Effect of a gibberellin-biosynthesis inhibitor treatment on the physicochemical properties of sorghum starch

Outer shell: Natural biomaterial derived from starch for effective anthocyanin interaction

Since starch is a native biomaterial for anthocyanin delivery, its binding capacity plays a crucial role in its applications. In this study, four starch fractions derived form starch (granule, outer shell, blocklet, molecules including AM and AP) were separated and characterized. Following that, their interactions with cyanidin-3-O-glucoside (C3G) under different pH conditions (3, 5, and 7) were investigated. The structural characteristics of outer shell appeared to increase its binding capacity. It was found that outer shell exhibited the highest binding capacity to C3G at pH 3, resulting in enhanced oxidation, photolysis, and simulated in vitro digestion stability. To explain the highest binding capacity of outer shell, interactions between each starch biomaterial and C3G was revealed through microscopic morphology, ordered structure, and interaction force. It was observed that C3G disrupted the morphology and ordered structures of starch biomaterials through bridging interactions. Additionally, electrostatic interactions played a dominant role in the binding of outer shell/granule with C3G, while hydrogen bonds were primarily involved in the binding of blocklet/AM/AP with C3G. In summary, C3G exhibited strong electrostatic interactions with both the exterior and interior of the outer shell, owing to its large spatial structure, which contributed to the enhanced binding capacity and stability of C3G.

Effect of different milling methods on isolation of pinto bean starch, and the characteristics of the isolated starches

This study investigated the effects of various dry milling methods (blade mill (BLM), stone mill (SM), hammer mill (HM), and burr mill (BM)) at different milling severities on pinto bean flour properties, influencing the starch isolation process and isolated starch characteristics. BLM and HM produced fine flours (<180 μm) with lower starch damage (<1 %) compared to SM and BM. The starch isolation yield and efficiency increased with a reduction in flour particle size. The highest isolation yield (38 %) and efficiency (85 %) were observed from flours of BLM at 5 min. The milling-induced changes in the starch properties of the flour also altered the characteristics of starch isolated from the flour. The gelatinization and pasting properties of flour were affected by the presence of non-starch components, and starch damage while in isolated starch, they were affected only by starch damage that occurred during milling. Both the flour and isolated starch exhibited changes in crystallinity based on particle size. The water and oil holding capacities were not significantly affected by milling.

Mechanism of multiscale structural reassembly controlled by molecular chains during amylase digestion of wheat starch

The digestive characteristics of wheat starch (WS) are closely related to its structure. However, the mechanisms underlying the multiscale structural evolution and reassembly controlled by molecular chains during digestion are poorly understood. To address this issue, amylopectin of wheat starch (APWS) and amylose of wheat starch (AMWS) were separated and digested in vitro. After digestion, chains in WS with a degree of polymerization (DP) < 12 or DP > 37 were degraded, the double-helix content decreased from 58.65 % to 48.77 %, and many particles were degraded. For APWS, the DP > 36 chains increased, the B-type crystallinity increased to 9.55 %, and the particles were transformed into new aggregated structures. For AMWS, the number of 18 < DP < 270 chains was increased, the double-helix content increased from 19.78 % to 37.92 %, the B-type crystallinity increased from 6.65 % to 19.40 %, and a dense granular structure was formed. Overall, our study confirmed that WS, APWS, and AMWS had distinct multiscale structural reassembly mechanisms during in vitro digestion. The DP > 36 chains in APWS and 18 < DP < 270 chains in AMWS were the primary contributors to the formation of enzyme-resistant multiscale structures. This study can serve as a theoretical basis for designing the WS multiscale structure using molecular chains to improve its nutritional value.

