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

Characterization of starch structures isolated from the grains of waxy, sweet, and hybrid sorghum (Sorghum bicolor L. Moench)

In this study, starches were isolated from inbred (sweet and waxy) and hybrid (sweet and waxy) sorghum grains. Structural and property differences between (inbred and hybrid) sweet and waxy sorghum starches were evaluated and discussed. The intermediate fraction and amylose content present in hybrid sweet starch were lower than those in inbred sweet starch, while the opposite trend occurred with waxy starch. Furthermore, there was a higher A chain (30.93-35.73% waxy, 13.73-31.81% sweet) and lower B₂ + B₃ chain (18.04-16.56% waxy, 24.07-17.43% sweet) of amylopectin in hybrid sorghum starch. X-ray diffraction (XRD) and Fourier transform infrared reflection measurements affirm the relative crystalline and ordered structures of both varieties as follows: inbred waxy > hybrid waxy > hybrid sweet > inbred sweet. Small angle X-ray scattering and ¹³C CP/MAS nuclear magnetic resonance proved that the amylopectin content of waxy starch was positively correlated with lamellar ordering. In contrast, an opposite trend was observed in sweet sorghum starch due to its long B₂ + B₃ chain content. Furthermore, the relationship between starch granule structure and function was also concluded. These findings could provide a basic theory for the accurate application of existing sorghum varieties precisely.

High temperature boosts resistant starch content by altering starch structure and lipid content in rice ssIIIa mutants

High temperature (HT) during grain filling had adverse influences on starch synthesis. In this study, the influences of HT on resistant starch (RS) formation in rice were investigated. Most genes in ssIIIa mutants especially in RS4 were upregulated under Normal Temperature (NT) while downregulated under HT when compared with those of wild parent R7954. ssIIIa mutants had higher RS content, more lipid accumulation, higher proportion of short chains of DP 9-15, and less long chains of DP ≥37. ssIIIa mutation exacerbated the influences of HT on starch metabolite and caused larger declines in the expression of BEI, BEIIa, BEIIb, and SSIVb when exposed to HT. HT reduced the contents of total starch and apparent amylose significantly in wild type but not in mutants. Meanwhile, lipids were enriched in all varieties, but the amounts of starch-lipid complexes and the RS content were only heightened in mutants under HT. HT led to greatest declines in the amount of DP 9-15 and increases in the proportion of fb3 (DP ≥37); the declines and increases were all larger in mutants, which resulted in varied starch crystallinity. The increased long-chain amylopectin and lipids may be the major contributor for the elevated RS content in mutants under HT through forming more starch-lipid complexes (RSV).

Insight into multi-scale structural evolution during gelatinization process of normal and waxy maize starch

By using a mimicked heating with ex-situ liquid nitrogen flash freezing method, multi-scale structural evolution behaviors of normal maize starch (NMS) and waxy maize starch (WMS) during gelatinization process were studied. The results from SEM, X-ray diffraction (XRD), FTIR/solid state NMR spectroscopy and small angle X-ray scattering (SAXS) showed that NMS and WMS exhibited differently structural evolution behavior during gelatinization process. As the temperature increase, the proportion of the NMS granules with cavity gradually increased, while after heating beyond (peak gelatinization temperature (Tp) + conclusion gelatinization temperature (Tc))/2 the disappearance of starch granule integrity occurred for WMS. The relative crystallinity of NMS declined from 32.8 to 15.26% gradually, as that of WMS declined from 42.43 to 13.09% with a sharply descent when heated beyond (Tp + Tc)/2. The loss of short-range order structure of NMS and WMS showed same trends according to FTIR and NMR. Semicrystalline lamellae of NMS became thinner gradually while that of WMS showed an apparently narrowing after heating beyond (Tp + Tc)/2. These results suggest that the destruction of double helix in amylopectin structure had greatly influence on the larger scale structure of starch samples. This strategy is important for thorough understanding and profiting starch-based food processing.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05520-2.

