Release Of Bound Phenolics From Dried Bamboo Shoots Prepared By Different Procceses During Digestion And Its Effect On Colonic Fermentation

Dried bamboo shoots(DBS)are a kind of agricultural products that are deeply loved by consumers after being cooked and dried with bamboo shoots as raw materials.According to the different processes,DBS are divided into salt-dried bamboo shoots(SDBS),steamed dried bamboo shoots(TDBS),fumigation-dried bamboo shoots(UDBS)and fermentationdried bamboo shoots(FDBS).Bamboo shoots are rich in nutrients such as dietary fiber and phenolic compounds,and most of the phenolics are present as bound phenolics.The release pattern of bound phenolics during digestion and the effect on colonic fermentation of DBS obtained from different treatments and drying conditions also differed considerably.In this work,SDBS,TDBS,UDBS and FDBS were used as experimental raw materials to compare the sensory quality and storage performance of four kinds of DBS,as well as the release pattern of bound phenolics during in vitro digestion and the effect on colonic fermentation.The main contents of this research are as follows.(1)Among four kinds of DBS,the eating qualities ranged from high to low for FDBS,UDBS,SDBS and TDBS,the moisture contents ranged from high to low for UDBS,TDBS,FDBS and SDBS,the rehydration properties ranged from strong to weak for FDBS,TDBS,SDBS and UDBS,and the hardness values ranged from high to low for SDBS,UDBS,TDBS and FDBS.UDBS has the highest color difference value,with a value of 22.73,while FDBS has the lowest,with a value of 2.75,which was more beautiful and popular among consumers.In addition,the color difference value,total bacterial colony and polyphenol loss of FDBS gradually increased during storage,and the result of shelf-life prediction model showed that FDBS could be stored at 25℃,35℃ and 45℃ for 69 d,57 d and 47 d respectively.(2)Phenolics of DBS mainly existed in the form of bound phenolics,among which the content of FDBS was the highest,followed by SDBS and TDBS,and UDBS was the lowest.The release amount of bound phenolics from SDBS,TDBS,UDBS and FDBS after gastrointestinal digestion were 19.61%,19.40%,45.64%and 19.66%of the total respectively,which were higher than that after gastric digestion.Moreover,the IC50 values for the scavenging ability of DPPH and ABTS free radicals by gastric digestive fluids and gastrointestinal digestive fluids of DBS were in the order of low to high for FDBS,UDBS,SDBS and TDBS.Rutin,p-coumaric acid and ferulic acid were discovered to be the predominant phenolic compounds in digestion supernatants.Furthermore,fluorescence micrographs of these residues at different digestion stages further confirmed the release regularity of bound phenolics.(3)Nine phenolic compounds were identified from four kinds of DBS,including seven phenolic acids and two flavonoids,and the contents of chlorogenic acid,p-coumaric acid and ferulic acid were higher than other phenolics.In addition,short-chain fatty acids(SCFAs)were produced while the contents of cellulose,hemicellulose and lignin were gradually decreased.Surprisingly,confocal laser scanning microscopy(CLSM)images could also characterize above changes.A significant positive correlation(P<0.05)was found between release of bound phenolics and production of total SCFA,and a significant negative correlation(P<0.05)was observed between release of bound phenolics and IC50 values for inhibition of α-amylase and α-glucosidase.These findings indicated that release of bound phenolics and production of SCFAs from DBS could promote the balance of intestinal flora and might be beneficial to health.