Slowly Digestible Starch: Concept, Mechanism, and Proposed Extended Glycemic Index

Abstract

Starch is the major glycemic carbohydrate in foods, and its nutritional property is related to its rate and extent of digestion and absorption in the small intestine. A classification of starch into rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) based on the in vitro Englyst test is used to specify the nutritional quality of starch. Both the RDS and RS fractions have been extensively studied while there are only limited studies on the intermediate starch fraction of SDS, particularly regarding its structural basis and slow digestion mechanism. The current understanding of SDS including its concept, measurement method, structural basis and mechanism, physiological consequences, and approaches to make SDS is reviewed. An in vivo method of extended glycemic index (EGI) is proposed to evaluate its metabolic effect and related health consequences.

Characterisation, in vitro digestibility and expected glycemic index of commercial starches as uncooked ingredients

“…Nowadays much attention is being given to SDS of starches for the development of foods low in rapidly digestible starch and hence of low glycemic index (GI). SDS is in fact considered to be beneficial for the slow and prolonged release of glucose in metabolic disorders such as diabetes or glycogen storage diseases (GSDs, in particular type I) (Bjorck and Asp 1994;Zhang and Hamaker 2009), and satiety (Lehmann and Robin 2007). The rate and extent to which starch is digested and absorbed (in vitro and in vivo hydrolysis) vary considerably depending on the structure, the conditions and the degree of food processing (i.e.…”

Effect of Cold Storage, Reheating, and Particle Sizes on In Vitro Glucose Release and Starch Digestibility among Five Rice Products in Auckland, New Zealand

“…The slowdown of rice starch digestion (i.e., hydrolysis) and thus the in vitro starch digestibility due to cold storage has been shown by others to be caused by retrogradation or recrystallisation of previously gelatinised starch [8,12,13,25].…”

“…The slower in vitro glucose release and higher RS and lower TAS and RDS of parboiled rice confirms the previous observation that parboiling (i.e., pre-cooking, drying, cooling, and then polishing) can increase starch retrogradation and alter the chemical structures of starch in ways that limit the rate of enzyme action. Furthermore, the gelatinisation of long-grain rice starch (i.e., high amylose starch) followed by hydrothermal processing (i.e., parboiling) can result in recrystallisation of starch and significantly rearranges the retrograded starch chain, thus increasing the proportion of RS [12,25,26].…”

Starch modification with microbial alpha-glucanotransferase enzymes

“…Resistant starch is mostly not degraded in the small intestine and enters the large intestine where it is degraded by gut bacteria via fermentation. Three classes of digestible starches are distinguished (Englyst, Kingman, & Cummings, 1992;Zhang & Hamaker, 2009):…”