C-type Starch Granules Research Articles

Impact of waxy protein deletions on the crystalline structure and physicochemical properties of wheat V-type resistant starch (RS5)

This study investigated the effects of waxy (Wx) protein on wheat V-type resistant starch (RS5) formation, molecular structure, and physicochemical properties. We discovered that waxy protein deletions led to a rise in B- and C-type starch granules, while reducing A-type starch granules, amylose, and slowly digestible starch contents. Further, dodecyl gallate (DG) addition significantly increased RS5 content, and molecular dynamics simulations indicated that amylose and DG can form stable complexes. Molecular docking indicated that DG could potentially aid in protecting wheat starch from digestion by human α-glucosidase. RS5 content was significantly reduced by waxy protein deletions. X-ray powder diffraction, Fourier-transform infrared spectroscopy, and laser confocal microscopy-Raman analyses revealed that waxy protein deletions decreased long-range crystalline structures and relative crystallinity and increased short-range crystalline structures，and full width at half maximum at 480 cm−1 of RS5. Pearson correlation analysis showed that RS5 content was highly correlated with its crystal structure, functional characteristics, and digestive characteristics. Principal component analysis revealed that five parameters (amylopectin, long-range crystalline structures, amylose, relative crystallinity, and RS5 content) had significant effect on the crystalline structure and functionality of RS5.

Accumulation characteristics and structural properties of starch in different spatial positions of wheat endosperm under nitrogen application

Starch accumulation in wheat endosperm has spatial differences. In this study, the accumulation, granule size distribution, physicochemical properties of starch in different spatial positions in wheat endosperm and response to nitrogen treatment were analysed. Results indicated that the starch content in the inner endosperm was higher than that in the outer endosperm. The total starch and amylose contents in the inner and outer endosperms decreased and increased after nitrogen treatment, respectively. The starch granules that accumulated in the inner endosperm were larger than those in the outer endosperm 10 days after anthesis. The amount of C-type starch granules in the inner endosperm was less than that in the outer endosperm, and nitrogen treatment increased the C-type starch granules in the inner endosperm. After nitrogen treatment, the short chains decreased, whereas the middle and long chains increased in the inner and outer endosperms. Nitrogen treatment also increased the crystal area in the inner and outer endosperms, especially the single helix in the inner endosperm. These conclusions provide new insights into the mechanism of starch accumulation in wheat endosperm and its response to the external environment.

Influence of waxy proteins on wheat resistant starch formation, molecular structure and physicochemical properties

This study investigated the influence of wheat waxy proteins on type III resistant starch (RS3) formation, molecular structure and physicochemical properties. Waxy deletions led to a significant increase in B- and C-type starch granules, particle size of RS3, and slowly digesting starch content, and a decrease in content of amylose and RS3. X-ray powder diffraction and Fourier-transform infrared spectroscopy analyses revealed high relative crystallinity and long-range (1047/1022 cm−1, IR1) and low short-range (1022/995, IR2) crystalline structures of RS3 in waxy wheat, which suggests that waxy deletions could produce a more ordered crystalline structure and fewer amorphous regions in RS3 crystals. Further laser confocal microscopy Raman spectroscopy analysis found that waxy deletions significantly increased the full width at half maximum and intensity of the bands at 480 cm−1, as well as leading to more ordered RS3 crystals. These changes in molecular structure resulted in improved physicochemical properties of RS3.

Yield, Grain Quality, and Starch Physicochemical Properties of 2 Elite Thai Rice Cultivars Grown under Varying Production Systems and Soil Characteristics.