Establishment of a quality evaluation system of sweet potato starch using multivariate statistics

Background

The quality of starch greatly affects the quality of processed products. There are many indexes for quality evaluation of starch. Currently, amylose content is considered the chief index in the quality evaluation of sweet potato starch, which is entirely based on tradition (experience) method. The existing evaluation standards lack quality evaluation standards for sweet potato starch.

Purpose

To screen reasonable evaluation indexes of sweet potato starch, and establish a scientific and systematic evaluation system of sweet potato starch.

Methods

Twenty-two components and quality indexes of sweet potato starch were measured. The evaluation indexes of sweet potato starch were screened based on a statistical description, correlation analysis, and principal component analysis (PCA), and a quality evaluation model of sweet potato starch for brewing was established based on analytic hierarchy process. The calculated values of the model were verified by linear fitting with standardized sensory evaluation values.

Results

The coefficient of variation of total starch content (%), amylose content (%), amylopectin content (%), L* value, ΔE, water absorption capacity (g/g), and pasting temperature was less than 6%, while the coefficient of variation of other indexes was larger. In addition, there were different degrees of correlation among the indexes. PCA was used to identify interrelated variables, and the first six principal components together account for 82.26% of the total variability. Then, seven core indexes — setback (cp), rate of regression (%), ratio of amylose to amylopectin (%), gel strength (kgf/cm2), a* value, ash content (%), and solubility (%) — were selected from the six principal components according to the load value of the rotation matrix. These seven core indexes replaced the original 22 indexes to simplify the evaluation of sweet potato starch. The quality evaluation model of sweet potato starch was Y = 0.034X2 + 0.321X6 + 0.141X8 + 0.08X17 + 0.023X19 + 0.08X21 + 0.321X22.

Conclusion

The comprehensive evaluation system of sweet potato starch can accurately predict the quality of sweet potato starch. The development of such a system is of great significance to the post-harvest processing of high-starch sweet potato and the breeding of high-quality and high-starch sweet potato varieties.

Organocatalytic acetylation of pea starch: Effect of alkanoyl and tartaryl groups on starch acetate performance

Organocatalytic acetylation of pea starch was systematically optimized using tartaric acid as catalyst. The effect of the degree of substitution with alkanoyl (DSacyl) and tartaryl groups (DStar) on thermal and moisture resistivity, and film-forming properties was investigated. Pea starch with DSacyl from 0.03 to 2.8 was successfully developed at more efficient reaction rates than acetylated maize starch. Nevertheless, longer reaction time resulted in granule surface roughness, loss of birefringence, hydrolytic degradation, and a DStar up to 0.5. Solid-state 13C NMR and SEC-MALS-RI suggested that tartaryl groups formed crosslinked di-starch tartrate. Acetylation increased the hydrophobicity, degradation temperature (by ~17 %), and glass transition temperature (by up to ~38 %) of pea starch. The use of organocatalytically-acetylated pea starch with DSacyl ≤ 0.39 generated starch-based biofilms with higher tensile and water barrier properties. Nevertheless, at higher DS, the incompatibility between highly acetylated and native pea starches resulted in a heterogenous/microporous structure that worsened film properties.

A review on application of molecular simulation technology in food molecules interaction

Molecular simulation is a new technology to analyze the interaction between molecules. This review mainly summarizes the application of molecular simulation technology in the food industry. This technology has been employed to assess structural changes of biomolecules, the interaction between components, and the mechanism of physical and chemical property alterations. These conclusions provide a deeper understanding of the molecular interaction mechanism in foods, break through the limitations of scientific experiments and avoid blind and time-consuming scientific research. In this paper, the advantages and development trends of molecular simulation technology in the food research field are described. This methodology can be used to contribute to further studies of the mechanism of molecular interactions in food, confirm experimental results and provide new ideas for research in the field of food sciences.

