Amylopectin Branch Chain Research Articles

Effects of Drying Conditions of Corn Kernels and Storage at an Elevated Humidity on Starch Structures and Properties

The objective of this study was to understand effects of sun drying (35 °C) and machine drying (80 °C) of corn kernels followed by storage at 27 °C and 85-90% relative humidity for up to 6 months on starch structures and properties. The peak viscosity and starch hydrolysis rate using porcine pancreatic α-amylase of finely ground samples decreased with storage of both sun-dried and machine-dried corn kernels. The rate of enzymatic hydrolysis of the isolated starch obtained from the sun-dried corn increased with storage time, but that from the machine-dried corn decreased. The gelatinization temperature, pasting temperature, and percentage crystallinity of the isolated starch increased but the gelatinization enthalpy-change and peak viscosity of the starch decreased with storage time. Numbers of damaged starch granules and starch granules with pinholes increased but the molecular weight of starch and long branch-chains of amylopectin decreased with storage time. The results indicated that endogenous enzyme activity remained after sun drying, which hydrolyzed starch and reduced viscosity.

Relationship between the structure, physicochemical properties and in vitro digestibility of rice starches with different amylose contents

The in vitro digestibility and molecular and crystalline structures of rice starches (Long-grain, Arborio, Calrose, and Glutinous) differing in amylose content were investigated and the relationship between the structure and in vitro digestibility of starch was studied. Long-grain showed the highest amylose content (27.2%), whereas Glutinous showed the lowest amylose content (4.2%). Long-grain had the highest average amylopectin branch chain length (18.8) and proportion (8.7%) of long branch chains (DP≥37), and the lowest proportion (26.9%) of short branch chains (DP 6–12). Among the non-waxy rice starches (Long-grain, Arborio, and Calrose), Calrose had the lowest average chain length (17.7) and the lowest proportion (7.1%) of long branch chains (DP≥37). The relative crystallinity of rice starch followed the order: Glutinous (33.5%)>Calrose (31.4%)>Arborio (31.0%)>Long-grain (29.9%). Long-grain had the highest gelatinization temperature and the lowest gelatinization temperature range, whereas Glutinous showed the highest gelatinization temperature range and gelatinization enthalpy. Arborio had the highest melting enthalpy for amylose–lipid complex among the tested rice starches. Pasting temperature, setback, and final viscosity increased with increasing amylose content, whereas the peak viscosity and breakdown showed negative correlations with amylose content. The rapidly digestible starch (RDS) content of the tested rice starches followed the order: Glutinous (71.4%)>Calrose (52.2%)>Arborio (48.4%)>Long-grain (39.4%). Contrary to this, the slowly digestible starch (SDS) and resistant starch (RS) contents showed an opposite trend compared to RDS. Digestibility (RDS, SDS, and RS) of the rice starches was significantly correlated (p≤0.05) with amylose content, proportions of DP 6–12 and DP 13–24, relative crystallinity, intensity ratio (of 1047cm−1 to 1022cm−1 from Fourier transform infrared spectroscopy), swelling factor, amylose leaching, onset temperature of gelatinization, gelatinization temperature range, gelatinization enthalpy, pasting temperature, peak viscosity, breakdown, setback, and final viscosity.

Physicochemical properties and amylopectin fine structures of A- and B-type granules of waxy and normal soft wheat starch

This work fractionated waxy and normal wheat starches into highly purified A- and B-type granule fractions, which were representative of native granule populations within parent native wheat starches, to accurately assess starch characteristics and properties of the two granule types. Wheat starch A- and B-type granules possessed different morphologies, granule specific surface area measurements, compositions, relative crystallinities, amylopectin branch chain distributions, and physical properties (swelling, gelatinization, and pasting behaviors). Within a genotype, total and apparent amylose contents were greater for A-type granules, while lipid-complexed amylose and phospholipid contents were greater for B-type granules. B-type (relative to A-type) granules within a given genotype possessed a greater abundance of short amylopectin branch chains (DP n < 13) and a lesser proportion of intermediate (DP n 13–33) and long (DP n > 33) branch chains, contributing to their lower relative crystallinities. Variation in amylose and phospholipid characteristics appeared to account for observed differences in swelling, gelatinization, and pasting properties between waxy and normal wheat starch fractions of a common granule type. However, starch granule swelling and gelatinization property differences between A- and B-type granules within a given genotype were most consistently explained by their differential amylopectin chain-length distributions.

