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.     

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.     

THE SUSCEPTIBILITY OF CEREAL STARCHES TO AMYLOLYSIS DURING GERMINATION AND MATURATION

During the maturation of normal and high amylose barley the susceptibility of the raw starches to attack by α-amylase remains constant until the moisture content of the grain falls below about 60%. Thereafter the starch develops a resistance to amylolysis which is directly proportional to the loss of grain moisture. The mean diameter of the starch granules of barleys and malt remains unchanged during digestion but the blue values of the residual starches decrease throughout. During the malting of wheat and barley the bulk of the starch solubilized is the amylopectin fraction although amylose is increasingly utilized when germination is prolonged. When high amylose barley is malted the blue value of the starch declines steadily throughout the growth period, suggesting that the spatial arrangements of the molecules within the granule influence the solubilization of the starch. The susceptibilities of wheats and normal and high amylose barleys to amylolysis were significantly lower than those of the corresponding malted products.     

Physicochemical changes in barley starch during malting

The objective of this work was to study the physicochemical modifications of starch during the malting of barley. The results showed that malting modifies the physicochemical properties of the starch over time by the action of barley enzymes. The gelatinisation temperature of starch increased as a function of the malting time owing to the selective enzymatic attack. The viscosity of starch decreased through malting. During germination, scanning electron microscopy showed that the enzymes degrade some starch granules which exhibited micro‐holes on the surface. X‐ray diffraction showed an apparent increase in the crystallinity during the first three days of germination, reflecting the consumption of amorphous regions. Such changes have not been previously reported. Infrared spectroscopy (1200–1500 cm^?1) showed the unfolding of carbohydrates as a result of enzymatic action. Such changes in the physicochemical properties of starch indicate that the amorphous area is consumed in the early stages of malting. © 2018 The Institute of Brewing & Distilling     

THE IN VIVO AND IN VITRO DEGRADATION OF BARLEY AND MALT STARCH GRANULES

The susceptibilities to amylolytic hydrolysis of the two different types of starch granule in barley and malt have been investigated. The large and small granules from both germinated and ungerminated grain were subjected to the sole action of malt α-amylase under conditions which otherwise simulated those of a conventional infusion mash. Large starch granules from barley are hydrolysed at a slower rate than those from malt. The faster conversion of the latter is attributed to prior modification of the starch granule structure during germination. The small granules from barley are extremely resistant to attack by α-amylase and even pre-cooking does not appreciably increase their susceptibility to amylase attack. Although the small starch granules from malt are less susceptible than the corresponding large granule fraction, they can be hydrolysed to a greater extent than can the small granules from barley. The increased susceptibility of small granules from malt is probably due to the partial removal of their protecting surface layer of protein. Although during malting the small granules of barley are hydrolysed more rapidly than the large granules, the situation is reversed during mashing. Very little loss of extract can be attributed to the enzymic resistance of small starch granules in all-malt mashes. If raw barley is used in the grist, substantial amounts of small starch granules may remain in the mash.     

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.     

Morphological changes of starch granules during grain filling and seed germination in wheat

In this study, the morphological changes of wheat starch granules during grain filling and seed germination were observed under scanning electron microscopy. Until 3 days post anthesis (DPA), the pericarp tissue was the major site of starch deposited. From 6 DPA, the size and the number of granules in endosperm gradually increased. The “double disk structure”, “pin holes”, and “equatorial groove” at the surfaces of the granules were observed during grain filling, these micro‐structural features might aid the enzymatic hydrolysis of starch granules during seed germination. The equatorial groove of granule was more susceptible to enzymatic hydrolysis than the flat surface.     

