Recent developments in methods and instrumentation have contributed to major advances in our understanding of the fine structure of amylose and amylopectin. The structure of the starch granule slowly unravels with new insight into key structural features. Following a brief presentation of the structural features common to all starches, the most recent findings for the structure of amylose and amylopectin are reported. The organization of different types of chains in amylopectin is discussed with a critical review of the 'cluster' model leading to the presentation of alternative models. The locations of molecular components in the starch granule are described according to a progress structural order. The description of the crystalline components is followed by a presentation of their supramolecular arrangements. The crystalline components comprise platelet nanocrystals which have already been identified and characterized, and other less well characterized 'blocklet components'. The location and state of amylose within the granule is also presented. This comprehensive review aims at distinguishing between those structural features that have received widespread acceptance and those that are still under debate, with the ambition of being educational and to provide stimulation for further fundamental investigation into the starch granule as a macromolecular assembly.

The molecular structures of starch components and their contribution to the architecture of starch granules: A comprehensive review

Starch retrogradation is a process in which disaggregated amylose and amylopectin chains in a gelatinized starch paste reassociate to form more ordered structures. Starch retrogradation has been the subject of intensive research over the last 50 years, mainly due to its detrimental effect on the sensory and storage qualities of many starchy foods. However, starch retrogadation is desirable for some starchy food products in terms of textural and nutritional properties. To better understand the effect of starch retrogradation on the quality of starchy foods, measurement methods of starch retrogradation and factors that influence starch retrogradation have been studied extensively. This article provides a comprehensive review of starch retrogradation including the definition of the process, molecular mechanisms of how it occurs, and measurement methods and factors that influence starch retrogradation. The review also discusses the effect of retrogradation on the in vitro enzyme digestibility of starch. Spectroscopic methods such as FTIR and Raman are considered to be very promising in characterizing starch retrogradation at a molecular level, although more studies are needed in the future.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/1541-4337.12143

Starch retrogradation: a comprehensive review

Grain legumes occupy an important place in human nutrition, especially in the dietary pattern of low-income groups of people in developing countries. Legumes, considered as poor man's meat, are generally good sources of slow release carbohydrates and are rich in proteins. Legumes are normally consumed after processing, which not only improves palatability of foods but also increases the bioavailability of nutrients, by inactivating trypsin and growth inhibitors and haemagglutinins. Starch, the major biopolymeric constituent of legumes, upon processing gets partially modified into resistant starch (RS). The latter, a man made functional dietary fibre, is a unique ingredient that can yield high quality foods, in addition to its significance on faecal bulk and butyrate production, which are the putative markers of colonic health of humans. The slow and reduced digestibility of legume starch has been attributed to its amylose, which is considerably branched and is of high molecular weight. Dietary fibre, which is a heterogeneous mixture of several types of polysaccharides, is rich in legumes, especially in their husk fractions and contributes to beneficial therapeutic health effects.

Grain legumes--a boon to human nutrition.

Nutritional value of bread: Influence of processing, food interaction and consumer perception

Starch is the most important glycemic carbohydrate in foods. The relationship between the rate and extent of starch digestion to produce glucose for absorption into the bloodstream and risk factors for diet-related diseases is of considerable nutritional interest. Native starch is attacked slowly by enzymes, but after hydrothermal processing its susceptibility to enzymatic breakdown is greatly increased. Most starch consumed by humans has undergone some form of processing or cooking, which causes native starch granules to gelatinize, followed by retrogradation on cooling. The extent of gelatinization and retrogradation are major determinants of the susceptibility of starch to enzymatic digestion and its functional properties for food processing. The type and extent of changes that occur in starch as a result of gelatinization, pasting and retrogradation are determined by the type of the starch, processing and storage conditions. A mechanistic understanding of the molecular disassembly of starch granules during gelatinization is critical to explaining the effects of processing or cooking on starch digestibility. This review focuses on the molecular disassembly of starch granules during starch gelatinization over a wide range of water levels, and its consequential effect on in vitro starch digestibility and in vivo glycemic index.

Molecular disassembly of starch granules during gelatinization and its effect on starch digestibility: a review.

