Barley Starch Research Articles

Gelatinisation Characteristics and Enzyme Susceptibility of Different Types of Barley Starch in the Temperature Range 48-72°C1

The gelatinisation temperatures, pasting characteristics and enzymic susceptibilities in the temperature range 48-72°C of normal, high amylose, low amylose and zero amylose barley starches were determined. Normal starches had the lowest gelatinisation temperatures, but low and zero amylose starches had the lowest pasting temperatures. Normal starches were the most readily soluble in water at 48-60°C in the presence of a mixture of α-amylase, β-amylase and limit dextrinase and were most readily broken down to reducing sugars by these enzymes. High amylose starch was the most resistant to enzymic hydrolysis in the temperature range 48-72°C and, hence, produced the lowest level of reducing sugars.

Gradual enzymatic modification of barley and potato amylopectin

New potato and barley starches with no amylose were used in order to explore structural changes in amylopectin due to hydrolysis with α-amylase from Bacillus amyloliquifaciens. The degradation pattern was monitored with size exclusion, with light scattering and viscometry detectors for determination of molecular weight and radius of gyration. Fractions with relatively narrow molecular weight distributions at high yields were obtained as a result of the gradual enzymatic degradation and the subsequent sequential ethanol precipitation technique used. Generally the fractions obtained showed a pattern of both decreasing molecular weight and radius of gyration with increasing enzymatic hydrolysis. Fractions that precipitated with the lowest ethanol concentration had the highest values of both average molecular weight and radius of gyration. The unit chain length distributions of the fractions were analysed and the results showed that the chain length distribution varied with the time of hydrolysis. There was also a decreasing trend in average molecular weight with enzyme degradation time for fractions that precipitated at the same ethanol concentration, indicating that the fractionation was affected by structure and not only by molecular weight. Data from this study could be useful for the production of modified amylopectin molecules that vary in composition and characteristics.

Molecular structure and some physicochemical properties of waxy and low-amylose barley starches

The molecular structures and physicochemical properties of starches from an actual waxy (HB 340) and two low-amylose (CDC Candle and Sumiremochi) cultivars of barley were examined and compared with those of a normal cultivar (CDC Dawn). HB 340 starch had no detectable amylose. The amylose content was 2.2 and 11.4% in CDC Candle and Sumiremochi starches, respectively, being much lower than that in CDC Dawn starch (25.4%). The starches of HB 340, CDC Candle and Sumiremochi showed a higher viscosity and breakdown on the viscogram than CDC Dawn starch, and HB 340 starch showed the highest Δ H of peak 1 and no peak 2 on the DSC thermogram. The amylopectins resembled each other in average chain-length (19–20), β-amylolysis limit (β-AL 53–54%) and chain-length distribution. The amyloses of CDC Candle and Sumiremochi were larger (DPn 1680 and 1560, respectively) and contained the branched amylose with a lower number of chains (NC 6.1–10.4) than CDC Dawn amylose (DPn 1220, NC 13.8) CDC Candle amylose had a higher molar fraction (45%) of the branched molecule than the others (21–26%).

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.

Starch and By‐Products from a Laboratory‐Scale Barley Starch Isolation Procedure

ABSTRACTStarch was isolated from three different barleys with normal, highamylose, or high‐amylopectin (waxy) starch. The laboratory‐scale starch isolation procedure included crushing of grains, steeping, wet milling, and sequential filtration and washing with water and alkali, respectively. Yield and content of starch, protein, and dietary fiber, including β‐glucan, were analyzed in isolated starch and in the by‐products obtained. Starch yield was 25–34%, and this fraction contained 96% starch, 0.2–0.3% protein, and 0.1% ash. Most of the remaining starch was found in the coarse material removed by filtration after wet milling, especially for the high‐amylose barley, and in the starch tailings. Microscopy studies showed that isolated starch contained mostly A‐granules and the starch tailings contained mostly B‐granules. Protein concentration was highest in the alkali‐soluble fraction (54%), whereas dietary fiber concentration was highest in the material removed by filtration after alkali treatment for the normal and waxy barleys (55%). The β‐glucan content was especially high for the waxy barley in this fraction (26%). The study thus showed that it was possible to enrich chemical constituents in the by‐products but that there were large differences between barleys. This result indicates a need for modifications in the isolation procedures for different barleys to obtain high yields of starch and different by‐products. Valuable by‐products enriched in β‐glucan or protein, for example, may render starch production more profitable.

Adhesion of bifidobacteria to granular starch and its implications in probiotic technologies.

