Exploring the surface morphology of developing wheat starch granules by using Atomic Force Microscopy

Structural, properties and digestion in vitro changes of starch subjected to high pressure homogenization: An update review

High pressure homogenization (HPH) is considered as a promising method for improving the ideal metabolic reaction of starch-based foods in the body, but there is still no comprehensive understanding of the structure-property relationship of starch treated with HPH. This study reviews the advantages and limitations of HPH in starch-based foods processing in recent years. It also elaborates the bidirectional regulation of HPH on starch structure-property and its potential in improving nutritional quality, which includes the regular modification effects of HPH on the multi-scale structure, physicochemical properties, and digestion characteristics of starch. It was found that HPH could lead to the degradation of amylopectin, destruction of amorphous structure, and homogenization of fine particles, promoting gelatinization and ultimately endowing starch with good solubility and digestibility. Moreover, it could reorganize and reorder the internal starch chains, or cause the particles to disintegrate into an amorphous state, thereby enhancing the anti-digestibility of starch. The interaction of starch with different nutrients during the HPH process could be further investigated in future studies and explored with other techniques for structure-property modifications, which would help expand the development of personalized starch foods to meet growing consumer demands.

Effects of nitrogen fertilizer application on the physicochemical properties of foxtail millet (Setaria italica L.) starch

The use of nitrogen fertilizer is a crucial agronomic practice to increase crop output and quality. This study investigated the impact of five nitrogen application levels (0, 60, 135, 210, and 285 kg N/hm2) on the physicochemical properties of foxtail millet (FM) starch. Optimal nitrogen application (210 kg N/hm2) significantly increased L*, a*, and b* values, water and oil absorption capacity, water solubility, and swelling power of starch. The number of small starch granules increased as the nitrogen application rate increased, but the granule morphology and typical A-type pattern did not change among the treatments. Nitrogen application increased the relative crystallinity and ordered structure, resulting in a higher gelatinization enthalpy. Compared to the control group (7.02 J/g), the enthalpy increased by 21.94 %, 66.38 %, 73.50 %, and 103.28 % under the nitrogen application rates, respectively. Moreover, nitrogen application greatly increased the percentage of A and B3 chains while it lowered the apparent amylose content, peak viscosity, and final viscosity. The effects of 210 and 285 kg N/hm2 treatments on the water solubility and swelling power, water and oil absorption, and light transmission of starch were greater compared to the 60 and 135 kg N/hm2 treatments. These results indicate that nitrogen fertilization significantly affects the physicochemical properties of FM starch.

Insights into starch synthesis and amino acid composition of common buckwheat in response to phosphate fertilizer management strategies

To investigate the response and the regulatory mechanism of common buckwheat starch, amylose, and amylopectin biosynthesis to P management strategies, field experiments were conducted in 2021 and 2022 using three phosphorus (P) levels. Results revealed that the application of 75 kg hm-2 phosphate fertilizer significantly enhanced amylopectin and total starch content in common buckwheat, leading to improved grain weight and starch yield, and decreased starch granule size. The number of upregulated differentially expressed proteins induced by phosphate fertilizer increased with the application rate, with 56 proteins identified as shared differential proteins between different P levels, primarily associated with carbohydrate and amino acid metabolism. Phosphate fertilizer inhibited amylose synthesis by downregulating granule-bound starch synthase protein expression and promoted amylopectin accumulation by upregulating 1,4-alpha-glucan branching enzyme and starch synthase proteins expression. Additionally, Phosphate fertilizer primarily promoted the accumulation of hydrophobic and essential amino acids. These findings elucidate the mechanism of P-induced starch accumulation and offer insights into phosphate fertilizer management and high-quality cultivation of common buckwheat.

Extraction, purification and characterization of amylose from sago and corn: Morphological, structural and molecular comparison

In the present work, a comprehensive study was carried out to better understand the molecular characteristics of amylose extracted from sago starch, using butanol as the extraction solvent. The sago derived amylose was compared with amylose extracted from corn starch and both characterized through different techniques, i.e. size exclusion chromatography, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, Raman spectroscopy, Scanning electron microscopy, Atomic force microscopy and Zeta potential measurements. The purity of the amylose extracted from sago and corn was 99.20 % and 93.46 %, respectively. From XRD results, it was revealed that sago amylose had more crystallinity with high thermal stability compared to corn amylose. Based on Raman spectra, single and double helices formed in both extracted amyloses, but due to their intrinsic differences, the intensities associated with these helices varied for sago and corn amylose. Purified amyloses were shown to have two different forms of spherulite morphology: torus and spherical shapes with varying degrees of roughness. Our findings demonstrated that sago starch is a novel and low-cost source for supplying amylose, a promising polymer for different applications.

