Long Amylopectin Chains Research Articles

Effect of high temperature on starch biosynthetic enzymes and starch structure in japonica rice cultivar ‘Akitakomachi’ (Oryza sativa L.) endosperm and palatability of cooked rice

Reduction in crop yield and quality due to global warming is a major concern. In this study, we investigated the effects of high temperature during endosperm development on the level of starch biosynthetic enzymes, including granule-bound starch synthase I (GBSSI), branching enzyme (BE)IIb, and SSI, and structure of starch in the endosperm using japonica rice cultivar, ‘Akitakomachi’. We also performed palatability sensory evaluation of rice grown under different temperatures after cooking. At high ripening temperature, the number of seeds showing opaque regions was significantly increased, and seed weight was significantly decreased. The apparent amylose content and ratio of short to long chains of amylopectin in seeds developed at high temperature was significantly lower and higher, respectively, than that in seeds developed at lower temperature; this was because of low levels of GBSSI and BEIIb, respectively. In general, the amylose content correlates negatively with the stickiness and taste of cooked rice. Rice grains developed at high temperature were less palatable after cooking than those developed under normal conditions, although their amylose content was lower, indicating that the structure of amylopectin has a major impact on the palatability of cooked rice.

Effect of Solid‐State Fermentation by Lactobacillus plantarum on the Cooking Quality, Microstructure, and Physicochemical Properties of Brown Rice

Brown rice (BR) is nutritious but difficult to cook, which limits its consumption. In this study, a novel processing technology, solid‐state fermentation (SSF), is developed to improve the cooking quality of BR. After SSF treatment with Lactobacillus plantarum JYI‐3913, BR hardness (821.20 g) decreased by 36.91%, and its cooking time (19.69 min) is reduced by 29.07% compared to untreated BR (1301.72 g and 27.76 min, respectively). In addition, some small gullies and holes appear on the BR grain cortex, and the connections between the starch particles become looser. Cellulose and hemicellulose in BR exhibit a certain degree of degradation. Furthermore, the molecular structures of BR starch granules are damaged; the long chains of amylopectin are partially broken; the crystal structure of starch is partially destroyed; gelatinization enthalpy is decreased; and the setback value of starch is decreased. All of these characteristics make the BR easier to cook, and the cooked BR presents an improved taste and slower retrogradation. The results show that applied SSF treatment improves the cooking quality of BR.

Structural, morphological, functional and digestibility properties of starches from cereals, tubers and legumes: a comparative study

A comparison between structural, morphological, functional and digestibility studies of starches from cereals i.e. wheat (WS), corn (CS), low amylose corn (LACS) and rice (RS), tubers i.e. potato (PS) and sweet potato (SP), and legumes i.e. kidney bean (KB) were investigated. The shape of granules varied from oval to elliptical or spherical according to the source. Distribution of iso- amylase debranched materials revealed that long and short side chains fractions of amylopectin ranged from 12.6 to 33.1% and 40.5 to 52.5% respectively. KB starch showed the highest amylose content (49.50%) while RS showed the lowest (8.51%). Starches with greater granule size (PS, SP and KB) showed higher proportion of long side chains of amylopectin (AP) (Fr.II) than short side chains of AP (Fr.III). Peak viscosity (PV), breakdown viscosity (BV) and final viscosity (FV) showed significant positive relationship with Fr. II and negative with apparent amylose content (AAC) and Fr.III. Tuber starches showed greater paste viscosities followed by legume starches. Tuber and legume starches with higher apparent amylose content and Fr. II showed greater crystallinity. Gel hardness and gelatinization temperatures showed inverse relationship with RS starch having higher proportion of smaller granules (0-10µm). KB with higher amylose content showed maximum rapidly digestible starch (RDS) content while SP showed the highest resistant starch. Above observations would be utilized in modifying properties of native starches and help in improving texture, moisture retention capacity and gel firmness of starch and its products.

Effects of Wx and Its Interaction With SSIII-2 on Rice Eating and Cooking Qualities.