Rice production systems and soil characteristics play a crucial role in determining its yield and grain quality. Two elite Thai rice cultivars, namely, KDML105 and RD6, were cultivated in two production systems with distinct soil characteristics, including net-house pot production and open-field production. Under open-field system, KDML105 and RD6 had greater panicle number, total grain weight, 100-grain weight, grain size, and dimension than those grown in the net-house. The amounts of reducing sugar and long amylopectin branch chains (DP 25–36) of the RD6 grains along with the amounts of long branch chains (DP 25–36 and DP ≥ 37), C-type starch granules, and average chain length of the KDML105 were substantially enhanced by the open-field cultivation. Contrastingly, the relative crystallinity of RD6 starch and the amounts of short branch chains (DP 6–12 and DP 13–24), B- and A-type granules, and median granule size of KDML105 starch were significantly suppressed. Consequently, the open-field-grown RD6 starch displayed significant changes in its gelatinization and retrogradation properties, whereas, certain retrogradation parameters and peak viscosity (PV) of KDML105 starches were differentially affected by the distinct cultivating conditions. This study demonstrated the influences of production systems and soil characteristics on the physicochemical properties of rice starches.

A-, B- and C-type starch granules coexist in root tuber of sweet potato

C-type starches isolated from different colored root tubers of sweet potatoes were investigated to reveal the distribution of A- and B-type crystals using differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and hot stage microscopy. The results showed that starches from different colored sweet potatoes all exhibited CA-type XRD patterns and wide DSC thermal peak curves. The thermal peaks could be highly fitted into three peaks, defined as Peak 1, 2 and 3, according to their gelatinization temperatures (GTs) from low to high. When starch was gelatinized in KCl solution, the peak temperature of Peak 1 increased slightly and then decreased, but those of Peak 2 and 3 increased first rapidly and then slowly with increasing KCl concentration. Starch was gelatinized from the interior to exterior of granules, and could be divided into three groups, defined as Group 1, 2 and 3, according to their GTs from low to high, corresponding to Peak 1, 2 and 3 of DSC thermogram, respectively. The starch granules in Group 2 had significantly wider GT range than those in Group 1 and Group 3. The starch granules with increasing GT exhibited XRD patterns from CA- to A-type and DSC thermograms from wide three-peak to narrow single peak. B-type starch granules had higher short-range ordered structure than A-type starch granules. The above results indicated that B-, C-, and A-type starch granules with GT from low to high coexisted in root tubers of sweet potato.

Comparison of starch physicochemical properties of wheat cultivars differing in bread- and noodle-making quality

Wheat cultivars that produce good-quality bread and noodles are important for the food industry and starch physicochemical properties greatly influence the reprocessing quality. In this study, six types of cultivars differing in bread and noodle quality were compared for starch characteristics and for future quality improvement. All six types exhibited significantly different starch physicochemical properties including starch components, amylopectin chain length distribution, granule size and distribution, pasting, swelling, and gelatinization. Most parameters investigated were significantly correlated with bread- and noodle-making performance, confirming significant effects of starch properties on wheat end-use quality. The ratio of amylopectin/amylose contents, proportion of amylopectin short chains (2 ≤ DP ≤ 10), amount of C-type starch granules, pasting peak viscosity and gelatinization conclusion temperature (Tc) were effective indicators for improvement of wheat processing quality, and cultivars with those parameters in ranges of 2.1–2.6, 47.8–51.0%, 36.2–46.7%, 2890–3450 cP, and 68.5–69.6 °C, respectively, would yield superior bread- and/or noodle-making quality.

Influence of heat-moisture treatment (HMT) on physicochemical and functional properties of starches from different Indian oat (Avena sativa L.) cultivars

The present work was aimed to study the effect of heat-moisture treatment (HMT) at 30% moisture content and temperature of 100 °C/12 h on physicochemical and functional properties of starches from eight Indian oat cultivars. As compared to native starches, HMT starches had significantly (p < 0.05) lower amylose content (6.18–16.87%), swelling power (11.4–14.3 g/g), solubility (4.7–8.5%) and proportion of B and C type starch granules. A reduction in starch paste clarity after HMT for all the cultivar starches was observed. The results revealed lower pasting viscosities for HMT starches in comparison to native starches, thereby indicating their thermostability, and lower retrogradation. The shape of oat starch granules did not change after HMT. Both native and HMT starches showed similar A-type X-ray diffraction pattern. Among all cultivars, HMT starch from OS-7 cv. had the lowest amylose content, swelling power, solubility, B- and C-type starch granules and lower peak and breakdown viscosities. HMT starches could be used as a substitute of chemically modified starches with the advantage of being safe and a greener modification. Such modifications will enhance versatility of oat starches in development of various fabricated food products.

