Starch Granule-associated Proteins Research Articles

Relationship between starch granule-associated proteins and in vitro digestibility of buckwheat starches: From the perspective of gelatinization degree.

To elucidate the impacts of starch granule-associated proteins (SGAPs) from buckwheat starch (BS) on structural changes and digestibility during hydrothermal treatment, BS before and after partial extraction of SGAPs were heated at 25, 65, 95°C to achieve different degree of gelatinization (DG). Divide the effects into three categories: (1) native granule state: partial extraction of SGAPs enlarged the pores in starches, increased the effective surface area for amylases bind with substrates, thus accelerated the digestion rate; (2) partial gelatinized state: partial extraction of SGAPs led to an augmentation in starch digestion rate due to higher DG and increased content of leached starch; (3) fully gelatinized state: the digestion process of starch with partially extracted SGAPs was faster at the later phase, primarily attributed to the lower integrity of residual granular fragments/ghosts. This finding demonstrated that the presence of SGAPs slowed down digestion progress of BS across various gelatinization states.

The evolution of granular surface structure and functional properties in rice starch during grain filling

The developmental changes in the granular surface structure and functional properties of starch during the entire grain filling period of rice (around 40 days) were investigated. The specific surface area of rice starch significantly decreased firstly then stabilized during growth due to increasing granular size. The pore volume decreased from 5.40 cm3/g at 6th day after anthesis (DAA-6) to 3.02 cm3/g (DAA-46). More starch granule-associated proteins (SGAPs) accumulated on the surface and in channels. Swelling power decreased by 46 %, whereas the flow behavior index (n) decreased by 32 % in upward curve during starch development from DAA-6 to DAA-30. Tan δ first dropped then remained steady at DAA 22–34 and lightly rebounded at the final stage, indicating that starch in the middle stage tended to have greater viscoelastic gel behavior at all sweeps. Mature starch showed lower in vitro hydrolysis rate and exhibited stronger enzymatic resistance. The results showed that granular surface features of rice starch may be an essential factor in determining rheological behavior and resistance to hydrolysis.

Unraveling the impact of starch granule-associated proteins on the emulsifying ability of quinoa starch granules at multiple scales

Total starch granule-associated proteins (tGAP), including granule-channel (GCP) and granule-surface proteins (GSP), alter the physicochemical properties of starches. Quinoa starch (QS) acts as an effective emulsifier in Pickering emulsion. However, the correlation between the tGAP and the emulsifying capacity of QS at different scales remains unclear. Herein, GCP and tGAP were selectively removed from QS, namely QS-C and QS-A. Results indicated that the loss of tGAP increased the water permeability and hydrophilicity of the starch particles. Mesoscopically, removing tGAP decreased the diffusion rate and interfacial viscous modulus. Particularly, GSP had a more profound impact on the interfacial modulus than GCP. Microscopically and macroscopically, the loss of tGAP endowed QS with weakened emulsifying ability in terms of emulsions with larger droplet size and diminished rheological properties. Collectively, this work demonstrated that tGAP played an important role in the structural and interfacial properties of QS molecules and the stability of QS-stabilized emulsions.

Transglutaminase and protease: How starch granule-associated protein modification affects starch retrogradation

This study investigated the effects of transglutaminase (TG) and protease on starch granule-associated proteins and their impact on starch properties, especially retrogradation. TG incorporated storage protein onto the starch surface, while protease removed starch-granule associated proteins from it. Neither treatment altered the basic structural characteristics of starch such as its crystallinity or thermal properties, but could significantly affect swelling power, amylose leaching, and retrogradation. TG-treated wheat starch (WST) showed reduced swelling power (11.50) and amylose leaching (28.92 mg/g) compared with the control wheat starch (WSC) at 11.95 and 30.53 mg/g, respectively, suggesting a more stable structure. Conversely, protease-treated starch (WSP) exhibited increased swelling power at 12.47 and amylose leaching at 33.17 mg/g, suggesting a disintegration of starch granules. Both WSC and WST showed the same degree of retrogradation at the equilibrium state (a) at 0.06, whereas WSP, with a higher degree at 0.08, promoted retrogradation. The rate constant (k) for WST was lower (1.41 d−1) than that for WSC (2.37 d−1), indicating that TG treatment effectively inhibited retrogradation. These findings illustrated the distinct mechanisms through which TG and protease modify starch properties by acting on starch granule-associated proteins. This also highlighted the potential of TG and protease to control starch modifications for specific applications.