Structural modification and characterization of rice starch treated by Thermus aquaticus 4-α-glucanotransferase

Rice starch was modified using Thermus aquaticus 4-α-glucanotransferase (TAαGTase) in this study. The changes in the molecular structure and the effect on the starch retrogradation by TAαGTase treatment were investigated on isolated rice starch. By treating TAαGTase, molecular weight profile of amylopectins shifted to higher elution time from 1.0 × 10 8 to 2.4 × 10 7 or 0.8 × 10 7, depending on the level of enzyme dosage. Meanwhile, there were huge increases in the proportions of content corresponding to amylose size and even smaller molecules. On treating with TAαGTase, short branch chains (DP 1–8) increased, and longer branch chains (>DP 19) increased significantly as well, with a broader distribution up to DP 46 compared to the control rice starch. Amylose content decreased from 30.0 to 21.8–23.7%. This indicated that the amylose could be transferred to the amylopectin branch chain by the disproportionation of TAαGTase, resulting in lowering the amylose content and the formation of amylopectin with a broader branch-chain length distribution. TAαGTase modified rice starch showed that X-ray diffraction pattern of the B-type crystalline even before cold storage, and that a variety of cyclic glucans (DP 5–19) were produced by enzymatic reaction. In particular, the accelerated rate of starch retrogradation was clearly observed compared to the control due to an overall increase in the number of elongated long-branch chains, decrease in the amount of amylose–lipid complex, and the possible synergistic effects of these factors.

Characterization of 4-α-glucanotransferase from Synechocystis sp. PCC 6803 and its application to various corn starches

A putative 4-alpha-glucanotransferase (alphaGTase) gene from Synechocystis sp. PCC 6803 was identified being composed of 1505 nucleotides, and the overexpressed protein was purified with an affinity chromatography. The recombinant alphaGTase had about 57kDa of molecular mass when judged by SDS-PAGE analysis. The optimum reaction condition of the alphaGTase was shown to be pH 7 at 45 degrees C in 50mm phosphate buffer. This enzyme displayed transglycosylating activity on various maltooligosaccharides, of which the smallest donor and acceptor molecules were determined to be maltose and glucose, respectively. Various corn starches consisting of different proportions of amylopectin and amylose were incubated with the recombinant alphaGTase. The change in molecular weight distribution of alphaGTase-modified starch was analyzed by HPSEC. The reaction pattern of alphaGTase showed substantial decrease in amylopectin and increase in the peak corresponding to cycloamylose (CA). The production yield of CA tended to increase from 5 to 30% along with the increase in the apparent amylose content in corn starch, which suggested that linear amylose chain would be preferred to produce CA in the alphaGTase treatment. The detectable minimum degree of polymerization (DP) of CA was shown to be 22 by MALDI-TOF-MS analysis. As another action mode of alphaGTase, the rearrangement of amylopectin branch-chain distribution occurred without hydrolysis to small oligosaccharides. After isoamylolysis, alphaGTase-treated starch displayed the increase in DP 4-9 and longer than DP 21 when the relative proportion of branch chains in amylopectin was determined by HPAEC.

Effect of Gamma Irradiation on Molecular Structure and Physicochemical Properties of Corn Starch

Carboxyl content and amylose leaching of gamma-irradiated corn starch increased and swelling factor decreased with increasing radiation dose. The apparent amylose content decreased gradually from 28.7% for native starch to 20.9% for 50 kGy irradiated starch. The proportion of short amylopectin branch chains (DP 6 to 12) increased, while the proportion of longer branch chains (DP > or = 37) decreased with increasing radiation dose. The relative crystallinity and the degree of granule surface order decreased from 28.5% and 0.631 in native starch to 26.9% and 0.605 in 50 kGy irradiated starch, respectively. Pasting viscosity and gelatinization temperatures decreased with an increase in radiation dose. At a high dose (50 kGy), melting of amylose-lipid complex in DSC thermogram was not observed. The rapidly digestible starch (RDS) content slightly decreased up to 10 kGy but increased at 50 kGy. The resistant starch (RS) content slightly decreased at 2 kGy and then increased up to 50 kGy. The slowly digestible starch (SDS) content showed the opposite trend to RS content. Slower irradiation dose rate reduced carboxyl content, swelling factor, and amylose leaching. The apparent amylose content and amylopectin chain length distribution were not significantly affected by dose rate of gamma irradiation. However, the relative crystallinity and gelatinization enthalpy increased with slower dose rate. Slower dose rate decreased RDS and SDS contents, and increased RS content.

