| Purple sweet potato is a special kind of sweet potato.It is not only rich in nutrients such as vitamins and minerals,but also contains functional components such as anthocyanins and dietary fiber.In addition,purple potato also contains a large number of trace elements,which strengthen the edible value and processing value of purple potato.In this study,Yuzi No.7 was used as raw material to carry out the optimization of lactic acid fermentation strains,the optimization of lactic acid fermentation process parameters and the analysis of functional active components,the analysis of volatile components of purple potato lactic acid fermentation juice,the in vitro digestion simulation test of live purple potato lactic acid fermentation juice,and the storage test of purple potato lactic acid fermentation juice.The purpose of this experiment is to explore the field of purple potato deep processing and provide reference for purple potato deep processing.The main results are as follows:(1)Six kinds of lactic acid bacteria were screened and compounded by pre-experiment,which showed that the highest evaluation value was 98.59 when lactobacillus was added according to the ratio of Lactobacillus plantarum:Lactobacillus brevis:Lactobacillus casei=1:2:1.Taking the total acid content and sensory evaluation value as response values,the fermentation conditions of purple sweet potato lactic acid were optimized.The optimal fermentation conditions were as follows:fermentation time 77.93 h,fermentation temperature 30.77℃,inoculation amount 7.46%,the predicted total acid content 6.65 g/L and sensory evaluation value96.87.In order to save cost,the optimal conditions were adjusted as follows:fermentation time 78 h,fermentation temperature 31℃and inoculation amount 7.5%.The actual total acid content was 6.73 g/L,and the sensory evaluation value was 95.67.The repeatability is good,which can be used to optimize the fermentation conditions of purple sweet potato lactic acid.(2)There was no significant difference in total acid,total sugar content and DPPH scavenging ability(P>0.05).The contents of total polyphenols,total flavonoids,anthocyanins,ORAC value and FRAP iron atom reduction ability of live purple potato lactic acid fermentation juice were stronger than those of sterilized purple potato lactic acid fermentation juice(P<0.05).The content of active components in purple potato juice was the highest,including 1364.28 mg/100m L total polyphenols,209.76mg/100m L total flavonoids and 121.05 mg/L anthocyanins;The content of total polyphenols,total flavonoids and anthocyanins were 554.31 mg/100m L,138.40mg/100ml and 53.43 mg/L respectively;Sterilized purple potato lactic acid fermented juice was the lowest,with total polyphenol content of 398.24 mg/100m L,total flavonoids content of 126.82 mg/100ml and anthocyanin content of 31.31 mg/L(P<0.05).Compared with the sterilization type,the processing technology of purple potato lactic acid fermentation juice with live bacteria can reduce the loss rate of total polyphenol content by 11.44%,total flavonoids content by 5.52%and anthocyanin content by 18.27%.(3)Three kinds of purple potato juice concentrates were analyzed by sde-gc-ms.a total of 123 volatile aroma components were detected,including 6 acids,22 esters,39alcohols,6 phenols,17 aldehydes,9 ketones,10 alkanes,10 olefins and 4 other substances.38 substances were detected in purple potato juice,while 76 and 74 volatile aroma components were identified in live purple potato lactic acid fermentation juice and sterilized purple potato fermentation juice respectively.(4)The results of in vitro digestion simulation test of live bacteria purple potato lactic acid fermented juice showed that the number of live bacteria in live bacteria purple potato juice decreased from 83.7x10~8 cfu/ml before digestion to 0.59x10~8 cfu/ml after 120 min digestion(P>0.05).However,there are still a certain number of residual lactic acid bacteria that can play the role of probiotics,indicating that the compound flora composed of Lactobacillus plantarum,Lactobacillus brevis and Lactobacillus casei can play the role of probiotics in human intestine.The contents of flavonoids and polyphenols increased significantly(P<0.05),while the contents of total sugar and soluble solids decreased significantly(P<0.05).(5)During the storage period of 30 days,the number of viable lactic acid bacteria in purple potato lactic acid fermentation juice increased in the first 15 days and decreased in the last 15 days.There was significant difference between the two stages(P<0.05).The total acid content of purple potato juice with live bacteria increased continuously during storage,and there was a significant difference before and after storage(P<0.05).The contents of total sugar,soluble solids,polyphenols and flavonoids decreased continuously during storage(P<0.05).(6)During the storage period of 8 months,the total acid content,total sugar content,flavone content and soluble solid content of sterilized purple potato lactic acid fermented juice had no significant change in the first 5 months(P>0.05),and the polyphenol content had no significant change in the first 3 months(P>0.05).During the subsequent storage period,the total acid content increased significantly(P<0.05),while the total sugar content,soluble solid content,flavone content and polyphenol content decreased significantly(P<0.05).. |
PDF Full Text Request