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.
Zhang
Genyi
G
School of Food Science and Technology, Jiangnan University, Wuxi 214122, Jiangsu Province, People's Republic of China. gzhang@purdue.edu
Sofyan
Maghaydah
M
Hamaker
Bruce R
BR
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