| Using papaya juice as a raw material,the degradation process of pigment was explored,and the degradation kinetics equation was established.The color protection tests were carried out.The quality changes at different fermentation stages were investigated in papaya beverages by different lactic acid bacteria strains.Finally,the fermented beverage formulation was improved and its stability was examined.In this paper,the conclusions are as follows:(1)The Lab value,browning index A420 and the content of Vc,?-carotene,total phenol,and lycopene in papaya juice were measured.The Pearson correlation analysis showed that the content of lycopene was significantly positively correlated with the a*value(R2 = 0.950,P<0.01).The lycopene degradation process was analyzed to obtain the degradation kinetics fitting equation:3/2(1-(1-DL)2/3)-DL =-8 x l0'8t3 + 9 x 104-6t2+ 0.0006t-0.0005(R2 ?0.9994).This fitted curve equation fits the kinetics of degradation of lycopene in papaya juice.The DL value is used as a measure index,and the regression equation is analyzed with SAS language to obtain the best color protection scheme:The Vc concentration was 0.19 mg/g,the maltodextrin concentration was 0.32 mg/g,and the citric acid concentration was 3.62 mg/g.Under this condition,the DL value is 25.91%.(2)The physiochemical properties and antioxidant activities had changed significantly during the 48 h fermentation of papaya juice by different lactic acid bacteria strains.After 48 h fermentation,the pH of the fermented papaya juice by Directed Vat Set(FPJD)was decreased from 5.36 to 3.11,and the pH of the fermentated papaya juice by Lactobacillus plants(FPJP)and Lactobacillus acidophilus(FPJA)decreased to 3.55 and 3.60,respectively.The content of flavonoid increased significantly.A large number of organic acids that are beneficial to human health were produced,such as lactic acid,acetic acid,and succinic acid,etc.The antioxidant capacity of the fermented papaya beverages was evaluate by four different assays,including DPPH,ABTS,FRAP and CUPRAC.The results showed that the antioxidant capacity of FPJP increased,while the FPJA and FPJD decreased to varying degrees.Therefore,L.plantarum was found to be more suitable for fermentation by comparison.(3)The volatile components in fermented papaya juice were tested.The results showed that the ingredients included acids,alcohols,esters,aldehydes,ketones,alkanes,and phenols.The volatiles of papaya juice changed signigicantly after fermentation.There were some difference between the fermentation products by three cultures.Linalool is the main aromatic compound in papaya fruit.The 17 kinds of volatile compounds were selected for principal component analysis,such as linalool.The statistical analysis of variables was used a correlation matrix which calculated by software SPSS V17.0.This data can be selected for extraction analysis,because the cumulative contribution rate of principal components is 100%.It can be distinguished by PC2 and other fermentation products due to the high content of acetic acid in the fermentation product of FJPA.(4)The best formulation process and parameters are determined.The sensory analysis was used as an indicator.The single factor test was conducted using the fermentation broth,white sugar,citric acid and lactic acid as the main factors.And the formula was optimized by response surface test.The best formula of FPJP is the amounts of fermentation broth,white granulated sugar,citric acid,and lactic acid were 63.54%,9.10%,0.25%,and 0.22%,respectively.(5)The best stabilizer formulation was determined.The precipitation rate was used as an indicator.The single factor test as the basis,the best stabilizer formula was obtained by the response surface optimization test.When the amount of CMC added was 0.20%,the amount of PGA added was 0.19%,and the amount of pectin added was 0.08%,the minimum sedimentation rate of the beverage was measured.At this time,the stability of the fermented papaya beverage by L.plantarum was the best. |
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