In this study, corn starch (CS) was debranched using pullulanase (PUL) and complexed with ovalbumin (OVA) under heat-moisture-treatment (HMT) conditions to investigate the physicochemical properties, structural properties and digestibility of corn starch-ovalbumin (CSOVA) complexes with different degrees of debranching. The results showed that PUL hydrolyzed the (1 → 6)-α glycosidic bonds to produce more linear chains as debranching time progressed, and these were able to form complexes between CSOVA complexes effectively. The combination of PUL and OVA treatment significantly changed the physicochemical properties of CS, as evidenced by the reduction in viscosity and swelling of the granules. In addition, the microscopic morphology of the CSOVA complexes gradually changed from small to large aggregates. After the addition of OVA and PUL treatment for 4 h, while X-ray diffraction (XRD) showed a crystallinity shift from A-type to B + V, with relative crystallinity decreasing from 19.45 % to 14.91 %. Fourier-transform infrared (FTIR) spectroscopy confirmed altered starch-protein interactions without new chemical bonds. In vitro digestion demonstrated resistant starch (RS) content increased to 45.6 % after 4 h of debranching. This study provides scientific evidence that the corn starch treated with PUL is a better source to form CSOVA complexes, providing a valuable slow-digesting starch.

Glycogen is a complex branched glucose polymer that serves as energy reservoir in animals and some bacteria; it has also been synthesized in vitro. It comprises small β particles linked in large aggregates termed α particles. Theory, based on the evolutionary processes which cause these particles to be formed, suggests that if all ingredients for in vitro particle synthesis were added to a suspension of α particles, then these will grow to a steady-state size distribution, after which new particles will be formed. Here, this prediction is experimentally tested and found to be verified, using in vitro glycogen β particles as the starting point. The latter were made by the method of Ciric and Loos, Carbohydrate Polymers 2013, 93, 31; this was chosen because there are considerably less components than in an in vivo system, namely glycogen synthase, glycogen branching enzyme, glycogen debranching enzyme, glycogen phosphorylase and α-glucosidase. It was also found that new-particle formation was only found starting with β particles formed in vivo, but not with those synthesized in vitro; this implies that in vivo β particles contain one or more substances additional to those in the "minimal" in vitro particle synthesis used here. HYPOTHESIS: In glycogen, β particles already contain some buds on their surface, so they might have the potential to form α particles.

Glycogen, a highly branched glucose polymer, plays a vital role in maintaining blood sugar homeostasis in vivo. Liver glycogen molecules contain small “β particles” bound together into larger composite “α particles”. Previous results showed that the structure of control and diabetic glycogen particles are different. However, changes in their mechanical properties remain unknown. The morphology and stiffness between diabetic and control murine liver glycogen were compared using an atomic force microscope. Morphological parameters of diabetic glycogen, namely particle size, height, and height-to-size ratio, were similar to those of control glycogen. However, the average Derjaguin-Muller-Toporov (DMT) modulus (a measurement of nanoscale stiffness) of diabetic glycogen was significantly higher than that of control glycogen (4.6 ± 0.7 and 3.7 ± 1.2 GPa, respectively). In addition, two types of modulus distribution patterns across glycogen particles were found from both diabetic and control livers, with diabetic glycogen having increases in stiffness towards the top center of particles. The DMT modulus of liver glycogen from control and diabetic mice was reported here for the first time. These findings indicate that diabetes induces a shift from softer to stiffer glycogen particles. This suggests functional and high-level structural differences between healthy and diabetic glycogen, which may have clinical implications, potentially leading to targeted therapies or diagnostic tools for diabetes management.

Starch nanoparticles have increasing applications as emulsion stabilizers in functional foods and drug delivery. The effects of amylose and amylopectin molecular structures on the emulsification performance of starch nanoparticles obtained from anti-solvent precipitation are explored here. From size-exclusion chromatography results, ten different starch nanoparticles with distinct molecular structures possessed a molecular size ranging from 63 nm to 111 nm. Rice-starch nanoparticles showed near-neutral wettability (contact angle 90.25°) with 100 % emulsifying stability index (ESI). Correlation analysis indicated that the maximum size of the amylopectin component was positively associated with ESI, while the amount of amylopectin long chains and the lengths of amylose short chains negatively correlated with ESI. Mechanistic reasons for these observations are put forward. These findings can help design new emulsifiers using starch nanoparticles, and development of "clean-label" (i.e. having relatively few ingredients, "natural" ingredients, and few synthetic additives) food emulsions.