Hydrothermal induced B → A allomorphic transition in retrograded starches with side chains elongated by amylosucrase to different lengths

In this study, chain-elongated starches were modified with hydrothermal treatment to produce hydrothermal-treated starches with different crystalline structures. All chain-elongated starches showed a B-type crystalline structure and the retrogradation of long branch chains accelerated the formation of starch crystallites. The hydrothermal treatment preserved the granular structure of starches but facilitated the rearrangement of starch chains to generate crystallites. Starches with short chain length favored the B → A allomorphic transition during the hydrothermal treatment. A longer chain length of starch led to greater stability of double helices and accordingly inhibited the B → A allomorphic transition, resulting from the hydrogen bonding along with the direction of helix restrained the displacement of the helix. The longer double helices resulted in higher gelatinization temperature of the chain-elongated starches. Moreover, the gelatinization temperature of the starches was further enhanced by the hydrothermal treatment, and both increased crystallinity and B → A allomorphic transition contributed to the improved thermal stability of the hydrothermal-treated starches.

Effect of dual modification with citric acid combined with ultrasonication on hydrolysis kinetics, morphology and structure of corn starch dispersions

Corn starch dispersions (CSD) were hydrolyzed with citric acid and compared with CSD co-treated with citric acid combined with ultrasonication for 1 to 18 days, which are designated as single modification (CSD-SM) and dual modification (CSD-DM), respectively. The logistic functions monitor the dynamics of the hydrolysis advance (%) of the CSD-SM and CSD-DM as a function of time, where the zones most vulnerable to the single-treatment and/or co-treatment of the corn starch granules (CSG) are the amorphous or disordered regions. The characterization results of CSD-DM suggest that the structural changes caused by dual modification affected the morphology, sequence, and microstructure of the CSG. The heterogeneous changes caused by the dual modification changed the configuration of the CSG, generating a kind of destemming of the amorphous lamellae (depolymerization), an increase in the percentage of relative crystallinity of the CSD-DM and an active rearrangement of the intralamellar chains that promoted the relative amount of double helix for 18 days of double modification. The synergistic effect of the dual modification for CSD by the sequential combination of a chemical treatment followed by a physical one improved the hydrolyzed advance by 12 %, the relative crystallinity by 10 %, and the promotion of double helices by 25 % during 18 days of co-treatment.

Tuning heterologous glucan biosynthesis in yeast to understand and exploit plant starch diversity

Background

Starch, a vital plant-derived polysaccharide comprised of branched glucans, is essential in nutrition and many industrial applications. Starch is often modified post-extraction to alter its structure and enhance its functionality. Targeted metabolic engineering of crops to produce valuable and versatile starches requires knowledge of the relationships between starch biosynthesis, structure, and properties, but systematic studies to obtain this knowledge are difficult to conduct in plants. Here we used Saccharomyces cerevisiae as a testbed to dissect the functions of plant starch biosynthetic enzymes and create diverse starch-like polymers.

Results

We explored yeast promoters and terminators to tune the expression levels of the starch-biosynthesis machinery from Arabidopsis thaliana. We systematically modulated the expression of each starch synthase (SS) together with a branching enzyme (BE) in yeast. Protein quantification by parallel reaction monitoring (targeted proteomics) revealed unexpected effects of glucan biosynthesis on protein abundances but showed that the anticipated broad range of SS/BE enzyme ratios was maintained during the biosynthetic process. The different SS/BE ratios clearly influenced glucan structure and solubility: The higher the SS/BE ratio, the longer the glucan chains and the more glucans were partitioned into the insoluble fraction. This effect was irrespective of the SS isoform, demonstrating that the elongation/branching ratio controls glucan properties separate from enzyme specificity.

Conclusions

Our results provide a quantitative framework for the in silico design of improved starch biosynthetic processes in plants. Our study also exemplifies a workflow for the rational tuning of a complex pathway in yeast, starting from the selection and evaluation of expression modules to multi-gene assembly and targeted protein monitoring during the biosynthetic process.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01408-x.

