Study On The Quality,Biological Activity And Mechanism Of Plant Fermented Milks

In this paper,four types of fermented milk were prepared,and the physicochemical properties,flavor compounds,antioxidant activity,hypoglycemic and hypolipidemic activity of fermented milk were studied,the mechanism of hypoglycemic and hypolipidemic was also revealed.The optimal conditions of plant fermented milks were explored by single-factor and Box-Behnken experimental design methods:?1?Kiwifruit fermented milk?KFM?:kiwifruit juice 8%,maltooligosaccharide 8.90%,sodium caseinate 0.52%,inoculum concentration 0.14 g/L,fermentation time 5 h,fermentation temperature 44?;?2?Bitter gourd fermented milk?BFM?:Bitter gourd juice 4%,maltooligosaccharide11.21%,sodium caseinate 0.48%,inoculum concentration 0.21 g/L,fermentation time 5h,fermentation temperature 45?;?3?Kiwifruit-bitter gourd fermented milk?KBFM?:kiwifruit juice 10%,maltooligosaccharide 10.97%,sodium caseinate 0.69%,inoculum concentration 0.13 g/L,fermentation time 4 h,fermentation temperature 44?;?4?Control fermented milk?CFM?:maltooligosaccharide 7.19%,sodium caseinate 0.31%,inoculum concentration 0.26 g/L,fermentation time 6 h,fermentation temperature45?.Under the above condition,the sensory scores of the fermented milk were 90.16,89.33,91.25 and 87.82,respectively.The viable count of KFM,BFM and KBFM was higher than that of CFM,and the main components of fermented milk in line with national standards,and the content of free amino acids was abundant.The firmness,cohesiveness,consistency and the index of viscosity of KFM,BFM and KBFM are higher than CFM,and storage modulus?G'?and loss modulus?G"?are also greater than CFM.In CFM,KFM,BFM and KBFM,26,29,28,31 kinds volatile compounds were detected respectively,mainly alcohol,ketone,aldehyde,acid and ester.During the 21days' storage period,the acidity and syneresis of fermented milk gradually increased with the increase of storage time,the pH and water-holding capacity decreased gradually with the increase of storage time.In addition,in order to study the effect of roselle on fermented milk,0.1%,0.2%,and0.3%roselle water extract were added to recovery milk to prepare the different concentrations of roselle fermented milk?RFM₁?RFM₂ and RFM₃?.The sensory score and the viable count were highest in RFM₂,and the main components of RFM₁,RFM₂and RFM₃ were in accordance with the stipulations of GB19302-2010,and the content of free amino acids was abundant.In RFM₁,RFM₂ and RFM₃,43,44,45 kinds volatile compounds were detected,mainly alcohols,ketones,aldehydes,acids and esters.Rheological properties of RFM₁,RFM₂ and RFM₃ can be analyzed to show that it is a stable gel system,and through analysis,it can be concluded that roselle extracts enhance the taste of fermented milk.During the 21 days' storage period,the acidity and syneresis value of fermented milk gradually increased with the increase of storage time,the pH and water-holding capacity decreased gradually with the increase of storage time.According to the results of the influence of different concentrations of roselle extract on the quality of fermented milk,RFM₂ was selected for the next study to evaluate the effect of antioxidant,hypoglycemic and hypolipidemic.The results showed that during 21 days' storage,KFM,BFM,KBFM,RFM₂ effect on DPPH·,ABTS+radical scavenging activity and reducing power,are higher than that of CFM.The diabetic mice model was induced by high fat feed and STZ,the results showed that the four types of fermented milk reduced the fasting glucose level,the levels of TC,TG,FFA in serum,and increased glycogen,serum insulin,the level of organ index and body weight,AMPK expression the expression of PPAR-?in skeletal muscle GLUT4 and adipose tissue,and reduced the expression of G6 P in liver tissue.The results showed that fermented milk had a significant effect of hypoglycemic and hypolipidemic activity,which could effectively alleviate hyperglycemia and hyperlipidemia in diabetic mice.