A Study of Starch Granule Size and Distribution in 29 Barley Varieties

The starch granule size and distribution has been determined on 29 different samples of barley. There is a wide range in the ratio of small to large granules which varies from a minimum of 5.5:1 to a maximum of 37:1. Small granules were separated from large granules in four varieties and the average weight of the granules determined. From these values the actual percentage of small granules in the original barley starch was determined. Small granule starch may account for from 6.2–30.6% of total starch weight in the varieties examined.     

Monitoring of barley starch amylolysis by gravitational field flow fractionation and MALDI-TOF MS

BACKGROUND: In barley, starch occurs in the form of granules with bimodal size distribution. Enzymatic hydrolysis of the starch granule is one of the most important reactions occurring during malting and mashing. Previous studies revealed the discrepancies in the assumption that barley varieties with better malting qualities should have a higher A/B (large/small starch granules) ratio. This led us to focus our attention on detailed analysis of two barley varieties, Jersey and Tolar, both with high malting quality but significantly differing in A/B (1.28 and 0.66, respectively), were chosen for more detailed analysis in the actual work. In this study, the capacity of gravitational field flow fractionation (GFFF) to monitor amylolysis of the starch granules was investigated. RESULTS: Isolated starch granules from these two barley cultivars were treated with amylases. The changes in starch granule size and bimodal distribution were studied by GFFF. Simultaneously, free sugars released during enzymatic digestion were observed by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry. The changes in the fractogram and in the mass spectra reflect a correlation with the progress of enzymatic hydrolysis. CONCLUSION: The results show the interest in utilization of GFFF as a simple and cheap method for monitoring changes in the distribution of the starch granule size during amylolysis. Copyright © 2011 Society of Chemical Industry     

Comparison of the GFFF and LALLS Methods for the Measurement of Starch Granule Size Distribution in Spring Barley Caryopses

A newly developed method GFFF (Gravitational Field‐Flow Fractionation) and the well known method LALLS (Low Angle Laser Light Scattering) were used to assess starch granule size distribution of ten varieties of spring barley. As a distribution criterion, the ratio of starch granule content larger than 8 μm (type A) and smaller than 8 μm (type B) was chosen. Both methods divided the observed set in a similar way. Varieties Akcent, Forum and Atribut formed a variety set with the highest ratio of large and small starch granules. Varieties Scarlet and Kompakt had intermediate ratios. The remaining five varieties Amulet, Novum, Olbram, Tolar and Krona had the lowest ratios of large and small starch granules. Statistical analysis showed that there was a highly significant correlation between the GFFF and LALLS methods.     

四种元麦淀粉粒形态结构与理化性质的比较

为探明不同品种元麦淀粉粒形态结构与理化性质的差异,以通麦6号、苏裸麦2号、青元麦、黑元麦为实验材料,采用扫描电镜观察、X-射线衍射、傅里叶变换远红外光谱等方法研究了这四类元麦淀粉粒形态特征及其理化性质,结果表明:青元麦,苏裸麦2号和通麦6号淀粉颗粒比较光滑,大小比较均匀,大颗粒多为圆饼形,小颗粒多为圆球形。黑元麦颗粒大小不均匀,差异较大。4类元麦的表观直链淀粉含量不同,其中黑元麦的直链淀粉含量显著高于其他品种;黑元麦和苏裸麦2号的B-型淀粉粒较多,通麦6号和青元麦的A-型淀粉粒较多。黑元麦的淀粉相对结晶度和表层结构有序度最高,溶解度最高、膨胀势最低。在淀粉葡萄糖苷酶水解过程中,青元麦水解程度最高,苏裸麦2号水解程度最低;在猪胰腺α-淀粉酶水解过程中,通麦6号水解程度最高,青元麦最低;在HCl水解过程中,青元麦水解程度最高,黑元麦水解程度最低。     

Comparison of Size Characterization of Barley Starch Granules Determined by Electron and Optical Microscopy,Low Angle Laser Light Scattering and Gravitational Field-Flow Fractionation

Several methods were used for the characterization of starch granules isolated from barley kernels. A procedure based on a combination of alkaline digestion, toluene treatment and filtration over sieves with pore diameters of 70 and 40 μm was used for isolation and purification of starch granules from kernels. The released starch granules were characterized by various methods: scanning electron microscopy (SEM), image analysis of optical microscopy data (IAOM), low angle laser light scattering (LALLS), and gravitational field-flow fractionation (GFFF). All methods showed the bimodal size distribution of the isolated starch granules, however, they differed in the ratio of large and small starch granules. LALLS and GFFF were also used for determination of the ratio of large and small starch granules (ratio A/B) isolated from two malting barley cultivars Kompakt and Akcent. Both techniques determined the higher ratio A/B for the cultivar Akcent. SEM was also used to examine the extent of digestion. The micrographs indicate that a significant proportion mainly of small granules are still embedded into residues of endosperm and a more extensive digestion must be performed to release all starch granules from barley kernels.     