Impact of long-term ultrasound treatment on structural and physicochemical properties of starches differing in granule size

Granule size is a critical parameter affecting starch processing properties. Ultrasound treatments of up to 22 h were applied on two starches differing in granule size (quinoa starch and maize starch). The two starches showed significantly different trends in both structural and physicochemical aspects affected by the ultrasound treatments. For the small granule starch (volume-weighted mean particle size of 1.79 μm), short-term ultrasonication caused an increase of swelling power. As the treatment time increased, the physicochemical properties were influenced by the degradation of amylopectin external chains. The X-ray diffraction results showed a decrease of relative crystallinity and changes of peak areas with long-term treatment. On the other hand, a balance between amylose leaching and surface damages was seen for the large granule starch (volume-weighted mean particle size of 18.3 μm). The effect of ultrasound modification on starches with different molecular and granular structures was discussed. A possible mechanism of the ultrasound effect was proposed.

Effects of elevated nitrogen fertilizer on the multi-level structure and thermal properties of rice starch granules and their relationship with chalkiness traits

BACKGROUND

Chalkiness in rice reduces its market value and affects consumer acceptance. Research on the mechanism of chalkiness formation has focused primarily on the activity of key enzymes of carbon metabolism and starch accumulation. The relationship between the formation of chalkiness induced by N fertilizer and rice starch's multi-level structure and thermal properties still needs to be fully elucidated.

RESULTS

In this study, the rates of chalky grains and degree of chalkiness decreased with the increase in N fertilizer dosage. This was attributed to an increased proportion of short chains, ordered structure carbon chains, small starch granules, and branched starches, and a higher degree of crystallinity and ΔHg in protein, and a decreased proportion of amylose, large starch granules, and weighted average diameter of starch granule surface area and volume. Application of N fertilizer promoted an increased proportion of short-branched chain amylopectin to develop a more ordered carbohydrate structure and crystalline lamella. These effects enhanced the normal development and compactness of starch granules in grains, and improved their arrangement morphology, thereby reducing the chalkiness in rice.

CONCLUSION

These changes in starch multi-level structure and protein improve the physicochemical characteristics of starch and enhance the fullness, crystallinity and compactness of starch granules, while synergistically increasing the regularity and homogeneity of starch granules and thus optimizing the stacking pattern of starch granules, leading to a reduction in rice chalkiness under nitrogen fertilization and thus improving the appearance of rice. © 2023 Society of Chemical Industry.

Understanding the Relationship between the Molecular Structure and Physicochemical Properties of Soft Rice Starch

The relationship between the molecular structure and physicochemical properties of soft rice starch (SRS) has been investigated in this research. The amylose content of SRS ranged from 10.76% to 11.85%, classified as the very low amylose type. Compared to waxy and japonica rice starch, the largest amount of small starch granules and the highest viscosity were shown in the SRS. The results of X-ray diffraction and Fourier transform infrared proved that the SRS depicted a typical A-type pattern with a low short-range ordered structure. Additionally, SRS had a great deal of A and B1 chains. Molecular weights and density of starch from soft rice were lower than those from waxy rice but higher than those from japonica rice. Furthermore, SRS possessed a higher amount of resistant starch. Correlation analysis indicated that the amylose content and the chain-length distributions of amylopectin play a major role in influencing the molecular structure and physicochemical properties of rice starch. In conclusion, the low amylose content, highest viscosity, and other excellent properties of soft rice starch make it have bright application prospects in instant rice and rice cakes.

Moderate Reduction in Nitrogen Fertilizer Results in Improved Rice Quality by Affecting Starch Properties without Causing Yield Loss

The quality and starch properties of rice are significantly affected by nitrogen. The effect of the nitrogen application rate (0, 180, and 230 kg ha^-1) on the texture of cooked rice and the hierarchical structure and physicochemical properties of starch was investigated over two years using two japonica cultivars, Bengal and Shendao505. Nitrogen application contributed to the hardness and stickiness of cooked rice, reducing the texture quality. The amylose content and pasting properties decreased significantly, while the relative crystallinity increased with the increasing nitrogen rates, and the starch granules became smaller with an increase in uneven and pitted surfaces. The proportion of short-chain amylopectin rose, and long-chain amylopectin declined, which increased the external short-range order by 1045/1022 cm^-1. These changes in hierarchical structure and grain size, regulated by nitrogen rates, synergistically increased the setback viscosity, gelatinization enthalpy and temperature and reduced the overall viscosity and breakdown viscosity, indicating that gelatinization and pasting properties were the result of the joint action of several factors. All results showed that increasing nitrogen altered the structure and properties of starch, eventually resulting in a deterioration in eating quality and starch functional properties. A moderate reduction in nitrogen application could improve the texture and starch quality of rice while not impacting on the grain yield.