The Wx gene encodes a granule-bound starch synthase (GBSS) and plays a key role in determining rice eating and cooking qualities (ECQs). SSIII-2 (SSIIIa), a member of the soluble starch synthases, is responsible for the synthesis of long chains of amylopectin. To investigate the effects of Wx and its interaction with SSIII-2 on grain ECQs, a population from a hybrid combination was established as a research material. The genotypes of SSIII-2 and the single nucleotide polymorphisms (SNPs) on intron1, exon6, and exon10 of Wx, and the physicochemical indicators and rapid visco analyzer (RVA) profile characteristics were analyzed. The results revealed various effects of SSIII-2 on rice quality under different backgrounds of Wx alleles. There was no obvious difference between different SSIII-2 alleles under the same background of Wxa, whereas there was a significant diversity under the same background of Wxb. Wxa had a dominant epistasis to SSIII-2 because the effect of SSIII-2 was masked by the massive synthesis of GBSS under Wxa. The apparent amylose content (AAC) was mainly controlled by the In1G/T SNP, and rice gel consistency (GC) was regulated by the Ex10C/T SNP. The combined effects of three SNPs had a significant influence on all ECQs and RVA profile parameters, except for gelatinization temperature. In1T-Ex6A-Ex10C and In1T-Ex6A-Ex10T were classified as being low AAC type. TT-AA-CC and TT-AA-TT had a low AAC and a soft GC. The combined effects of different SNPs of Wx are very important for rice quality breeding.

Biosynthesis of waxy starch - a review

Starch comprises nearly linear amylose and branched amylopectin, whilst waxy starches are a special form, containing almost exclusively amylopectin. Modern techniques in plant breeding together with new data from starch biosynthesis research have enabled new food and non-food uses of waxy starches. This paper describes the basic ways of glucose conversion to waxy starch in plants. The recent evidence of ADP-Glc accumulation in cytosol of photosynthetically competent cells proposes a more complex pathway of starch biosynthesis based on a tight interconnection of sucrose and starch metabolic pathways. Also many studies indicate the existence of different pathways for the sucrose-starch conversion process in heterotrophic organs of dicotyledonous and monocotyledonous plants. At least six classes of starch synthases (SS) have been recognised in plants including soluble SS1, SS2, SS3, SS4, SS5, and granule bound SS (GBSS), required for the synthesis of short and long chains of amylopectin, till now. As to amylose (not-present in waxy starches), GBSS is the only starch synthase isoform encoded by the waxy genes situated at independent loci.

Morphological and structural changes of starch during processing by melt blending

The morphological and structural changes of the granule architecture of normal starch during the melt blending in a batch mixer were investigated. Native potato, maize, and chestnut starch with different crystal structures were used as raw materials. Samples obtained at different times of melt blending were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and polarized light (PL) microscopy techniques. The variation of torque versus time depended on the starch type; the thermo-plasticization of potato starch (B-type) occurred in two steps, whereas that of maize (A-type) and chestnut (C-type) starches took place in one step. An enhancement of the thermo-plasticization after 15 min of starch processing was not observed by SEM and PL microscopy. However, the potato starch with longer amylopectin chains and higher phosphorus content presented a higher extent of destructurization when compared with the maize and chestnut starches. The XRD patterns of the plasticized starch samples showed residual and V-type induced crystallinity, corroborating the partial thermo-plasticization of starches. The extent of thermo-plasticization depended on the crystallinity type and phosphorus content of normal starch.

Relationships between protein content, starch molecular structure and grain size in barley

Correlations among barley protein, starch molecular structure and grain size were determined using 30 barley samples with variable protein contents. Starch molecular structure was characterized by fluorophore-assisted carbohydrate electrophoresis and by size-exclusion chromatography (SEC, also termed GPC). The chain-length distributions of amylopectin were fitted using a mathematical model reflecting the relative activities of starch branching enzymes and starch synthase enzymes. Increased protein content significantly and negatively correlated with higher amounts of amylose with longer chains (degree of polymerization, DP 1600⿿40000) while barley grain sizes positively associated with starch contents. Protein content also positively correlated with the proportion of longer chains of amylopectin (DP 34⿿100). These results showed that the enzyme activities of starch synthases change with protein content, leading to altered starch contents, structures and grain sizes. From this perspective, selecting for large grain size (or low protein content) does not necessarily relate to starch structure, although may suggest long chains of amylopectin. Measuring starch structure could give a good indication of process performance in human food, animal feed and brewing, as all these structural features contribute to significant functional properties.

Production of starch nanoparticles using normal maize starch via heat-moisture treatment under mildly acidic conditions and homogenization

Normal maize starch was subjected to heat-moisture treatment (HMT) under mildly acidic conditions (0.000, 0.050, or 0.075M H2SO4) for various treatment times (3, 5, or 8h) followed by homogenization up to 60min to prepare nanoparticles. The combination of HMT (0.075M, for 8h) and homogenization (60min) produced nanoparticles with diameters of less than 50nm at a yield higher than 80%. X-ray diffractometry and size-exclusion chromatography revealed that HMT under mildly acidic conditions selectively hydrolyzed the starch chains (especially amylose and/or long chains of amylopectin) in the amorphous region of the granules without significant damage to the crystalline structure, however, modification of the molecular structure in the amorphous region increased fragility of the granules during homogenization. Homogenization for 60min caused obvious damage in the long-range crystalline structure of the HMT starch (0.15N, for 8h), while the short-range chain associations (FT-IR) remained intact.

