Study On Preparation,Nutrition And Quality Of Quinoa(Chenopodium Quinoa Willd.)Yoghurt

Plant-based yogurt attracts great attention for its abundance of various bioactive substances and none cholesterol,which prevent metabolic chronic diseases such as diabetes and hypercholesterolemia.Plant-based yogurt meets the requirements of consumers for health and nutrition,leading a rapid growth in the market worldwide in recent years.Quinoa has high protein content and balanced amino acids,and it is regarded as the only single plant to the basic nutritional needs of the human body,which is recognized by the United Nations Food and Agriculture Organization.In addition,quinoa is recommended as the most suitable"complete nutrition food"for human beings.Development of the plant-based yogurt with quinoa has been a hotspot in the food industry.However,there are still some common problems between quinoa and other plant materials remaining in making such yoghurts,including:（1）poor sensory acceptance;（2）insufficient research on fermentation technology and inappropriate strains;（3）poor storage stability and prone to precipitation.Therefore,improving the nutritional and sensory quality of quinoa yogurt,screening suitable fermentation strains,and improving the storage stability of quinoa yogurt need to be solved urgently.In this study,a fermentation system suitable for the preparation of quinoa yogurt was developed through the screening of lactic acid bacteria,and the stability of quinoa yogurt was enhanced.In addition,the study showed that the quinoa yogurt had good antioxidant and digestive enzyme inhibition abilities.Methods and results are presented as follows:（1）Commercial starter utilization and soybean addition were applied in quinoa yoghurt manufacturing.The fermentation parameters and the nutrition quality of the sample with different soybean ratios were investigated.Fermentation kinetics（p H and acidity）and the cell viabilities of the lactic acid bacteria during storage showed that a higher ratio of soybean content led to a better fermentation capacity.This results might be attributed to the increased content of protein donated by the soybean.However,results suggested 100%quinoa yoghurt had the highest sensory and stability values.Fermentation could enhance the textural ability,rheological property,polyphenol content,antioxidant activity and digestive enzyme inhibition activity,revealing that quinoa yoghurt was a potential function food with antioxidant,hypoglycemic,and hypolipidemic properties.Although the addition of soybean could improve the fermentation characteristics of quinoa yogurt,with the continuous increase of soybean content,factors such as water holding capacity,viscosity,and beany flavor reduced the sensory acceptance of the quinoa yogurt.（2）The above results proved that the commercial starter was not suitable for quinoa yoghurt manufacturing,and some other lactic acid bacteria strains need to be screened.In this study,it was found that Weissella confusa is suitable for quinoa yogurt fermentation.Compared with the commercial starter,W.confusa could enhance the fermentation kinetics and the cell viabilities,indicating W.confuse had a better utilization of the substrate of quinoa.Hence,the commercial starter was modified with the addition of W.confuse.In order to further improve the physical stability of the yoghurt,carboxymethylcellulose sodium was used as the stabilizer.When the content of carboxymethylcellulose sodium reached 0.3%,quinoa yoghurt presented the highest water holding capacity and textural properties.Soybean protein was also added to improve the protein content of the yoghurt.Under the optimal conditions above,the acidity of the quinoa yoghurt reached 70°T within 8 hours during the fermentation.Additionally,modified starter and formulation enhanced the content of total polyphenol,catechin,epicatechin and the organic acids（including lactic acid,acetic acid,citric acid,and succinic acid）.Cell viability of the fresh prepared yoghurt was 10¹⁰ CFU/g,and it maintained at 10⁸ CFU/g after 21 days storage.It showed that the cell viability of yoghurt made from the modified starter was superior to the commercial starter.In addition,the physicochemical indicators such as p H,acidity,and color difference of yogurt were stable during storage,which proved that W.confuse could be suitable strain for quinoa yoghurt fermentation.（3）Based on the formulation and fermentation processing above,the digestive parameters of the developed yoghurt were investigated.Compared with unfermented samples,the antioxidant activities,assayed by Fe³⁺reduction ability,ABTS scavenging capacity,and hydroxyl radical scavenging capacity,of the quinoa yoghurt made from the modified starter were two fold higher than the commercial starter.The inhibition rate ofα-glucosidase andα-amylase increased by 5%and 30%,respectively,suggesting that the newly developed quinoa yoghurt had potential effects on blood sugar lowing,which was further confirmed with the animal experiments.In addition,during the simulated gastrointestinal digestion process,it was found that the release of polyphenols from quinoa yogurt and the hydrolysis of carbohydrates,proteins and fats were mainly performed in intestinal digestion state.Correlation analysis showed that the changes of different components had synergistic effects.The quinoa yogurt fermented with the improved starter had higher digestibility of protein and fat.The results were also verified by laser confocal experiments,indicating that the enhanced strains could ferment quinoa more fully and improve its digestive properties.Quinoa yogurt fermented with a modified starter in this study is a healthy plant-based yogurt rich in nutrients and well digested in gastrointestinal tract.