| Chinese yam,purple cabbage,tomato and carrot as the main raw materials,active dry yeast and selected Lactobacillus plantarum were used as fermentation agents to study the production process of compound vegetable juice,and the production process parameters were optimized.Sixty-eight strains were screened from commercial kimchi by BCG bovine milk medium.After isolation and purification,ten strains were rescreened in MRS medium supplemented with calcium carbonate by a transparent circle method.According to a series of identification methods such as colony morphology,bacterial characteristics,physiological and biochemical experiments and 16S rDNA analysis,a strain as Lactobacillus plantarum numbered Y3-2 was screened.Based on the DE value,the effects of liquefaction enzyme addition,liquefaction temperature,liquefaction time,saccharification enzyme addition,saccharification temperature and saccharification time on the DE value during liquefaction and saccharification of yam were studied.The single-factor and orthogonal tests were utilized to optimize the liquefied and saccharified conditions of Chinese yam.And the test results showed that the optimum conditions of liquefaction enzyme addition,liquefaction temperature,liquefaction time were found to be 60 min,95℃,2 U/g,respectively.And the optimum conditions of saccharification enzyme addition,saccharification temperature and saccharification time were found to be 3 h,60℃,200 U/g.Under these conditions,the DE value was 3.96%vol.The effects of fermentation time,fermentation temperature and inoculum on the fermentation process were studied by using alcohol as the index.The fermentation conditions were optimized by single factor and orthogonal experiments.The optimum fermentation conditions of fermentation time,fermentation temperature,inoculum volume were found to be 20 h,30℃,2‰,respectively.Under these conditions the alcohol content was 3.96%vol.The effects of different colour fixativess on vegetable color protection at different concentrations were studied.The chromatic aberration,absorbance residual rate and residual activity of POD were investigated to determine the best colour fixative and its concentration.The carrot was preserved with 0.4%citric acid solution,the tomato was treated with 0.5%ascorbic acid solution,and the 1.0%ascorbic acid solution was selected to protect the purple cabbage.The effects of blanching temperature and blanching time on the inactivation of enzymes in vegetables were studied with POD residual activity as the index.The results showed that the optimum blanching temperature for carrots was 90℃and blanching time was 60 s,the optimum blanching temperature for tomatoes was 95℃and blanching time was 90 s,the optimum blanching temperature for purple cabbage was 90℃ and blanching time was 60 s.The effects of inoculation amount,fermentation temperature and fermentation time on total acid content in vegetable juice during fermentation were studied.The fermentation conditions of vegetable juice were optimized by single factor and response surface design,and the regression model was established.The results showed that the optimum fermentation conditions were inoculation 4.2%,fermentation temperature 35 ℃ and fermentation time 80 h.Under these conditions,the average total acid content was 11.74 g/L.The formulation of vegetable juice beverage was studied by sensory evaluation.According to response surface analysis,the optimum proportion was yam juice 12.0%,sugar 9.0%and jujube juice 8.0%.The mixed vegetable juice was analyzed by GC-MS.A total of 44 volatile components were detected,including 17 esters,11 olefins,7 alcohols,4 alkanes,3 ketones,1 aldehydes and 1 aromatic.The main volatile component was isoamyl acetate,which accounted for 22.21%in the total aroma components.The amino acid analysis of mixed vegetable juice beverage showed that 11 kinds of amino acids were detected,including 5 essential amino acids for human body.The total content of amino acids in mixed vegetable juice was 1.43 mg/mL. |
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