Effects of selenium solution on the crystalline structure, pasting and rheological properties of common buckwheat starch

Selenium is an important element that affects human growth and development, and also affects the yield and quality of common buckwheat. In our study, two common buckwheat varieties were sprayed with different concentrations (0 g/hm², 5 g/hm², 20 g/hm²) of sodium selenite solution at the initial flowering period and the full flowering period, respectively, to determine the effects of selenium solution on the physicochemical properties of common buckwheat starch. With increasing selenium levels, the amylose content, peak viscosity, breakdown, relative crystallinity, pasting temperature and gelatinization enthalpy first decreased and then increased, while the transparency showed a trend of increasing and then decreasing. All samples exhibited a typical A-type pattern, while at high selenium level, the degree of short-range order of common buckwheat starches changed. From the rheological properties, it can be seen that the starch paste is dominated by elastic properties, while the low selenium treatment decreases the viscosity of the starch paste. These results showed that spraying different concentrations of selenium solutions at different periods significantly affected the physicochemical properties of common buckwheat starch.

Formation of Starch-Lipid Complexes during the Deep-Frying Process and Its Effects on Lipid Oxidation

In the present study, maize starch (MS), potato starch (PS), high-amylose maize starch (HAMS), and wheat starch (WS) were deep-fried in soybean oil that was continuously heated for 40 h under 180 °C. The thermodynamic and pasting properties of deep-fried starch samples were determined. The results suggested that starch−lipid complexes formed with the extension of frying oils’ usage; however, their number was not dependent on the frying oils’ life cycle. Importantly, the results of pasting properties revealed the following strength of intermolecular force in deep-fried starch samples: PS > MS > HAMS > WS. The results of XRD and FTIR analysis confirmed the formation of starch−lipid complexes during the deep-frying process. Furthermore, the results of the in vitro digestibility of deep-fried starch revealed that the formation of starch−lipid complexes inhibited the swelling of starch granules and prevented the entrance of amylase into the interior. Additionally, the results of the oxidation stability of deep-frying oil indicated that the formation of starch−lipid complexes did not alter the trend of lipid oxidation as an effect of the limited number of starch−lipid complexes. These results could have critical implications for the development of healthier deep-fried foods.

Methods for characterizing the structure of starch in relation to its applications: a comprehensive review

Starch is a major part of the human diet and an important material for industrial utilization. The structure of starch granules is the subject of intensive research because it determines functionality, and hence suitability for specific applications. Starch granules are made up of a hierarchy of complex structural elements, from lamellae and amorphous regions to blocklets, growth rings and granules, which increase in scale from nanometers to microns. The complexity of these native structures changes with the processing of starch-rich ingredients into foods and other products. This review aims to provide a comprehensive review of analytical methods developed to characterize structure of starch granules, and their applications in analyzing the changes in starch structure as a result of processing, with particular consideration of the poorly understood short-range ordered structures in amorphous regions of granules.

Starch granule size: Does it matter?

Nature has developed starch granules varying in size from less than 1 μm to more than 100 μm. The granule size is an important factor affecting the functional properties and the applicability of starch for food and non-food applications. Within the same botanical species, the range of starch granule size can be up to sevenfold. This review critically evaluated the biological and environmental factors affecting the size of starch granules, the methods for the separation of starch granules and the measurement of size distribution. Further, the structure at different length scales and properties of starch-based on the granule size is elucidated by specifying the typical applications of granules with varying sizes. An amylopectin cluster model showing the arrangement of amylopectin from inside toward the granule surface is proposed with the hypothesis that the steric hindrance for the growth of lamellar structure may limit the size of starch granules.

Effects of mid-stage nitrogen application timing on the morphological structure and physicochemical properties of japonica rice starch

BACKGROUND

Nitrogen management of crops, especially when mid-stage nitrogen is applied, is a key factor affecting the yield and grain quality of rice (Oryza sativa). Here, the timing of mid-stage nitrogen application was evaluated for its effect on rice grain quality by assessing the morphological structure and physicochemical properties of starch from two japonica rice cultivars growing in fields (Nangeng 9108 and Nangeng 5055).

