Research On Effects Of Pomegranate Juice Powder On Yogurt Fermentation And Its Quality

Background: Yogurt is a fermented dairy product for all ages,which can be easily digest and absorb,it can also improve intestinal environment and enhance body constitution.However,for some specific people who are already in sub-health,such as old,weak,young,and other patients with certain conditions,ordinary yogurt can not achieve the desired results.In order to improve the health benefits of yogurt,researchers keep developing functional yogurt uninterruptly.Pomegranate is rich in polyphenols and is an excellent source of antioxidants.Eating pomegranate helps to prevent aging and reduce the incidence of coronary heart disease,stroke and other diseases.Huaiyuan pomegranate has seasonality and harvest concentratly.The undesirable appearance of pomegranate fruit seriously affect consumers' desire to purchase.Meanwhile,eating pomegranate is inconvenient,resulting in limited sales of its fresh fruit.Therefore,the processing of pomegranate is beneficial to the appreciation of pomegranate resources.Objective: In this paper,we studied the effects of different pomegranate juice powder(PJP)substitutions on the fermentation process index,the quality change of yogurt during storage and the functional characteristics of yogurt,and provide theoretical basis and new ideas for the application of pomegranate in yogurt.Methods: 1.To study the effects of different PJP substitutions on the yogurt fermentation process indicators by detecting the pH,acidity,apparent viscosity,lactic acid bacteria activity and composition changes of yogurt.2.The effects of different PJP substitutions on the quality change of yogurt during storage were studied by detecting nutrient composition,quality,texture characteristics,rheological characteristics,antioxidant activity and microstructure during storage of yogurt.3.The digestion characteristics of yogurt in vitro and the effects of antioxidant and intestinal flora regulation in vivo were studied by in vitro digestion simulation experiment and animal experiment.Results: 1.The research on yogurt fermentation process shows that,the replacement of sucrose by PJP defered the solidification time of yogurt,the exponential growth time and the maximum activity time of lactic acid bacteria,but it significantly increased the maximum activity of lactic acid bacteria in yogurt.It took the control,LD,MD and HD groups 300 minutes,240 minutes,260 minutes and 280 minutes,respectively,to reach 4.6±0.1 of pH value,suggesting PJP replacement shortened the fermentation time.The lactic acid bacteria activity of pomegranate yogurt is 6~7 times of that of the control yogurt.2.The research on quality change of yogurt during storage showed that the addition of PJP can significantly improve the quality and health benefits of yogurt,pomegranate yogurt had higher content of free amino acid and soluble protein during storage.PJP promoted the acid production of lactic acid bacteria,the viscosity and water holding capacity of pomegranate yogurt increased significantly.Pomegranate yogurt exhibited higher colloidal strength,and its protein gel network was more uniform,exhibited stronger viscoelasticity.In addition,pomegranate yogurt has higher polyphenol content and antioxidant capacity during storage.At the beginning of storage,the total polyphenol content,FRAP,DPPH·scavenging rate and ABTS radical scavenging rate of HD were 1.8 times,2.2 times,1.8 times and 1.7 times of the control,respectively.3.The results of in vitro digestion analysis of yogurt showed that the FAA content of pomegranate yogurt was significantly higher than that of the control yogurt during the whole in vitro digestion simulation.At the end of intestinal digestion,the DH of Control,LD,MD and HD were 62.47 %,64.28 %,67.86 % and 71.27 %,respectively,indicating that the replacement of sucrose with PJP can increase the bioavailability of yogurt.4.The results of animal experiments show that pomegranate yogurt could effectively improve the total antioxidant capacity(T-AOC)and glutathione peroxidase(GSH-Px)activity in serum,and T-AOC in liver,as well as reduce the content of malondialdehyde(MDA)in serum and liver.The effect of pomegranate yogurt on the antioxidant capacity of mice is positively correlated with the amount of PJP substitution.The T-AOC and GSH-Px in serum of the HD-fed mice were 1.7 times and 1.25 times higher than those in control mice,respectively,and the MDA in serum and liver of the HD-fed mice decreased to 75.3 % and 71.1 % of the control mice,respectively.Pomegranate yogurt has a good regulating effect on intestinal flora in mice colon.The contents of Lactobacillus and Bifidobacterium in the colon of HD-fed mice were 8.5 times and 6.1 times of that of control mice,respectively,and the content of Bacteroides and Enterococcus in the colon of HD-fed mice were reduced to 55.2 % and 10.2 % of that of control mice,respectively.In summary,addition of PJP would shorten the fermentation time of yogurt,increase the lactic acid bacteria activity when yogurt fermentation end,and improve the quality and health benefits during yogurt storage.In addition,PJP-added yogurt has higher bioavailability and in vivo antioxidant activity as well as better colonic intestinalflora regulation.Therefore,PJP pomegranate juice powder can be applied to yogurt as an excellent functional additive.