Impact of molecular structure of amylopectin and amylose on amylose chain association during cooling

The effect of amylose molecular size and amylopectin branch chain length on thermal behavior of native starch, defatted starch and isolated amylose during cooling was studied. Six starches from corn, amylomaize, rice, potato, bean and pea with varying amylose content (20–70%) were heated to 180 °C at 10 °C/min and subsequently cooled at 10 °C/min to 5 °C in a differential scanning calorimeter (DSC) in excess water. On cooling of native corn and amylomaize starches, two distinct exotherms were observed at around 70 and 30 °C, which were attributed to amylose–lipid complex formation and amylose chain association, respectively. After defatting, a larger exotherm at a higher temperature during cooling was observed for corn and amylomaize starches, whereas bean and pea starches showed a smaller exotherm at a lower temperature. Amylomaize, with a large amount of lipid and longer amylopectin branch chains, exhibited the lowest onset temperature of amylose chain association in native and defatted starches among the tested starches, indicating the lipid and long branch chains in amylopectin restrict amylose chain association. The enthalpy of amylose chain association in defatted starch was positively correlated with apparent amylose content ( R 2 = 0.999). In amylose isolated from each starch, a larger exotherm with a peak temperature around 60 °C was observed on cooling. Potato amylose, which had a long average chain length ( DP ¯ n = 4915), showed the lowest temperature and enthalpy of amylose chain association. The peak temperature of amylose chain association increased with increasing solid concentration of isolated amylose, whereas enthalpy reached a maximum at a concentration of 20–30% (w/w) solid.

Molecular Structure of Selected Tuber and Root Starches and Effect of Amylopectin Structure on Their Physical Properties

The objectives of this study were to characterize starches isolated from potato, canna, fern, and kudzu, grown in Hangzhou, China, for potential food and nonfood applications and to gain understandings of the structures and properties of tuber and root starches. Potato and canna starches with B-type X-ray patterns had larger proportions of amylopectin (AP) long branch chains (DP >or=37) than did fern (C-type) and kudzu (C(A)-type) starches. The analysis of Naegeli dextrins suggested that fern and kudzu starches had more branch points, alpha-(1,6)-D-glycosidic linkages, located within the double-helical crystalline lamella than did the B-type starches. Dispersed molecular densities of the C- and C(A)-type APs (11.6-13.5 g/mol/nm(3)) were significantly larger than those of the B-type APs (1.4-6.1 g/mol/nm(3)) in dilute solutions. The larger proportion of the long AP branch chains in the B-type starch granules resulted in greater gelatinization enthalpy changes (Delta H). Retrograded kudzu starch, which had the shortest average chain length (DP 25.1), melted at a lower temperature (37.9 degrees C) than the others. Higher peak viscosities (550-749 RVU at 8%, dsb) of potato starches were attributed to the greater concentrations of phosphate monoesters, longer branch chains, and larger granule sizes compared with other tuber and root starches.

Structure and Physicochemical Properties of Starches from Sieve Fractions of Oat Flour Compared with Whole and Pin‐Milled Flour

ABSTRACTOne oat cultivar grown in Idaho (three field sites) was pin‐milled and separated by sieving to investigate whether starch from oat bran differs from the remainder of kernel. Ground oat particles were classified into three sieve fractions: 300–850 μm, 150–300 μm and &lt;150 μm). β‐Glucan content in sieve fractions was analyzed and starch was extracted from kernels without milling and from kernels of each sieve fraction. β‐Glucan contents of 300–850, 150–300, and &lt;150 μm sieve fractions were 4.2, 2.3, and 0.8%, respectively. Therefore, starch in bran (300–850 μm sieve fraction) and endosperm (&lt;150 μm sieve fraction) were separated. Starch isolated from entire kernels had significantly higher apparent and absolute amylose content than starch from the 300–850 μm sieve fraction. Starch from different sieve fractions was not significantly different in the apparent amylose, absolute amylose, amylopectin molecular weight, gyration radii, starch gelatinization, and amylose‐lipid complex thermal transition temperatures. Starch from the 150–300 μm sieve fraction had significantly lower peak, final, and setback viscosity compared with the starch isolated from the 300–850 μm and &lt;150 μm sieve fractions. Starch removed from the oat bran fraction during β‐glucan enrichment may have different applications compared with starch obtained from other kernel compartments. Because pin‐milling decreased apparent amylose content and shortened amylopectin branch chains, its potential to alter starch structure should be considered.