Adhesion of 19 Bifidobacterium strains to native maize, potato, oat, and barley starch granules was examined to investigate links between adhesion and substrate utilization and to determine if adhesion to starch could be exploited in probiotic food technologies. Starch adhesion was not characteristic of all the bifidobacteria tested. Adherent bacteria bound similarly to the different types of starch, and the binding capacity of the starch (number of bacteria per gram) correlated to the surface area of the granules. Highly adherent strains were able to hydrolyze the granular starches, but not all amylolytic strains were adherent, indicating that starch adhesion is not a prerequisite for efficient substrate utilization for all bifidobacteria. Adhesion was mediated by a cell surface protein(s). For the model organisms tested (Bifidobacterium adolescentis VTT E-001561 and Bifidobacterium pseudolongum ATCC 25526), adhesion appeared to be specific for alpha-1,4-linked glucose sugars, since adhesion was inhibited by maltose, maltodextrin, amylose, and soluble starch but not by trehalose, cellobiose, or lactose. In an in vitro gastric model, adhesion was inhibited both by the action of protease and at pH values of < or =3. Adhesion was not affected by bile, but the binding capacity of the starch was reduced by exposure to pancreatin. It may be possible to exploit adhesion of probiotic bifidobacteria to starch granules in microencapsulation technology and for synbiotic food applications.

Stability and function of interdomain linker variants of glucoamylase 1 from Aspergillus niger.

Several variants of glucoamylase 1 (GA1) from Aspergillus niger were created in which the highly O-glycosylated peptide (aa 468--508) connecting the (alpha/alpha)(6)-barrel catalytic domain and the starch binding domain was substituted at the gene level by equivalent segments of glucoamylases from Hormoconis resinae, Humicola grisea, and Rhizopus oryzae encoding 5, 19, and 36 amino acid residues. Variants were constructed in which the H. resinae linker was elongated by proline-rich sequences as this linker itself apparently was too short to allow formation of the corresponding protein variant. Size and isoelectric point of GA1 variants reflected differences in linker length, posttranslational modification, and net charge. While calculated polypeptide chain molecular masses for wild-type GA1, a nonnatural proline-rich linker variant, H. grisea, and R. oryzae linker variants were 65,784, 63,777, 63,912, and 65,614 Da, respectively, MALDI-TOF-MS gave values of 82,042, 73,800, 73,413, and 90,793 Da, respectively, where the latter value could partly be explained by an N-glycosylation site introduced near the linker C-terminus. The k(cat) and K(m) for hydrolysis of maltooligodextrins and soluble starch, and the rate of hydrolysis of barley starch granules were essentially the same for the variants as for wild-type GA1. beta-Cyclodextrin, acarbose, and two heterobidentate inhibitors were found by isothermal titration calorimetry to bind to the catalytic and starch binding domains of the linker variants, indicating that the function of the active site and the starch binding site was maintained. The stability of GA1 linker variants toward GdnHCl and heat, however, was reduced compared to wild-type.

Effect of lactic acid fermentation of wheat and barley whole meal flour on carbohydrate composition and digestibility in mink ( Mustela vison)

Wheat and barley whole meal flours (WMFs) were subjected to treatment by fermentation, autoclaving, and fermentation followed by autoclaving. The WMFs were analysed for chemical composition, formulated into wet diets (282 g kg −1) and fed to adult mink ( Mustela vison) for determination of total tract digestibility of total starch, total carbohydrate, crude protein and fat. Fermentation of WMF/water mixtures inoculated with a Lactobacillus sp. (strain AD 2) was performed at 30°C for 16 h. Autoclaving was carried out for 60 min at 120°C. Fermentation increased colony-forming units (CFUs) to about 10 8 g −1 and lowered pH to 3.7–3.8 in both WMFs. All carbohydrate parameters were affected by type of cereal, and were, except for total starch, affected by treatment. Levels of total dietary fibre and β-glucans decreased by fermentation in both WMFs. The decrease in total β-glucans from 33.5 to 18.4 g kg −1 in barley WMF, was mainly restricted to the soluble fraction. Glucose levels in barley WMF increased simultaneously from 0.6 to 12.3 g kg −1. The main effects of autoclaving were increased levels of total dietary fibre, maltose, and increased hydration capacity. With fermentation prior to autoclaving, increases in levels of the fibre fractions and maltose were prevented while hydration capacity prevailed as an effect of autoclaving. Compared with fermentation alone, the combined treatment increased damaged starch levels and hydration capacity. Digestibilities of total carbohydrate, crude protein and fat were significantly higher for wheat than for barley. Fermentation had no effect on digestibility of total starch or total carbohydrate of wheat, but increased digestibility of total starch of barley significantly from 0.742 to 0.880, and of total carbohydrate from 0.457 to 0.616. Autoclaving had no significant effect on digestibility of total starch and total carbohydrate of wheat. Digestibility of total starch and total carbohydrate in barley increased significantly after autoclaving. Total starch and total carbohydrate digestibility of both wheat and barley were significantly enhanced by combined fermentation and autoclaving compared with fermentation alone. Compared with autoclaving alone, combined fermentation and autoclaving promoted no significant improvement of total starch and total carbohydrate digestibility in wheat, whereas total carbohydrate digestibility in barley increased from 0.605 to 0.672. Fat digestibility was slightly improved by both fermentation and autoclaving. Autoclaving of cereals reduced significantly the faecal dry matter contents of mink. This effect could be counteracted by preceding fermentation. In conclusion, lactic acid fermentation of wheat and especially barley provided chemical changes of benefit for carbohydrate digestion in the mink.

