Study On The Technology And Aroma Change Of Jujube Juice Fermented By Lactobacillus Plantarum

The fermentation of fruit and vegetable juices by probiotics was a new nutrition food with health care function,which also caters to the needs of vegetarians,lactose intolerance and people with high cholesterol,showing a good development momentum.Jujube(Ziziphus jujube Mill.)is rich in nutrients such as sugar,fat,protein and cellulose,which is a good substrate for lactic acid bacteria fermentation.In this study,jujube juice was used as experimental material to explore the effects of enzyme hydrolysis(EH)and sterilization on the quality of fermented jujube juice,and the release rule of glycosidically bound volatiles(GBVs)of jujube juice fermented by Lactobacillus plantarum CICC 20022(L.plantarum CICC 20022),in order to provide reference for the production of jujube juice fermented by lactic acid bacteria.1.The effects of enzymatic hydrolysis(EH)pretreatment on some physicochemical and nutritional properties of jujube juice fermented with L.plantarum CICC 20022 were evaluated,jujube juice with non-enzymatic hydrolysis(NEH)was used as control.The results showed that viable counts were greater than 8.80 lg CFU/m L with or without EH group jujube juice after fermentation.However,the survival rate of L.plantarum CICC 20022 in NEH group jujube juice was significantly higher than that in EN group during 28 d of storage at 4 ?(P<0.05).Meanwhile,EH effectively improved the stability of fermented jujube juice during storage.In the detection results of Electronic nose(E-nose),the types of aroma compounds corresponding to the three sensors W1 S,W1W and W2 W are the main aroma components of jujube juice,and the response values(G/G0)of W1 S,W1W and W2 W in EH group jujube juice are increased by 37.50%,46.08%and 51.51% respectively compared with NEH group jujube juice;the contents of total phenols,flavonoids,reducing sugars,minerals(K,Mg,Zn,Fe)and organic acids(tartaric acid,formic acid,ascorbic acid,lactic acid,acetic acid and citric acid)in the EH jujube juice were significantly higher than those in the NEH jujube juice(P<0.05).Therefore,EH treatment prior to L.plantarum CICC20022 fermentation could improve the contents of aroma,total phenols,flavonoids,reducing sugar,minerals and organic acids in fermented jujube juice.2.Evaluate the jujube juice treated by four different sterilization treatments as substrates for producing a probiotic beverage fermented by L.plantarum CICC 20022: sterilization by autoclaving(SA at 0.1 MPa,121°C,and 20 min),pasteurization(PS at 85°C,30 min),cold plasma sterilization(CPS at 700 W,120 s)and pulsed strong light sterilization(PLS at 1.0 Hz,600 J,and10 times),while jujube juice without sterilization treatment used as control(CK).The results showed that the growth ability of L.plantarum CICC 20022 in jujube juice was not affected by different sterilization treatments.After SA and PS treatment,the particle size of jujube juice increased by 440.51% and 222.29%,respectively,and the reducing sugar content decreased by33.83% and 24.51%,respectively.Compared with SA,PS and CPS treatments,PLS was beneficial to improve the stability of jujube juice,and tartaric acid content in jujube juice was significantly increased after CPS treatment.There was no significant difference in sensory and nutritional quality between PLS treated jujube juice and control,and the color of PLS treated jujube juice was significantly better than that of the other three sterilization treatments.Therefore,PLS treatment is expected to be a sterilization method for processing fermented jujube juice.3.Electronic nose and head space-solid phase microextraction-gas chromatography mass spectrometry,HS-SPME-GC-MS)were used to study the effects of L.plantarum CICC 20022 fermentation on free aroma compounds in jujube juice.At the same time,the release regularity of GBVs in jujube juice by three treatment methods of ?-D-glucosidase enzymolysis,acidolysis and ultrasound was compared,as well as the changes of intracellular and extracellular ?-D-glucosidase activity during the growth of L.plantarum CICC 20022.The results showed that the content of the main aroma compounds such as nonanoic acid,lauric acid,stearic acid,myristic acid,ethyl nonanoate,ethyl tetradecanoate,dibutyl phthalate,2,4-dimethyl-Benzaldehyde,benzaldehyde,benzyl alcohol and damascenone increased after L.plantarum CICC 20022 fermentation,respectively.At the same time,new aroma compounds such as palmitic acid isopropyl ester,citral,geranyl acetone,geraniol,(+)-cedrol and acetophenone were detected in fermented jujube juice,respectively.There had 20,25 and 36 kinds of aroma compounds were released from jujube juice after ultrasonic treatment(280 W,30 min),acidolysis(p H 1.0,38?,4 d)and ?-D-glucosidase treatment(38?,48 h),respectively,and among which phenols,alcohols and acids were the main aroma compounds.According to the content of released aroma compounds,ethyl nonanoate,ethyl myristate,benzaldehyde and benzyl alcohol only existed in ?-D-glucosidase treatment group.L.plantarum CICC 20022 is a strain producing ?-D-glucosidase,and the ?-D-glucosidase activity in fermentation broth is positively correlated with the biomass of L.plantarum CICC 20022.Therefore,the release of endogenous ?-D-glucosidase from L.plantarum CICC 20022 to GBVs in jujube juice can improve the aroma contour of fermented jujube juice.