response surface experiment,and the optimum technological conditions were as follows:mixed yeast inoculation amount 1.8 g/L,apparent sugar content 26%,fermentation pH 3.6,fermentation temperature 26°C,stirring rate 120r/min,fermentation time 7 d.Under this process condition,the alcohol degree of new Ponkan fruit wine was 13.3%?v/v?.2.The results of new ponkan wine after the aging experiment were as follows:under the sensory evaluation index,4 kinds of aging methods can partially improve the appearance,aroma,and taste of Ponkan fruit wine,but the Ponkan fruit wine treated with H2O2-ceramic-oak?HTX?was golden yellow,shiny,and the aroma of fruit,wine and oak was elegant and rich,the body of the wine was full,mellow and slightly bitter,the best results.Under the index of physical and chemical evaluation,the effect of each method on the alcohol degree?v/v?of Ponkan fruit wine was not obvious.The ultrasonic-ceramic-oak?CTX?and H2O2-ceramic-oak?HTX?aging methods had a significant effect on the acid reduction of Ponkan fruit wine,were reduced to 6.2 g/L and 5.8 g/L,respectively.The total ester content of Ponkan fruit wine treated with ultrasonic-ceramic-oak?CTX?and H2O2-ceramic-oak?HTX?was higher and similar,which were 7.8 g/L and 7.83 g/L,respectively.The 4 kinds of ageing methods significantly improved the color of the Ponkan fruit wine.Among them,the color of Ponkan fruit wine treated with H2O2-ceramic-oak?HTX?increased from 0.23?new wine?to 0.52,which was the best.3.The results of the clarification test on the aged Ponkan fruit wine were as follows:The comparison test shows that the mixed clarifying agents has better effect than single clarifying agents.The mixed clarifier formulation optimized by mixture design was found to consist of 51%chitosan,23%bentonite and 26%gelatin.On the basis of single factors and orthogonal optimization experiment,the clarifying conditions were as followed:mixed clarifying agents 1.5 g/L,clarification temperature 25°C,clarification time 20 h,stiring speed 150 r/min.Under these conditions,the transmission rate of Ponkan fruit wine was 98.2%,and the content of total ester was 7.36 g/L.4.The aroma components in ponkan fruit wine during different brewing stages was studied with GC-MS,and the results were as followed:2 of aroma components were detected by 100um PDMS,and the relative content was 16.92%;5 of aroma components were detected by 65um PDMS/DVB,and the relative content was 56.29%;7 of aroma components were detected by 75um PDMS,and the relative content was78.38%;11 of aroma components were detected by 50/30um DVB/CAR/PDMS,the relative content was 91.37%,significantly higher than the previous three,which was most suitable for the study of aroma components of ponkan fruit wine.The aroma components of fresh ponkan juice,new ponkan fruit wine,and aged ponkan fruit wine were extracted by 50/30um DVB/CAR/PDMS and detected by GC-MS.The results were as follows:6 of aroma components were detected in Ponkan juice,including 5 of alkenes,the relative content was 99.42%,including 1 of phenols,the relative content was 0.58%;11 of aroma components were detected in new Ponkan fruit wine,including 3 of alkenes,the relative content was 12.23%,including 1 of phenols,the relative content was 1.51%,including 1 of alcohol,the relative content was56.28%,including 6 of esters,the relative content was 21.35%;16 of aroma components were detected in aged Ponkan fruit wine,including 4 of hydrocarbons,the relative content was 17.42%,4-?prop-2-enoyloxy?octane?0.54%?,3-vinyl-1,2-dimethyl-1,4-cyclohexadiene?4.86%?,3-decene?11.56%?,?+?-?-longleafene?0.46%?,inclu ding 4 of alcohols,the relative content was 56.54%,2-aminoethanethiol?0.43%?,isoamyl alcohol?13.41%?,2-methyl-1-butanol?5.56%?,phenylethyl alcohol?37.14%?,including 7 of esters,the relative content was 18.18%,which were ethyl benzoate?2.97%?,ethyl undecanoate?3.81%?,phenylethyl acetate?3.47%?,ethyl caprate?2.46%?,ethyl laurate?1.23%?,E-11-ethyl hexadecenoate?0.85%?and ethyl palmitate?3.39%?,including 1 of ketones,the relative content was 0.42%,which was 3,5-bis-trimethylsilyl-2,4,6-cycloheptatrien-1-ketone?0.42%?.During the brewing process of Ponkan fruit wine,the aroma components are gradually transferred from alkenes to alcohols and esters,the variety of aroma is increasing and the aroma components are more complex,and alcohols and esters are the most important aroma types.5.The results of the shelf-life experiment on the bottled Ponkan fruit wine were as followed:with the extension of storage time,the correlation between the changes of the total number of bacteria and the storage temperature was not obvious,but sensory and physic-chemical characteristics?VFA?were suitable for the establishment of shelf-life prediction model,respectively.Under the sensory evaluation index,based on the principle of Weibull Hazard Analysis?WHA?,the shelf-life prediction model of Ponkan fruit wine in different storage temperatures was:lgts=53095.02/?2.303RT?-6.508,and the relative error was in the range of-5.48%to 5.52%.Under the physic-chemical characteristics?VFA?index,combining the first-order chemical kinetics model and Arrhenius equation to establish the VFA kinetic model of Ponkan fruit wine in different storage temperatures:T1=T0eKt,K=1.29×109e-67715.04/RT,the shelf-life prediction model of Ponkan fruit wine in different storage temperatures was:y=3510e-0.068x,R2=0.9605,and the relative error was in the range of-2.74%to 8.96%.The comparison experiment found that the prediction error of the shelf-life prediction model under sensory evaluation has less fluctuation,and the effect is better. |
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