RESULTS

The experiment was arranged in a split-plot design, with the two rice cultivars as the main plot factor and three timings of mid-stage nitrogen application as the within-plot factor. Briefly, three applications were made: at the emergence of the top-sixth-leaf (ahead), the top-fourth-leaf (normal), and the top-second-leaf (delayed) of the main stem. Delaying mid-stage nitrogen application caused the starch granule surface to become uneven and significantly reduced its particle size, whereas it increased the polished rice rate, chalkiness degree, and protein content. Furthermore, the apparent amylose content decreased with a delay in mid-stage nitrogen application, thereby resulting in higher relative crystallinity, swelling power, water solubility, gelatinization enthalpy, and low retrogradation. Finally, we also found that delaying this nitrogen application lowered the characteristic values of rice flour viscosities, leading to cooking quality deterioration.

CONCLUSION

These results therefore suggest that delaying mid-stage nitrogen application enhances the processing and nutritional qualities of japonica rice but evidently has an adverse effect upon its appearance and cooking qualities. © 2020 Society of Chemical Industry.

Diverse effects of nitrogen fertilizer on the structural, pasting, and thermal properties of common buckwheat starch

At present, the yield of common buckwheat, which is mainly grown in northern Shaanxi of China, is low and the grain quality is poor. Nitrogen is an important nutrient for the growth of common buckwheat, and appropriate nitrogen application can improve the grain quality. Nitrogen fertilizer could alter the starch granule morphology shapes and the granule size distribution. With increasing nitrogen levels, branch number, flower clusters number, grain number per plant, contents of protein and fat, size distribution of "C" granules, and percentages of light transmittance significantly increased, whereas amylose content and retrogradation decreased. All the samples displayed typical A-type X-ray diffraction patterns. Starch showed higher pasting temperature and gelatinization enthalpy but lower trough and final viscosities under high nitrogen levels. These results suggested N₂ treatment was more suitable for common buckwheat growth, principal components and correlation analysis revealed that nitrogen fertilizer significantly affected the physicochemical properties of common buckwheat starches.

Rice starch accumulation at different endosperm regions and physical properties under nitrogen treatment at panicle initiation stage

The quality of rice grain is characterized by the component, structure and physicochemical properties of starch accumulated in endosperm cell. Nitrogen uptake strongly affects rice growth and starch development. In this study, Nangeng 9108 was used to investigated the accumulation of starch in different positions of the endosperm and physical properties of starch under nitrogen treatment of panicle initiation (PI) stage. Compared with the control group (CG), nitrogen treatment group (NTG) featured a higher number of grains per panicle and 1000-grain weight. Nitrogen treatment significantly increased starch accumulation among different regions during endosperm development, which was expressed as central endosperm cells > sub-aleurone cells of abdominal endosperm > sub-aleurone cells of dorsal endosperm. The amyloplast increased by constricting and budding-type division, generated a bead-like structure and derived some vesicles. The particle size of the starch granules obtained from the NTG was smaller and the apparent amylose content was lower than those of the CG, resulting in higher relative crystallinity. Nitrogen treatment promoted double helical components and provided a higher degree of order at short-rang scale for the starch granules. This study indicated that nitrogen significantly affected the accumulation and physicochemical properties of starch in the endosperm.

Effects of high temperature during two growth stages on caryopsis development and physicochemical properties of starch in rice

Global warming may affect the development of rice at different growth stages, thereby decreasing rice yield and deteriorating grain quality. The difference in rice responses to high temperature during primordial differentiation (PD) and pollen filling (PF) stages has been rarely studied. In this paper, two temperature treatments (40 °C and 30 °C) at the two stages (PD and PF) were imposed to four rice groups under the controlled temperature chambers. Compared with rice under normal temperature, high temperature-stressed rice showed accelerated growth rate, smaller caryopsis and decreased yield. Moreover, high temperature affected the starch physicochemical properties, resulting in lower apparent amylose content and higher order degree, gelatinization temperatures, and thereby increased peak, trough and final viscosities in starch. High temperature during PD stage inhibited cell development and starch deposition, thus leading to small starch granule and low retrogradation. However, temperature-stressed rice during PF stage showed increased starch accumulation and larger granule size. Therefore, effects of high temperature during the two stages on caryopsis development and starch properties were partly similar but also notably different. These results enriched and deepened the study of high temperature-stressed rice and served as an important reference for the processing and utilization of rice starch in food industry.