Structure and physicochemical properties of starches from six accessions of the genus Pueraria in China

Kudzu (Pueraria lobata) root contains abundant starch, but the physicochemical properties of kudzu starch are not well understood. In this study, we compared the compositions and physicochemical properties of starches isolated from six Pueraria accessions in China. Caige starch exhibited the highest purity (96.99 %) and amylose content (24.76 %), while Yege starch contained higher levels of puerarin (493.37 μg/g) and daidzein (38.68 μg/g). All kudzu starches were rich in resistant starch, with RS2 content ranging from 38.61 % to 46.22 % and RS3 content from 3.59 % to 6.04 %. The granules of kudzu starches varied in morphology, with Yege starch featuring larger polygonal granules. The kudzu starches presented either A-type or A-type-like C-type diffraction patterns. Caige starch had a higher IR2 value (1.28), higher gelatinization temperatures, wider temperature ranges, and greater enthalpy changes. Yege (JX) starch exhibited the highest peak viscosity but the lowest setback viscosity and pasting temperature. Fenge starch showed the highest final viscosity, with Fenge (ZJ) starch demonstrating the highest crystallinity (25.7 %) and IR1 value (0.80). These results indicated that kudzu starches derived from various Pueraria species possess unique structural and physicochemical properties, which provide significant potential for applications in food and other industrial fields.

Enhancing cassava beer quality: Extrusion-induced modification of cassava starch structure boosts fermentable sugar content in wort

The high starch content and cost-effectiveness of cassava make it an attractive adjunct in beer brewing, with the fine structure of starch playing a crucial role in determining the composition of fermentable sugars (FS) and overall beer quality. This study investigated the effect of extrusion-induced changes in the starch structure of cassava flour on the FS profile of the wort and, consequently, on the quality attributes of cassava beer. The findings revealed that the shear stress during extrusion significantly reduced the molecular weight to 1.20 × 105g/mol and the branching degree of amylopectin. Simultaneously, there was an increase in the concentrations of short- and intermediate- chain amylose by 5.61% and 42.72%, respectively. These structural changes enhanced the enzymatic hydrolysis of extruded cassava flour (ECF), resulting in a higher total fermentable sugars content (22.00g/100 mL) in the ECF wort, predominantly composed of maltose and glucose. Furthermore, the altered FS profile led to an increased production of higher alcohols and esters in extruded cassava beer (ECB), particularly noted for the elevation of 2-phenylethyl alcohol levels, which imparted a distinctive rose aroma to the ECB. Consequently, the sensory profile of ECB showed significant improvement. This study offers critical insight into optimizing cassava beer quality and broadens the potential applications of cassava flour in the brewing industry.

Near infrared spectroscopy combined with chemometrics as tool to monitor starch hydrolysis

The objective of this study was to evaluate the feasibility of using near infrared (NIR) spectroscopy combined with principal component analysis (PCA) and partial least squares (PLS) regression to monitor the in vitro hydrolysis of different starch substrates. Potato and rice starches, and pre-gelatinised corn starch were used, where samples collected at different time points (5 to 120 min) during the in vitro hydrolysis and analysed using a Fourier transform NIR instrument with a gold-coated integrating sphere (diffuse reflection). PLS regression models between the spectra and reference data yield a coefficient of determination in cross validation (R2CV) and standard error in cross validation (SECV) of 0.94 and 1105. 8 μg mL-1; 0.81 and 440.81 μg mL-1; 0.45 and 338 μg mL-1; 0.70 and 276 μg mL-1; 0.75 and 296. 2 μg mL-1 for the prediction of the concentration of maltose using all samples, rice and potato combined, and pre-gelatinised corn, potato and rice starches analysed separately, respectively. It was concluded that the combination of NIR spectroscopy with both PCA and PLS regression might provide with a rapid and efficient tool to rapidly monitor changes that occur during the in vitro hydrolysis of starch.

Exploration of unique starch physicochemical properties of novel buckwheat lines created by crossing Golden buckwheat and Tatary buckwheat

Buckwheat is considered as a healthy cereal food, and it is essential to cultivate new buckwheat lines with good starch physicochemical properties for both consumers and food producers. Six novel buckwheat (Duoku, Dk) were generated by crossing of Golden buckwheat and Tatary buckwheat, and their kernel appearance properties and starch physicochemical properties were analyzed together with one domestic line (Cimiqiao) and one wild line (Yeku). The results showed that Dk samples had better appearance properties than two control samples. The Dk samples showed lower amylose content, similar amylopectin molecular structure and chain length distributions, and larger starch granules compared with Cimiqiao. The digestion results showed that two Dk samples: Dk6 & Dk9 had high resistant starch content; while the other two Dk samples: Dk37 & Dk38 had a steady glucose releasing rate. The Dk samples also showed high gelatinization temperature, indicating they were good raw materials for producing glass noodle. This study proved that Dk buckwheat had unique starch physicochemical properties, and could be used as new food materials in the future.