Development of formulae for estimating amylose content and resistant starch content based on the pasting properties measured by RVA of Japonica polished rice and starch.

We searched for the easy and simple method to measure the novel indicators which reflect not only AAC, but also (RS) based on pasting properties using RVA. Novel indexes such as SB/Con and Max/Fin (Maximum viscosity/Minimum viscosity) ratios had a very high correlation with proportion of intermediate and long chains of amylopectin; Fb1+2+3 (DP≧13). In Japonica polished rice, estimation formulae for AAC and RS content were developed using novel indexes based on pasting properties by RVA, and these equations showed determination coefficients of 0.89 and 0.80 for calibration and 0.71 and 0.75 for validation test. We developed the estimation formulae for AAC and RS content for Japonica starch samples. These equations showed determination coefficients of 0.86 and 1.00 for calibration and 0.76 and 0.83 for validation test, which showed that these equations can be applied to the unknown rice samples.

Physicochemical and structural characteristics of rice starch modified by irradiation

This work evaluated the physicochemical and structural properties of rice starch of the cultivars IAC 202 and IRGA 417 modified by irradiation. Starch samples were irradiated by 60Co in doses 1, 2 and 5kGy, on a rate of 0.4kGy/h. A control not irradiated was used for comparison. The granule morphology and A-type X-ray diffraction pattern were not altered by irradiation. There was an increase in amylose content, carboxyl content and acidity with irradiation. Gamma radiation did not affect the thermal properties of IAC202, but increased gelatinization temperature of IRGA417, in the higher dose (5kGy). The number of long chains of amylopectin was reduced and short chains were increased for IAC202, whereas for IRGA 417, the opposite was observed, probably due to cross-linking of starch chains. Starches had their physicochemical and structural properties modified by irradiation differently.

Structural and physicochemical characteristics of starch from sugar cane and sweet sorghum stalks

The starch present in sugar cane and sorghum juice has been considered a problem to the sugar industry. The objective of this work was to study the structural and physicochemical characteristics of the starch present in sugar cane and sweet sorghum. Sugar cane and sweet sorghum starches presented small granules (maximum 5.9 and 7.9μm), A-type diffraction pattern, high degree of relative crystallinity (44.4 and 42.0%), and low amylose content (17.5 and 16.4%), respectively. Sugar cane starch presented more uniformity in granule shape and size, more homogeneity in amylose chain length, higher number of long lateral chains of amylopectin, and higher susceptibility to enzymatic digestion. Besides being in higher amount in the juice, sweet sorghum starch presented lower values for thermal properties of gelatinization, as well as higher swelling factor, which can cause more problems during processing. Additional studies are needed to evaluate the variety and maturity influence on these properties.

Differences in Starch Granule Composition and Structure Influence In Vitro Enzymatic Hydrolysis of Grain Meal and Extracted Starch in Two Classes of Canadian Wheat (Triticum aestivum L.)

ABSTRACTStarch granule composition and amylopectin structure affect starch digestibility, an important factor influencing wheat grain utilization for human food consumption. Six bread wheat cultivars with four belonging to the Canada Western Red Spring (CWRS) and two Canada Prairie Spring Red (CPSR) market classes were analyzed for the relationship between their grain constituents and in vitro enzymatic hydrolysis of starch. CPSR cultivars had higher starch and amylose concentrations compared with CWRS cultivars, which had a higher protein concentration. Starch granule size distribution did not differ among the genotypes, except AC Foremost, which had significantly (P < 0.05) higher volume percent of B‐type starch granules (≈15%) and lower volume percent of A‐type starch granules (≈9%) compared with other cultivars. Fluorophore‐assisted capillary electrophoresis revealed a lower content of R‐IV (DP 15–18, ≈6%) and a higher content of R‐VII (DP 37–45, ≈7%) chains in the CPSR cultivars compared with the CWRS cultivars. Starch in vitro enzymatic hydrolysis showed that compared with CWRS cultivars, the two CPSR cultivars had reduced amounts of readily digestible starch and higher amounts of slowly digestible starch and resistant starch. Consequently, the two CPSR cultivars also showed lower hydrolysis indexes in grain meal as well as extracted starch. CPSR cultivars, with higher starch and amylose concentrations, as well as a higher content of long chains of amylopectin, showed a reduced starch in vitro enzymatic hydrolysis rate.

