Changes And Control On Quality Of Lactic Acid Bacteria Fermented Fruit And Vegetable Juice During Processing And Storage

Although many researches have proven the benefit of increasing nutrition value and functional properties of F&V juice after fermentation,Jiaosu has caused considerable controversy.This article singled out a lactic acid bacteria with better potential in fermenting F&V juice,then studied the influence of raw material varieties,the processing techniques of pretreatment,fermentation and post processing on the nutrition and sensory properties of fermented F&V juice,aiming at providing theoretical basis for the production of such product.(1)The acid resistance ability of Streptococcus thermophilus(ST),Lactobacillus bulgaricus(LB),Lactobacillus acidophilus(LA),Lactobacillus casei(LC),and Lactobacillus plantarum(LP)was: LP>LC>LA>LB?ST.Only LC and LP could grow and metabolize well when initial pH<4.0.Thus,LC and LP was picked for further screening.It was found that LP could adapt to wider range of carbon and nitrogen concentration than LC.Moreover,only LP could make use of sucrose.Adding soy protein could improve the growing and metabolizing ability of both LABs.Under comprehensive consideration,LP was selected as the best of the 5 in fermenting F&V juice.(2)10 kinds of fruits and vegetables was taken as materials to study the influence of LAB fermentation on their quality.The results showed that LP could increase 2~3 orders of magnitude in F&V.LAB fermentation could maintain or even improve the antioxidant activity of F&V juice: Total phenol and ·DPPH scavenging ability had a positively significant correlation(p<0.01)with each other,and mainly depended on the value of fresh F&V juice;SOD-like value of F&V juice had a 14%~55% increased after fermentation.In terms of sensory properties,LAB fermentation could enhance the overall strength of flavor and reduced warmed-over flavor;it had a positive effect on F&V juice with intensive and acid flavor,while had negative effect on those with weak and sweeter flavor.Taking antioxidant activity and sensory ability into account,orange juice was selected as material of the following researches.(3)Orange juice respectively pretreated with heat and HPP was taken as materials to study the influence of different pretreatments on the quality of LP fermented orange juice during fermentation and storage.After pretreatment,antioxidant activity of HPP orange juice was higher than heated orange juice.During fermenting process,compared with unfermented juice,LP fermentation could better maintain antioxidant activity.Pretreatment mainly affected the initial value.SPME-GC-MS detection proved that LP fermentation consumed nonanal,so warm-over odor was reduced;the specific fermentation flavor was mainly contributed by Vanillyl alcohol,Geraniol,Undecanone ?-Pinene and ?-Phellandrene;HPP pretreatment could better maintain characteristic flavors of orange juice.During storage,the reduction speed of ·DPPH scavenging ability and SOD-like value were significantly slower in those pretreated by HPP than those pretreated by heat.Thus,HPP pretreatment could better maintain antioxidant activity during both fermentation and storage.(4)The higher the storage temperature,the quicker the viable LAB dropped and the fewer viable LAB could stably sustain;based on the fitted curve,viable LP could stay above 106 CFU/mL if stored below 15?.Oxygen was the major factor that led to deterioration of antioxidant substances,and light also speed up such process.Post processing had limited influence on the quality of fermented orange juice during storage,but the control group(viable type)could better sustain total phenol,·DPPH scavenging ability and SOD-like value,as well as the orange color,showing the advantage of probiotic fermented juice in sustaining antioxidant activity.