Inactivation of SSIIIa enhances the RS content through altering starch structure and accumulating C18:2 in japonica rice

SSIIIa was the key gene responsible for RS formation in rice endosperm. The higher RS content in ssIIIa mutant has been proposed to be majorly due to the increased amylose-lipid complexes (RS5). However, the formation of RS5 elicited by ssIIIa mutation and the importance of RS5 for total RS content in rice are still unclear. With japonica ssIIIa loss-of-function mutants created by CRISPR/Cas9 gene editing, the effects of SSIIIa mutation on RS5 were furtherly evaluated through investigating the transcriptome and metabolites. Inactivation of SSIIIa caused significant enhancement in amylose and RS content but without depletion in starch reserves. SSIIIa mutation modulated the genes involved in carbohydrate and lipid metabolisms and the redistribution of substances, led to accumulated protein, glucose, fructose, and C18:2. Besides the increased amylose content and altered amylopectin structure, the increased C18:2 contributed greatly to the enhancement in RS content in japonica ssIIIa mutants through complexing with amylose to form RS5, while the existence of lipid counted against the enhancement of RS content in indica rice. RS5 showed discrepant contributions for the total RS in rice with different genetic background. Inactivation of SSIIIa has great potential in improving RS5 content in japonica rice without great yield loss.

Combined ultrasound and germination treatment on the fine structure of highland barley starch

Highland barley is a grain crop grown in Tibet, China. This study investigated the structure of highland barley starch using ultrasound (40 kHz, 40 min, 165.5 W) and germination treatments (30℃ with 80% relative humidity). The macroscopic morphology and the barley's fine and molecular structure were evaluated. After sequential ultrasound pretreatment and germination, a significant difference in moisture content and surface roughness was noted between highland barley and the other groups. All test groups showed an increased particle size distribution range with increasing germination time. FTIR results also indicated that after sequential ultrasound pretreatment and germination, the absorption intensity of the intramolecular hydroxyl (-OH) group of starch increased, and hydrogen bonding was stronger compared to the untreated germinated sample. In addition, XRD analysis revealed that starch crystallinity increased following sequential ultrasound treatment and germination, but a-type of crystallinity remained after sonication. Further, the Mw of sequential ultrasound pretreatment and germination at any time is higher than that of sequential germination and ultrasound. As a result of sequential ultrasound pretreatment and germination, changes in the content of chain length of barley starch were consistent with germination alone. At the same time, the average degree of polymerisation (DP) fluctuated slightly. Lastly, the starch was modified during the sonication process, either prior to or following sonication. Pretreatment with ultrasound illustrated a more profound effect on barley starch than sequential germination and ultrasound treatment. In conclusion, these results indicate that sequential ultrasound pretreatment and germination improve the fine structure of highland barley starch.

Comparison of the physicochemical properties of starches from maize reciprocal F1 hybrids and their parental lines

Heterosis on maize yield and quality is highly variable and depends on parental selection. This study investigated and compared the starch structure and physicochemical properties among four sweet-waxy maize lines, four waxy maize lines, and their eight reciprocal F1 hybrids. Compared with the sweet-waxy maize, waxy maize and F1 hybrids had lower extent of branching of amylopectin and relative crystallinity, and larger starch granule size. Waxy maize starch had higher breakdown viscosity and retrogradation percentage, and lower setback viscosity and gelatinization enthalpy than the sweet-waxy maize starch. Meanwhile, the peak and setback viscosities, and retrogradation enthalpy of most F1 hybrid starches were higher than those of their female parent, while gelatinization enthalpy was the opposite. The F1 hybrid starches had higher onset temperature and retrogradation percentage and lower gelatinization enthalpy than their male parent in general. In conclusion, this study provides a framework for the production of new hybrids.