Characterisation of Dextrins Solubilised by α‐Amylase from Barley Starch Granules

Large granules from barley starch were packed into a column and hydrolysed with α‐amylase by pumping a diluted enzyme solution through the starch bed. The enzyme was then trapped onto an ion‐exchanger and the dextrins that solubilised from the granules were collected and characterised. The size‐distribution of the solubilished dextrins ranged from degree of polymerisation (DP) 2—500. The linear and branched products originated from both the amylose and the amylopectin components. The rate of solubilisation and the composition of the solubilised dextrins from barley starch were very similar to those found for large wheat starch granules.     

Effect of damaged starch on the rheological properties of wheat starch suspensions

The influence of damaged starch content on particle size distribution and rheological properties of unheated starch suspensions and pasting properties were investigated. Four samples containing different amounts of damaged starch were studied. Particle size distribution curves shifted toward higher diameters, and a greater overlap of both populations of particles (A- and B-type granules) and a decrease of both peak heights were produced. The flow curves of unheated starch suspensions were fitted using the power law model. The flow behavior indexes were higher than the unit. The consistency coefficient increased with the increment of damaged starch content. Unheated starch suspensions showed time-dependent rheological behavior and were described by the Weltman model. The unheated suspensions exhibited a thixotropic behavior. With regard to the pasting process, the increment of damaged starch content produced gradual reductions in peak viscosity, final paste viscosity, breakdown and setback. Results demonstrated the importance of the presence of physically damaged granules in wheat starch rheological characteristics.     

Changes in Starch Granule Size Distribution and Starch Gelatinization Properties During Development and Maturation of Wheat,Barley and Rye

Changes in starch granule size distribution of wheat, rye and barley during the development were followed with a Coulter Counter. Changes in starch gelatinization properties were determined by DSC-measurements. The “large granules” are laid down in the earliest stage of development and increase in size during the ripening period, even after the appearance of the “small granules”. In the mature grains the proportion of small granules is larger in wheat and rye than in barley. The gelatinization temperature is lower for the mature starch than for starch from an early stage of development. The enthalpy for the gelatinization of the starch increases during development which indicates that the structure of starch granules changes as a result of ripening. The content of amylose-lipid complexes in the starch increases during development, partly depending on the increasing proportion of “small granules”.     

Rapid Separation and Measurement of Particle Size Distribution of Starch Granules by Sedimentation/Steric Field-Flow Fractionation

Sedimentation/steric field-flow fractionation (Sd/StFFF) is introduced as a new technique for the size analysis of starch granules. Sd/StFFF provides both high speed and high resolution, and narrow size fractions of starch granules can be collected from the eluting stream for further characterization by microscopy or other techniques. The sedimentation FFF instrument was calibrated and applications were made to 12 starch samples derived from wheat, durum wheat, corn, oat, tapioca, and potato. The instrument response curve (the fractogram) and the size distribution curves for several of these samples were recorded. The mode or bimodal diameters and the percentages of A-and B-granules were compiled.     

Barley starch granules characterization

Native starch granules are composed mainly of two polysaccharides, amylose and amylopectin. The genetic variability gives rise to a wide range of amylose/amylopectin ratios. However, the ratio is not linked to the size fractionation of a single starch sample. X-Ray diffraction showed that barley starch was mainly crystallized in the ‘A’ form and the crystallinity level seemed to be related to varieties, e.g. waxy and normal. No evidence of crystallinity differences between small and large granules was shown. After lintnerization, X-ray diffraction scans were highly similar to waxy starch diffractograms. Crystalline structures were analysed by gel-permeation chromatography and iodine staining. These were made mainly of amylopectin. By electron diffraction these crystalline amylopectin-enriched structures were characterized as ‘B’ or ‘V’ forms.     