Structure of Starch Granules

Starch granules are synthesized in a semicrystalline structure and have characteristic morphology and properties depending on the botanical origin and the organ of the plant. Surface gelatinization studies have shown that the internal structures of starch granules are not homogeneous and vary with radial locations, from the hilum to the periphery. The internal structure of maize starch granule coincides with the biosynthesis and development of starch granules and the expression of starch synthase activities during the maturation of maize kernels. The enzyme digestibility of starch granules relates to the internal structure and the internal surface area of the starch granule as revealed by confocal laser-scattering micrographs. Short branch-chains of amylopectin (DP 6–12) destabilize the granule structures, resulting in lobed or compound starch granules and small granules. Ratios of long branch-chains to short branch-chains of amylopectin molecules affect the shape of the molecule, e.g., cylindrical versus conical shapes. The shape of the amylopectin molecule may affect the packing of the molecules in the granule and, in turn, determines the morphology and the size of the starch granule.

Some Structural and Physicochemical Characteristics of Tuber and Root Starches

Starches from six different species (cassava, arrowroot, sweet potato, yam, canna and ginger) were isolated and some structural and physicochemical characteristics analysed and correlated. Phosphorous and amylose contents were determined using a colorimetric method and measuring iodine affinity, respectively. Molecular weight distributions of starches were analysed by Sepharose CL 2B. Granular shape and size distribution were performed using an image analyser system attached to a light microscope. Swelling power was determined at 60, 70, 80 and 90°C. Pasting and thermal properties were measured using a rapid viscoanalyser, and a differential scanning calorimeter, respectively. Phosphorous content varied from 0.007 to 0.031% for cassava and canna starches, respectively. Yam, canna and ginger starches displayed higher amylose contents (32.6, 31.7 and 26.5%, respectively) than cassava, arrowroot and sweet potato starches (19.8, 20.8 and 22.6%, respectively). These last three starches displayed amylose molecules of higher molecular weight than those shown for yam, canna and ginger starches. Canna starch showed higher proportions of longer branch chains of amylopectin than others starches. The size and shape of granules were quite variable among all starches and the average size of granules varied from 13.9 to 42.3μ for sweet potato and canna, respectively. Swelling power, pasting, and thermal properties were affected by structural characteristics of the starches.

Effects of molecular size and structure of amylopectin on the retrogradation thermal properties of waxy rice and waxy cornstarches

Starches from waxy rice and waxy corn were treated in anhydrous methanol with 0.36% HCl at 25 °C for 1–15 days to obtain starches with different molecular weights. The retrogradation thermal properties of the HCl–methanol-treated starches, after gelatinized and stored at 4 °C for 7 days, were determined by using differential scanning calorimetry, and effects of molecular size and structure of amylopectin on the retrogradation thermal properties were elucidated. Results indicated that the degree of retrogradation (DR%) of waxy starches increased with decreasing molecular weight. The DR% of waxy starches was found negatively correlated with the logarithmic value of its weight-average degree of polymerization (DP w ) ( r 2=0.847 for waxy rice and 0.951 for waxy corn). The increment of DR% with the decreasing DP w of waxy cornstarch (slope=−13.98) was profoundly lower than that of waxy rice starch (slope=−25.42). In spite of the botanical source of starch, the DR% and the melting temperature of retrograded waxy starch depended on not only the molecular size, but also the molecular structure such as average chain length and chain length distributions of amylopectin branch chains and its subfractions.

Molecular Degradation Rate of Rice and Corn Starches during Acid−Methanol Treatment and Its Relation to the Molecular Structure of Starch

The degradation rates of rice and corn starches with different contents of amylose treated in methanol containing 0.36% HCl at 25 degrees C for 1-15 days were evaluated by monitoring the weight average degree of polymerization of starch. A two-stage degradation pattern during acid-methanol treatment was found for the starches studied, which were the slow (first) and the rapid (second) degradation stages. Waxy starches showed a shorter time period of the first stage than that of nonwaxy starch. Rice starch showed a shorter time period of the first stage and a higher degradation rate of the second stage than the counterpart corn starch with similar amylose content. Despite the botanic source and amylose content of starch, the degradation rate of starch in the second stage significantly (p < 0.05) correlated to the S/L ratio (r = -0.886) and polydispersity (r = 0.859) of amylopectin branch chains of native starch.