Development of Barley (Hordeum vulgareL.) Lines with Altered Starch Granule Size Distribution

Microscope analysis of starches prepared from 139 barley genotypes identified a Japanese genotype, Kinai Kyoshinkai-2 (KK-2), with altered starch granule size distribution. Compared to normal barley starch, KK-2 produced consistently higher volumes of starch granules with 5-15 μm diameter and reduced volumes of starch granules with >15 μm diameter when grown in different environments. A cross between KK-2 and normal starch cultivar CDC Kendall was made and led to the production of 154 F5 lines with alterations to the normal 7:3:1 distribution for A-:B-:C-type starch granule volumes. Three F5 lines showed unimodal starch granule size distribution due to apparent lack of very small (<5.0 μm diameter) C-type starch granules, but the phenotype was accompanied by reduced grain weight and total starch concentration. Five F5 lines produced a significantly larger population of large (>15 μm diameter) A-type starch granules as compared to normal starch and showed on average a 10:4:1 distribution for A-:B-:C-type starch granule volumes. The unusual starch phenotypes displayed by the F5 lines confirm starch granule size distribution in barley can be genetically altered.

Genome-Specific Granule-Bound Starch Synthase I (GBSSI) Influences Starch Biochemical and Functional Characteristics in Near-Isogenic Wheat (Triticum aestivum L.) Lines

Near-isogenic wheat ( Triticum aestivum L.) lines differing at the Waxy locus were studied for the influence of genome-specific granule-bound starch synthase I (GBSSI/Waxy; Wx-A, Wx-B, Wx-D) on starch composition, structure, and in vitro starch enzymatic hydrolysis. Grain composition, amylose concentration, amylopectin unit-chain length distribution, and starch granule size distribution varied with the loss of functional GBSSI. Amylose concentration was more severely affected in genotypes with GBSSI missing from two genomes (double nulls) than from one genome (single nulls). Unit glucan chains (DP 6-8) of amylopectin were reduced with the complete loss of GBSSI as compared to wheat starch with a full complement of GBSSI. Wx-A and Wx-B had an additive effect toward short-chain phenotype of waxy amylopectin. Loss of Wx-D isoprotein alone significantly (p < 0.05) reduced the C-type starch granules. However, the absence of Wx-D in combination with Wx-A or Wx-B increased the B-type and C-type starch granules but decreased the volume of A-type starch granules. The rate of in vitro starch enzymatic hydrolysis was highest in completely waxy grain meal and purified starch. However, the presence of Wx-D reduced wheat starch hydrolysis as it increased the large A-type starch granule content (volume %) and reduced short chains (DP 6-8) in amylopectin. Factors such as small C-type starch granules, amylose concentration, and long chains of amylopectin (DP 23-45) also influenced wheat starch hydrolysis.

Starch Granule and Protein Accumulation during Seed Development of Ginkgo biloba L.

We investigated starch and protein formation and accumulation in the seed of Ginkgo biloba L. In the testa, starch granules and protein bodies (PBs) started to form and accumulate 30 days after pollination; they decreased in size and completely disappeared before maturity. In the endosperm, starch granules began to accumulate 45 days after pollination, and the number and size of starch granules increased gradually within 65 days after pollination. Starch granules, which were mainly produced in plastids, proliferated mainly by constricting in the center and dividing to form smaller granules. Before harvest, there were ellipsoidal or irregularly shaped types, including A-type starch granules and some B- and C-type starch granules. In addition, PBI and PBII formed mainly in the outermost cells of the endosperm. However, the starch granules and protein bodies in endosperm cells around the embryo disappeared completely. The embryo cells contained many organelles, C-type starch granules, and PBI-type protein bodies. These results suggested that the starch granules were A-, B-, and C-types, and the protein bodies were PBI- and PBII-types in G. biloba. In addition, there were many significant differences in the formation, accumulation, and types of starch granules and protein bodies among the testa, endosperm, and embryo.

