Study On Preparation And Properties Of Apple Pectin In Linzhi City,tibet

Apple is rich in a variety of nutrients.As the world’s largest apple production and consumption country,it is necessary to fully develop and utilize it.Apple is rich in pectin substances,which is an excellent pectin resource and has broad application prospects.In this study,Water-soluble pectin（WSP）,CDTA-soluble pectin（CSP）and Na₂CO₃-soluble pectin（NSP）of different apple varieties and different drying methods were prepared from the apple fruits of Linzhi,Tibet,and their physicochemical properties,basic structure and biological activity were determined.The main conclusions are as follows:（1）Among the pectin components prepared by different apple varieties,WSP pectin content was the highest,followed by NSP pectin content,and CSP pectin content was the lowest.Among them,the total pectin content of’Heizuan’was the highest,and the total pectin content of’Golden delicious’was the lowest.The total sugar content was WSP>NSP>CSP,and the total sugar content of WSP pectin of’Huashuo’variety was the highest.The protein content of pectin components prepared by different varieties was less than 4%.The pectin content of pectin components prepared under different drying methods was WSP>NSP>CSP,and the pectin content of WSP was the highest under hot air drying at 60°C.The total sugar content of WSP was the highest,followed by NSP,CSP was the lowest,and the total sugar content of WSP pectin was the highest under hot air drying at 75°C.The degree of esterification was WSP>CSP>NSP,only the degree of esterification of WSP pectin under hot air drying at 60°C was more than 50%,which was high ester pectin.（2）There was no significant difference in the infrared spectra of WSP,CSP and NSP pectin components of different apple varieties.All pectins had the characteristic absorption bands of carbohydrate compounds in the range of4000～400 cm^-1,and the functional group types in the infrared section were basically the same,but the pectin structure was slightly different.There was no significant difference in the infrared spectra of pectin after different drying methods.According to the infrared spectra,it can be seen that the degree of esterification of WSP pectin was the highest,and the degree of esterification of NSP pectin was the lowest,which was consistent with the results of titration.（3）In different varieties of pectin components,WSP pectin contains six monosaccharides:arabinose,mannose,galactose,galacturonic acid,glucose;the monosaccharide composition of CSP pectin and NSP pectin was consistent,both of which contained mannose,rhamnose,galacturonic acid and arabinose.All pectin components were dominated by RG-I structure.The side chain length of WSP pectin was the longest,followed by NSP pectin,and the side chain length of CSP pectin was the shortest.（4）The molecular weight distribution of pectin is affected by different drying methods and pectin types.Except for three chromatographic peaks of WSP under freeze-drying method,two chromatographic peaks of WSP pectin under other drying methods appeared.The molecular weight distribution of CSP pectin was wider than that of WSP and NSP pectin under different drying methods.NSP pectin showed three chromatographic peaks,and the chromatographic peak with the earliest peak time had the largest molecular weight.（5）In the in vitro antioxidant test,WSP pectin had a certain degree of antioxidant capacity under different varieties and different drying methods,and its antioxidant capacity was positively correlated with the concentration,but the antioxidant capacity of WSP pectin was significantly lower than that of the reference ascorbic acid.Among the pectin components of different varieties,the antioxidant capacity of’Heizuan’WSP pectin was the strongest.Among the pectin components under different drying methods,the antioxidant activity of WSP pectin under hot air drying at 90°C was the highest.（6）In vitro simulated adsorption of nitrite and cholesterol test:When simulating the adsorption of nitrite,the adsorption amount in the gastric control group was WSP>NSP>CSP,and the adsorption amount of WSP pectin in the intestinal control group was the highest.By comparing the gastric test group and the intestinal test group,it can be seen that the nitrite adsorption amount of the pectin component in the simulated intestine is much larger than the adsorption amount in the simulated stomach,so the intestinal environment in the human body is more suitable for pectin to play a role;when simulating the adsorption of cholesterol,the adsorption capacity of WSP pectin in the gastric control group was the highest,and the adsorption capacity of’Golden delicious’WSP,CSP and NSP pectin in the intestinal control group was the largest of the same type of pectin.Comparing the gastric test group with the intestinal test group,all pectin components in the gastric test group not only had greater total cholesterol adsorption than the intestinal test group,but also had higher adsorption capacity for each pectin component than in the intestinal test group,indicating that the stomach was more suitable for pectin components to exert their ability to adsorb cholesterol than the intestinal environment.