Preparation and Characterization of Annealed‐Enzymatically Hydrolyzed Tapioca Starch and the Utilization in Tableting

Tapioca starch was annealed at 60°C for 90 min followed by hydrolysis with α‐amylase at 60°C at various lengths of time (30, 60 and 120 min) to obtain high‐crystalline starches. The reaction products were subjected to spray drying to obtain annealed–enzymatically hydrolyzed–spray dried tapioca starch (SANET) in the form of spherical agglomerated granules. The properties of SANET were compared with those of annealed–spray dried tapioca starch without enzymatic treatment (SANT) and native–spray dried tapioca starch (SNT). Scanning electron micrographs of the starch samples were used to study the morphological changes and to suggest the mode of enzyme attack during hydrolysis. The á‐amylase preferentially attacked the interior of the starch granules, leaving a deep round hole on the starch granule surface. It was found by X‐ray diffraction that both annealing and amylolysis did not alter the A type diffraction pattern. The% relative crystallinity of SANET was raised with increasing hydrolysis time and with decreasing amylose content. High performance size exclusion chromatography (HPSEC) demonstrated the decrease of the degree of polymerization (DP) of the amylose fraction of SANET after prolonged hydrolysis. For the utilization of SANET as tablet filler, it was directly compressed by a tablet compression machine at 4 kN to obtain tablets. The increased relative crystallinity of starch resulted in increased crushing strength and disintegration time, but in a decreased tablet friability.     

Studies of Starch Size and Distribution in 33 Barley Varieties with a Celloscope

Detailed starch particle distribution curves for 33 Finnish barley varieties were determined by a Celloscope technique. All of the curves showed two maxima with respect to both the number and mass. Reproducibility of the counting method was controlled by making duplicate samples to test critical points in the sample treatment. Amounts of the small granules in the barley varieties were rather similar, but average volumes of the large particles varied by even more than 100%. This showed that the essential differences between the varieties appeared in the region termed here as the medium size granules. Based on the knowledge of the accurate size distribution curves from 33 different barley varieties an easy and simple procedure was developed to evaluate granule size distributions of starch in barley samples well enough for practical purposes.     

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”.     

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.     

Compositional changes in whole grain flours as a result of solvent washing and their effect on starch amylolysis

Whole grain flour is used most often as raw material for fuel alcohol production. However, the dry-milling process and the non-starch components of flours may impact the enzymatic hydrolysis of starch to glucose. The particle size distributions of flours prepared from whole grain triticale, barley, wheat and corn were determined and the effects of pre-washing with water, hexane, 100% ethanol or 50% ethanol on flour composition and the amylolysis of starch were studied. Scanning electron microscopy of the flours revealed that grinding grain to pass a sieve with an aperture size of 0.5 mm effectively released starch granules from endosperm cells. Pre-washing with water or 50% ethanol decreased the protein, phytic acid and total free phenolic contents of flours and, except for corn flour, increased starch content. Pre-washing with water reduced the ash contents of all flours, and reduced the ??-glucan content of barley flour by 98%. Pre-washing with hexane or 100% ethanol removed much of the lipid from the flours. Pentosan content was affected only slightly by any of the pre-washing treatments. Each of the pre-washings was associated with a significant change, positive or negative, in the extent of ??-amylolysis for one or more of the flours. The degree of ??-amylolysis in unwashed flours ranged from 22.4 to 26.1%, and from 21.6 to 28.1% in pre-washed flours, varying with flour source and solvent treatment. Pre-washing of flours increased the degree of hydrolysis achieved with sequential ??-amylase/amyloglucosidase treatment, with values ranging from 61.4 to 72.8% in pre-washed flours compared to 56.2-57.8% in unwashed flours. The highest degrees of hydrolysis were achieved with 50% ethanol pre-washing (72.4 and 72.8% for triticale and barley flours, respectively). The degree of ??-amylase/amyloglucosidase hydrolysis obtained for isolated starches ranged from 83.7 to 93.0%. This study demonstrated clearly that the partial removal of non-starch components from whole grain flours by solvent pre-washing enhanced the degree of amylolysis of starch.     