Editing of the starch branching enzyme gene SBE2 generates high-amylose storage roots in cassava

The production of high-amylose cassava through CRISPR/Cas9-mediated mutagenesis of the starch branching enzyme gene SBE2 was firstly achieved. High-amylose cassava (Manihot esculenta Crantz) is desirable for starch industrial applications and production of healthier processed food for human consumption. In this study, we report the production of high-amylose cassava through CRISPR/Cas9-mediated mutagenesis of the starch branching enzyme 2 (SBE2). Mutations in two targeted exons of SBE2 were identified in all regenerated plants; these mutations, which included nucleotide insertions, and short or long deletions in the SBE2 gene, were classified into eight mutant lines. Three mutants, M6, M7 and M8, with long fragment deletions in the second exon of SBE2 showed no accumulation of SBE2 protein. After harvest from the field, significantly higher amylose (up to 56% in apparent amylose content) and resistant starch (up to 35%) was observed in these mutants compared with the wild type, leading to darker blue coloration of starch granules after quick iodine staining and altered starch viscosity with a higher pasting temperature and peak time. Further ¹H-NMR analysis revealed a significant reduction in the degree of starch branching, together with fewer short chains (degree of polymerization [DP] 15-25) and more long chains (DP>25 and especially DP>40) of amylopectin, which indicates that cassava SBE2 catalyzes short chain formation during amylopectin biosynthesis. Transition from A- to B-type crystallinity was also detected in the starches. Our study showed that CRISPR/Cas9-mediated mutagenesis of starch biosynthetic genes in cassava is an effective approach for generating novel varieties with valuable starch properties for food and industrial applications.

Leached starch content and molecular size during sorghum steaming for baijiu production is not determined by starch fine molecular structures

Sorghum steaming properties are important for both flavor and brewing efficiency of baijiu (Chinese alcohol liquor). However, it is currently unclear with respects to structural factors that affect sorghum steaming properties during baijiu production. In this study, starch fine molecular structures were characterized by size-exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis for 8 sorghum varieties used in baijiu production. Starch crystalline structures and ordering of double helices were characterized by the X-ray diffraction and differential scanning calorimetry. Results showed that only small differences were observed for starch molecular size distributions and chain-length distributions in the raw sorghum flour. Of significance, the leached starch content and molecular size during steaming was very different among these sorghum varieties. Furthermore, Spearman correlation analysis showed that there was no significant correlation between starch fine structural parameters with the leached starch content. On the other hand, the correlation analysis showed that leached starch molecular size was negatively correlated with starch crystallinity, while positively correlated with the onset and peak gelatinization temperatures. It is concluded that the sorghum steaming property is controlled by the starch crystalline structures instead of starch fine molecular structures. These results could help the baijiu industry to produce baijiu with more desirable properties.

The multi-scale structure, thermal and digestion properties of mung bean starch

Identification and selection one special variety mung bean for lower GI food is very useful, however, the fundamental study for mung bean starch is still insufficient to meet its demand. In this study, four varieties of mostly planted mung bean in China were selected as model materials. The multi-scale structure of mung bean starch was characterized by SEC, HPAEC, XRD, SAXS, and SEM. SEC and HPAEC give the amylose contents, amylose and amylopectin fine structure of mung bean starch. Mung bean starch from XRD spectrum display C_A type semi crystallinity. The crystalline lamellar thickness from SAXS curves were 7.34-7.60 nm. DSC indicated that the peak gelatinization temperature is at 67 °C-68 °C. Resistant starch in mung bean disappears rapidly after cooking, although the amount of slowly digested starch was still more than half of the total starch. Since the gene backgrounds of the mung bean starch samples are very close, there was no obvious difference in their molecular and aggregated state structure, and the digestion properties were similar, too. Unique SEC and HPAEC profiles of starch chain length distribution can be utilized to help find more genetic resources and cultivate variety to meet the needs for starch applications.

