Study On Quinoa-Milk Fermentation Beverage By Lactic Acid Bacteria

Quinoa is rich in protein,amino acid,fat,mineral elements,dietary fiber and other nutrients,which has many physiological functions such as anti-oxidation and anti-tumor.In this paper,five kinds of lactic acid bacteria were used to ferment quinoa to prepare beverage.The physicochemical and nutritional characteristics of quinoa germ were determined in the fermentation process,and the most suitable lactic acid bacteria to ferment quinoa was screened.At the same time,the fermentation process,blending process and stability of the quinoa-milk fermentation beverage were studied,and the quality changes of the beverage during storage were measured.The beverages were prepared by pure fermentation of Bifidobacterium,L.bulgaricus,S.thermophilus,and L.acidophilus.The changes of viable count,pH value,titratable acidity,reducing sugar,free amino acid soluble protein,polyphenols,flavonoids content and volatile flavor compound of quinoa germ were analyzed during fermentation,the sensory quality of beverages was also evaluated.The results showed that the Lactobacillus acidophilus proliferated fastest,meanwhile it had the strongest ability in producing acid,flavonoids,polyphenols and consumpting sugar.It also producing the most kinds of volatile flavors compounds.At the same time,Lactobacillus bulgaricus and Streptococcus themophils had the the strongest ability in degradating protein.The sensory evaluation results showed that the quality of the beverage prepared by Lactobacillus acidophilus is the best.L.bulgaricus,S.thermophilus,and L.acidophilus were mixed with 1:1 and 1:1:1 respectively.The viable count,pH values,titratable acidity,free amino acid,soluble protein,organic acid,polyphenols,flavonoids,reducing sugar and volatile flavors compounds contents were determined.The sensory quality of the baverages was also evaluated.Finally,the combination of L.acidophilus:L.bulgaricus:S.thermophilus was choosen as the optimal starter for the fermentation beverage.The optimum fermentation parameters of the quinoa-milk fermentation beverage by Lactic acid bacteria were determined by single factor and orthogonal experiments.The results showed that the milk was added at 15%,the fermentation ended at pH 5.0,and the amount of the starter was inoculated at 3%was the best fermentation condition.Through single factor and Box-Behnken response surface optimization experiments,the optimal stabilizer formulation for the quinoa-milk fermentation beverage by Lactic acid bacteria was analyzed with the centrifugal sedimentation rate as index.The result showed that carboxymethyl cellulose sodium,carrageenan,xanthan gum added at 0.037%,0.06%,and 0.059%respectively was the best.Under this condition,the centrifugal sedimentation rate of the beverage was 1.78%.The viable count,pH value,titratable acidity,and centrifugal sedimentation rate of the beverage during storage were measured,the sensory quality of the beverage was also evaluated.The result showed that the sensory quality of the beverage decreased rapidly after 20 days at refrigeration.The shelf life of the beverage is hence 20 days...