Effect of Mild Alkali Treatment on the Structure and Physicochemical Properties of Normal and Waxy Rice Starches.

Mild alkali treatment can potentially be developed as a greener alternative to the traditional alkali treatment of starch, but the effect of mild alkali on starch is still understudied. Normal and waxy rice starches were subjected to mild alkali combined with hydrothermal treatment to investigate their changes in physicochemical properties. After mild alkali treatment, the protein content of normal and waxy rice starches decreased from 0.76% to 0.23% and from 0.89% to 0.23%, respectively. Mild alkali treatment decreased gelatinization temperature but increased the swelling power and solubility of both starches. Mild alkali treatment also increased the gelatinization enthalpy of waxy rice starch from 20.01 J/g to 25.04 J/g. Mild alkali treatment at room temperature increased the pasting viscosities of both normal and waxy rice starches, whereas at high temperature, it decreased pasting viscosities during hydrothermal treatment. Alkali treatment significantly changed the properties of normal and waxy rice starch by the ionization of hydroxyl groups and the removal of starch granule-associated proteins. Hydrothermal conditions promoted the effect of alkali. The combination of hydrothermal and alkali treatment led to greater changes in starch properties.

Mild alkali treatment alters structure and properties of maize starch: The potential role of alkali in starch chemical modification

Normal and waxy maize starches were treated with mild alkali treatment (pH 8.5, 9.9, 11.3) in two temperature-time combinations (25 °C for 1 h and 50 °C for 18 h) to investigate the effect on starch structure and properties. Mild alkali treatment partly removed the starch granule-associated proteins and lipids of normal (from 0.31 % to 0.24 % and from 0.77 % to 0.55 %, respectively) and waxy maize starches (from 0.22 % to 0.18 % and from 0.24 % to 0.15 %, respectively). Gelatinization enthalpy of waxy maize starch increased with alkali treatment from 16.20 J·g−1 to 21.95 J·g−1, indicating that amylopectin (AP) rearrangement and AP-AP double helices formation might occur. But amylose could inhibit these effects by restricting mobility of amylopectin, and no such changes occurred for normal maize starch. Alkali treatment decreased gelatinization temperature and increased peak and final viscosity. Alkali treatment decreased trough viscosity and increased setback of normal maize starch. The hydrothermal treatment promoted the effect of alkali, attributed to the more rapid molecular motion at higher temperature. Normal and waxy starches showed different changes after alkali treatment, indicating that amylose played an important role in controlling the effect of alkali and hydrothermal treatment, primarily as an obstructer of amylopectin rearrangement in mild alkali treatment.

Potential relation between starch granule-associated proteins and retrogradation properties of buckwheat starch

To elucidate the effect of starch granule-associated proteins (SGAPs) on retrogradation properties of buckwheat starch, the retrogradation properties of Tartary buckwheat starch (TBS) and common buckwheat starch (CBS) before and after removal of SGAPs were systematically investigated, with wheat starch (WS) as reference. A significant decrease in gel strength of starches and density of starch aggregates were observed after removing SGAPs. The results were in line with the changes in retrogradation enthalpy of starches and short-range ordered structure of starch aggregates. After removing SGAPs, the retrogradation enthalpy of TBS decreased from 4.16 J/g to 3.74 J/g, CBS decreased from 4.05 J/g to 3.35 J/g and WS decreased from 3.27 J/g to 2.81 J/g, respectively. Taken together the results of LF-NMR, FTIR and rheological analysis, it can be concluded that SGAPs could promote the hydrogen bond interactions between starch molecules by competitively binding with water molecules, enhancing the rearrangement of starch molecules and forming a more ordered structure. Overall, the study suggested that the presence of SGAPs could enhanced the interaction between starch molecules chains, thus accelerated the retrogradation process. The research results provide more information about SGAPs in buckwheat starch and support further study for manipulation of starch properties.