Physicochemical, morphological, and rheological characterization of Xanthosoma robustum Lego-like starch

This work presents the physicochemical and pasting characterization of isolated mafafa starch and mafafa flour (Xanthosoma robustum). According to SEM images of mafafa starches in the tuber, these starches form Lego-like shaped structures with diameters between 8 and 35μm conformed by several starch granules of wedge shape that range from 2 to 7μm. The isolated mafafa starch is characterized by its low contents of protein, fat, and ash. The starch content in isolated starch was found to be 88.58% while the amylose content obtained was 35.43%. X-ray diffraction studies confirm that isolated starch is composed mainly by amylopectin. These results were confirmed by differential scanning calorimetry and thermo gravimetric analysis. This is the first report of the molecular parameters for mafafa starch: molar mass that ranged between 2×108 and 4×108g/mol, size (Rg) value between 279 and 295nm, and molecular density value between 9.2 and 9.7g/(molnm3). This study indicates that mafafa starch shows long chains of amylopectin this fact contributes to higher viscosity development and higher gel stability. The obtained gel phase is transparent in the UV–vis region. The viscosity, gel stability and optical properties suggest that there is potential for mafafa starch applications in the food industry.

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.

Iodine binding to explore the conformational state of internal chains of amylopectin

Previous studies have found that the proportion of long chains of amylopectin correlates to its functional and nutritional properties. As a possible explanation of this correlation, the iodine binding property of amylopectin internal chains was investigated as an indirect evidence of their ability to form helices for intra- or inter-molecular interactions. Waxy and amylose-extender waxy corn starches were hydrolyzed by β-amylase for varying periods of time to incrementally remove the external chains, and the absorbance and the wavelength of maximum absorbance of iodine binding were examined. Experimental results suggest that iodine can bind with both external and internal chains; a significant amount of absorption comes from the latter, as stepwise removal of external chains only somewhat reduced absorption. Internal amylopectin chains, thus, were concluded to likely pre-exist in helical form, as opposed to a conformational change into helices facilitating iodine binding in the absence of external chains. Such internal chain helical structures possibly drive intermolecular interactions that would explain why amylopectin with high proportion of internal chains form harder gels, create pastes less prone to shear breakdown, and are more slowly digesting.

Molecular Structure and Physicochemical Properties of Acid-Methanol-Treated Chickpea Starch

The molecular structure and physicochemical properties of acid-alcohol-treated (0.36% HCl in methanol at 25°C up to 216 h) chickpea starch were investigated. The recovery for modified chickpea starch ranged from 82 to 91%. A significant decrease in the swelling power, pasting viscosity, and gel strength was observed upon treatment with acid-methanol; however, the granule morphology remained unchanged. Structural studies revealed preferential degradation of amylose and long-chain amylopectin during treatment and the same was attributed to cause alterations in the functional properties. Molecular studies further revealed that the lower content ratio of short-chains to long-chains of amylopectin in chickpea starch resulted in the faster degradation rate upon acid-methanol treatment. An exponential model was also developed from the average molecular weight data to illustrate the degradation kinetics of acid-methanol-treated chickpea starch.

Lack of starch synthase IIIa and high expression of granule-bound starch synthase I synergistically increase the apparent amylose content in rice endosperm

Rice endosperm starch is composed of 0–30% linear amylose, which is entirely synthesized by granule-bound starch synthase I (GBSSI: encoded by Waxy, Wx). The remainder consists of branched amylopectin and is elongated by multiple starch synthases (SS) including SSI, IIa and IIIa. Typical japonica rice lacks active SSIIa and contains a low expressing Wxb causing a low amylose content (ca. 20%).WAB2-3 (SS3a/Wxa) lines generated by the introduction of a dominant indica Wxa into a japonica waxy mutant (SS3a/wx) exhibit elevated GBSSI and amylose content (ca. 25%). The japonica ss3a mutant (ss3a/Wxb) shows a high amylose content (ca. 30%), decreased long chains of amylopectin and increased GBSSI levels. To investigate the functional relationship between the ss3a and Wxa genes, the ss3a/Wxa line was generated by crossing ss3a/Wxb with SS3a/Wxa, and the starch properties of this line were examined. The results show that the apparent amylose content of the ss3a/Wxa line was increased (41.3%) compared to the parental lines. However, the GBSSI quantity did not increase compared to the SS3a/Wxa line. The amylopectin branch structures were similar to the ss3a/Wxb mutant. Therefore, Wxa and ss3a synergistically increase the apparent amylose content in rice endosperm, and the possible reasons for this increase are discussed.