Long branch-chains of amylopectin with B-type crystallinity in rice seed with inhibition of starch branching enzyme I and IIb resist in situ degradation and inhibit plant growth during seedling development : Degradation of rice starch with inhibition of SBEI/IIb during seedling development

BACKGROUND

Endosperm starch provides prime energy for cereal seedling growth. Cereal endosperm with repression of starch branching enzyme (SBE) has been widely studied for its high resistant starch content and health benefit. However, in barley and maize, the repression of SBE changes starch component and amylopectin structure which affects grain germination and seedling establishment. A high resistant starch rice line (TRS) has been developed through inhibiting SBEI/IIb, and its starch has very high resistance to in vitro hydrolysis and digestion. However, it is unclear whether the starch resists in situ degradation in seed and influences seedling growth after grain germination.

RESULTS

In this study, TRS and its wild-type rice cultivar Te-qing (TQ) were used to investigate the seedling growth, starch property changes, and in situ starch degradation during seedling growth. The slow degradation of starch in TRS seed restrained the seedling growth. The starch components including amylose and amylopectin were simultaneously degraded in TQ seeds during seedling growth, but in TRS seeds, the amylose was degraded faster than amylopectin and the amylopectin long branch-chains with B-type crystallinity had high resistance to in situ degradation. TQ starch was gradually degraded from the proximal to distal region of embryo and from the outer to inner in endosperm. However, TRS endosperm contained polygonal, aggregate, elongated and hollow starch from inner to outer. The polygonal starch similar to TQ starch was completely degraded, and the other starches with long branch-chains of amylopectin and B-type crystallinity were degraded faster at the early stage of seedling growth but had high resistance to in situ degradation during TRS seedling growth.

CONCLUSIONS

The B-type crystallinity and long branch-chains of amylopectin in TRS seed had high resistance to in situ degradation, which inhibited TRS seedling growth.

Comparison of Structural and Functional Properties of Wheat Starch Under Different Soil Drought Conditions

Drought influences cereal crop yield and quality. However, little is known about changes in the structural and functional properties of wheat starch under soil drought conditions. In this study, two wheat cultivars were subjected to well-watered (WW), moderate soil-drought (MD), and severe soil-drought (SD) from 7 tillers in the main stem to maturity. The structural and functional properties of the resultant endosperm starch were investigated. In comparison with WW soil, the MD increased starch accumulation in grains, the proportion of large starch granules, amylose and amylopectin long branch chain contents, and average amylopectin branch chain length, which were accompanied by the increase in activities of granule bound starch synthase and soluble starch synthase. MD treated-starch had a lower gelatinization enthalpy, and swelling power, but a higher gelatinization temperature, retrogradation enthalpy, and retrogradation percentage when compared to WW conditions. The MD also increased starch resistance to acid hydrolysis, amylase hydrolysis, and in vitro digestion. The SD had the opposite effects to the MD in all cases. The results suggest that soil drought more severely affects amylose synthesis than amylopectin synthesis in wheat grains, and moderate soil-drought improves molecular structure and functional properties of the starch.

Improved understanding of rice amylose biosynthesis from advanced starch structural characterization

BACKGROUND

It has been shown from the chain length distributions (CLDs) that amylose chains can be divided into at least two groups: long and short amylose chains. These molecular structures influence some functional properties of starch, such as digestibility and mouth-feel. GBSSI is the key enzyme for the elongation of amylose chains; however, the effect of other starch biosynthesis enzymes in amylose synthesis is still not fully understood. Two advanced starch characterization techniques, size exclusion chromatography (SEC) and fluorophore-assissted carbohydrate electrophoresis (FACE), together with a newly developed starch biosynthesis model, are used to improve understanding of amylose biosynthesis.

RESULTS

SEC and FACE were used to determine the CLD of amylose and amylopectin in various native and mutant rice starches. The types of starch branching enzymes (SBEs) involved in the synthesis of the distinct features seen for shorter degrees of polymerization, DP, < 2000, and longer (DP > 2000) amylose chains are identified by combining these data with a mathematical model of amylopectin biosynthesis. The model enables each feature in the amylopectin CLD to be parameterized in terms of relative SBE activities, which are used to explain differences in the genotypes.

