The Study On Enzymatic Preparation Of Slowly Digestible Starch

As a main carbohydrate in people’s daily diet, starch plays an important economic role.With increasing emphasis on nutrition and health, digestibility of starch in human bodybecomes an important indicator to measure the nutritional value of carbonhydrates. If starch isthoroughly digested by the body within a short time, it will lead to some negative effects suchas dramatic fluctuations in blood sugar levels, an increase of insulin levels, especiallydamages to the patients suffering from chronic metabolic diseases. Slowly digestiblestarch(SDS), serving as a kind of important functional food additives, can slow down thedigestion rate, control energy to release slowly, improve the nutritional value of products.Normal maize starch, which comes from plant resource, is common and quite easy to obtain,it’s widely used in the food industry for its low cost. To improve digestibility of normal maizestarch is meaningful. Currently few researches focus on the structure of SDS, consequentlythe novelty of this study lies in finding out the relationship between starch fine structure andcharacteristics of digestion.Firstly, the optimal experimental conditions in vitro digestion was determined, use5mLmixed enzyme containing300U/mL porcine pancreatic α-amylase and40U/mLamyloglucosidase in sodium acetate buffer of pH5.2to hydrolyze400mg maize starch, theresults showed that in native starch SDS content was15.16%, RS(resistant starch) contentwas1.36%, and RDS(ready digestible starch) content was83.48%.Secondly, the properties of starch products formed in β-amylase treatments andβ-amylase, transglucosidase compound treatments was examined detailedly. The resultsshowed that improving the adding volume and processing time of enzymes could increasestarch hydrolysis rate, and reduce the viscosity value of the reaction solution. The capabilitiesto combine iodine molecules were weakened after treatments, and the maximum absorptionwavelength decreased with time passed by. The product A5formed after2hours’ processingof0.032%β-amylase, had the maximum SDS content of22.38%, RS content was10.77%,RDS content was66.85%, its average chain length was16.16, branch density was6.19%. Inprocessing of β-amylase, transglucosidase compound enzyme, product D8, which was formedafter8hours’ treatment, had SDS content of33.52%, RS content of12.27%, RDS content of54.21%, its average chain length was14.36, branch density was6.96%. These resultssuggested that, both processings of β-amylase and β-amylase, transglucosidase compoundenzyme could increase the SDS content, while the compound treatment would be moreeffective, the main reason was that β-amylase hydrolyzed maize starch, shortening theaverage chain length, and transglucosidase catalyzed the formation of side chain withincreasing the branch density.The research investigated starch hydrolysis curves and viscosity curves in maltogenicamylase processing, then found out that the enzyme had a high transgalactosylation activityand hydrolytic activity. In products group H which was formed with enzyme amount of40ppm, the H4sample whose processing time was16h had the optimum digestibility, SDScontent was38.07%, RS content was12.45%, average chain length was10.95, branch density was9.13%. Therefore, maltogenic amylase treatment can gain higher levels of SDS.In order to study the relationship between the chain structure and SDS content, we choseproducts group of optimum digestibility, by using SPSS regression analysis to fit the curve ofthe branch density-SDS content, we got a quadratic relationship between the branch densityand SDS content, only when starch was treated to achieve an optimum branch density, thedigestion rate could be slow down effectively, and reached the max value of SDS content.