Isoamylase debranched fractions and granule size in starches from kidney bean germplasm: Distribution and relationship with functional properties

Fine structure, granule size distribution, thermal and rheological properties of starch separated from twenty kidney bean lines were determined. Apparent amylose content (AAC), intermediate fraction (mixture of relatively short amylose and long side chains of amylopectin), long-side chains of amylopectin (AP) and short side chains of amylopectin (AP) of starches were measured after debranching with isoamylase and fractionating using gel permeation chromatography. Starches from different lines showed unimodal, bimodal and trimodal distribution profiles for the granules size, majority of starches showed bimodal profile. The granule size ranged between 0.4 and 103μm, however, granules of 10 to 30μm were present in the highest proportion. Paste viscosities (Peak-, breakdown- and final-viscosity) had negative relation with AAC and positive with short side chains of AP. Starches with high proportion of granules of size between 1 to ≤10μm and >10 to 30μm size, respectively had lower and higher paste viscosities. Starches with higher proportion of long side chains of AP had higher gelatinization temperature (To, Tp, Tc) and enthalpy. Starches with higher proportion of granules of size >10 to 30μm had lower AAC and higher To, Tp and Tc. Gel hardness, To, Tp and Tc were lower for starches with higher proportion of granules of size >1 to ≤10μm. Viscoelasticity of cooked starch varies with AAC, short side chains of AP and granules size distribution.

Physicochemical properties of potato and cassava starches and their mutants in relation to their structural properties

Physicochemical properties [swelling power (SP), pasting behaviour and retrogradation] of five wild type (wt), five amylose free (amf), four high-amylose (ha) potato starches (ps) and one wt and amf cassava starch (cs) were investigated. While swelling of wtps occurred in two phases, amfps showed a very fast swelling and no gel of swollen granules was observed at higher temperatures (>90 °C). Haps underwent only restricted swelling. SP of cassava starches were lower than those of potato starches. Wtps leached mainly amylose (AM) during heating at low temperatures. Molecules of higher molecular weight (MW) leached out at higher temperatures. Longer amylopectin (AP) chains [degree of polymerisation (DP) > 18] inhibited swelling while short chains (DP < 14) favoured swelling. Starch pasting behaviour of 5.0 and 8.0% starch suspensions was studied using Rapid Visco Analyser (RVA). For 5.0% suspensions, increased levels of high-MW AP and decreased levels of AM molecules led to higher peak viscosity. Longer AP chains (DP > 18) depressed peak viscosity, while short chains (DP < 14) increased peak viscosity for both concentrations. At 8.0%, peak viscosity increased with starch granule size. After 1 day of storage of gelatinised starch suspensions, wtps and especially amfps showed only limited AP retrogradation. In contrast, the high enthalpies of retrograded AP (ΔH retro) and peak and conclusion temperatures of retrogradation (T p ,retro and T c ,retro) of haps suggested partial cocrystallisation between AM and AP. Chains with DP 18–25 seemed to be more liable to AP retrogradation. Wtcs and amfcs did not retrograde at room temperature.

Comparative NMR relaxometry of gels of amylomaltase-modified starch and gelatin

With the aim of generating gelatin-like starch gel functionality, starches extracted from normal potato, high amylose potato, maize, waxy maize, wheat and pea and oxidized potato starch were modified with amylomaltase (AM) (4-α-glucanotransferase; E.C. 2.4.1.25) from Thermus thermophilus. Gel characteristics after storage for 1 and 10 days at 20 °C of 12.0% gels were assessed by monitoring proton relaxation for the resulting 51 enzyme-modified starches and two gelatins using low-field 1H nuclear magnetic resonance (LF NMR) relaxometry. Discrete and distributed exponential analysis of the Carr–Purcell–Meiboom–Gill (CPMG) LF NMR relaxation data revealed that the pastes and gels contained one water component and that the spin–spin relaxation time constants ( T 2) and distributions differed with respect to starch type and enzyme modification. Typically, AM modification resulted in starches with decreased T 2 relaxation time and a more narrow T 2 distribution indicating a more homogeneous water population. In contrast, treatment with a branching enzyme (BE) (EC 2.4.1.18) combined with AM increased T 2 relaxation time and a broadened T 2 distribution. As evaluated by the principal component analysis (PCA), long chains of amylopectin generated hard gels and decreased T 2 relaxation time at both day 1 and day 10. Especially at day 10, T 2 relaxation time could be predicted from the amylopectin chain length (CL) distribution. Reconstructed amylopectin CL distribution required to emulate gelatin LF NMR data suggest the importance of combined fractions of long (DP 60–80) and short (DP 10–25) amylopectin chains.