Starch-Based Electrochemical Sensors and Biosensors: A Review

Natural green compounds for sensor modification (binders) are challenging in electrochemistry. Starch is a carbohydrate biopolymer that has been used extensively in the development of biomaterials for the food industry due to its ability to impart textural characteristics and provide gelling or film formation. In particular, the excellent film-forming characteristics have been used for the development of new surface modifying architectures for electrodes. Here, we highlight a very comprehensive overview of the properties of interest of various types of starch in conjunction with (bio)materials in the chemical modification of sensors and biosensors. Throughout the review, we first give an introduction to the extraction, applications, and properties of starches followed by an overview of the prospects and their possible applications in electrochemical sensors and biosensors. In this context, we discuss some important characteristics of starches and different strategies of their film formation with an emphasis on their role in the development of electrochemical sensors and biosensors highlighting their main contributions to enhancing the performance of these devices and their applications in environmental and clinical samples.

A more efficient synthesis and properties of saturated and unsaturated starch esters

This work presents a series of starch esters synthesized via 1,5,7-triazabicyclo[4.4.0]-dec-5-ene (TBD) catalyzed transesterifications in dimethyl sulfoxide (DMSO). The reaction was performed with saturated and unsaturated fatty acids (8, 11, and 18 carbon atoms). The degree of substitution (DS) was raised by purging the reaction flask with nitrogen instead of simply performing the reaction under a nitrogen atmosphere. The increase of DS was most obvious for long-chain fatty acids, as an almost complete DS was observed for starch stearate (2.8) and starch oleate (2.7). The products were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction. Starch esters from unsaturated fatty acids have a lower T_g than their saturated analogues. Moreover, contact angle and moisture uptake measurements showed increased hydrophobicity for all starch esters in comparison to pristine starch. Our results show a more efficient method for synthesizing a biobased material that steers into the direction of a material that could replace conventional plastics.

Effect of pH on the Redox and Sorption Properties of Native and Phosphorylated Starches

Starch is a common biopolymer that can be used for removing heavy metal ions from aqueous solutions. A valuable property of starch is its functional diversity, which can be enhanced by chemical modification. Hydroxyl groups enclosed in the starch and formed during hydrolysis act as reducing agents of Cr(VI). The sorption properties of native starch depend mainly on the presence of carboxyl groups formed during redox processes and basic centers created during acid hydrolysis, while the superiority of phosphorylated starch is related to the presence of phosphate groups binding Cr(III) ions. The effectiveness of starch depends on a series of equilibria established in its aqueous suspension and chromate ions solution, where the pH is the driving force for these processes. In this article, a systematic discussion of pH changes being the consequence of chemical reactions unraveling the extraordinary functionalities of starch was given. It also explained the influence of establishing equilibria and chemical modifications of starch on the efficiency of chromium ion removal. This allowed for the development of a comprehensive mechanism for the interaction of Cr(VI) and Cr(III) ions with native and phosphorylated starch.

Combined Effects of Different Alleles of FLO2, Wx and SSIIa on the Cooking and Eating Quality of Rice

The improvement of the cooking and eating quality (CEQ) of rice is one of the major objectives of current rice-breeding programs. A few major genes such as Waxy (Wx) and starch synthase IIa (SSIIa) have been successfully applied in molecular breeding. However, their interactive effects on CEQ have not been fully understood. In this study, a recombinant inbred line (RIL) population was constructed by crossing the white-core mutant GM645 with the transparent phenotype of the japonica rice variety Tainung 67 (TN67). GM645 and TN67 contain different alleles of FLOURY ENDOSPERM2 (FLO2), Wx, and SSIIa. The effects of different allele combinations of FLO2, Wx, and SSIIa on the CEQ of rice were investigated. The inbred lines with the mutation allele flo2 had a significantly lower apparent amylose content (AAC), viscosity characteristics except for setback (SB), and gel texture properties compared to those lines with the FLO2 allele. The allelic combination of FLO2 and Wx significantly affected the AAC, breakdown (BD), and gel textural properties, which could explain most of the variations in those rice quality traits that were correlated with AAC. The allelic combination of FLO2 and SSIIa significantly affected the hot paste viscosity (HPV) and pasting temperature (PT). The Wx × SSIIa interaction had a significant effect on the PT. The interaction of FLO2, Wx and SSIIa significantly affected the AAC, cold paste viscosity (CPV), PT, and consistency viscosity (CS). These results highlight the important roles of these quality-related genes in regulating the CEQ of rice and provide new clues for rice-quality improvement by marker-assisted selection.

