Study On The Preparation And Properties Of Slowly Digestible Starch With Dual-Enzymes Treatment

Slowly digestible starch (SDS) was completely digested in the small intestine but at aslower rate of absorption of starch, which owned the special effects on releasing glucoseslowly and took control in improving the level of blood glucose response. The preparation ofhigh content of slowly digestible starchsamples was conducted by acting on the corn andpotato starch based on the treatments of β-amylase, β-amylase and transglucosidase,respectively. The amylose contents, iodine adsorption capability, crystallinity, thermodynamicproperties, starch particle morphology of slowly digestible starch were investigated by usingthe starch-iodine compound absorbance value method, X-diffraction, DSC and SEM.Meanwhile, the similarities and differences were also compared between A and B type in thepreparation of SDS. The applied research of making cookies using the high content of SDSwas also studied.Frist, the gelatinized corn and potato starch were enzymatic hydrolysis using theβ-amylase. The results showed that the content of SDS reached to8.02%with the conditionsof slurry concentration of8%, the enzyme content of200U/g and the reaction time of5h forcorn starch. The content of SDS reached to6.63%with the conditions of slurry concentrationof8%, the enzyme content of56U/g and the reaction time of4h for potato starch. Comparedwith the native starch, the content of SDS was increased by the treatment of β-amylase.Second, the gelatinized corn and potato starch was enzymatic hydrolysis combined withthe β-amylase and transglucosidase. The results showed that the content of SDS reached to16.37%with the conditions of adding the β-amylase content of160U/g for4h and then addingthe transglucosidase content of7.5kU/g for12h for corn starch. The content of SDS reachedto13.70%with the conditions of adding the β-amylase content of64U/g for5h and thenadding the transglucosidase content of13kU/g for24h for potato starch. Compared with theSDS content obtained by the single β-amylase, the content of SDS was increased by thetreatment of combining with β-amylase and transglucosidase.Third, the physical-chemical properties of corn and potato SDS obtained by thedual-enzymes treatment were studied. The results indicated that the maximum absorptionpeak position deviation of starch-iodine adsorption compounds was increased with theincrease of SDS content. The more content of SDS, the greater the degree of deviation. Thecrystal forms of the samples disappeared after dual-enzymes treatment by the X-raydiffraction. Based on the DSC data, the samples with highest levels of SDS showed thestrongest thermal stability and higher gelatinization enthalpy, which made it difficult to make starch gelatinized. The samples showed the irregular fragments obtained by the scanningelectron microscopy (SEM).Finally, the cookies containing SDS were made by using corn SDS instead of differentproportion of low-gluten flour and their corresponding properties were analyzed. Theresults showed that SDS content played little effect on the moisture content and ash content,while had certain influence on the hardness and chewiness of cookies. Combined with sensoryevaluation scores, when the degree of substitution was15%, the sensory evaluation of cookiesposed the highest score, which can be used in the fine food as special dietary uses.