The molecular structure, morphology, and physicochemical property and digestibility of potato starch after repeated and continuous heat–moisture treatment

Abstract

The multiscale structural, physicochemical, and digestible properties of potato starch before and after heatmoisture treatment were investigated, and further compared between repeated heat-moisture treatment (RHMT) and continuous heat-moisture treatment (CHMT). After heat-moisture treatment, there appeared partial disruption and pits on the starch granules, and the birefringence edges of HMT starch particles became blurred. Besides, the molecular weight of samples conspicuously decreased after two kinds of treatments. The crystal type of HMT starches transformed from B-type to C-type according to X-ray analysis. A decrease in the solubility and swelling power in high temperatures were identified. The pasting temperature, the gelatinization transition temperature (T o , T p , T c), and the slowly digestible starch (SDS) content of HMT starches were significantly higher than native potato starch, while the peak viscosity, the trough viscosity, the final viscosity, the breakdown, and the gelatinization enthalpy (H) of RHMT and CHMT potato starches decreased compared to the native. RHMT potato starches displayed significantly higher relative crystallinity degree and gelatinization transition temperatures. The cooling process of RHMT in which the linkage between the recombinant amylose/amylopectin was enhanced compared with CHMT, which contributed to that RHMT potato starches exhibited greater advantages in practical applications.

Heat-Moisture Treatment Further Reduces In Vitro Digestibility and Enhances Resistant Starch Content of a High-Resistant Starch and Low-Glutelin Rice

“…Similar observations have also been made in other B-type starches of tuber and legume plants under thermal treatments [30,43,44]. The alteration in the crystalline structure of starch might be attributed to the rearrangement of starch chains during the process of HMT [30,43]. Notably, the intensity of a diffraction peak at 2θ angle of ~20 • became gradually stronger in the course of HMT treatment for sbeIIb/Lgc1, suggesting the increasing presence of the starch-lipid complex [29,36], which might be positively related to the increased RS content in the gelatinized HMT rice flour (Figure 1).…”

“…Concomitantly, the relative crystallinity of HMT sbeIIb/Lgc1 rice flours gradually increased when the rice flour mass fraction was 90% to 70%. Similar observations have also been made in other B-type starches of tuber and legume plants under thermal treatments [30,43,44]. The alteration in the crystalline structure of starch might be attributed to the rearrangement of starch chains during the process of HMT [30,43].…”

“…Compared with chemical modifications that need additional chemical reagents, hydrothermal treatment as a widely used physical modification method is considered to be more readily accessible and environmentally friendly [28,29]. Among different hydrothermal treatment methods, heat-moisture treatment (HMT), which applies low moisture content (generally below 35%) and high temperature (generally 80~140 • C) for certain durations, has been proven to be effective in changing the susceptibility of cereal starch to α-amylase [29,30]. HMT affects the crystalline structure of starch and changes the interactions of starch chains in the amorphous and crystalline regions [30].…”

“…Among different hydrothermal treatment methods, heat-moisture treatment (HMT), which applies low moisture content (generally below 35%) and high temperature (generally 80~140 • C) for certain durations, has been proven to be effective in changing the susceptibility of cereal starch to α-amylase [29,30]. HMT affects the crystalline structure of starch and changes the interactions of starch chains in the amorphous and crystalline regions [30]. In many cases, the proportion of slowly digestible starch (SDS) and RS content increased to various extents following HMT, but in other cases, HMT raised the digestibility of starch [29][30][31].…”

“…HMT affects the crystalline structure of starch and changes the interactions of starch chains in the amorphous and crystalline regions [30]. In many cases, the proportion of slowly digestible starch (SDS) and RS content increased to various extents following HMT, but in other cases, HMT raised the digestibility of starch [29][30][31]. The incongruence and variations in the effects of HMT on starch digestibility in the literature could well be attributed to a number of factors, such as different plant species or genetic background, the innate properties of starch (e.g., amylose content, starch crystalline structure, starch granule size), the content of other components (e.g., protein and lipids), heat sources, and the parameters of HMT [29,32].…”