Distribution of short to medium amylose chains are major controllers of in vitro digestion of retrograded rice starch

Abstract

In many cultures, rice is let to cool for a while after cooking before being consumed, which results in some retrogradation of the starch. The in vitro digestibility of 16 cooked rice starches after extended cold (4 °C) storage, which leads to extensive retrogradation, was investigated from the perspective of their starch molecular fine structure. Size-exclusion chromatography (SEC) and fluorophore-assisted carbohydrate electrophoresis (FACE) were used to characterize the starch chainlength distributions (CLD) and whole molecular size distributions. The retrograded starch gel network was studied by differential scanning calorimetry and scanning electron microscopy. Pearson correlation analysis with in vitro digestibility revealed that the starch digestion rate was positively correlated with cell size and cell wall thickness within the formed gel network, which was mainly derived from the interactions of amylose short-medium chains and not strongly related to amylopectin molecular structure. This suggests that rather than just altering amylose content, modification of amylose fine molecular structure (e.g. increasing the amount of shortmedium amylose chains) can also slow rice starch digestibility.

What makes starch from potato (Solanum tuberosum L.) tubers unique: A review

“…It is of note here that biosynthesis‐based models for the chain length distribution of both AP (Wu et al., 2013) and AM (Nada, Zou, Li, & Gilbert, 2017) have recently been developed, which are based on the fact that the starch chain distributions generally show several distinct features (maxima and/or shoulders) each of which arises from a particular enzyme set including a (GB)SS, SBE, and DBE. Fitting these models to experimental AP and AM chain length distributions provides a small set of nonempirical, biologically meaningful parameters (Gong, Cheng, Gilbert, & Li, 2019), which allow relating starch functionality to the relative activities of the three core enzymes during starch biosynthesis (i.e., (GB)SS, SBE, and DBE) that bring about its chain length distribution (Yu et al., 2019). In recent years, these models have been used by several authors in studies of the biosynthesis of cereal starches, for example, rice (Fan, Li, Lu, et al., 2019; Fan, Li, Zhang, et al., 2019; Zhu et al., 2020) and wheat (Li, Yu, Dhital, Gidley, & Gilbert, 2019) starch, and in how the distribution of their chains relates to their functionality (Gong et al., 2019; Li, Yu, Yu, Li, & Gilbert, 2019; Zhang et al., 2020).…”

“…Fitting these models to experimental AP and AM chain length distributions provides a small set of nonempirical, biologically meaningful parameters (Gong, Cheng, Gilbert, & Li, 2019), which allow relating starch functionality to the relative activities of the three core enzymes during starch biosynthesis (i.e., (GB)SS, SBE, and DBE) that bring about its chain length distribution (Yu et al., 2019). In recent years, these models have been used by several authors in studies of the biosynthesis of cereal starches, for example, rice (Fan, Li, Lu, et al., 2019; Fan, Li, Zhang, et al., 2019; Zhu et al., 2020) and wheat (Li, Yu, Dhital, Gidley, & Gilbert, 2019) starch, and in how the distribution of their chains relates to their functionality (Gong et al., 2019; Li, Yu, Yu, Li, & Gilbert, 2019; Zhang et al., 2020). In the years to come, it will be interesting to use such state‐of‐the‐art methodology to further shed light on the (biosynthesis‐related) impact of the chain length distribution of PS during food processing.…”

Molar mass effect in food and health

“…Though the digestion process of starch is complex involving the diffusion of enzyme to the substrate, adsorption of enzyme to starch granules, and the subsequent catalytic reaction, also interfered by the coexisting protein, lipid, and other compounds, improved analytical methods to study the digestion is developed recently ( Yu et al, 2018 ). Effects of chain length of amylose and amylopectin on the digestion rate of starch have recently been studied ( Gong, Cheng, Gilbert, & Li, 2019 ; Martinez et al, 2018 ). Gong et al (2019) analysed the chain length distribution by size –exclusion chromatograph (SEC) and fluorophore-assisted carbohydrate electrophoresis (FACE) for freeze-dried retrograded starch (16 different varieties rice) samples after subjecting to in vitro enzyme digestion.…”

“…Effects of chain length of amylose and amylopectin on the digestion rate of starch have recently been studied ( Gong, Cheng, Gilbert, & Li, 2019 ; Martinez et al, 2018 ). Gong et al (2019) analysed the chain length distribution by size –exclusion chromatograph (SEC) and fluorophore-assisted carbohydrate electrophoresis (FACE) for freeze-dried retrograded starch (16 different varieties rice) samples after subjecting to in vitro enzyme digestion. The starch digestion was monitored by concentration of glucose, and the digestion curves are fitted to the first order kinetics.…”

“…Starches with different weight distribution of hydrodynamic volume, V h, as a function of degree of polymerisation (DP) with different chain length distribution show different digestion processes. Higher amounts of amylose short-medium chains and relatively shorter amylose medium chains form the compact retrograded amylose networks into which digestive enzymes cannot penetrate ( Gong et al, 2019 ). …”