The Chinese liquor baijiu is made from fermented sorghum grain. During fermentation, the cooking resistance (starch leaching rate) is an important factor for both baijiu producers and sorghum breeders, to select and breed suitable sorghum varieties. The factors and mechanisms which affect this resistance are not well understood. To investigate this, fifteen brewing sorghum varieties were used for brewing, with sampling over cooking time. The components, starch molecular structure and particle morphology of these samples were characterized and correlated with cooking parameters. In this study, high crystallinity and gelatinization enthalpy in sorghum grains were found to reduce cooking resistance by enhancing swelling power to break the seed coat and cell wall. This is the opposite of what happens in other cereal grains. High protein content, high particle size and high amylose content are the main factors for improving cooking resistance, which occurs by the formation of a crosslinked 3D structure and reduced water absorption to inhibit gelatinization. Both the average and the distribution of chain lengths of amylopectin and amylose are important factors affecting cooking resistance because, among other things, of their influence on crystal structure. This information might help manufacturers select and breed sorghum varieties which have optimal behavior for a given brewing method.

Glycogen is a glucose-storage polysaccharide molecule present in animals, fungi and bacteria. The enzyme glycogenin can self-glycosylate, forming an oligosaccharide chain that primes glycogen synthesis. This priming role of glycogenin was first believed to be essential for glycogen synthesis, but glycogen was then found in the skeletal muscle, heart, liver and brain of glycogenin-knockout mice (Gyg KO), thereby showing that glycogen can be synthesized without glycogenin. Within the liver, glycogen is present in the form of individual glycogen particles, called β particles, and larger composite aggregates of linked β particles, called α particles. Previous studies suggested that liver glycogenin plays a role in linking β particles into α particles and thus participating in glucose homeostasis, which implies that α particles would be absent in Gyg KO mice liver. Here we test this through targeted characterization of glycogen structure and through proteomic and metabolic studies on Gyg KO mice. The results show that, contrary to what had been believed, glycogenin is not necessary for normal liver-glycogen metabolism.

The chain-length distribution (CLD) of starch influences many functional properties of starch-containing substances, and also contains information about starch biosynthetic processes. The commonest method for measuring this CLD is to debranch the starch enzymatically, and then to measure the molecular weight distribution of the resulting linear chains using size-exclusion chromatography (SEC). However, SEC suffers from various artifacts, including shear scission of longer chains. Here, a method of correcting for such shear scission is developed: fitting the apparent CLDs (affected by shear scission) with biosynthesis-based models, over a range of flow rates, and extrapolating the resulting model-based parameters to zero flow rate. To apply this, the apparent CLDs of five rice starches were measured using SEC with a range of flow rates, and these apparent CLDs were parameterized using biosynthesis-based models. The model parameters fitted from CLDs at different flow rates were extrapolated to zero flow rate, and were then used to calculate the CLD that would be obtained with zero flow rate, thereby taking partial account of shear scission. The extrapolation suggests that shear scission significantly degrades extra-long (degree of polymerization, DP, >1500) amylose chains to shorter chains (DP ~ 500–1500), which, if uncorrected, would vitiate inferences from SEC results. The partial correction method devised here can be used to develop more reliable relationships between structural and biosynthesis-related parameters of starch and functional properties of starch-containing substances. Graphical Abstract

Starch and glycogen, as the primary reservoirs of energy in most living organisms, play a pivotal role in regulating metabolic processes and maintaining health. The molecular structure of these polysaccharides is a major determinant of their impact on the metabolism and overall health of the organism. This review discusses the effects of the molecular structures of starch and glycogen on human health, and provides an analysis of their structural levels, extraction methods, structural characterization techniques, mathematical models of structure, and the implications of their molecular structures for health. It offers insights into the similarities and differences between the molecular structures of starch and glycogen, and examines the role these structures play in pathological conditions. Furthermore, it presents a perspective on how the relationship between the fine structure of these biopolymers and health could lead to new findings in the biosynthesis-structure-property relations for these polymers and their impact on human well-being.

Plants produce storage and transient starches in seeds and in leaves, respectively. Understanding molecular fine structure and synthesis of transient starch can help improve plant quality (e.g. by helping breeders produce slowly digested amylopectin, which is beneficial for human nutrition). In the present study, leaf starches from rice, wheat and barley were isolated with cesium chloride gradient centrifugation. Starch fine structure was measured using size-exclusion chromatography and flurophore-assisted carbohydrate electrophoresis. The chain-length distribution (CLD) of amylopectin leaf starch was trimodal in wheat and barley leaf starch. The global peak of leaf starch was at degree of polymerization (DP) 22, and leaf amylopectin containeds more long branches, which are generally considered to hinder starch digestion, suggesting that leaf-specific starch synthesis enzymes could be expressed in the endosperm by genetic modification to produce amylopectin with more long chains, which would be more slowly digested, with advantages to human health. Hypothesis The biosynthetic processes for leaf starch and storage starch in a given plant species will show significant differences.

