The Effects Of Fermentation On Functional Properties And Glycometabolism Of Wholegrain Yogurts

Yogurt was a nutritious fermented dairy product,while the yogurts sold on the market were mainly whole-fat yogurts,and high sugar content,which were not suitable for people with diabetes and those who need to control their weight.The historical researches showed that wholegrains were rich in dietary fiber,vitamins,phenols and other functional components,the starch rich in wholegrain could improve the structure in the yogurt,and the starch could form resistant starch or detrin with physiological function under certain conditions.In this paper,the wholegrain yogurts were prepared with yam,barley,red bean,juglans regia,black sesame,and milk powder.The effects of the fermentative on the basic physical and chemical properties,rheological properties,antioxidant activity,anti digestive properties and glycometabolism of wholegrain yogurts were studied.The main results were as follows:Firstly,under the condition of mixed fermentation of XPL-1 and LGG(Lactococcus lactis subsp.cermoris,Lactococcus lactis subsp.lactis,Lactococcus lactis subsp.lactisbiovar diacetylactis,Leuconostoc mesenteorides subsp.cremoris,Streptococcus thermophilus and Lactobacillus rhamnosus),with 1.5%yam and 1.5%barley as fixture,1.5%of juglans regia,red bean and black sesame as variables to prepare low-fat low-sugar wholegrain yogurts with a total solid of 16.5%.The pH,acidity,water holding capacity,rheological properties,sensory evaluation,antioxidation,anti digestibility and total calorie of yogurts were studied with whole-fat yogurt,low-fat yogurt and skimmed yogurt as control groups.The results showed that compared with pure yogurts(P<0.05),the pH values of wholegrain yogurts were lower,the water holding capacity were equal to the skimmed-yogurt,the texture were loose and soft,and the overall acceptability were good,in which the overall acceptability of the low-fat yogurt added yam,barley and red bean and the low-fat yogurt added yam,barley and black sesame were as same as the whole-fat yogurt.The application of wholegrains could significantly increase the antioxidant activity of yogurts,and the ability of scavenging ABTS free radical,DPPH radical and reduction of trivalent iron ions by the low-fat yogurt added yam,barley and red bean were 1.13 mmol/L,246 mol/L and 294μmol/L.After simulated in vitro digestion,the value of glucose in wholegrain yogurts were much lower than that of the theoretical value.The value of glucose in wholegrain yogurts were only 50.2%~78.8%of the theoretical value.In addition,the total calories of wholegrain yogurts were between 251.96 to 283.09 kJ/100g,far below the total calories of 420.16 kJ/100 g provided by whole-fat yogurt.Secondly,under the condition of Lactobacillus amylolyticus L6 fermentation(CGMCC NO.9090),with 1.5%yam and 1.5%barley as a fixture,1.5%of juglans regia,red bean and black sesame as variables to prepare low-fat low-sugar wholegrain yogurts with a total solid of16.5%.The p H,acidity,water holding capacity,rheological properties,antioxidation and anti digestibility of yogurts were studied with low-fat yogurt as control group.The results showed that compared with pure yogurts(P<0.05),the p H values of wholegrain yogurts were lower,the acidity and the water holding capacity were higher and the texture were loose and soft.The application of wholegrains could significantly increase the antioxidant activity of yogurts,and the ability of scavenging ABTS free radical,DPPH radical and reduction of trivalent iron ions by the low-fat yogurt added yam,barley and red bean were 1.01 mmol/L,199 mol/L and 367μmol/L.After simulated in vitro digestion,the value of glucose in wholegrain yogurts were much lower than that of the theoretical value.The value of glucose in wholegrain yogurts were only 52.6%~64.9%of the theoretical value.Thirdly,under the fermentation of XPL-1 and LGG or Lactobacillus amylolyticus L6,the wholegrain powders were prepared with 4.5%yam,barley and red bean.The glycometabolism,antioxidation and anti digestibility of wholegrain powders were studied.The results showed that XPL-1 and LGG fermentation could decompose glucose and maltose,produce lactate,acetate and mannitol,the acidity values of the fermented yam,coix seed,red bean and their mixtures were 48.18 ~oT,57.48 ~oT,87.15 ~oT and 51.75 ~oT.Lactobacillus amylolyticus L6fermentation could decompose glucose and amylopectin in wholegrain powders,produce lactate and maltose,the acidity values of the fermented yam,coix seed,red bean and their mixtures were 96.67 ~oT,110.90 ~oT,156.75 ~oT and 99.49 ~oT.After the simulated digestion in vitro,the glucose value of the barley was 84.4%of the theoretical value,the glucose value of the barley fermentated by XPL-1 and LGG was 77.3%of the theoretical value,the glucose value of the barley fermentated by Lactobacillus amylolyticus L6 was 46.0%of the theoretical value.In summary,low-fat and low-sugar yogurts prepared with wholegrain were well structured,unique in flavor,antioxidant and anti digestion,suitable for diabetic patients to drink and to meet the needs of healthy people for low calorie food.