Effects of potassium fertilization on potato starch physicochemical properties

Potato starch serves as an excellent raw material or food additive in the food industry. With the advancement of the potato staple food strategy in China, improving the potato starch yield and quality has attracted more and more attention. Potassium is an essential nutrient for potato due to its direct effects on the yield and quality of potato tubers. Here, the effects of three different potassium levels on potato starch physicochemical properties were evaluated by field experiments. With increasing potassium fertilization rates, the amylose content, phosphorus content and particle size decreased, thereby resulting in low gelatinization temperature, breakdown and setback viscosity, and high swelling power, relative crystallinity and transparency. Our study indicated that enhanced potassium fertilization improved the resistance to heat and shear stress and decreased the retrogradation of starch, and the 270 kg/ha potassium fertilization rate could obtain the highest tuber and starch production with desirable starch physicochemical properties. The integrated results also provide some novel insights into the management of the fertilization conditions to obtain native starches with special properties.

Understanding Starch Structure: Recent Progress

Starch is a major food supply for humanity. It is produced in seeds, rhizomes, roots and tubers in the form of semi-crystalline granules with unique properties for each plant. Though the size and morphology of the granules is specific for each plant species, their internal structures have remarkably similar architecture, consisting of growth rings, blocklets, and crystalline and amorphous lamellae. The basic components of starch granules are two polyglucans, namely amylose and amylopectin. The molecular structure of amylose is comparatively simple as it consists of glucose residues connected through α-(1,4)-linkages to long chains with a few α-(1,6)-branches. Amylopectin, which is the major component, has the same basic structure, but it has considerably shorter chains and a lot of α-(1,6)-branches. This results in a very complex, three-dimensional structure, the nature of which remains uncertain. Several models of the amylopectin structure have been suggested through the years, and in this review two models are described, namely the “cluster model” and the “building block backbone model”. The structure of the starch granules is discussed in light of both models.

Revealing the frictional transition in shear-thickening suspensions

Shear thickening in dense particulate suspensions was recently proposed to be driven by the activation of friction above an onset stress needed to overcome repulsive forces between particles. Testing this scenario represents a major challenge because classical rheological approaches do not provide access to the frictional properties of suspensions. Here we adopt a different strategy inspired by pressure-imposed configurations in granular flows that specifically gives access to this information. By investigating the quasi-static avalanche angle, compaction, and dilatancy effects in different nonbuoyant suspensions flowing under gravity, we demonstrate that particles in shear-thickening suspensions are frictionless under low confining pressure. Moreover, we show that tuning the range of the repulsive force below the particle roughness suppresses the frictionless state and also the shear-thickening behavior of the suspension. These results, which link microscopic contact physics to the suspension macroscopic rheology, provide direct evidence that the recent frictional transition scenario applies in real suspensions.

Effect of Nitrogen Management on the Structure and Physicochemical Properties of Rice Starch

Nitrogen management (nitrogen application ratio at transplanting, tillering, and panicle initiation growth stages) is an important parameter in crop cultivation and is closely associated with rice yield and grain quality. The physicochemical and structural properties of starches separated from two rice varieties grown under three different nitrogen management ratios (9:1; 7:3; 6:4) were investigated. As the percentage of nitrogen used in the panicle initiation stage increased, the content of small starch granules improved, whereas the content of large granules decreased. Amylose content decreased with increasing nitrogen ratio at the panicle initiation stage, thereby resulting in high swelling power, water solubility, gelatinization enthalpy, and low retrogradation. The X-ray diffraction patterns of the starches were found to be A type. The present study indicated that the best nitrogen management ratio for the cultivation of rice with the highest yield, desirable starch physicochemical properties for high quality cooked rice, and a moderate protein level is 7:3.

Structure of Arabidopsis leaf starch is markedly altered following nocturnal degradation

Little is known about the thermal properties and internal molecular structure of transitory starch. In this study, granule morphology, thermal properties, and the cluster structure of Arabidopsis leaf starch at beginning and end of the light period were explored. The structural properties of building blocks and clusters were evaluated by using diverse chromatographic techniques. On the granular level, starch from end of day had larger granule size, thinner crystalline lamellae thickness, lower free surface energy of crystals, and lower tendency to retrograde than that from end of night. On the molecular level, the starch had lower amylose content, larger cluster size, and higher number of blocks per cluster at the end of day than at end of night. It is concluded that the core of the granules contains a more permanent molecular and less-ordered physical structure different from the transitory layers laid down around the core at daytime.