Cluster Size of Amylopectin and Nanosized Amylopectin Fragments Characterized by Pyrene Excimer Formation

Amylopectin from waxy corn and the three nanosized amylopectin fragments (NAFs)—NAF(56), NAF(20), and NAF(8)—from waxy corn starch with a hydrodynamic diameter of 227, 56, 20, and 8 nm, respectively, were randomly labeled with 1-pyrenebutyric acid. The efficiency of these pyrene-labeled amylopectin-based polysaccharides (Py-AbPS) for pyrene excimer formation (PEF) upon diffusive encounter between an excited and a ground-state pyrene increased with increasing concentration of unlabeled NAF(56) in Py-AbPS dispersions in DMSO. Fluorescence decay analysis of the Py-AbPS dispersions in DMSO prepared with increasing [NAF(56)] yielded the maximum number (N_blob^exp) of anhydroglucose units (AGUs) separating two pyrene-labeled AGUs while still allowing PEF. Comparison of N_blob^exp with N_blob^theo, obtained by conducting molecular mechanics optimizations on helical oligosaccharide constructs with HyperChem, led to a relationship between the interhelical distance (d_h-h) in a cluster of oligosaccharide helices, [NAF(56)], and the number of helices in a cluster. It was found that the AbPSs were composed of building blocks made of 3.5 (±0.9) helices that self-assembled into increasingly larger clusters with increasing [NAF(56)]. The ability of PEF-based experiments to yield the cluster size of AbPSs provides a new experimental means to probe the interior of AbPSs at the molecular level.

The effects of fermentation of Qu on the digestibility and structure of waxy maize starch

The fermentation of Qu (FQ) could efficiently produce enzymatically modified starch at a low cost. However, it is poorly understood that how FQ influences the waxy maize starch (WMS) structure and the digestion behavior. In this study, WMS was fermented by Qu at different time and starches were isolated at each time point, and its physico-chemical properties and structural parameters were determined. Results showed that the resistant starch (RS), amylose content (AC), the average particle size [D(4,3)] the ratio of peaks at 1,022/995 cm^-1, and the onset temperature of gelatinization (T _o ) were increased significantly after 36 h. Conversely, the crystallinity, the values of peak viscosity (PV), breakdown (BD), gelatinization enthalpy (ΔH), and the phase transition temperature range (ΔT) were declined significantly after 36 h. It is noteworthy that smaller starch granules were appeared at 36 h, with wrinkles on the surface, and the particle size distribution was also changed from one sharp peak to bimodal. We suggested that the formation of smaller rearranged starch granules was the main reason for the pronounced increase of RS during the FQ process.

Polysaccharide-based nanosystems: a review

Polysaccharide-based nanosystem is an umbrella term for many areas within research and technology dealing with polysaccharides that have at least one of their dimensions in the realm of a few hundreds of nanometers. Nanoparticles, nanocrystals, nanofibers, nanofilms, and nanonetworks can be fabricated from many different polysaccharide resources. Abundance in nature, cellulose, starch, chitosan, and pectin of different molecular structures are widely used to fabricate nanosystems for versatile industrial applications. This review presents the dissolution and modification of polysaccharides, which are influenced by their different molecular structures and applications. The dissolution ways include conventional organic solvents, ionic liquids, inorganic strong alkali and acids, enzymes, and hydrothermal treatment. Rheological properties of polysaccharide-based nano slurries are tailored for the purpose functions of the final products, e.g., imparting electrostatic functions of nanofibers to reduce viscosity by using lithium chloride and octenyl succinic acid to increase the hydrophobicity. Nowadays, synergistic effects of polysaccharide blends are increasingly highlighted. In particular, the reinforcing effect of nanoparticles, nanocrystals, nanowhiskers, and nanofibers to hydrogels, aerogels, and scaffolds, and the double network hydrogels of a rigid skeleton and a ductile substance have been developed for many emerging issues.

