Analysis Of Jujube Lactic Acid Fermented Juice Rich In γ-aminobutyric Acid And Its Functional Components

Jujube is a medicinal and food homologous food,rich in nutrients and contains sugars that can provide favorable conditions for the fermentation of lactic acid bacteria.In this study,Jujube was used as raw material to screen out the most suitable strains for jujube juice fermentation.Studied the optimal conditions and process optimization of high GABA yield of jujube juice fermented by lactic acid bacteria,analyzed the dynamic changes of physical and chemical indexes and nutrient components in the fermentation process,and explored the changes of aroma components and the stability of fermentation liquor storage.The purpose is to develop GABA jujube juice lactic acid bacteria beverage with good export sense,good flavor,containing active probiotics,purely natural fermentation,in order to increase the value of jujube products and promote the development of jujube industry.Obtained the following results:1.After screening,Lactobacillus plantarum and Lactobacillus brevis were selected as fermentation strains.Single factor test and orthogonal optimization test were used to determine the monosodium glutamate addition amount as 5 g/L,Lactobacillus plantarum and Lactobacillus brevis instillation amount as 4%,respectively.The fermentation was 60 h at 37℃,and the content of GABA in the fermentation broth was 215.71 μg/mL.2.Single factor experiment and box-behnken design were used to optimize the nutritional components of jujube juice matrix to increase the yield of GABA.The results showed that when the addition of whey powder was 11 g/L,the addition of magnesium sulfate was 0.4 g/L,and the addition of dipotassium phosphate buffer was 15 g/L,the soluble solid was 20%,the content of GABA in the fermentation broth was 412.54 μg/mL,which was significantly higher than that before the optimization.3.After fermentation,the total acid content of jujube juice improved by 15.45 g/L,while the reducing sugar content decreased by 67.92 g/L.During the fermentation process,the total phenol content increased first and then decreased.Using HPLC to determine the changes of organic acids during fermentation,eight kinds of organic acids were detected before fermentation of jujube juice.Oxalic acid,lactic acid and acetic acid were the main organic acids in jujube juice.Nine kinds of organic acids were detected after fermentation.After fermentation,the content of lactic acid and malic acid increased significantly,while the content of oxalic acid,quinine and citric acid decreased,and fumaric acid also increased.4.After jujube juice was fermented by lactic acid bacteria,the total amount of amino acids was 1423.1 mg/100g,an increase of 932.74 mg/100g compared with before fermentation.The composition of flavored amino acids changed significantly,in which the content of sweet amino acids increased by 422.41 mg/100g and the content of umami amino acids increased 503.64 mg/100g,bitter amino acids and aromatic amino acids have almost no change before and after fermentation.After fermentation,the antioxidant activity of ABTS,DPPH and hydroxyl radicals are all improved.In vitro antibacterial test showed that the antibacterial activity of jujube juice increased significantly after fermentation,and the order of antibacterial activity against pathogenic microorganism strains was:E.coli>S.typhimurium>S.aureus.5.Using GC-MS analysis apparatus aroma composition before and after fermentation,jujube juice after fermentation of alcohols,acids,aroma substances are significantly increased,among them 2-heptene acid,docosahexaenoic acid,n-decanoic acid,9-decanoic acid,2-octene acid five acids aroma substances are produced by fermentation,ketone substance increases slightly,the relative contents of esters,aldehydes scent.6.The stability of jujube juice after lactic acid fermentation was studied.In the low temperature storage of 4℃ for 21 d,the jujube juice beverage could maintain uniform taste and uniform color and taste good.After the storage time exceeded 21 d,the fermentation broth of jujube juice had a sour taste and poor overall acceptability.Therefore,the optimal storage time was within 21 d when the number of viable bacteria was 7.4 logcfu/mL,the total acid content was 21.07 g/L and the pH was 3.19.