Morphology and structure of chestnut starch isolated by alkali and enzymatic methods

The structure and morphology of starch from fruits of two chestnut (Castanea sativa Mill.) varieties, Martainha and Longal, isolated by alkaline (A3S) and enzymatic (ENZ) methods were assessed. Chestnut starch granules were found to be round and oval in shape, consisting of medium/small granules, with a mean granule size ranging between 9 and 13μm. Isolated chestnut starch appeared to the naked eye as a white powder, with high values of L∗, and the Longal variety produce starches duller than Martainha. No differences between samples were observed by FTIR analysis. The X-ray patterns of isolated starches are of C-type (more specifically of Cb type) with a relative crystallinity between 31.5% and 39.8%. The 13C CP/MAS NMR spectra are similar for both varieties but different for the used isolation methods. The amorphous phase in the starch granules isolated by A3S methods was lower than that of the starch extracted by the ENZ method, making the B-type allomorph in the C-type starch granules more evident than in the A-type. Those differences in the structure of isolated starches are shown by a lower degree of damage, and a higher level of crystallinity of starches isolated by the A3S method, which means that its original structure is less affected or partially destroyed. This study would be helpful to better understand the relationships among structure and functional properties for a eventual industrial application of chestnut starches.

Granule Structure and Distribution of Allomorphs in C-Type High-Amylose Rice Starch Granule Modified by Antisense RNA Inhibition of Starch Branching Enzyme

C-type starch, which is a combination of both A-type and B-type crystal starch, is usually found in legumes and rhizomes. We have developed a high-amylose transgenic line of rice (TRS) by antisense RNA inhibition of starch branching enzymes. The starch in the endosperm of this TRS was identified as typical C-type crystalline starch, but its fine granular structure and allomorph distribution remained unclear. In this study, we conducted morphological and spectroscopic studies on this TRS starch during acid hydrolysis to determine the distribution of A- and B-type allomorphs. The morphology of starch granules after various durations of acid hydrolysis was compared by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The results showed that amorphous regions were located at the center part of TRS starch subgranules. During acid hydrolysis, starch was degraded from the interior of the subgranule to the outer surface, while the peripheral part of the subgranules and the surrounding band of the starch granule were highly resistant to acid hydrolysis. The spectroscopic changes detected by X-ray powder diffraction, 13C cross-polarization magic-angle spinning NMR, and attenuated total reflectance Fourier transform infrared showed that the A-type allomorph was hydrolyzed more rapidly than the B-type, and that the X-ray diffraction profile gradually changed from a native C-type to a CB-type with increasing hydrolysis time. Our results showed that, in TRS starch, the A-type allomorph was located around the amorphous region, and was surrounded by the B-type allomorph located in the peripheral region of the subgranules and the surrounding band of the starch granule. Thus, the positions of A- and B-type allomorphs in the TRS C-type starch granule differ markedly from those in C-type legume and rhizome starch.

Formation of Semi-compound C-Type Starch Granule in High-Amylose Rice Developed by Antisense RNA Inhibition of Starch-Branching Enzyme

Cereal starch granules with high-amylose and resistant starch (RS) always show irregular morphology and special crystalline structure, but their formation during grain development is not yet clear. In our previous studies, we had generated a transgenic rice line (TRS) enriched with amylose and RS, which contained semi-compound starch showing a C-type crystalline structure. In this study, the formation of semi-compound C-type starch granule during TRS endosperm development was carefully investigated with light, scanning electron, and transmission electron microscopes and X-ray powder diffraction. The results showed that the TRS starch subgranules, each with a central hilum, were individually initiated in amyloplast and showed an A-type crystal at the early stage of starch granule development, which was similar to that in its wild type. However, with the endosperm development, the amylose content in TRS endosperm starch increased and the B-type starch crystal was deposited in the periphery of subgranules; then, the adjacent subgranules fused together and finally formed a continuous outer layer band surrounding the entire circumference of the starch granule. Accordingly, a mechanistic model for the formation of semi-compound C-type starch granules is proposed.

