Inhibitory Effect Of Fermented Jujube Juice On Obesity In High-fat Diet Mice

Jujube has high nutrition and health value,and it is a peculiar medicine and food fruit resource in China.China has abundant jujube resources,and its output of jujube has reached 9 million tons in 2019,accounting for 99%of the world's total output.At present,the processed products of jujube on the market are mainly dried ones with laggard producing style and low added values,while other deep-processed products are few.Lactic acid fermentation is an important way to improve the flavor and nutritional value of products,and it has become a new way for deep processing of fruits and vegetables.However,few research have been done on the fermentation of jujube juice by lactic acid bacteria,which can not only improve the development and utilization level of jujube resources,but also provide new ideas for the development of functional jujube products.In this study,dried jujubes were used as raw materials,and a symbiotic effect of yeast and lactic acid bacteria was used to prepare an inactivated fermented jujube juice that is resistant to storage,high in nutritional value and excellent in sensory quality.The main metabolites and their precursors in jujube juice before and after fermentation were analyzed based on metabolomics.In addition,the effect of fermented jujube juice on the obesity of mice induced by high-fat diet was investigated by the experiment of mice administering.This research is divided into three parts,and the results obtained are as follows:1.Co-fermentation of jujube juice by yeast and lactic acid bacteria and analysis of qualities during its storageYeast and lactic acid bacteria were used to synergistically ferment jujube juice.Based on the analysis of color difference,clarity,and sensory quality,the optimal conditions for fermented jujube juice were choosed as follows:0.1%yeast,fermentation at 37? for 10 hours,1%lactic acid bacteria(Lactobacillus plantarum:Lactobacillus acidophilus=2:1),fermentation at 37? for another 30 hours.After the fermentation,the jujube pulp was centrifuged,filtered and sterilized,then the inactivated fermented jujube juice was obtained.The original and fermented jujube juice were stored at 37? in the dark for 12 weeks,and their quality changes during the storage were analyzed.The results showed that the pH and acidity of the original and fermented jujube juice did not change significantly during their storage,while the color,clarity,total phenol contents,FRAP values,and DPPH free radical scavenging rates all decreased,and the change of quality of the original jujube juice was significantly higher than that of fermented one.2.Metabolomics of fermented jujube juiceJujube is rich in biologically active ingredients.However,at present,it is not clear about the changes in the chemical composition during the fermentation of jujube juice.In this study,UHPLC-QTOFMS was used to comprehensively analyze the changes of metabolites in jujube juice after the fermentation.A total of 43 1 significantly different metabolites were screened,including 8 flavonoids,16 amino acids,18 organic acids,and 5 sugars.The results of metabolic pathways of differential metabolites showed that metabolic pathways with significant effects are:?-alanine metabolism,nicotinate and nicotinamide metabolism,flavone and flavonol biosynthesis,isoquinoline alkaloid biosynthesis,starch and sucrose metabolism and tyrosine metabolism.Based on this,a metabolic map of some compounds was drawn,providing a general overview of the changes in metabolites during the fermentation of jujube juice.3.Effect of fermented jujube juice on obesity induced by high-fat diet in miceThe main functional compounds in fermented jujube juice are quercetin and luteolin,and quercetin has the effect of reducing fat and losing weight.Therefore,this part aims to study the inhibitory effect of fermented jujube juice with different doses on obesity induced by high fat diet in mice.Fifty mice were randomly divided into 5 groups:control group,high-fat group,low-dose control group,low-dose and high-dose high-fat group,with 10 in each group.Thirteen weeks after gavage,the serum biochemical indicators of the mice and the abundance of the intestinal flora were measured.The results showed that compared with the high-fat group,the total cholesterol(TC),low-density lipoprotein cholesterol(LDL-C)and triglyceride(TG)in the low-dose high-fat group and high-dose high-fat group were significantly decreased(P<0.05),and high-density lipoprotein cholesterol(HDL-C)all increased(P<0.05).At the phylum level,compared with the high-fat group,F/B levels in the intestine of mice in the high-dose high-fat group significantly decreased,and the low-dose high-fat group had a higher level of verrucomicrobia.At the genus level,the Akkermansia content in the low-dose high-fat group was significantly higher than in the other four groups.In summary,fermented jujube juice can effectively regulate the lipid metabolism and intestinal flora of high-fat diet mice to prevent obesity.