Slowly digestible state of starch: mechanism of slow digestion property of gelatinized maize starch.
The mechanism underlying the previously reported parabolic relationship between amylopectin fine structure, represented by the weight ratio of linear short chains [degree of polymerization (DP < 13) to long chains (DP >/= 13], and slowly digestible starch (SDS) content was investigated from the viewpoint of starch retrogradation and substrate susceptibility to enzyme hydrolysis. A maize mutant sample, termed "highest long-chain starch" (HLCS) representing group I samples with a higher proportion of long chains, showed a bell-shaped SDS pattern with retrogradation time, whereas insignificant changes in SDS were found for the sample termed "highest short-chain starch" (HSCS) representing group II samples with a higher proportion of short chains. This corresponded to results from X-ray powder diffraction and differential scanning calorimetry that showed a rapid increase of crystallinity and enthalpy for HLCS during retrogradation, but negligible changes for sample HSCS. Therefore, retrogradation was associated with SDS content for group I samples, but not for group II samples. Analysis of amylopectin fine structure, SDS content, retrogradation enthalpy, SDS material debranching profile, and hydrolysis pattern demonstrated, for group I samples, that linear branched chains of DP 9-30 of amylopectin may act as anchor points to slow the digestion of branced-chain fractions of DP > 30, which constitute the major slowly digestible portion, whereas for group II samples, it is the inherent molecular structure of amylopectin with a higher amount of branches and shorter chains that is not favorable for rapid enzyme digestion. The concept of a slowly digestible starch state (SDS state) that could be a chemical or physical entity is proposed to better describe the mechanistic underpinning of the slow digestion property of starches.
School of Food Science and Technology, Jiangnan University, Wuxi 214122, Jiangsu Province, People's Republic of China. gzhang@purdue.edu
Genyi
G
Zhang
Maghaydah
M
Sofyan
Bruce R
BR
Hamaker
D000687:Amylopectin / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D004063:Digestion; D006868:Hydrolysis; D009154:Mutation; D013213:Starch / Q000737:chemistry / Q000378:metabolism*; D013816:Thermodynamics; D013997:Time Factors; D014961:X-Ray Diffraction; D003313:Zea mays / Q000737:chemistry* / Q000235:genetics; D000516:alpha-Amylases / Q000378:metabolism
D013213:Starch; D000687:Amylopectin; D000516:alpha-Amylases