While cooked rice is widely consumed as a whole food, the specific characteristics and impact of its resistant starch (RS) on gut microbiota are largely unexplored. In this study, three rice varieties with distinct starch molecular structures were used to prepare RS from cooked rice. All three types of RS had a crystalline structure characterized as B + V type, with the V type being the predominant crystalline polymorph. Distinct differences in chain-length distributions were observed among different RSs, with rapidly fermentable starch fractions comprising short amylopectin and long amylose chains, while the degrees of polymerization (DPs) ∼ 10, 37, 65, and 105 fractions comprised the slowly fermentable starch. Jasmine rice RS showed the highest proportion of this slowly fermentable starch fraction, which appeared to be specifically utilized by Megasphaera_elsdenii_DSM_20460 OTU198. The fermentation of Jasmine RS resulted in the highest production of butyrate after 24 h, which was positively correlated with the relative abundance of Megasphaera_elsdenii_DSM_20460 OTU198. These findings collectively indicate that RS in cooked rice with a higher V type crystallinity and DPs ∼ 10, 37, 65, and 105 fractions promote butyrate production and stimulate the growth of butyrate-producing bacteria in the human gut, thereby conferring beneficial effects on gut health.

In fermentation to produce the alcoholic liquor baijiu, sorghum starch is the main carbohydrate source, being hydrolyzed and converted into ethanol and aromatics. The mechanisms of starch hydrolysis which affect fermentation quality and efficiency are not fully understood. To investigate this, three sorghum varieties were used as fermentation material, with two fermentation methods. Changes in the amounts of various components and in starch molecular structure in lees (sediment) during fermentation were investigated. The lees from waxy sorghum had higher fermentation rates and saccharification power than those from normal sorghum in the early stage of fermentation, but decreased below those of normal sorghum in the end stage of fermentation, due to increased accumulation of acid, which inhibited enzyme activities, and even stopped fermentation. The chain-length distributions of both amylopectin and amylose in the lees did not show significant changes with fermentation, showing that starch in sorghum grain cannot be hydrolyzed directly, but only by hydrolysis of starch leached from the grain into the water; this is in accord with data from electron micrographs indicating that starch hydrolysis happened in the leachate rather than in the lees. This information can help manufacturers fine-tune their processes to improve production processes and product.

Glycogen is a glucose polymer that plays a crucial role in glucose homeostasis by functioning as a short-term energy storage reservoir in animals and bacteria. Abnormalities in its metabolism and structure can cause several problems, including diabetes, glycogen storage diseases (GSDs) and muscular disorders. Defects in the enzymes involved in glycogen synthesis or breakdown, resulting in either excessive accumulation or insufficient availability of glycogen in cells seem to account for the most common pathogenesis. This review discusses glycogen metabolism and structure, including molecular architecture, branching dynamics, and the role of associated components within the granules. The review also discusses GSD type XV and Lafora disease, illustrating the broader implications of aberrant glycogen metabolism and structure. These conditions also impart information on important regulatory mechanisms of glycogen, which hint at potential therapeutic targets. Knowledge gaps and potential future research directions are identified.

Chinese steamed bread (CSB), which is widely consumed in East Asia, usually undergoes storage before consumption, but it is unclear how different storage temperatures affect CSB starch retrogradation and digestion properties, which are important for consumers. CSB was stored for 2 days at 25 °C, 4 °C, −18 °C, 4 °C/25 °C temperature cycling (i.e., 24 h at 4 °C, followed by 24 h at 25 °C) and −18 °C/ 25 °C temperature cycling. The results revealed for the first time that more orderly starch double helices are formed when CSB was stored at 4 °C or 4 °C/25 °C. Storage under −18 °C produced lower amounts of, but more heterogenous, starch double helices, with fewer B-type, but more V-type, crystallites. Compared to other storage temperatures, more long-range intermolecular interactions formed between the starch and protein at 4 °C or 4 °C/25 °C. CSB samples showed the slowest starch digestibility when stored at 4 °C. The impact of storage temperature on the starch retrogradation properties and digestibility of CSB also depended on the wheat variety, attributed to differences in the starch molecular structure. These results have significance and practical applications to help the CSB food industry to control starch retrogradation and digestibility. For example, CSB could be stored at 4 °C for 2 days in order to reduce its starch digestibility.

Normal rice starch consists of amylopectin and amylose, whose relative amounts and chain-length distributions (CLDs) are major determinants of the digestibility and rheology of cooked rice, and are related to metabolic health and consumer preference. Here, the mechanism of how molecular structural features of pure amylopectin (waxy) starches affect starch properties was explored. Following debranching, chain-length distributions of seven waxy varieties were measured using size-exclusion chromatography, and parameterized using biosynthesis-based models, which involve breaking up the chain-length distribution into contributions from five enzyme sets covering overlapping ranges of chain length; structure-property correlations involving the fifth set were found to be statistically significant. Digestibility was measured in vitro, and parameters for the slower and longer digestion phase quantified using non-linear least-squares fitting. The coefficient for the significant correlation involving amylopectin fine structure for the fifth set was -0.903, while the amounts of amylopectin short and long chains were found to dominate breakdown viscosity (correlation coefficients 0.801 and - 0.911, respectively). This provides a methodology for finding or developing healthier starch in terms of lower digestion rate, while also having acceptable palatability. As rice breeders can to some extent control CLDs, this can help the development of waxy rices with improved properties.