CONCLUSIONS

The results suggest that while GBSSI is the predominant enzyme controlling the synthesis of longer amylose chains, some branching enzymes (such as BEI and BEIIb) also play important roles in the synthesis of shorter amylose chains.

Roles of GBSSI and SSIIa in determining amylose fine structure

This study examines the relationships between genetics (single nucleotide polymorphisms (SNPs) in GBSSI and SSIIa genes), starch structure (amylose and amylopectin fine structures), and starch properties (relating to gelatinization). GBSSI and SSIIa SNPs did not alter the starch content of rice grains. GBSSI SNPs can affect the amylose content, but they are incapable of altering the chain-lengths of amylopectin and amylose. The amounts of both long and short amylose branches changed with the same trend as amylose content, and they appeared to affect starch gelatinization properties. SSIIa synthesizes intermediate single-lamella amylopectin chains (DP 16-21), and consequently impacts the gelatinization temperature. Mathematical modelling suggests that the reduction in SSIIa activity significantly increases the activity of SBEII, resulting in a decreased activity ratio of SS to SBE in the enzyme set governing an appropriate chain-length distribution range. This application of the genetics-structure-property paradigm provides selection strategies to produce rice varieties with improved qualities.

Relationship between structure and functional properties of normal rice starches with different amylose contents

The structures (morphology, molecule, and crystallinity) and functional properties (gelatinization, hydrolysis, and in vitro digestion) of normal rice starches with different amylose contents were investigated and their relationships were analyzed. The results showed that the morphology, granule size, and crystalline type did not significantly change among rice starches. The molecular structure (amylose content, amylopectin branch-chain content, and amylopectin branching degree) and crystalline structure (relative crystallinity, IR ratio of 1045/1022 cm(-1), lamellar peak intensity, and lamellar distance) significantly varied among rice starches, which resulted in different functional properties. The gelatinization temperature and water solubility were significantly positively correlated with amylose content but significantly negatively correlated with amylopectin short branch-chain. The swelling power, hydrolysis and in vitro digestion were significantly positively correlated with amylopectin short branch-chain, relative crystallinity, IR ratio of 1045/1022 cm(-1), and lamellar peak intensity but significantly negatively correlated with amylose content and lamellar distance.

Different structural properties of high-amylose maize starch fractions varying in granule size

Large-, medium-, and small-sized granules were separated from normal and high-amylose maize starches using a glycerol centrifugation method. The different-sized fractions of normal maize starch showed similar molecular weight distribution, crystal structure, long- and short-range ordered structure, and lamellar structure of starch, but the different-sized fractions of high-amylose maize starch showed markedly different structural properties. The amylose content, iodine blue value, amylopectin long branch-chain, and IR ratio of 1045/1022 cm(-1) significantly increased with decrease of granule size, but the amylopectin short branch-chain and branching degree, relative crystallinity, IR ratio of 1022/995 cm(-1), and peak intensity of lamellar structure markedly decreased with decrease of granule size for high-amylose maize starch. The large-sized granules of high-amylose maize starch were A-type crystallinity, native and medium-sized granules of high-amylose maize starch were CA-type crystallinity, and small-sized granules of high-amylose maize starch were C-type crystallinity, indicating that C-type starch might contain A-type starch granules.

Different structures of heterogeneous starch granules from high-amylose rice

High-amylose cereal starches usually have heterogeneous starch granules in morphological structure. In the present study, the polygonal, aggregate, elongated, and hollow starch granules were separated from different regions of the kernels of high-amylose rice, and their structures were investigated. The results showed that the polygonal starch granules had low amylose content and high short branch-chain and branching degree of amylopectin, and exhibited A-type crystallinity. The aggregate starch granules had high long branch-chain of amylopectin, relative crystallinity, and double helix content, and exhibited C-type crystallinity. The elongated starch granules had high amylose content and low branching degree of amylopectin and relative crystallinity, and exhibited C-type crystallinity. The hollow starch granules had very high amylose content, proportion of amorphous conformation, and amylose-lipid complex, and very low branch-chain of amylopectin, branching degree of amylopectin, and double helix content, and exhibited no crystallinity. The different structures of heterogeneous starch granules from high-amylose rice resulted in significantly different thermal properties.