Study On Preparation Of CaREW Fermented Milk And Its Antioxidant Properties

This paper mainly studied how to add Cynanchum auriculatum Royle ex Wight(CaREW)to fermented dairy products,and developed the CaREW fermented yogurt of with both functional characteristics and yogurt flavor.In order to make the CaREW fermented yogurt give full play to its functional characteristics as much as possible and ensure the quality of the yogurt,this study selected the appropriate fermentation starter by comparing the effects of different commercial fermentation starter on the CaREW fermented yogurt,and optimized the proportion of the amount of CaREW,starter,sucrose,and the fermentation temperature The storage characteristics of the CaREW fermented yogurt,the content of certain active functional components,and volatile flavor compounds were studied.The main results are as follows:1.Effect of starter on the quality of CaREW fermented yogurtThe CaREW fermented yogurt was prepared by using four kinds of commercial fermentation starters as Y170E,Y180B,Y438B and Y450A respectively.The effects of different fermentation starters during fermenting stage on acidity degree,acidity growth rate,viscosity,water holding rate,sensory and total antioxidant capacity of the CaREW fermented yogurt were studied.The results showed that Y180B had the strongest acid production ability,and the acidity degree was 94.41°T,but there was no significant difference in the acid production ability of Y170E.Y438B and Y450A(P>0.05).The acidity degree of the yogurt prepared by Y180B and Y450A was weak,and the increase rate of acidity was only 4.23%and 5.48%after refrigerated for 3 days.The viscosity of Y450A was the best,the highest viscosity of the yogurt was 2780.34mPa.s,and the water holding rate was 81.75%.The yogurt prepared by Y438B and Y450A had better flavor and texture,and its sensory scores were 89 and 87 respectively.The total antioxidant capacity of yogurt prepared by Y450A was the strongest,which was 0.1247mM.So that,Y450A was selected as the starter of the CaREW fermented yogurt processing.2.Optimization the fermentation conditions of the CaREW fermented yogurtThe single factor experiment was conducted to explore the effects of the amount of added CaREW,starter,sucrose and the fermentation temperature on the yogurt fermentation,and then the optimal conditions of the fermented yogurt were determined by orthogonal experiment.The results showed that the best preparation conditions were:adding 2.0%CaREW and 5.0%sucrose to the mixed ingredients,inoculating with Y450A at 15.0U/ton.fermenting at 40.0℃ for 5h,the total antioxidant capacity of the final yogurt was 0.1292 mM,and the taste was good,the ratio of sour and sweet was reasonable3.Analysis of volatile flavor compounds in theThe volatile flavor compounds in the CaREW fermented yogurt were determined,and the olatile flavor compounds with relative content more than 0.1%were screened out.The results showed that 48 kinds of volatile flavor compounds were detected in the CaREW fermented yogurt,the relative content of which was 78.31%,mainly including 5 kinds of compounds:alcohols,ketones,acids,esters and aldehydes.The relative content of alcohol is the highest,42.63%.In addition,the relative content of 2,3-butanedione,an important characteristic flavor substance of fermented dairy products,reached 7.72%in the CaREW fermented yogurt.The synergistic effect of various volatile flavor compounds makes the CaREW fermented yogurt have good sensory quality4.Analysis of functional active components in the CaREW fermented yogurtThe concentrations of stilbene glycosides,flavonoids,polyphenols and polysaccharides in the CaREW fermented yogurt were determined.The results showed that the the yogurt contained stilbene glycosides,flavonoids,polyphenols and polysaccharides,which were 3.9739mg/L,0.0174mg/ml,0.0677mg/ml and 11.3484mg/ml respectively.The fermentation of lactic acid bacteria was beneficial to the release of active substances of CaREW multiflorum5.Storage characteristics of the CaREW fermented yogurtThe CaREW fermentation yogurt was prepared under the optimal conditions,and then the changes of the number of viable bacteria,acidity,viscosity,sensory quality and total antioxidant capacity were studied.The results showed that after 15 days storage at 4℃,the CaREW fermented yogurt could still keep a high grade of viable bacteria,and the acidity and viscosity of the product also remained at a good level.However,affected by the effect of CaREW,the sensory quality and total antioxidant capacity of fermented yogurt changed greatly after 15 days storage,resulting in unpleasant experience and weakening of functional characteristics.But,it still maintained good sensory and total antioxidant capacity after 9 days storage.The optimal shelf life of the CaREW fermented yogurt was 9 days.