Starch is a primary source of food energy for human beings. Its chain-length distribution (CLD) is a major structural feature influencing physiologically-important properties, such as digestibility and palatability, of starch-containing foods. Diabetes, which is of epidemic proportions in many countries, is related to the rate of starch digestion in foods. Isoforms of three biosynthesis enzymes, starch synthase, starch branching enzymes and debranching enzymes, control the CLDs of starch, which can be measured by methods such as size-exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis. Fitting observed CLDs to biosynthesis-based models based on the ratios of the activities of those isoforms yields biosynthesis-related parameters describing CLD features. This review examines CLD measurement, fitting CLDs to models, relations between CLDs, the occurrence and management of diabetes, and how plant breeders can develop varieties to optimize digestibility and palatability together, to develop starch-based foods with both a lower risk of diabetes and acceptable taste.

Glycogen, a complex branched glucose polymer, is responsible for sugar storage in blood glucose homeostasis. It comprises small β particles bound together into composite α particles. In diabetic livers, α particles are fragile, breaking apart into smaller particles in dimethyl sulfoxide, DMSO; they are however stable in glycogen from healthy animals. We postulate that the bond between β particles in α particles involves hydrogen bonding. Liver-glycogen fragility in normal and db/db mice (an animal model for diabetes) is compared using various hydrogen-bond breakers (DMSO, guanidine and urea) at different temperatures. The results showed different degrees of α-particle disruption. Disrupted glycogen showed changes in the mid-infra-red spectrum that are related to hydrogen bonds. While glycogen α-particles are only fragile under harsh, non-physiological conditions, these results nevertheless imply that the bonding between β particles in α particles is different in diabetic livers compared to healthy, and is probably associated with hydrogen bonding.

Glycogen, a complex branched glucose polymer, is found in animals and bacteria, where it serves as an energy storage molecule. It has linear (1 → 4)-α glycosidic bonds between anhydroglucose monomer units, with branch points connected by (1 → 6)-α bonds. Individual glycogen molecules are referred to as β particles. In organs like the liver and heart, these β particles can bind into larger aggregate α particles, which exhibit a rosette-like morphology. The mechanisms and bonding underlying the aggregation process are not fully understood. For example, mammalian liver glycogen has been observed to be molecularly fragile under certain conditions, such as glycogen from diabetic livers fragmenting when exposed to dimethyl sulfoxide (DMSO), while glycogen from healthy livers is much less fragile; this indicates some difference, as yet unknown, in the bonding between β particles in healthy and diabetic glycogen. This fragility may have implications for blood sugar regulation, especially in pathological conditions such as diabetes.

Starch structure is often characterized by the chain-length distribution (CLD) of the linear molecules formed by breaking each branch-point. More information can be obtained by expanding into a second dimension: in the present case, the total undebranched-molecule size. This enables answers to questions unobtainable by considering only one variable. The questions considered here are: (i) are the events independent which control total size and CLD, and (ii) do ultra-long amylopectin (AP) chains exist (these chains cannot be distinguished from amylose chains using simple size separation). This was applied here to characterize the structures of one normal (RS01) wheat and two high-amylose (AM) mutant wheats (an SBEIIa knockout and an SBEIIa and SBEIIb knockout). Absolute ethanol was used to precipitate collected fractions, then size-exclusion chromatography for total molecular size and for the size of branches. The SBEIIa and SBEIIb mutations significantly increased AM and IC contents and chain length. The 2D plots indicated the presence of small but significant amounts of long-chain amylopectin, and the asymmetry of these plots shows that the corresponding mechanisms share some causal effects. These results could be used to develop plants producing improved starches, because different ranges of the chain-length distribution contribute independently to functional properties.

Glycogen is a highly branched glucose polymer that is an energy storage material in fungi and animals. Extraction of glycogen from its source in a way that minimizes its molecular degradation is essential to investigate its native structure. In this study, the following extraction methods were compared: sucrose gradient density ultracentrifugation, thermal alkali, hot alcohol and hot water extractions. Molecular-size and chain-length distributions of glycogen were measured by size-exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis, respectively. These two fine-structure features are the most likely structural characteristics to be degraded during extraction. The results show that the thermal alkali, hot alcohol and hot water extractions degrade glycogen molecular size and/or chain-length distributions, and that sucrose gradient density ultracentrifugation with neither high temperature nor alkaline treatment is the most suitable method for fungal glycogen extraction.