Digestibility, physicochemical and structural properties of octenyl succinic anhydride-modified cassava starches with different degree of substitution.

The octenylsuccinylated cassava starch (OSCS) samples with a degree of substitution (DS) in the range of 0.008 to 0.035 were prepared in this study. The structural, physicochemical, and in vitro digestibility properties of OS-starch samples were investigated. Intensities of characteristic peaks at 1724cm-1 and 1572cm-1 increased with increasing DS, which confirmed successful introduction of ester carbonyl groups into starch molecules. The esterification occurred primarily in the amorphous regions and surface of starch granule, and the crystalline pattern did not change. SEM results revealed that the modification had slight effects on the morphological structure of native starch. Differential scanning calorimetry (DSC) thermograms of OS-starch samples showed lower onset temperature, peak temperature, conclusion temperature, and endothermic energy than their native counterpart. This study also showed that esterification with OSA was an effective method for increasing slowly digestible starch and resistant starch contents in starch samples.

Effects of citric acid esterification on digestibility, structural and physicochemical properties of cassava starch.

In this study, citric acid was used to react with cassava starch in order to compare the digestibility, structural and physicochemical properties of citrate starch samples. The results indicated that citric acid esterification treatment significantly increased the content of resistant starch (RS) in starch samples. The swelling power and solubility of citrate starch samples were lower than those of native starch. Compared with native starch, a new peak at 1724 cm(-1) was appeared in all citrate starch samples, and crystalline peaks of all starch citrates became much smaller or even disappeared. Differential scanning calorimetry results indicated that the endothermic peak of citrate starches gradually shrank or even disappeared. Moreover, the citrate starch gels exhibited better freeze-thaw stability. These results suggested that citric acid esterification induced structural changes in cassava starch significantly affected its digestibility and it could be a potential method for the preparation of RS with thermal stability.

Effects of continuous and intermittent retrogradation treatments on in vitro digestibility and structural properties of waxy wheat starch.

The effects of continuous retrogradation (CR) and intermittent retrogradation (IR) treatments under 4 °C and 25 °C or temperature-cycled condition of 4/25 °C on the digestibility and structural properties of waxy wheat starch were investigated. The results indicated that IR treatment under temperature cycles of 4/25 °C (IR-4/25) was more beneficial to the formation of slowly digestible starch (SDS, 42.24%). Moreover, the gelatinisation enthalpy of IR-4/25-treated starch sample was lower than that of CR-4/25-treated sample. Variation in infrared absorbance ratio of 1047 cm(-1)/1022 cm(-1) of IR-treated starch samples was consistent with relative crystallinity. Through retrogradation treatment under 4/25 °C or 4 °C, starch samples exhibited X-ray diffraction pattern of B-type, while CR-25 and IR-25-treated samples showed a mixed A+B type pattern. Besides, the swelling power of CR-4/25-treated starch sample was higher than that of IR-4/25-treated sample. The pasting temperatures of IR-treated starch samples were higher than those of the CR-treated samples.