Insight into the promoted recrystallization and water distribution of bread by removing starch granule - surface and - associated proteins during storage

The influence of starch granule surface proteins (SGSPs) and starch granule-associated proteins (SGAPs) on bread retrogradation was investigated in a reconstituted dough system. The removal of both SGSPs and SGAPs resulted in poor bread qualities, decreasing specific volume and crumb porosity, leading to more baking loss and compact crumb structure. Particularly, removing SGSPs was effective in promoting the bread retrogradation. After 7 days of storage, the hardness of bread without SGSPs showed an increase of 353.34 g than the bread without SGAPs. Proton population and relaxation times exhibited that the absence of SGSPs significantly decreased the content of bound water from 11.51 % to 7.03 %, indicating lower water-holding capacity due to the loosen gelling structure. Compared to the control group, bread without SGSPs accelerated the starch recrystallinity by a reduction in soluble starch content, thereby increasing the retrogradation enthalpy and relative crystallinity through promoting the molecular reassociation in starch.

The Influence of Starch Granule-Associated Protein Removal on Starch Properties and Retrogradation

The Influence of Starch Granule-Associated Protein Removal on Starch Properties and Retrogradation

Freezing-induced loss of wheat starch granule-associated proteins affected dough quality: From water distribution, rheological properties, microstructure, and gluten development

This study aimed to explore the effect of freezing/thawing (F/T) treatment on starch granule-associated proteins (SGAPs) and its mechanism for modifying dough quality. SDS-PAGE showed that F/T mainly induced a loss of proteins from the starch surface (SGSPs). It was found that the decrease in associated protein content increased the content of bound water from 27.04% and 18.94% to 32.40% and 27.78% in starch and reconstituted dough systems, respectively. The absence of SGSPs resulted in a rheological behavior with higher dynamic modulus and lower strain detected by frequency sweep and creep-recovery experiments. CLSM exhibited a local aggregation of the gluten network and more starch granules dissociated. The glutenin macropolymers (GMP) content increased from 76.45% to 83.31% while the values of fluorescence intensity and free sulfhydryl (SH) decreased to 2821 and 1.85 μmol/g, respectively. These results suggested that SGSPs acted as a contact site in the “starch-gluten” matrix, facilitating macromolecular adhesion.

Removal of starch granule associated proteins affects annealing of normal and waxy maize starches

The effects of starch granule associated proteins (SGAPs) removal on the annealing of waxy and normal maize starch were investigated. Annealing significantly decreased the crystallinity, pasting viscosity, gelatinization temperature range, pseudoplasticity, and thixotropy of waxy and normal maize starches. Annealing little affected digestibility of the starches. Removal of SGAPs reduced the stability of starch granules, but significantly increased pasting viscosity, pseudoplasticity and thixotropy. Both annealing and SGAPs removal decreased the G′ and G″ of normal maize starch in dynamic rheological testing, but had little effect on waxy maize starch. Removal of SGAPs increased rapidly digestible starch (RDS) but reduced resistant starch (RS) for in vitro digestibility. SGAPs removal changed the effect of annealing on starches, and annealing showed different effect on waxy and normal maize starch with SGAPs removal. Annealing increased gelatinization enthalpy and RS of both normal and waxy maize starches after SGAPs removal, and decreased their pasting viscosities and RDS. The rheological properties of starches with SGAPs removal prior to annealing were impacted by amylose content. Annealing decreased pseudoplastic and thixotropy of waxy maize starch with SGAPs removal while increasing dynamic rheological properties of normal maize starch with SGAPs removal. • Annealing reduced crystallinity, pasting viscosity, and pseudoplasticity of starch. • SGAPs removal reduced the stability of starch granules. • Effect of SGAPs removal on starch properties was greater than that of annealing. • Effect of annealing and SGAPs removal depended on amylose content. • SGAPs removal inhibited annealing of normal amylose maize starch.