Characteristics of native and enzymatically hydrolyzed Zea mays L., Fritillaria ussuriensis Maxim. and Dioscorea opposita Thunb. starches

Comparative studies on glucoamylase hydrolysis of A-type Zea mays L., B-type F. ussuriensis Maxim., and C-type Dioscorea opposita Thunb. were carried out by scanning electron microscope (SEM), X-ray diffractometer (XRD), Fourier transform infrared (FT-IR) spectra and differential scanning calorimetry (DSC). Maize, Fritillaria, Dioscorea starches were hydrolyzed with glucoamylase for 2, 4, 8, 12 and 24 h, respectively. The SEM and XRD results revealed that A-type, B-type starch and C-type starch displayed different hydrolysis mechanisms. A-type starch was digested with enzyme penetrating into starch granules through natural pores on the surface and disrupted the interior of the starch granules. The glucoamylase worked by attacking the surface of B-type starch and forming cracks. When endo-corrosion occurred, the internal part of the granule was corroded through small cracks. However, the glucoamylase primarily attacked the interior of the C-type starch granules and then the exterior of starch granules. FT-IR confirmed that the amorphous regions in the starch granules are firstly hydrolyzed and could be hydrolyzed completely as long as the hydrolysis time is sufficient. The transition temperatures and enthalpy of gelatinization (Δ H gel) were determined using DSC. According to the gelatinization parameters, it could be further proved amorphous and crystalline structures were hydrolyzed.

Physicochemical properties and development of wheat large and small starch granules during endosperm development

Wheat mature seeds have large, lenticular A-type starch granules, and small, spherical B-type and irregular C-type starch granules. During endosperm development, large amyloplasts came from proplastid, divided and increased in number through binary fission from 4 to 12 days after flowering (DAF). Large starch granules formed and developed in the large amyloplast. One large amyloplast had only one large starch granule. Small amyloplasts came from the protrusion of large amyloplast envelope, divided and increased in number through envelope protrusion after 12 DAF. B-type starch granules formed and developed in small amyloplast from 12 to 18 DAF, C-type starch granules formed and developed in small amyloplast after 18 DAF. Many B- and C-type starch granules might form and develop in one small amyloplast. The amyloplast envelopes were asynchronously degraded and starch granules released into cell matrix when amyloplasts were full of starch granules. Apparent amylose contents of large starch granules were higher than that of small starch granules, and increased with endosperm development. The swelling powers and crystallinity of large starch granule were lower than that of small starch granules, and decreased with endosperm development. Small starch granules displayed broader gelatinization temperature ranges than did large starch granules.

Starch granules size distribution in superior and inferior grains of wheat is related to enzyme activities and their gene expressions during grain filling

Mature wheat endosperm contains A-, B-, C-type starch granules, and each class has unique physiochemical properties which determine the quality of starch. The dynamics of the starch granule size distribution, activities of starch synthases and expression of starch synthase encoding genes were studied in superior and inferior grains during grain filling. Compared with inferior grains, superior grains showed higher grain weight, contents of starch, amylose and amylopectin. The formation of A-, B-, C-type starch granules initiated at 4, 8, 20 DAF, respectively, and was well consistent with the temporally change patterns of starch synthase activities and relative gene expression levels. For instance, activities of soluble and granule-bound starch synthases (designated SSS and GBSS) peaked at 20 and 24 DAF. Genes encoding isoforms of starch synthases expressed at different grain filling periods. In addition, SS I was generally expressed over the grain filling stage; the SS II and SS III were expressed over the early and mid grain filling stage, and the GBSS I was expressed during the mid to late grain filling stage. In addition, the time-course changes in activities of starch synthases and expression of starch synthase encoding genes explained well the dynamics of the starch granule size distribution.