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。     

Assessment of Enzymatic Endosperm Modification of Malting Barley Using Individual Grain Analyses

Enzymatic modification of the endosperm of malting barley is a main feature of the malting process. Uneven enzymatic modification of the endosperm (heterogeneity) can cause brewhouse problems. Although there is a general correlation between endosperm modification, beta‐glucan breakdown and endo‐beta‐glucanase development, it is based on average results from sample analyses and may conceal heterogeneity. The primary aim of this work was to use individual grain analyses to investigate factors that control endosperm modification and beta‐glucan breakdown. In terms of beta‐glucan breakdown and physical modification, the barley variety Chariot malted faster than Decanter. However, both varieties showed similar distribution of endo‐beta‐glucanase in individual grains during malting. Further work on individual grains showed that the correlation between beta‐glucan breakdown and endo‐beta‐glucanase activity was not significant. Surprisingly beta‐glucan breakdown did not always correlate with the physical modification of the endosperm. Both these findings suggest that sample analyses of beta‐glucan levels and malt beta‐glucanase activities are not reliable indicators of the degrees of which malt samples are modified during malting. Since the distribution of beta‐glucan in individual grains of the unmalted barley varieties was similar, the total beta‐glucan levels of the original barley did not determine the rate at which beta‐glucan was broken‐down during malting. Although protein studies are at a preliminary stage, the rate of protein breakdown was not correlated with the rate at which beta‐glucan was broken down in the malting grain. It is possible that the physico‐chemical properties of endosperm storage proteins may limit the rate of beta‐glucan breakdown during malting.     

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.     

BRAZILIAN HULL-LESS AND MALTING BARLEY GENOTYPES: I. CHEMICAL COMPOSITION AND PARTIAL CHARACTERIZATION

Barley represents an important source of total dietary fiber (TDF) and β‐glucans. The chemical composition and partial characterization of two Brazilian barley experimental lines, hull‐less and malting, are reported. The range in diameter of the A‐ and B‐type granules was similar in both barley lines, 15 to 28 µm and 8 to 10 µm, respectively. Higher values for total starch, damage starch, ash, TDF and insoluble dietary fiber (IDF) were observed in the malting line while β‐glucan content was similar in both samples. The malting barley line had higher values of total isolated starch, as well as residual protein and total lipids in starch. The starch from the hull‐less barley line had lower swelling power and higher solubility than malting barley.     

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.     

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.     

Influence of α‐amylolysis on the formation of electron density inhomogeneities on the surface of starch granules

Low‐temperature nitrogen adsorption and SAXS were used to analyze the granule surface of wheat and rice starches before and after an action of Bacillus subtilis α‐amylase. Results obtained by the first method showed that α‐amylolysis caused surface changes arising of new pores or enlarging diameters of pores already existing. According to the SAXS results, the action of enzymes caused complete sharpening of a solid skeletal boundary in the case of wheat starch granules. Partial sharpening of this boundary in the case of rice starch granules could be attributed to the relatively high content of proteins in rice starch.     

Paste and Gel Properties and In Vitro Digestibility of Tef [Eragrostis tef (Zucc.) Trotter] Starch

Properties of tef starch from five varieties were compared with commercial maize starch. In most tef varieties the paste clarity (measured as % T) was similar to that of maize starch, but the paste was visually less white in colour. Tef starch gel texture was short and in most varieties was slightly firmer than that of maize starch. Tef starch adhesiveness was less than maize starch. Retrogradation extent of tef starch evaluated, as % gel syneresis under storage at 4 °C and ‐18 °C at 3, 7, 10 and 21 storage test days, was lower than that of maize starch. Storage with three freeze‐thaw cycles (‐18 °C 24 h; 23 °C 6 h) gave a similar trend. In tef starch initial digestion by α‐amylase and hydrolysis by mild HCl treatment was slightly higher than in maize starch, probably in part because of the smaller granule size and higher amorphous portion of tef starch. Alpha‐amylase degradation of tef starch granules was by surface erosion, probably due to the absence of surface pores in the granules.