Physiochemical and thermal characterisation of faba bean starch

The structure and physicochemical properties of starch isolated from the cotyledon and hull of faba beans and from wheat (as reference) were examined using 16 different methods. The amylose content in faba bean cotyledon and hull starch was 32% and 36%, respectively, and that in wheat starch was 21%. The faba bean cotyledon and hull starch were structurally alike both displaying C-polymorphic pattern, a similar degree of branching and similar branch chain length distributions. Wheat starch had a significantly greater prevalence of short amylopectin chains (DP < 12) and a higher degree of branching. Granules in both faba bean starches exhibited surface cracks and were more homogenous in size than the smoother wheat starch granules. Gelatinisation temperature was higher for the faba bean starches, likely as an effect of high amylose content and longer starch chains delaying granular swelling. Cotyledon starch produced pastes with the highest viscosities in all rheological measurements, probably owing to larger granules. Higher prevalence of lipids and resistant starch reduced the viscosity values for hull starch. For all starches, viscosity increased at faster heating rates. During the rheological analyses, the samples were exposed to different instruments, heating rates and temperatures ranges, differing from standard rheological procedures, which could help predict how different processing techniques effect the final starch textures.

Graphical abstract

Dual-modified starch micelles as a promising nanocarrier for doxorubicin

Natural amphiphilic polymer micelles have garnered considerable research attention as nanocarriers for delivering drugs. The objective of this study was to explore the possibility of applying biocompatible dual-modified starch micelles as drug delivery vehicles. To this end, a dual-modified corn starch polymer (SCD) was synthesized with zwitterionic sulfobetaine and deoxycholic acid; spherical micelles with an average particle size of ~200 nm were prepared through the self-assembly of SCD. The effects of dual modification on the degree of substitution, molecular structure, and functional properties of SCD were investigated. Further, doxorubicin was successfully incorporated into the micelles, and an in vitro drug release study was performed to confirm that the drug-loaded micelles displayed pH-sensitive properties with controlled and sustained release. The dissolve-diffuse-erosion-degradation release process was described according to the dynamic models of drug release for SCD micelles. The results can be used as reference information for further studies in the biotechnology and pharmaceutical domains.

Supramolecular structure of quinoa starch affected by nonenyl succinic anhydride (NSA) substitution

Quinoa starch granular structure as affected by nonenyl succinic anhydride (NSA) substitution was investigated by multiple approaches, including scattering, spectroscopic, and microscopic techniques. The modification had little impact on the morphology of starch granules. The NSA substitution was found mainly in the amorphous lamellae and amorphous growth rings. The NSA modification increased the thickness of the amorphous lamellae. The homogeneity of the ordered structure in the granules was improved, probably because the NSA modification reduced the amount of defects in the semi-crystalline growth ring. Compared to other chemical modifications such as acylation, succinylation was more effective in modifying the starch lamellar structure. A possible reaction pattern of NSA modification on quinoa starch is proposed, in which the NSA modification may follow the sequence of amorphous growth rings, the amorphous matrices among blocklets, amorphous and crystalline lamellae in semi-crystalline growth rings. This study provides new insights on the structural changes of starch granules induced by succinylation on the supramolecular level.

