| Heat-moisture treatment is a highly secure physical method to change thephysicochemical properties of starch and its digestibility. Starch is the main source of energyfor humans, and its digestibility is closely related to many human diseases. In this study,normal corn starch was treated by heat-moisture treatment, and cassava starch was subjectedto heat-moisture combined with microwave treatment. Furthermore, the morphology, thermalproperty, crystallinity, viscosity and digestibility of treated starch were characterized bypolarizing microscope, scanning electron microscopy, differential scanning calorimetry, X-raydiffraction, Viscograph and In vitro digestibility, respectively.After normal corn starch with different moisture contents were treated by heat-moisturetreatment (HMT) at120℃for12h, the integrity of HMT treated starch granules wasn’tchanged, but fragment was observed. Reduced peak viscosity and increased pastingtemperature of HMT starch were found. The gelatinization temperatures (To, Tp, and Tc),gelatinization temperature range (Tc-To) increased and enthalpies of gelatinization (ΔH)decreased significantly. Both the native and HMT starches showed A-type X-ray diffractionpattern, the crystal pattern of the sample treated at highest moisture treatment (NCS-35) wastransformed to A+V pattern, indicating the formation of starch-lipid complex. The RS andSDS content of HMT starch increased significantly, and the starch treated at35%moisturecontent possessed the highest RS content. After normal corn starch (20%) was treated byheat-moisture treatment (HMT) based on different time at120℃; solubility and swellingpower decreased, and was negatively correlated with the processing time; the pastingtemperature increased, and was positively correlated with the processing time, viscositydecreased and was negatively correlated with the processing time; To, Tp, Tc increased, andwas found to be positively correlated with processing time, ΔH was gradually decreased, andwas negatively correlated with the treatment time; little change in the degree of crystallinitywas observed, crystal type is not changed; the highest SDS and RS content was fund inNCS-14and NCS RS-12, of which the SDS and RS were increased by4.91%and12.19%,respectively, compared with that of native starch. When the processing time exceeded12h,the RS content decreased. Therefore, by selecting appropriate heat treatment time, can notonly save energy, but also can get a higher content of SDS and RS content of starch.The physiochemical and digestibility properties of cassava starch with different moisturecontents were studied after they were treated by heat-moisture combined with microwave treatment at1W/g for20min. The shape of the starch granules weren’t changed, theappearance became rough. Solubility and swelling power was decreased, and was negativelycorrelated with the moisture content. Pasting temperature,95℃viscosity,95℃to50℃cooling stage viscosity and terminal viscosity improved, and was found to be positivecorrelated with the moisture contents. To, Tp gradually increased, and a positive correlationwith moisture contents was observed, Tc, ΔH was gradually decreased, and a negativecorrelation with the moisture content was found, Tc-To decreased with increasing watercontent; crystallinity decreased, and was negatively correlated with the moisture content andthe crystallinity of MWT-35was decreased by12.1%compared to that of the native starch;the SDS content showed a first increased then decrease trend with the moisture contentincreasing, RS content increased with moisture content increasing, the highest SDS contentand RS content were found in MWT-25and MWT-35, respectively, of which the SDS contentand RS content was improved by13.51%and7.43%, respectively, compared to that of nativestarch.The physiochemical and digestibility properties of cassava starch with different moisturecontents was studied after it was subjected to a range of heat-moisture treatment combinedwith microwave treatment and0.3%citric acid treatment at1W/g for20min. The pastingtemperature, increased,95℃viscosity,95℃to50℃cooling stage viscosity and Terminalviscosity decreased, and was negatively correlated with the moisture contents. To, Tpgradually increased, and showed a positive correlation with moisture contents, Tc decreased,ΔH changed little; crystallinity decreased, showed a positive correlation with moisture content,Compared with native starch, the crystalline of CA-MWT-35was decreased by14.1%, lowerthan the simple heat-moisture combined with microwave treatment; showed no ester bondwas found in the IR spectrum indicating that, there is no citric acid esterified with starch; SDSwas significantly increased, and didn’t change with water content, RS content was increasedwith moisture content increasing, the maximum RS and SDS content were found inCA-MWT-35and CA-MWT-30, respectively, of which the SDS content and RS content wasimproved by10.85%and15.43%, respectively,, compared to that of native starch. |
PDF Full Text Request