MORPHOLOGY OF STARCH GRANULES IN CEREAL GRAINS AND MALTS

During malting, amylases have limited action on large starch granules of barley endosperm but rapidly degrade the small granules. In contrast, the small starch granules of wheat endosperm are resistant to enzymic attack. High levels of exogenous gibberellic acid increase the production of α-amylase and encourage the appearance of radial channels in the partially-degraded large starch granules. These endo-corroded granules are mainly found in the proximal (embryo) half of the endosperm where levels of α-amylase are much higher than at the distal end. Degradation of malt starch can therefore result from enzymic attack both outside and inside the granules. Malting of barley reduces the population of small starch granules which are slower to gelatinize than large granules at the infusion mashing temperatures of 65° C. During germination of barley multiple starch granules are rapidly synthesized in single amyloplasts in the scutellum. The endosperm of high amylose barley is devoid of small starch granules and the average size of the large granules is reduced. Steeliness in sorghum is related to the close packing of the starch-protein matrix rather than to unequal distribution of protein. The significance of these results is discussed, particularly in relation to the morphology of starch granules, the nature of their outer covering, the distribution of amylopectin and amylose within the granule, and the site of enzymic attack.     

Some Anomalies in Starch Chemistry Are They Due to Granule Structure ?

The small granule starch from cow cockle, pigweed, catch fly and several varieties of dasheens was examined. Although the data suggested that absence of pasting peak, the cooking stability and lack of set-back may be associated with granule size it must due to granule structure since these characteristics were not observed with small granule barley starches. An examination of the “chunk” starch from pigweed indicates that the small granules are cemented together with non-granular starch.     

Barley Starch Granules Subject to SPLITT Cell Fractionation and Sd/StFFF Size Characterization

The coupling of two separation techniques is proposed as a methodology able to fractionate, starch granules of different botanical origins, both on preparative and analytical scale. The split flow thin cell (SPLITT cell) was optimized to produce a binary separation of the starch granules into two different size classes with a 5 μm cutoff point. The size separation was always better than 80%. The Sedimentation Steric Field Flow Fractionation (Sd/StFFF) provides sample particle size distribution (PSD) and is used here to control the SPLITT fractions. The proposed techniques, especially the former, are gentle and easy to use. Both the SPLITT and Sedimentation Fractionation results were checked by scanning electron microscopy (SEM). The procedure was originally applied to two samples from barley. The bimodal diameters were computed.     

Influence of molecular structural characteristics on pasting and thermal properties of acid-methanol-treated rice starches

Rice starches from TKW1, TNG67 and TCS17 varieties, differing widely in amylose contents (0.1, 18.3 and 29.2%) were treated at 45 °C for 1 h in methanol containing various amounts of HCl. The recovery, pasting properties, thermal behaviors, molecular size and chain length distribution of starch were observed. Starches exhibited widely different pasting and thermal behavior upon acid-methanol treated (AMT). Degradation of starches upon AMT affected the leaching extent and chain length of amylose. No obvious changes were found on chain length and content of chain fractions of amylopectin. The pasting viscosity of rice starch decreased with increasing concentration of HCl, and the pasting profiles depended on the variety of rice. The pasting profile of AMT-TNG67 starch showed a two-step increasing pattern during heating, while TKW1 and TCS17 starches showed smoothly increasing pasting curves. The relationship between pasting patterns of AMT-TNG67 starches with amylose leaching and two stages of swelling behavior of starch granules was investigated. Results indicated that the pasting of starch granules depend on the amount, as well as the chain length, of amylose in granules.     

Effect of Processing of Sword Beans (Canavalia gladiata) on Physicochemical Properties of Starch

The effect of various processing methods on physico‐chemical properties of sword bean starch was studied. Seed grits and flour were cooked with and without soaking, wet‐autoclaved, and roasted. The changes in starch associated with these processing methods were studied by observing changes in granular structure, water solubility index, water absorption index, molecular size distribution and the degree of gelatinization estimated by differential scanning calorimetry. Intact, ungelatinized starch granules of raw and dry‐heat treated samples were observed under the light microscope. The starch granules were elliptical in shape and had an average length and breadth of 37–40 μm and 27 μm, respectively. Wet‐processed samples had the lowest water solubility, higher water absorption and lower gelatinization enthalpies than the raw bean flour, whereas the dry heat‐treated samples showed higher water solubility and higher gelatinization enthalpies. The starch molecular size distribution pattern showed a higher amount of high molecular size carbohydrates in dry heat‐treated samples and a large fraction of intermediate molecular size carbohydrates in the wet‐processed samples. The low molecular size carbohydrate content was low in wet‐processed samples where processing was done with excess water.     

A Reassessment of the Chemical Structure of Barley and Wheat Starch Granules

Barley starch exists in two clearly defined populations of large (ca. 25 μ diameter) and small (ca. 5, μ diameter) granules, whilst in wheat there is a range of granule sizes with no similar bimodal distribution. The small granules of barley represent about 90% of the total starch granules by number, but account for only about 10% of the total starch in weight. Fractions containing only large or only small granules have been isolated from both barley and wheat. The small granules from barley have a higher amylose content than the large granules, a higher gelatinisation temperature, and are usually associated with more protein. In contrast, large and small granules from wheat differ only slightly in their respective amylose contents but, like barley differ in gelatinisation temperatures and amounts of associated protein. It is proposed that starch synthesis in the small starch granules of barley is under different genetic control from that in the large granules.     