The role of starch granule-associated proteins in enhancing the strength of indica rice starch gels

The gel properties of indica rice starch strongly influence the quality of foods in which it is used. This study investigated the effects of chymotrypsin treatment on the rheological and pasting properties of starch prepared by different treatment methods. The results demonstrated that all the starches contained starch granule-associated proteins (SGAPs). Specifically, chymotrypsin-treated fermented extracted starch (E-FS) and chymotrypsin-treated alkali extracted starch (E-AS) exhibited a storage modulus (Gʹ) about 4 times higher than that of fermented extracted starch (FS) and alkali-extracted starch (AS). The flow consistency coefficients (K), loss moduli (Gʺ) and setback values tended to increase, while the characteristic rheological indices (n) and loss tangent (tan δ) tended to decrease after chymotrypsin treatment. This suggested that the starch gel was significantly enhanced by the proteinase modification. The protein composition of AS and E-AS only contained the 66 kDa of granule-bound starch synthase I (GBSS I) subunit. Therefore, the significant increase in gel strength was attributed to the exclusive modification effects of GBSS I. Microstructural analysis also confirmed that the three-dimensional gel network of indica rice starch was formed by a backbone of SGAP polymers filled with starch granules. The mechanism underlying GBSS I-enhanced gel was also elucidated based on the sequence and structure of GBSS I. The gel network formed by SGAP polymers of FS and AS was mainly caused by disulfide bonds between GBSS Is, while that of E-FS and E-AS was mainly caused by hydrophobic interactions. • The gel properties of indica starch treated by different methods were studied. • Enzymatic modification of starch granule-associated proteins (SGAPs) increased the starch gel strength significantly. • The SGAPs were mainly composed of granule-bound starch synthase I (GBSS I). • Gel formation driving force changed from disulfide bonds to hydrophobic interactions. • The gel structure comprised a polymerized SGAP network filled with starch granules.

Three Diverse Granule Preparation Methods for Proteomic Analysis of Mature Rice (Oryza sativa L.) Starch Grain

Starch is the primary form of reserve carbohydrate storage in plants. Rice (Oryza sativa L.) is a monocot whose reserve starch is organized into compounded structures within the amyloplast, rather than a simple starch grain (SG). The mechanism governing the assembly of the compound SG from polyhedral granules in apposition, however, remains unknown. To further characterize the proteome associated with these compounded structures, three distinct methods of starch granule preparation (dispersion, microsieve, and flotation) were performed. Phase separation of peptides (aqueous trypsin-shaving and isopropanol solubilization of residual peptides) isolated starch granule-associated proteins (SGAPs) from the distal proteome of the amyloplast and the proximal ‘amylome’ (the amyloplastic proteome), respectively. The term ‘distal proteome’ refers to SGAPs loosely tethered to the amyloplast, ones that can be rapidly proteolyzed, while proximal SGAPs are those found closer to the remnant amyloplast membrane fragments, perhaps embedded therein—ones that need isopropanol solvent to be removed from the mature organelle surface. These two rice starch-associated peptide samples were analyzed using nano-liquid chromatography–tandem mass spectrometry (Nano-HPLC-MS/MS). Known and novel proteins, as well as septum-like structure (SLS) proteins, in the mature rice SG were found. Data mining and gene ontology software were used to categorize these putative plastoskeletal components as a variety of structural elements, including actins, tubulins, tubulin-like proteins, and cementitious elements such as reticulata related-like (RER) proteins, tegument proteins, and lectins. Delineating the plastoskeletal proteome begins by understanding how each starch granule isolation procedure affects observed cytoplasmic and plastid proteins. The three methods described herein show how the technique used to isolate SGs differentially impacts the subsequent proteomic analysis and results obtained. It can thus be concluded that future investigations must make judicious decisions regarding the methodology used in extracting proteomic information from the compound starch granules being assessed, since different methods are shown to yield contrasting results herein. Data are available via ProteomeXchange with identifier PXD032314.