Crystallography of polysaccharides: Current state and challenges

Polysaccharides are the most abundant class of biopolymers, holding an important place in biological systems and sustainable material development. Their spatial organization and intra- and intermolecular interactions are thus of great interest. However, conventional single crystal crystallography is not applicable since polysaccharides crystallize only into tiny crystals. Several crystallographic methods have been developed to extract atomic-resolution structural information from polysaccharide crystals. Small-probe single crystal diffractometry, high-resolution fiber diffraction and powder diffraction combined with molecular modeling brought new insights from various types of polysaccharide crystals, and led to many high-resolution crystal structures over the past two decades. Current challenges lie in the analysis of disorder and defects by further integrating molecular modeling methods for low-resolution diffraction data.

Polysaccharides: Sources, Characteristics, Properties, and Their Application in Biodegradable Films

Biodegradable films emerge as alternative biomaterials to conventional packaging from fossil sources, which, in addition to offering protection and increasing the shelf life of food products, are ecologically sustainable. The materials mostly used in their formulation are based on natural polysaccharides, plasticizing agents, and bioactive components (e.g., antimicrobial agents or antioxidants). The formulation of biodegradable films from polysaccharides and various plasticizers represents an alternative for primary packaging that can be assigned to specific food products, which opens the possibility of having multiple options of biodegradable films for the same product. This review describes the main characteristics of the most abundant polysaccharides in nature and highlights their role in the formulation of biodegradable films. The compilation and discussion emphasize studies that report on the mechanical and barrier properties of biodegradable films when made from pure polysaccharides and when mixed with other polysaccharides and plasticizing agents.

Combined effects of starch fine molecular structures and water content on starch digestibility of cooked white rice

Although the starch digestibility of cooked white rice has been investigated with regard to its relation to starch structure, it is not yet clear how starch molecular structure and water content affect its digestion rate. To investigate this, the in vitro starch digestibility and molecular structure of 10 rice varieties with a range of rice-to-water cooking ratios were investigated. As expected, starch digestibility varied with different conditions. Typically, a higher amylose content resulted in a lower maximum digestion extent for a given water content. Having relatively more and longer amylopectin intermediate chains caused a slower starch digestion rate, but only with rice-to-water ratios between 1:1 and 1:1.2. These results could prove useful to find combinations of starch fine molecular structures and water contents to produce cooked rice with low glycemic index.

Starch molecular structural differences between chalky and translucent parts of chalky rice grains

Chalky rice has an undesirable appearance and reduced commercial value. To understand the relationship between starch structural characteristics and chalkiness, a comprehensive investigation was conducted of molecular structural differences between starch in chalky and translucent parts of the same chalky grains (three Japonica and two Indica rices), this strategy being such as to minimize genetic and environmental effects. Compared to translucent parts, chalky parts had a larger ratio of large to small branched molecules and more short amylopectin chains (degree of polymerization < 35), but fewer longer chains, which affect higher-level starch structures, such as crystallinity. No significant differences in amylose structure were observed. White-belly and white-core chalky grains showed distinguishable starch characteristics, suggesting studying different chalkiness types separately. These findings extend understanding of chalkiness from the perspective of starch structure, and control of this structure can in the future help breeders to develop strategies against the formation of chalkiness.

Structural and physicochemical properties of composites between starch nanoparticles and β-carotene prepared via nanoprecipitation

To apply starch nanoparticles (SNP) as host materials for β-carotene encapsulation, aqueous SNP dispersions (10, 25, 50, and 100 mg/10 mL) and β-carotene in acetone (10, 50, 100, 150, and 200 μg/mL) were mixed. The acetone in the mixture was evaporated to prepare SNP and β-carotene composites, which were homogeneously dispersed in aqueous media with over 90 % solubility. When SNP content was higher than 50 mg, over 80 % of β-carotene was encapsulated in the composite matrix. X-ray diffraction, nuclear magnetic resonance spectroscopy, and transmission electron microscopic analyses confirmed the micellar-shaped composite particles with diameters <120 nm and an amorphous structure. High SNP content in the composites enhanced β-carotene stability under extremely hot and acidic conditions as well as against ultraviolet rays and oxidation reactions. The encapsulated β-carotene was not readily released in simulated gastric fluid, but was gradually released in simulated intestinal fluid via SNP digestion in the composites.

