| Passion fruit has rich aroma,unique flavor and rich nutrition,which is deeply loved by consumers.Using purple passion fruit as raw material to prepare passion fruit juice wine and whole fruit wine with rich nutrition and antioxidant capacity can not only reduce the waste of passion fruit resources,but also enrich the types of fruit wine products on the market.In this paper,purple passion fruit was used as raw material to ferment fruit juice wine and whole fruit wine,and the brewing process,fermentation kinetics and antioxidant activity were studied.The results of this study can provide a technical basis for the large-scale production of passion fruit wine and promote the development of passion fruit industry.The main results are as follows:1.Optimization of preparation process of passion fruit juice.The effect of pectinase on the juice yield of passion fruit was explored.Throμgh single factor experiment and orthogonal experiment optimization,the optimum enzymatic hydrolysis conditions were obtained as follows:pectinase addition amount 0.22%,enzymatic hydrolysis temperature50°C,enzymatic hydrolysis time 3.5 h.The juice yield of passion fruit was 67.89%,and the juice yield without pectinase was 40.50%.The difference was significant.Enzymatic hydrolysis can effectively improve the juice yield of passion fruit.2.Optimization of brewing process of passion fruit wine.The fruit juice obtained by enzymatic hydrolysis of passion fruit pulp was used as raw material.The fermentation broth of fruit juice wine was fruit juice with sterile water,and the fermentation broth of whole fruit wine was fruit juice with peel pulp.On the basis of single factor,the response surface optimization was carried out.The optimum fermentation conditions of passion fruit juice wine were as follows:yeast addition 0.04%,initial sugar content 21.5%,fermentation temperature 28.7°C,fermentation time 6 d,alcohol content 10.2%vol.The optimum fermentation conditions of passion fruit wine were as follows:yeast addition 0.03%,initial sugar content 20.6%,fermentation temperature 25.5°C,fermentation time 5 d,alcohol content 9.8%vol.Sensory quality analysis results:Juice wine was bright yellow,fruity,sour entrance;the whole fruit wine is uniform dark red with strong wine aroma.The intensity of’clarity’attribute was the highest in juice wine,and the intensity of’concentration’attribute was the highest in whole fruit wine.The overall score of whole fruit wine was higher than that of juice wine.3.Fermentation kinetics of passion fruit wine.The Dose Resp model,Logistic model,SGompertz model and Boltzmann model were used to fit the total sugar content,alcohol content and yeast growth in the fermentation process of passion fruit wine.The substrate consumption model,product generation model and cell growth model were established respectively.The model reflects the kinetic characteristics of the process of yeast fermentation to produce alcohol.The results showed that the Boltzmann model and the Dose Resp model had the highest fitting degree for the change of total sugar consumption during the fermentation of juice wine,R2=0.99682.The Dose Resp model had the highest fitting degree for the change of alcohol content,R2=0.99841;the fitting degree of Dose Resp model was the highest,R2=0.99796,and the above models could well describe the fermentation kinetic characteristics.The Logistic model,Dose Resp model and Dose Resp model were used to fit the nonlinear curve of the fermentation process data,and the kinetic model equations of substrate consumption,product formation and cell growth were established.The fitting coefficients of the three models were 0.99941,0.99882 and 0.99954,respectively,and the fitting degree was higher than 0.99,indicating that the dynamic changes of the whole fruit wine fermentation process can be well predicted.4.Antioxidant analysis of passion fruit wine.The antioxidant active substances in the fermentation process of passion fruit wine were detected and analyzed,and the changes of antioxidant properties were studied.The antioxidant capacity was evaluated by total phenol content,flavonoid content,DPPH free radical scavenging rate and Fe3+reduction ability.The results showed that the total phenol content,flavonoid content,DPPH free radical scavenging ability and Fe3+reduction ability of juice wine and whole fruit wine increased first and then decreased with the progress of fermentation,and the antioxidant activity showed a peak change during fermentation.The order of antioxidant activity was passion fruit juice>passion fruit>passion fruit wine>passion fruit juice wine. |