Architecture of outer shell and inner blocklets of rice starch granule is related to starch granule-associated proteins

Waxy, low-amylose and high-amylose rice starches were chosen to separate inner blocklets and outer shell from their granules under incomplete gelatinization. Isolated outer shells and swollen or merged inner blocklets, based on morphological structure of broken granules, were used as a probe to study the mechanism of differences between outer and inner blocklets formation, through molecular characteristics and starch granule-associated proteins (SGAPs) analyses. On the basis of molecular composition, it was concluded that shorter branched-chain amylopectin and some amylose chains were involved in the formation of inner blocklets (shells). While the stronger interaction occurred among outer blocklets (shell), those are composed of longer branched-chains amylopectin and few amylose molecules. SGAPs types and content of inner shells (blocklets) were higher than outer shell (blocklets). SGAPs not only interacted with amylose chains but also with amylopectin chains. The enzymatic machinery for biosynthesis, such as starch branching enzyme, plays a critical role in blocklet architecture.

Effects of endogenous proteins on the hydrolysis of gelatinized starch and their mechanism of inhibition

This study investigated the effect of endogenous proteins on the α-amylase-catalyzed hydrolysis of gelatinized corn starch, to analyze the influence of starch granule-associated protein (SGAP) and storage protein on the hydrolytic reaction and the structure of the hydrolysate molecules. The effect of chemicals that disrupted starch/protein binding interactions on the rheology of gelatinized starch revealed the mechanism of starch hydrolysis inhibition. Native corn starch had a lower degree of hydrolysis and a higher proportion of incompletely hydrolyzed long chains than corn starch with the SGAP removed. Storage protein also inhibited starch hydrolysis, but less strongly than SGAP. Rheological analysis showed that SGAP interacted strongly with starch chains by hydrogen bonding, hydrophobic and electrostatic interactions, whereas storage protein only interacted strongly by hydrogen bonding. The stronger binding interactions between SGAP and starch appeared to be the main reason for its stronger inhibition of starch hydrolysis than that of storage protein.

Removal of starch granule-associated proteins alters the physicochemical properties of diverse small granule starches

The properties of four small-granule (oat, quinoa, amaranth and rice) starches before and after removal of starch granule-associated proteins (SGAPs), particularly surface-proteins and channel-proteins, were investigated and compared with two large-granule (waxy and normal maize) starches. The hypothesis, which was confirmed by results, was that the small-granule starches would be more susceptible to water and heat than the large-granule starches after removal of SGAPs on surfaces and in channels using protease. Surface-proteins of some granules in oat and rice starch presented as a film and channel-proteins were observed in oat, quinoa and rice starches. Compared to large-granule starches, removing SGAPs led to a greater reduction in gelatinization temperature for small granule starches. Meanwhile the reduced extent of rigidity of swollen small-granules during shearing was greater after removing SGAPs, corresponding to the reduced peak, breakdown and final viscosities. Furthermore, the removal of SGAPs for small-granule starch pastes weakened pseudoplasticity and shear-thinning behaviour. Removing SGAPs contributed to amylose leaching, accelerated the recrystallization and rearrangement of starch molecules, and facilitated retrogradation, thereby leading to a stronger gel network.