Polyiodide Confinement by Starch Enables Shuttle-Free Zn-Iodine Batteries

Aqueous Zn-iodine (Zn-I₂ ) batteries have been regarded as a promising energy-storage system owing to their high energy/power density, safety, and cost-effectiveness. However, the polyiodide shuttling results in serious active mass loss and Zn corrosion, which limits the cycling life of Zn-I₂ batteries. Inspired by the chromogenic reaction between starch and iodine, a structure confinement strategy is proposed to suppress polyiodide shuttling in Zn-I₂ batteries by hiring starch, due to its unique double-helix structure. In situ Raman spectroscopy demonstrates an I₅ ^- -dominated I^- /I₂ conversion mechanism when using starch. The I₅ ^- presents a much stronger bonding with starch than I₃ ^- , inhibiting the polyiodide shuttling in Zn-I₂ batteries, which is confirmed by in situ ultraviolet-visible spectra. Consequently, a highly reversible Zn-I₂ battery with high Coulombic efficiency (≈100% at 0.2 A g^-1 ) and ultralong cycling stability (>50 000 cycles) is realized. Simultaneously, the Zn corrosion triggered by polyiodide is effectively inhibited owing to the desirable shuttling-suppression by the starch, as evidenced by X-ray photoelectron spectroscopy analysis. This work provides a new understanding of the failure mechanism of Zn-I₂ batteries and proposes a cheap but effective strategy to realize high-cyclability Zn-I₂ batteries.

Effects of psyllium fiber on in vitro digestion and structure of different types of starches

BACKGROUND

Starch digestibility in foods strongly depends on the structure, other ingredients and processing conditions used. This study aimed to investigate the effect of psyllium fiber on gelatinization, crystallinity and in vitro digestibility of starches having different crystalline structures (A, B and C). Wheat, potato and tapioca starches with and without added psyllium fiber were heated at 90 °C for 10 min at three different solid:water (w:v) ratios (1:1, 1:2 and 1:5). The added fiber content was 50% (dry base) in the solid fraction for the fiber-added samples.

RESULTS

Wheat, potato and tapioca starches showed different structural, morphological and starch digestibility properties. The effect of cooking and fiber addition on starch digestion differed for the starch types, mainly wheat starch. Psyllium addition during cooking decreased the rapidly digestible starch (RDS) fractions while increasing the slowly digestible starch (SDS) and remaining/resistant starch (RS) fractions. The effect of psyllium fiber addition was not limited to restricting the swelling and gelatinization of starch granules during heating. Psyllium fiber effectively restricted the mobility of digestive enzymes during digestion.

CONCLUSION

Understanding the relationship between psyllium and starch digestibility for different types of starch could assist in designing food formulations with lower starch digestibility. These in vitro data, however, should be confirmed by in vivo studies. © 2021 Society of Chemical Industry.

Physicochemical properties of A- and B-type granules isolated from waxy and normal hull-less barley starch

Large A-type and small B-type starch granules separated from waxy and normal hull-less barley starches were investigated for their physicochemical properties. Hull-less barley starch granules were covered by a membrane composed mainly of phospholipids. Channels of waxy A- and B-type granules were rich in proteins and phospholipids. Compared with A-type starch, B-type starch exhibited higher specific surface area, volume and average diameter of mesopores. Waxy A-type granules exhibited the higher peak, breakdown, final and setback viscosity than did B-type granules, while normal A-type granules showed the lower peak, breakdown, final viscosity and the higher setback viscosity than did B-type granules. B-type starch gels with lower storage modulus exhibited a less elastic gel network structure and retrograded more slowly. Moreover, in vitro hydrolysis of starch showed that the B-type granules exhibited a higher hydrolysis extent and rate than the A-type granules in the first stage, which was consistent with higher initial α-amylase binding ability of B-type granules. The study showed that the A-type and B-type starch separated from waxy and normal hull-less barley exhibited very different physicochemical properties.