Preparation,Structure And Properties Of Resistant Starch From Wheat Starch

In the present study,three different methods including pullulanase debranching-repeatedheat-moisturetreatment?PUL-RHMT?,citricacid esterification-repeated heat-moisture treatment?CT-RHMT?and debranching-glycerin monostearin-heat-moisture treatment?DS-GMS-HMT?were applied to prepare resistant starch?RS?from wheat starch?WS?,A-type?AS?and B-type wheat starch granules?BS?.The effect of these three methods on structural,physicochemical properties and in vitro digestibility were investigated.First of all,PUL-RHMT was utilized to prepare RS from WS,AS and BS,and the impacts of pullulanase concentration and the cycling times of RHMT on the formation of RS₃ were investigated.Under the conditions of pullulanase concentration of 60U/g and cycling times of 2,the RS contents of WS and AS were 80.24%and 81.85%,respectively.And under the conditions of pullulanase concentration of 40U/g and cycling times of 2,the RS content of BS was 82.77%.PUL-HMT2 sample exhibited higher gelatinization temperatures?T_o and T_p?and enthalpy change??H?in comparison with native starches.The full width at half maximum?FWHM?of the band at 480 cm^-1,the absorbance ratio of 1047/1022 cm^-1 and the relative crystallinity of PUL-HMT2 sample increased,and the crystal type was changed from A-type to A+V-type;while the ratio of?-1,6 glycosidic bond in the starch molecules,the absorbance ratio of 1022/995 cm^-1,swelling power,solubility,amylose content and the iodine binding ability decreased.Moreover,the surface of the starch granules became rough,and more agglomerates appeared on the surface of the PUL-HMT2 starch granules.In the second place,CT-RHMT was applied to prepare RS from WS,AS and BS,and the effect of the amount of citric acid and the cycling times of RHMT on the formation of RS₄ were studied.The results showed that the amount of citric acid was40%,and after one cycling of RHMT,the maximum RS contents reached 85.54%,78.89%and 86.46%for WS,AS and BS,respectively.Compared with the native starches,the endothermic and crystalline peaks of CT-HMT starch sample disappeared;More collapses and destructiveness appeared on the surfaces of CT-HMT starch granules.The FWHM of the band at 480 cm^-11 and the absorbance ratios of 1047/1022cm^-1 increased;CT-HMT starch sample had higher RS content and better thermal stability after cooking,and the hydrolysis kinetic parameters?C?and k?in first-order kinetic equation reduced after CT-HMT.Furthermore,the effect of DS-GMS-HMT on the structural properties and digestibility of WS,AS and BS were explored.The effect of debranching time and the amount of GMS on the formation of RS₅ were studied.The results showed that under the conditions of the debranching time of 6 h and the amount of GMS of 2%,the RS contents of WS,AS and BS significantly increased and reached 81.46%,83.55%and82.30%,respectively.Compared with native starch and DS-GMS starch sample,DS-GMS-HMT starch sample exhibited higher gelatinization temperatures?T_o and T_p?,enthalpy change??H?and broader gelatinization temperature range;Fourier transform infrared?FT-IR?spectroscopy confirmed the formation of the complexes between debranched starches and GMS,and the crystal type of DS-GMS complexes displayed a mixture of A-type and V-type patterns.More ordered structure of starch was formed during HMT;the amylose contents and iodine affinity of DS-GMS complexes decreased after HMT.Confocal laser scanning microscope?CLSM?revealed that GMS was distributed mostly on the surfaces of starch granules.And the hydrolysis kinetic parameters?C?and k?of DS-GMS-HMT starch sample decreased.Based on study on the three methods for preparing wheat resistant starch as mentioned above,the present study show that wheat resistant starch prepared by PUL-RHMT has simple operation process and no chemical agent contamination;CT-RHMT is an effective method for preparing RS with thermal stability.The RS₅type resistant starch prepared by DS-GMS-HMT is a new type of RS,which is potential to be applied in the food industry.