The structure of C-type Rhizoma Dioscorea starch granule revealed by acid hydrolysis method

Scanning electron microscope (SEM), X-ray powder diffraction (XRD) and cross polarisation/magic-angle spinning (CP/MAS) 13C nuclear magic resonance (NMR) have been used for the structural characterisation of C-type starch granule during acid hydrolysis. SEM shows that the amorphous areas mainly locate the core part of C-type starch granules, while the crystalline areas mainly exist in the peripheral region of starch granules. XRD analysis reveals that the B-type polymorph present in the C-type starch granule are preferentially degraded or degraded faster than the A-type polymorph. NMR spectra confirm that the amorphous regions in the starch granules are firstly hydrolysed and could be hydrolysed completely as long as the hydrolysis time is sufficient. After 40 days of hydrolysis, the acid-modified starch shows typical A-type characteristics upon analysis of the XRD pattern or the 13C CP/MAS NMR spectra.

Effect of the Alkaline Treatment on the Ultrastructure of C-Type Starch Granules

The effect of alkaline treatment on the ultrastructure of C-type starch granules was investigated during the alkaline extraction of Araucaria angustifolia (pinhao) starch. The efficiency in protein removal was evaluated using intrinsic fluorescence and Kjeldahl's method. In parallel, morphological changes of starch granules were observed using scanning electron microscopy and atomic force microscopy. The starch crystallinity was monitored by wide-angle X-ray scattering and the lamellar structure was studied by small-angle X-ray scattering (SAXS). The paracrystalline model was employed to interpret the SAXS curves. It was found that the granular organization was significantly altered when alkaline solutions were used during the extraction. A partial degradation of B-type allomorph of starch and a significant compression of semicrystalline growth rings were observed.

The new insight on ultrastructure of C-type starch granules revealed by acid hydrolysis

C-type starch granule could be considered as the mixture of A- and B-polymorphs. The ultrastructure of C-type starch granules has not been elucidated detailedly by comparison with that of A- or B-type starch. To better understand the ultrastructure of C-type starch granules, Environment Scanning Electron Microscope (ESEM) and Field Emission Gun Transmission Electron Microscope (FEG-TEM) have been used to analyze the conformation and ultrastructure of C-type starch granule from Rhizoma Dioscorea during acid hydrolysis. SEM results showed that the amorphous areas were mainly located interior part of C-type starch granules whereas the crystalline regions were found mostly in the peripheral region of the granules. The grain size can be confirmed to be about 4.5–9 nm from the HR-TEM micrographs. The nanocrystals from acid-thinned starch displayed the typical face-centered cubic structure. This selected area electron diffraction patterns showed that individual C-type starch granule consisted of A- and B-type polymorphs.

The semi-crystalline growth rings of C-type pea starch granule revealed by SEM and HR-TEM during acid hydrolysis

Semi-crystalline growth rings and the crystalline lamella of C-type pea starch were studied by Scanning Electron Microscope (SEM) and Field Emission Gun Transmission Electron Microscope (FEG-TEM) during acid hydrolysis. The alternating growth rings (semi-crystalline and amorphous growth rings) are clearly observed under SEM. The thickness of semi-crystalline growth rings is variable and approximately 200 nm apart. SEM results also reveals that the amorphous areas mainly locate core part of C-type starch granules, while the crystalline areas mainly exist in the peripheral region of starch granules. The crystalline and the amorphous areas are hydrolyzed concomitantly, although slowly. The clear lattice fringes with different orientation corresponding to the different thickness of crystalline lamella were observable from high-resolution-TEM (HR-TEM) images. The crystalline lamella size can be confirmed to be about 20 nm with the length of 20 nm and the thickness of 20 nm. The clear lattice fringes should correspond to the crystalline phases in the semi-crystalline growth rings while the blurry regions correspond to the amorphous growth rings among the semi-crystalline growth rings.