Study On Fermentation Of Raspberry Juice By Lactic Acid Bacteria And Its Antioxidant And Antitumor Activities

Rubus corchorifolius L.is a shrub plant of the genus Rubus of Rosaceae.Raspberry fruit is sweet and juicy,which is rich in ellagic acid,flavonoids and other bioactive components.Raspberry fruit is very perishable after ripening,so it is very necessary to carry out deep processing of raspberry fruit.Fruit and vegetable juice with fermentation of lactic acid bacteria can not only increase the types of organic acids and aroma substances,but also improve its hypoglycemic,antioxidant and other health effects.In order to develop functional raspberry juice,the excellent functional lactic acid bacteria suitable for raspberry juice fermentation were screened and used to ferment raspberry juice in this study.The effects of technological conditions on raspberry juice lactic acid bacteria fermentation were studied.The antioxidant and anti-tumor properties of fermented raspberry juice were evaluated.The main conclusions are as follows:(1)A suitable strain of lactic acid bacteria was screened out for raspberry juice fermentation.Twelve strains of lactic acid bacteria were screened from five aspects of tolerance to simulated gastrointestinal environment,antibacterial activity,adhesion,antioxidation and inhibition of tumor cell activity.Five strains of lactic acid bacteria with good properties were obtained: Lactobacillus paracasei YJ1,YJ10,Lactobacillus rhamnosus SL,Lactobacillus plantarum T34,Lactobacillus acidipiscis YJ5.These five strains of lactic acid bacteria were used to ferment raspberry juice,among which Lactobacillus paracasei YJ1 had the strongest growth ability in raspberry juice.Therefore,Lactobacillus paracasei YJ1 is a suitable strain for raspberry juice fermentation.(2)The fermentation technology of raspberry juice was studied and its composition was analyzed by HPLC.Taking the viable count as the response value,the effects of fermentation temperature,fermentation time,the amount of inoculation,amount of sugar and initial pH on the fermentation process of raspberry juice were studied,and the process was optimized.The optimum fermentation process were shown as following: inoculation3%,sugar 6%,temperature 35 ?,time 65.6 h,initial pH 4.5,and the final viable count reached 9.71 log CFU/mL.After fermentation,the concentration of total phenols in raspberry juice increased by 18.58%,the concentration of flavonoids increased by 23.00%,the concentration of total acids increased significantly,and the types of organic acids and phenolic acids increased.The raspberry juice fermented by lactic acid bacteria tastes good.(3)Antioxidant function of fermented raspberry juice was evaluated in vitro.Compared with the raspberry juice without fermentation of lactic acid bacteria,the antioxidant activity of fermented red raspberry juice was significantly improved(P<0.05),and its 1,1-diphenyl-2-trinitrophenylhydrazine(DPPH)and hydroxyl free radical scavenging capacity increased by 35.13% and 25.08%,respectively.The total antioxidant capacities of fermented raspberry juice were determined respectively by the methods of 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid(ABTS)and Ferric ion reducing antioxidant power(FRAP),and its total antioxidant capacity of ABTS and FRAP increased by 36.31% and 39.48%,respectively.The contents of total phenols and total flavonoids in raspberry juice were positively correlated with the free radical scavenging ability of DPPH and ABTS and the total antioxidant activity of FRAP.In a word,compared with that of pre-fermentation,the antioxidant capacity of raspberry juice was significantly improved after fermentation.(4)Antitumor activity of fermented raspberry juice was evaluated in vitro.The cell activity was determined by Cell Counting Kit(cck-8)method to determine the effect of raspberry juice on human colon cancer cell HCT116,and the causes were further analyzed from three aspects: lactate dehydrogenase(LDH)release rate,cell cycle and apoptosis.It was found that raspberry juice with fermentation of lactic acid bacteria could inhibit the cell activity of human colon cancer cell HCT116 in a dose-dependent manner,and its IC50 of 17.047 ?L/mL.It could increase the release rate of lactate dehydrogenase(LDH)in a dose-dependent manner.It could block the cell cycle in G0/G1 phase and promote apoptosis.When the concentration was 16 ?L/mL,the apoptotic cells reached 66.37%.Compared with unfermented raspberry juice,fermented raspberry juice significantly improved the ability of inhibiting tumor cell activity,promoting lactate dehydrogenase release and promoting cell apoptosis.