Preparation, Flavor Compounds And Antioxidant Activity Of Plant Yogurt

Three kinds of plant yogurt and starter culture were prepared in this paper, andtheir physicochemical properties, flavor compouds and antioxidant activity werestudied, main conclusions were as follows:Single experiment, Box-Behken experiment and orthogonal test were used toproliferating Lactobacillus delbrueckii subsp bulgaricus1.1480(Lb) andLactobacillus acidophilus ys14(St), separately, determining the centrifugation conditionand blending cryoprotectants. Results showed that the adding concentration of proliferatingfactors of vitamin D, serine and sodium tripolyphosphate were0.21mg/L,10.39mg/L and143.06mg/L separately, centrifugation time was15min, ratating speed was6000rpm,temperature was4℃for Lb. The adding concentration of proliferating factors of vitamin D,serine and sodium tripolyphosphate were0.21mg/L,9.47mg/L and150.41mg/L separately,centrifugation time was10min, ratating speed was8000rpm, temperature was4℃for St.On the basis of skim milk solution with the concentration of15%, sugar: sorbierite:Twain80=3:2:1were used as cryoprotectants for Lb and St, the survival rate for Lb and StweSingle experiment, Box-Behken experiment and orthogonal test were used toproliferating Lactobacillus delbrueckii subsp bulgaricus1.1480(Lb) andLactobacillus acidophilus ys14(St), separately, determining the centrifugation conditionand blending cryoprotectants. Results showed that the proliferating factors of Lb and Stwere vitamin D, serine and sodium tripolyphosphate, adding concentration of Lb and Stwere0.21mg/L,10.39mg/L,143.06mg/L and0.21mg/L,9.47mg/L and150.41mg/Lrespectively. Centrifugation conditions of Lb and St: centrifugation time was15min,ratating speed was6000rpm, temperature was4℃and centrifugation time was10min,ratating speed was8000rpm, temperature was4℃. On the basis of skim milk solution withthe concentration of15%, sugar: sorbierite: Twain80=3:2:1were used as cryoprotectants forLb and St, the survival rate for Lb and St were83.3%and84.2%respectively. Freezingenrichment starter made by the above scheme has good fermentation ability.Three kinds of plant yogurt were prepared and freezing enrichment starters of Lb andSt were inoculated, the optimal fermentation of the yogurts were as follows:(1) walnutyogurt (WMY), the volume proportion of walnut milk and reconsititue milk was3:7, concentration of fructooligosaccharid and sodium caseinate were9.79%and0.98%,sterilization time and temperature was95℃20min, inoculum concentration was2.52g/L,fermentation time was6h, fermentation temperature was42℃, the sensory score of WMYwas89.56.(2) black soybean yogurt (BMY): the volume proportion of walnut milk andreconsititue milk was4:6, concentration of fructooligosaccharid and sodium caseinate were10.06%and1.36%, sterilization time and temperature was95℃20min, inoculumconcentration was2.50g/L, fermentation time was6h, fermentation temperature was40℃,the sensory score of WMY was87.95.(3) walnut-black soybean yogurt (WBMY): thevolume proportion of walnut milk and reconsititue milk was4:6, concentration offructooligosaccharid and sodium caseinate were9.09%and1.43%, sterilization time andtemperature was95℃20min, inoculum concentration was2.51g/L, fermentation time was6h, fermentation temperature was42℃, the sensory score of WMY was91.78.Compared with their raw milks, fat content of three yogurts were decreased, but ashcontent, total solid content, non-fat solid content and crud protein content were increased.Content of every amino acid in WBMY was significantly higher than that of WMY, BMYand CMY (P<0.05). Apparent viscosity of WBMY was significantly higher than CMY(P<0.05), viscosity of WMY and BMY has no significant difference (P>0.05), butsignificantly higher than that of CMY (P<0.05).31,30,31and28kinds of volatilecompounds including aldehydes, ketones, acids, a small amount of alcohols and esters wereidentified in WMY, BMY, WBMY and CMY, respectively. No2-pentylfuran was detectedin WMY, no2-ethylfuran and p-xylene were detected in BMY, no2-ethylfuran wasidentified in WBMY, and no butyraldehyde, ethyl acetate,2-pentylfuran and2-ethylfuranwere detected in CMY. Content of protein and fat, the total count of lactic acid bacteria inthe three yogurts showed the declining trend during the1-20days’ storage time, but theirsusceptibility to syneresis and acidity showed the rising trend.Antioxidant activity of yogurt was assessed by scavenging DPPH· and·OH, inhibitinglipid peroxidation and chelating Fe2+. Results showed that, scavenging ability in reletion toDPPH· and·OH, inhibiting ability in reletion to lipid peroxidation and chelating ability inreletion to Fe2+of WBMY was all higher than those of the other two yogurt and controlyogurt, it suggested that, the antioxidant activity of WBMY was the strongest among thethree yogurts, then it was BMY, antioxidant activity of WMY was the lowest, butantioxidant activity of all these three yogurts were higher than that of CMY.