Three high-amylose maize starches (HAS) and a common corn starch (CCS) were subjected to differential alcohol precipitation using isoamyl alcohol and 1-butanol to obtain fractions designated as amylose (AM), amylopectin (AP), and intermediate material (IM). For each starch, IM had a blue value and an iodine binding wavelength maximum (λmax) between the λmax of the respective AM and AP. Size-exclusion chromatography (SEC) showed similarities in the AM from CCS and HAS. HAS AP had higher blue values and iodine binding λmax values than CCS AP. SEC of the intact HAS AP and IM both showed large proportions of material eluting after the void volume (45–85%) when compared to CCS AP and IM. Chain length (CL) distributions of debranched AP and IM indicated that these fractions from each starch were highly branched, and that AP had a shorter average chain length than IM. Consequently, the differential precipitation behavior of the HAS AP and IM appears dependent on general branching structure rather than s...

Fractionation of High-Amylose Maize Starches by Differential Alcohol Precipitation and Chromatography of the Fractions

Retrogradation of three high-amylose starches (HAS: ae du, ae V, and ae VII) and common corn starch (CCS) was examined by dynamic oscillatory rheometry (7.5% [w/w] starch in 20% [v/v] dimethyl sulfoxide [DMSO]), differential scanning calorimetry (DSC; 30% [w/w] starch in water), and turbidity (0.5% [w/w] starch in 20% [v/v] DMSO). Nongranular lipid-free starch and starch fractions (amylose [AM], amylopectin [AP], and intermediate material [IM]) were studied. Gels were prepared by dispersing starches or fractions in 90% DMSO and diluting with water, followed by storage for seven days at 4°C. For AM from each starch, the elastic modulus (G′) was similar when heated from 6 to 70°C. The G′ of HAS AP gels at 6°C was higher than for CCS AP gels. For nongranular CCS and ae du gels, G′ dropped dramatically (≈100×) when heated from 6 to 70°C, less (≈10×) for ae V gels, and least (≈5×) for ae VII gels. By DSC, each AM endotherm had a peak temperature of ≈140°C, whereas all AP endotherms were complete befor...

Amylose and Amylopectin Interact in Retrogradation of Dispersed High-Amylose Starches

The importance of the nature of the amylopectin and the amylose-to-amylopectin ratio in the gelation of high-amylose maize starch was examined by preparing gels of model systems using amylose (AM) from a high-amylose maize starch mixed with an amylopectin (AP): either wx starch, acid-hydrolyzed wx starch (AH-wx), ae wx starch, or wx β-limit dextrin. Mixtures of 7.5% starch in 20% dimethyl sulfoxide (DMSO) were examined by differential scanning calorimetry and dynamic oscillatory rheometry. Mixtures of 1.88 or 3.75% AM with the remainder either wx or AH-wx developed a measurable elastic modulus (G′) within one day, more quickly than for the corresponding AP without AM. Gels of AM with either wx or AH-wx starch developed a higher retrogradation enthalpy (ΔH) than corresponding AP without AM when the ΔH values were normalized to the amylopectin content. The G′ and ΔH of all gels containing ae wx did not change after one day. During heating of the gels to 80°C, most of the G′ at 25°C was lost, indica...

Amylopectin Nature and Amylose-to-Amylopectin Ratio as Influences on the Behavior of Gels of Dispersed Starch

Le fractionnement de l'amidon de mais donne de l'amylose, de l'amylopectine et un materiau intermediaire . L'amylopectine ne peut etre precipite par l'alcool isoamylique et le butanol. Les travaux concernant la determination de la structure fine et des branchements de l'amylopectine sont presentes ici.

Jeffrey D. Klucinec

Papers

Fractionation of High-Amylose Maize Starches by Differential Alcohol Precipitation and Chromatography of the Fractions

Amylose and Amylopectin Interact in Retrogradation of Dispersed High-Amylose Starches

Amylopectin Nature and Amylose-to-Amylopectin Ratio as Influences on the Behavior of Gels of Dispersed Starch

Structure of Amylopectins from ae-Containing Maize Starches