Physicochemical and Biochemical Characterization of Starch Granules Isolated of Pigmented Maize Hybrids

In this study, the morphological and physicochemical of pigmented maizes as well as the initial characterization of the corresponding starch granule enzymes are described. Starch granules were isolated from blue, black, and white maize. They were analyzed using scanning electron microscopy, particle size distribution, pasting characteristics, sorption isotherms, differential scanning calorimetry, and two‐dimensional gel electrophoresis. The morphology of the starch granules of pigmented maizes was different from the granules of white maize; the pattern was related to the endosperm type of these varieties. The average starch granule size was higher for black than for white and blue maizes. The average gelatinization temperature was similar in the three starches, but the pigmented maizes had higher gelatinization enthalpy; black maize starch showed the lowest enthalpy of retrogradation. These results indicated that the starches from the three maizes analyzed had different organization level. Black maize starch showed the highest peak viscosity followed by white and blue maize starches. In the gel electrophoresis three starch granules presented one main spot at pI of 5 and MW of 60 kDa that corresponds to the granule‐bound starch synthase. Blue and white starches presented some spots near 97 kDa at pI of 5.3–5.7 (white maize) and 5.1–5.5 (blue maize), spots that were not observed for black maize starch. The morphological and physicochemical characteristics of maize starch are related to the enzymes involved in its biosynthesis.     

Identification of characteristic starch properties of wheat varieties used to commercially produce dried noodles

The starch physicochemical properties of wheat varieties used to commercially produce dried noodles were studied. Scanning electron microscopy and laser microparticle size analyser were used to observe the starch particles; the polymorphism of the waxy (Wx) protein of each wheat variety was also studied. The correlation analysis among commonalities of the starch physicochemical properties and noodle textural properties was performed. Results indicated that the amylose contents of the noodle wheat varieties ranged from 17.8% to 21.7%. There was a significant, positive correlation between the thermodynamic temperature of starch and the volume distribution of particle size. The correlation between the volume distribution of B-type starch granules and noodle springiness was significant, which means that volume distribution of starch particle size could be used as one of the indicators to evaluate the springiness of noodles. Molecular polymorphism identification of Wx protein was also useful to select desirable noodle wheat variety. The results of this study provide useful information for wheat breeding works and wheat variety selection of noodle-making company.     

Characteristics of pores in native and hydrolyzed starch granules

Low‐temperature nitrogen adsorption and mercury porosimetry were applied for analyzing effect of α‐amylolysis upon the porosity of granules of native corn, wheat, rice, and potato starches. Specific surface area (S_BET), porosity, pore size distribution, total pore area, and mean pore radius were determined for native and digested granules. It was found that native starch granules are macroporous materials with a small participation of mesopores. In the case of native starches, the highest value of S_BET was obtained for rice starch (1.27 m²/g) and the lowest – for potato starch (0.14 m²/g). Pore size distribution curves obtained by nitrogen adsorption showed peaks in the range of diameters 2–3 nm (for all starches) and 100–200 nm (for corn and rice starches). After 60 min of enzyme action, surface area of all starches doubled in comparison to native ones. Arising of the new pores was also noted. The results of mercury porosimetry measurements showed that rice starch had the highest total area of pores and porosity but the lowest mean pore radius among all native starches. The pore size distribution curves for all starches exhibited solely one peak corresponding to the dominant group of pores of the radii in the range 0.5–8 µm, dependent on the starch source. There were also much smaller peaks situated within the range of 3–30 µm. After α‐amylolysis of corn and rice starches, the average radius of the dominant group of pores diminished. No substantial changes in the pore radii could be noted for potato starch.     

Characterisation of starch quality from barley varieties grown in South Africa

Starch is a major determinant of grain quality in cereals but the variation in starch structure has yet to be fully explored in its relation to processing impacts. This study examined the starch properties of South African grown malting barley varieties. Starch amounts, amylose content, covalently bound phosphate, starch granule size, starch molecular structure and pasting properties were examined. There was no difference in amylose content but there was variation in the amylose chain length distribution, despite all barleys showing similar granule parameters. The longer amylose chain length resulted in increased pasting temperature. There was no difference in phosphate content for these samples. Starch properties for the brewing industry are important in the context of the production of fermentable sugars. The variation in starch structure was not observed when measuring content and could impact on fermentation efficiency through variation in fermentable sugars hydrolysed from the starch.