Removal of starch granule associated proteins alters the physicochemical properties of annealed rice starches

The effect of removal of starch granule associated proteins (SGAPs), annealing and dual-treatment on physicochemical properties of three rice starches with different amylose content (AC) was investigated. SGAPs removal reduced stability of starch granules, thus increasing amylose leaching, swelling power, solubility, and pseudoplasticity of Qiuguang (15.6% AC) and Luhui (22.1% AC) rice starches, decreasing pseudoplasticity of Yangfunuo (1.56% AC) starch, and decreasing To, Tp, and Tc, pasting viscosity and storage modulus of all three rice starches. Annealing decreased amylose leaching of the three starches, and pasting properties, pseudoplastic and storage modulus of Yangfunuo starch, but increased swelling power of the three starches, ΔH and To of Qiuguang starch, and pasting properties and pseudoplasticity of Qiuguang and Luhui starches. The effect of dual-treatment was generally the sum of effect of SGAPs removal and annealing treatment. But an interaction effect of the dual-treatment was observed for some parameters. The effect of annealing was closely related to the variety and composition of the starch.

Effects of drying temperature on the properties of starch in pasta

The effects of manufacturing process and drying temperature on the properties of starch in pasta were investigated. Starch was isolated from durum wheat semolina, raw pasta, and pasta dried under low temperature, high temperature, and very high temperature. The following measurements were carried out on the extracted starch samples: protein content, ash, amylose content, resistant starch, starch damage, swelling power, amount of solubilized starch, X-ray diffraction spectral analysis, gelatinization temperature, granule size distribution, compression behavior of the gels, and the amount of starch granule-associated protein. The starch isolated from each sample had different physicochemical properties. Starch isolated from raw pasta formed a soft gel and had a low amount of starch granule surface-bound protein compared to starch isolated from semolina. In contrast, increasing the drying temperature of pasta increased the hardness and brittleness of gels formed by the extracted starch, and increased the amount of starch granule surface-bound protein. These results suggest that the amount of starch granule surface-bound protein may be an indicator of starch-protein interaction, which affects the physical properties of extracted starch gels.

Impact of starch granule-associated channel protein on characteristic of and λ-carrageenan entrapment within wheat starch granules

This study investigated the physicochemical characteristics of protease-treated wheat starch (PT-WST) to understand the role of starch granule-associated proteins (SGAPs) and the potential capability of PT-WST to provide a nutrient delivery system (NDS). Protease treatment was conducted at 4 °C and 37 °C (PT04 and PT37), respectively. A model delivery system was assessed with PT37 granules infiltrated by λ-carrageenan (λC) under variations of molecular size (λC hydrolysates produced from 0, 2.5, 100, and 500 mM HCl solution), agitation time, and temperature. Protein-specific (3-(4-carboxybenzyl)quioline-2-carboxaldehyde) or non-reactive (methanolic merbromin) fluorescent dye staining revealed that removal of SGAPs on surfaces and channels were more effective for PT37 than for PT04. Consistent amylose content, swelling, and gelatinization temperature before and after protease treatment suggested minimal impact on the starch structure. PT37 presented higher solubility and pasting viscosity than PT04. This resulted from excessive SGAP removal, which enhanced entrapment capacity. λC molecular size and agitation temperature showed a negative correlation with the content of λC entrapped within PT37, and this content depended on the interplay between the agitation time and λC molecular size. As λC molecular size decreased, the λC distribution became uniform throughout the granules, which confirmed the potential of PT-WST as a carrier for NDS.

Impact of starch granule-associated surface and channel proteins on physicochemical properties of corn and rice starches

The objective of this study was to investigate the impact of removing starch granule-associated proteins (SGAPs), especially starch granule-associated surface and channel proteins, on the overall characteristics of corn and rice starches. Protease treatment predominantly removed SGAPs on surfaces and in channels of the starches without significant damage, as evidenced by confocal laser scanning microscopy coupled with protein-specific and non-reactive fluorescent dye staining. Compared to untreated starches, protease-treated (PT) starches showed higher solubility and lower swelling power. However, there were no changes in their gelatinization and melting temperatures, despite their higher relative crystallinity. The stability of swollen starch granules during shearing was reduced following SGAP removal, reducing their peak, final and setback viscosities of the paste. Taken together these results indicate that SGAP removal predominantly affects the rheological properties of starch. Furthermore, the lower setback in PT-starch pastes suggests short-term retrogradation may be retarded by protease treatment of starch.