Study On The Physical And Chenical Effects Of Seabuckthorn On Fermented Yougurt And Its Antioxidant Activity

In this academic dissertation,seabuckthorn in Linzhi area of Tibet was taken as the research object,and the best process formula of seabuckthorn yogurt was explored through single factor and orthogonal experiments.The nutritional components of seabuckthorn yogurt and the changes of physical and chemical properties during storage were determined.The stability and antioxidant capacity of polyphenols during storage and digestion were studied.The main conclusions are as follows:（1）The results of single factor and orthogonal experiments showed that the optimum process of seabuckthorn yoghurt was 7%seabuckthorn juice,4%inoculation amount,7%sugar content and 65%milk content.The degree of influence on the sensory score of sea buckthorn yogurt was sugar content>milk addition>inoculum>sea buckthorn juice;the degree of influence on the water holding capacity of sea buckthorn yogurt was milk content>inoculation amount>sea buckthorn juice amount>sugar content.（2）The nutritional components of sea buckthorn yoghurt were higher than those of control yoghurt except water.The highest mineral content in sea buckthorn yoghurt was potassium,followed by calcium and sodium,and the lowest mineral content was zinc.The contents of calcium,magnesium,copper and manganese were not significantly different from those of control yoghurt.The contents of potassium,sodium,iron and zinc were higher than those of control yogurt.Eight kinds of seabuckthorn juice were detected in 10 polyphenols:ferulic acid>proanthocyanidin B₂>p-coumaric acid>gallic acid>epicatechin>protocatechuic acid>caffeic acid>luteoloside;seabuckthorn yoghurt:ferulic acid>proanthocyanidin B₂>caffeic acid>p-coumaric acid>protocatechuic acid>gallic acid,both of which had the highest content of ferulic acid.Only 4kinds were detected in the control yoghurt.Adding seabuckthorn juice to the yoghurt increased the content of polyphenols.（3）During the storage period:the p H value of the two yogurts decreased with the increase of storage time,and the acidity continued to rise;the brightness and yellow-blue strength of seabuckthorn yogurt were higher than those of the control,and the red-green strength was lower than that of the control.At the end of storage,the brightness of seabuckthorn yogurt was slightly lower than that of the control yogurt,the red-green strength was reddish,and the blue-yellow strength was yellow.The total phenols of sea buckthorn yoghurt and sea buckthorn juice showed a downward trend within 21 days,which was 20.4%and 15.8%lower than that at the beginning of storage.The stability of polyphenols in sea buckthorn juice was higher than that in sea buckthorn yoghurt,and the total phenols of control yoghurt did not change significantly.The stability of total flavonoids in seabuckthorn yogurt and seabuckthorn juice was higher than that of control yogurt.The vitamin C content of sea buckthorn yogurt and sea buckthorn juice continued to decline during storage,and the stability of sea buckthorn juice VC during storage was higher than that of sea buckthorn yogurt.The antioxidant capacity of the two yogurt samples at the end of storage was higher than that at the beginning of storage.The total antioxidant and DPPH free radical scavenging rate of seabuckthorn juice decreased during storage,and the superoxide anion scavenging rate and reducing power increased.（4）Seabuckthorn yoghurt and control yoghurt increased the content of total phenols and flavonoids in the digestion stage.The total phenols and total flavonoids of seabuckthorn juice showed a downward trend after the end of digestion,especially in the intestinal digestion（2h）stage.The total phenol content of the three groups of experimental samples in the intestinal digestion stage was lower than that in the gastric digestion stage.The increase rate of total phenols and total flavonoids in seabuckthorn yoghurt and control yoghurt was more significant than that in seabuckthorn juice.The 4 antioxidant capacity of the three groups of samples In the process of simulated in vitro digestion,except that the reducing power of the control yogurt and sea buckthorn juice in the intestinal digestion stage was higher or equal to that in the gastric digestion stage,the other experimental results showed that the activity of various antioxidant components in the gastric digestion process was the highest and higher than that in the intestinal digestion stage.The total antioxidant capacity of sea buckthorn juice decreased after digestion,and the other three antioxidant capacities increased.The antioxidant capacities of sea buckthorn yogurt and control yogurt after digestion were higher than those before digestion.