Study On Preparation And Quality Characteristics Of Cyperus Esculentus L. Fermented Milk

Cyperus esculentus L.is a new crop with high quality,high yield,and comprehensive utilization value.It has excellent nutritional,edible,medicinal,and health value.This thesis starts from the different variety resources of C.esculentus,analyzes the variety differences in nutrition and physicochemical indicators,optimizes the processing technology of C.esculentus fermented milk,establishes the suitability evaluation of C.esculentus fermented milk variety processing,and conducts research on the functional properties of C.esculentus during storage.This study is of great significance in enriching the types of C.esculentus products and enhancing the technological content of the C.esculentus.industry.The main research contents are as follows:（1）Analysis of basic physicochemical indicators of C.esculentus variety resources.The correlation analysis,principal component analysis,and cluster analysis were used to study the variety differences of 10 basic physicochemical indicators of 42 C.esculentus varieties in Jilin Province.The results showed that the varieties with vitamin C content,raffinose content,and glucose content had greater variability,while the varieties with branched starch content,total starch content,and fat content had smaller variability.The correlation analysis results indicate that there is a certain correlation between various physical and chemical traits.Principal component analysis extracted four principal components,with a cumulative variance contribution rate of 73.49%.A comprehensive evaluation model was established through principal component analysis:F=0.424 F₁+0.225 F₂+0.188 F₃+0.163 F₄.The comprehensive quality of 42 C.esculentus varieties was evaluated using this model,and the results showed that the variety with the best nutritional quality was JS34,while the one with the worst nutritional quality was JS35.Through cluster analysis,42 C.esculentus were divided into four categories:the first category had higher oil content,the second category had rich sucrose content,the third category had higher hundred-grain-weight and starch content,and the fourth category had higher protein and vitamin C content.（2）Optimization of the processing technology for C.esculentus fermented milk.Through single factor and response surface experiments,the effects of fermentation agent addition,fermentation temperature,fermentation time,white sugar addition,soy protein isolate addition,and carrageenan addition on the p H,acidity,viscosity,water holding capacity,texture characteristics,chromatism,and sensory evaluation of C.esculentus fermented milk were investigated.The optimal fermentation process conditions were obtained as follows:0.01%of fermentation agent,43℃of fermentation temperature,12 h of fermentation time,4%of white sugar,2%of soy protein isolate,and 0.3%of carrageenan.（3）Analysis and evaluation of the quality characteristics of C.esculentus fermented milk.The correlation analysis,principal component analysis,and cluster analysis were used to study the variety differences of 11 physicochemical indicators of fermented milk prepared from 42 C.esculentus varieties in Jilin Province.The results showed that there were significant differences in p H,hardness,consistency,and viscosity index among varieties of C.esculentus fermented milk,while the differences in L^*value,acidity,and water holding capacity among varieties were relatively small.There is a certain correlation between the quality indicators of fermented milk from different C.esculentus.Through principal component analysis,three principal components were extracted,with a cumulative variance contribution rate of 62.09%.A comprehensive evaluation model was established using principal component analysis:F=0.512 F₁+0.314 F₂+0.174 F₃.The model was used to analyze the comprehensive quality of fermented milk from different varieties of C.esculentus.The results showed that JS19 had the best quality of fermented milk and JS32 had the worst quality.The study on the correlation between the quality indicators of fermented milk prepared from 42 C.esculentus varieties and their physicochemical properties indicates a strong correlation between the two.（4）Functional study on the storage period of C.esculentus fermented milk.The antioxidant activity of fermented milk prepared by the best variety（JS19）during storage period was investigated.The results showed that the DPPH radical scavenging capacity,ABTS radical scavenging capacity,hydroxyl radical scavenging capacity and superoxide anion radical scavenging capacity of fermented milk reached the peak value on the third day of storage,which were 22.30%,69.64%,34.05%and 21.17%,respectively.The iron ion reducing capacity and total reducing capacity also reached the maximum value on the third day,The antioxidant activity showed a gradually decreasing trend after 3 days,with values of 0.95 and 1.71,respectively.The research results on hypoglycemic activity indicate that:the inhibition ability ofα-amylase showed a trend of first increasing and then decreasing with storage time,reaching a maximum value of 47.36%on the third day;the inhibitory ability ofα-glucosidase showed a trend of first decreasing and then increasing,reaching a minimum value of 41.29%on the third day.The trend of cholesterol lowering activity and antioxidant activity is the same,reaching a maximum value of 47.33%on the third day of storage.In summary,the nutritional quality and health function of C.esculentus fermented milk reached their best on the third day.In addition,compared with commercially available plant-based fermented milk,it was found that C.esculentus fermented milk has better antioxidant,hypoglycemic,and cholesterol lowering activities than commercially available fermented milk.