Characterization of Physical Properties of Flour and Starch Obtained from Gamma-Irradiated White Rice

Physical and structural characteristics of rice flour and starch obtained from gamma-irradiated white rice were determined. Pasting viscosities of the rice flour and starch, analyzed by using a Rapid Visco Analyser, decreased continuously with the increase in irradiation dosage. Differential scanning calorimetry showed that gelatinization onset, peak and conclusion temperatures of rice flour and starch changed slightly but the enthalpy change decreased significantly with increase of irradiation dosage. All irradiated starch displayed an A-type X-ray diffraction pattern like the native starch. Gel permeation chromatography showed that the blue value ratio of the first peak (amylopectin) to the second one (amylose) decreased with the increase of the irradiation dosage. The weight-average molecular weight (Mw) and gyration radius (Rz) of amylopectin analyzed by using HPSEC-MALLS-RI (high-performance size-exclusion chromatography equipped with multiangle laser-light scattering and refractive index detector) decreased gradually from 1.48×109 (Mw) and 384.1 nm (Rz) of native rice starch to 2.36×108 (Mw) and 236.8 nm of 9 kGy-irradiated starch. The branch chain-length distribution of amylopectins determined by HPAEC-ENZ-PAD (high-performance anion-exchange chromatography with amyloglucosidase post-column on-line reactor and pulsed amperometric detector) showed that gamma irradiation had no significant effect on the amylopectin branch chains with 13≤DP≤24 and 37≤DP, but produced more branch chains with 6≤DP≤12 when the irradiation dosage was less than 9 kGy. It might be deduced that gamma irradiation caused the breakage of the amylopectin chains at the amorphous regions, but had little effects on the crystalline regions of starch granules, especially at low dosage irradiation.

Starches from different botanical sources II: Contribution of starch structure to swelling and pasting properties

Swelling and pasting properties of 15 starches from different plant origins were studied to elucidate their relationship with structural features using simple and multiple regression analyses. Avoidance of additional effects of starch minor components showed that swelling power and pasting parameters were associated with the ratio of the relative molar distribution of amylopectin branch-chains with a degree of polymerization (DP) of 6–12 to that of chains with DP 6–24 (amylopectin unit-chain (APC) ratio). Swelling power of starch granules increased with APC ratio. Multiple regression analysis revealed that the peak viscosity (PkV) of starch paste increased with low APC ratio, low amylose content (AC) and large average granule size (AGS). At a high starch concentration, pasting temperature (PT) was reduced by a high APC ratio and large AGS. Peak time (PkT) decreased with increasing APC ratio and AC. Percentage of breakdown viscosity (BD%) and setback viscosity (SB) were primarily affected by APC ratio. At a low concentration, AC and AGS had more profound effects on BD%. SB was also reduced by higher AC. Models of pasting profile, which is influenced by individual factors, were also proposed.

Effects of microwave heat-moisture treatment on properties of waxy and non-waxy rice starches

Waxy and non-waxy rice starches adjusted to 20% moisture (wet basis, w.b.) were heat-moisture treated in a microwave oven to determine the effects of the microwave heating characteristics on digestibility, pasting, and morphological properties of the heated starches. Microwave heating produced only minimal changes in digestibility as well as the physical characteristics of heated starches. Significant changes in viscosity properties after microwave heat treatment were observed for both waxy and non-waxy starches heat-treated in a microwave oven, relative to non-treated samples. Non-waxy starch heated in microwave oven showed an increase in breakdown viscosity from 29.8 RVU (non-treated starch) to 35.8 RVU after heating for 60 min. However, for waxy starch, breakdown viscosity decreased from 112.7 to 35.9 RVU after 60 min of microwave heat treatment, reflecting an increased stability of microwave heat-treated starch under cooking. The data obtained in this study indicate that there was much higher re-aggregation of starch granules in waxy starch after microwave heat treatment than occurred in non-waxy starch, suggesting a re-association of amylopectin branch chains in the heat-treated waxy starch.

Studies on tuber and root starches. I. Structure and physicochemical properties of innala ( Solenostemon rotundifolius) starches grown in Sri Lanka

Starches from two cultivars ( Bola and Dik) of innala tubers ( Solenostemon rotundifolius) grown in the same location and under identical environmental conditions in Sri Lanka was isolated and some of the characteristics determined. The yield of starch from both cultivars was 16.0% on initial tuber weight. The shape of the granules in both cultivars was dome shaped and hemispherical with 4–5 slightly concaved facets. Pores were found randomly distributed over the surface of both starch granules. The amylopectin branch chain length distribution was nearly similar for both starches. However, the starches differed with respect to granular swelling, amylose leaching, susceptibility towards acid and enzyme hydrolysis, gelatinization characteristics, pasting properties and retrogradation kinetics. The results showed that differences in amylose content, lipid complexed amylose chains, relative crystallinity and extent of interaction between amylose chains in the amorphous regions of the granule had a substantial impact on the observed differences in physicochemical properties.

