Study On The Antioxidant Peptides Of Products Fermented From Different Base Of Goat Milk And Its Functionalities

The good effects of food-derived antioxidant peptides substance in health promotion and disease prevention are being increasingly recognized.Recently,there has been a particular focus on milk-derived peptides,dairy products and milk are potential sources of antioxidant peptide.A large number of research literature showed that there are some lactic acid bacteria can ferment milk or dairy products(milk,whey powder),in the process can produce a few small molecular peptides,including a kind of peptide with strong antioxidant activity.At present the preparation main method of antioxidant peptides from milk protein source focuses on enzyme hydrolysis,using fermentation research less,and the preparation of antioxidant peptides from different goat milk base about fermented method using lactic acid bacteria has few been reported.In this study,the radical scavenging capacity and the degree of hydrolysis(DH)as an index,aiming at high antioxidant peptides,using the screen strains of bacteria and commercial strain compounded of formed into 2 compound strains with synergy good.Use the compound strains fermenting goat milk whey and goat milk,and optimized the fermentation condition of the preparation of antioxidant peptides respectively,and compared the base merits.On this basis,the antioxidant activity and stability of the fermentation products were studied with five indexes.And the fermented products were separated and purified by ultrafiltration,gel chromatography,and the antioxidant functions were evaluated.At the same time,the optimum process parameters of fermented goat milk with this compound strains were studied,in order to obtained goat yogurt with strong antioxidant activity provide certain technical reference.Main conclusions are as follows:(1)From 4 strains of lactic acid bacteria strains selected 1 plant lactobacillus(LPGY-L086)formed compound strains with thermophilic strains streptococcus(ST,Yo-Mix 300)of the commercial strains.As cultures fermented different goat milk bases.(2)Using the response surface and orthogonal experiment,optimization of fermentation conditions of goat milk whey and goat milk.Got the best condition of fermented goat whey as follows: the inoculation quantity was 4%,LPGY-L086 and ST bacteria mix ratio was 1:1,fermentation temperature was 42 ?,fermentation time was 16 h,under this condition,DPPH and ?OH clearance rate of the fermentation products was 54.57% and 67.13% respectively.Got the best condition of fermented goat milk as follows: inoculum was 3%,fermentation temperature was 42 ?,fermentation time was 24 h,LPGY-L086 and ST bacteria mix ratio was 2:1.Under this condition,DPPH and ?OH clearance rate of the fermentation products was 70.03% and 88.42% respectively.In contrast to antioxidant activity,goat milk base was better than the goat whey base.(3)The antioxidant capacity was evaluated with five indexes: DPPH removal ability,?OH removal ability,Fe2+ chelating ability,reducing power and total antioxidant capacity.The research showed that antioxidant activity of goat milk after fermented were significantly higher(P < 0.05)than before fermented,and there is positive dose effect relationship,and Fe2+ chelating ability was better than VC.(4)This paper use ?OH clearance ability and reducing power evaluated the stability of the goat milk fermented product.The results showed:(1)Under the condition of within the scope of 20 to 80 ?,normal temperature conditions to join different sugar,pH was around 6.0,NaCl concentration < 4%,K + and Ca2 + the ?OH clearance ability of the goat milk antioxidant peptides were generally stable.However,high temperature,strong acid or alkaline environment,5% NaCl,adding Fe2+,Cu2+,Fe3+ and simulated gastrointestinal digestive system had adverse effect on ?OH scavenging ability,and the influence degree is not the same.(2)The reduction ability as index,pH value,high temperature,add different sugar under different environment,add a certain amount of K+,Ca2+ and simulated gastrointestinal digestion had not significant influence on reduction ability;but add 5% NaCl and a certain amount of Cu2 +,Fe2 + and Fe3 + had adverse effect on the reduction ability.(5)The goat milk fermented product was ultrafiltrated by ultrafiltration membranes with the molecular cut off of 6 kDa.The optimum conditions was as follows: the pressure was 0.4 MPa,the time was 10 min,and the liquid temperature was about 25?.The result shows: the component of FA(molecular weight < 6 kDa)had higher antioxidant activity.The component was separated and purificated by Glucan gel chromatography G-25 and Glucan gel chromatography G-15,finally obtained the component FA-3-2 with higher antioxidant activity.(6)The optimum technological for the preparation of goat milk fermented milk product were: strain ratio(LPGY-L086 : ST)of 1:1,the inoculation quantity was 4%,fermentation temperature was 42 ?,fermentation time was 5.5 h,the taste of goat yogurt is best,and its Clearance ability of ?OH and DPPH and chelating ability of Fe2+ was 89.85%,85.30% and 20.76%,respectively.Storage test showed that 4 ? under the condition of the best,the indicators are in good condition,after 30 d storage number of living bacterium still comply with the requirement of national standard(>106 CFU/m L),and forced the ?OH clearance rate remained above 75%.