Effects of Environmental Temperature on Structure and Gelatinization Properties of Wheat Starch

ABSTRACTThe effects of environmental temperature on gelatinization properties and amylopectin structures of wheat endosperm starch were examined by isolating starches from four wheat cultivars matured in growth chambers at daytime temperatures of 15, 20, 25, or 30°C. Kernel weight and starch content per kernel were reduced by high maturation temperature. Amylose content showed no significant change at high maturation temperature in some cultivars; in other cultivars, there was a slight increase. Principal component analysis of data on relative peak areas of debranched amylopectin showed that amylopectin from wheat grown at a lower temperature had a greater proportion of shorter chains. Amylopectin branch chains were classified into three groups based on the correlation coefficients between the data of branch chain length distribution and principal component scores, degree of polymerization (DP) of 6–12, DP 13–34, and DP ≥ 35. The gelatinization temperature of starches increased markedly at a higher maturation temperature, with increases exceeding 10°C at high maturation temperatures. Gelatinization properties correlated significantly with amylopectin chain length distribution.

Physicochemical properties of Canadian oat starches

Starch from six cultivars of oat grains (grown under the same environmental conditions) was isolated and some of the characteristics determined. The yield of starch ranged from 30.9 to 32.3% on a whole grain basis. The shape of the granule ranged from irregular to polygonal in shape with an average granule diameter of 7.0–7.8 μm within a range of 3.8–10.5 μm. Lipids were extracted by acid hydrolysis and by selective solvent extraction with chloroform–methanol 2:1 v/v (CM) at ambient temperature followed by n-propanol–water 3:1 v/v (PW) at 90–100 °C. The acid hydrolyzed extracts, which represented the total starch lipids ranged from 0.85 to 1.31%. The free lipids in the CM extract ranged from 0.05 to 0.09%, whereas the free and bound lipids in the PW extracts ranged from 0.75 to 1.18%. The total amylose content ranged from 10.60 to 24.50%, of which 9.02–18.91% was complexed by native starch lipids. The X-ray diffraction pattern was of the ‘A’ type. The relative crystallinity (RC) ranged from 28.0 to 36.5%. The starches differed widely in the degree of granular swelling, extent of amylose leaching, paste viscosity, gelatinization transition temperatures, gelatinization enthalpy, susceptibility towards acid hydrolysis, and retrogradation characteristics. The results showed that the above differences were influenced by variations in bound lipid content, RC and amylopectin branch chain length.

Starch from hull-less barley: I. Granule morphology, composition and amylopectin structure

Starch was extracted from 10 hull-less barley (HB) genotypes [waxy (CDC Candle, CDC Alamo, SB 94912, and SB 94917), normal amylose (Phoenix, CDC Dawn, SR 93102, and SB 94860), and high amylose (SB 94893 and SB 94897)]. Starch content ranged from 56 to 65%. The purity of the isolated starches was greater than 96%. Average starch yield and extraction efficiency were 44 and 71%, respectively. The starches from all genotypes consisted of a mixture of large lenticular and small irregularly shaped granules. The granules of most starches were intact, whereas in others (SB 94917, SR 93102, and SB 94860) they were compound (clustered). The proportions of small (diameter⩽10 μm) and large granules (diameter>10 μm), by total number and by total weight differed among genotypes. Bound lipid content was positively correlated (r=0.92, P<0.01) with total amylose content. Free and bound lipid contents ranged from 0.1–0.3% and 0.3–1.7%, respectively. The apparent and total amylose contents ranged from 0–39% and 0–45%, respectively. The amounts of amylose complexed with native lipids (total amylose–apparent amylose) ranged from 0.5 to 7.8%. The proportion of small granules was correlated with total amylose content (r=0.59, P<0.1). However, the average granule diameter was negatively correlated (r=−0.65, P<0.05) with total amylose content. The debranched amylopectins of all starches exhibited the highest peak in the MALDI-MS spectrum at DP 12. The average chain length (CL) and degree of branching ranged from 17.6–22.7% and 4.4–5.5%, respectively. The short (DP 5-17) and long (DP⩾35) chains ranged from 58.2–59.1% and 3.0–12.8%, respectively. The study showed that amylose/amylopectin ratio and amylopectin branch chain length have high correlation with granule size and size distribution in this set of barley genotypes.