Optimization of experimental conditions for the separation of small and large starch granules by gravitational field-flow fractionation

Separation of small and large barley starch granules by gravitational field-flow fractionation was investigated from the point of view of sample pre-treatment, amount of injected sample, and elution conditions. The sample pre-treatment study resulted in the conclusion that it is reasonable to soak the starch granules for at least 24 h prior to separation. The experiments with different amounts of injected sample show that it is possible to increase as well as decrease twofold the sample amount usually used without any change in retention ratios. The implementation of flow-rate gradients for elution of the starch granules reduced total separation time. However, the applied flow-rate gradients did not improve the resolution of peaks A and B compared with the generally used constant flow-rate. Thus, for barley starch granules, the constant flow-rates within the range from 0.8 to 1.0 ml/min seem to provide the best compromise of total separation time, peak resolution and instrumental expense.

Fine Structures of Amylose and Amylopectin from Large, Medium, and Small Waxy Barley Starch Granules

ABSTRACTAmylose and amylopectin were prepared from large, medium, and small granule starches of classified waxy barley flour, and their fine structures were investigated. The amylose content had a wide distribution range (≈1.4–9.4%). Number‐average degrees of polymerization (DPn) of the amyloses were similar among the samples (≈1,200–1,300). But number of chains per molecule (NC) decreased from the surface to the center (≈6–10 chains). DPn of the amylopectins varied from 4,657 to 14,604; decreased in the order of large, medium, and small granules in same fractions of the grain; and increased from the surface layer to the center. Longest chains (LC) were not found in any of the amylopectin molecules. The large amylopectin molecule had more long chains and fewer A chains than the small molecule. The amylose content had definite effects on the transition temperature range and crystal formation of the starch granules. There were positive correlations between DPn of the amylopectin and relative crystallinity (γ = +0.69) and enthalpy value (γ = +0.80), respectively. These findings may help to elucidate biosynthesis mechanism of starch.

Molecular Structure and Pasting Properties of Normal Barley Starches.

Molecular Structure and Pasting Properties of Normal Barley Starches.

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.

Size Analysis of Barley Starch Granules by Sedimentation/Steric Field Flow Fractionation

In the present work the relatively new technique of sedimentation/steric field-flow fractionation (Sd/StFFF) was used for the size analysis of the large, medium and small starch granules of barley grain. The experimental parameters varied were the time from the preparation of the starch sample dispersion — in order to study the disintegration or the aggregation of the starch granules — and the concentration of the sample — in order to study the sample overloading effect on the measured size of the starch granules. A bimodal or trimodal size distribution curve, depending on the experimental conditions used, was found by Sd/StFFF, and the number and weight average diameters of the starch granules were calculated. Finally, the experimental results are compared with those obtained by scanning electron microscopy and light scattering, and useful conclusions concerning the destruction or the aggregation of the starch granules, as well as the sample overloading effect on the granule's size, measured by Sd/StFFF, are extracted.

Effect of high pressure on the physical properties of barley starch

The kinetics of the high-pressure gelatinization of barley starch suspensions at two different concentrations (10 and 25%) were studied in the pressure range 400–550 MPa. The pressure-treated samples were examined using rheological methods, microscopy and differential scanning calorimetry (DSC). The rheological properties, the microstructure and loss of birefringence, as well as the melting of amylopectin crystals as determined by DSC, were all both pressure- and time-dependent. For the 10% suspension, only a slight increase in viscosity was observed, while a strong paste with a creamy texture and a maximum storage modulus of approximately 23 kPa was formed during pressurisation of the 25% suspension. The rheological properties and the microstructure of the pressure-treated samples were different from those of the heat-treated samples. The starch granules remained intact after the pressure treatment and no leaching of amylose was observed. The retrogradation of pressure-induced gels was investigated by DSC and was shown to be similar to that of a heat-induced gel.

Effect of Partial Gelatinization and Lipid Addition on α‐Amylolysis of Barley Starch Granules

ABSTRACTThe effect of partial gelatinization with and without lipid addition on the granular structure and on α‐amylolysis of large barley starch granules was studied. The extent of hydrolysis was monitored by measuring the amount of soluble carbohydrates and the amount of total and free amylose and lipids in the insoluble residue. Similarly to the α‐amylolysis of native large barley starch granules, lipid‐complexed amylose (LAM) appeared to be more resistant than free amylose and amylopectin. Partial gelatinization changed the hydrolysis pattern of large barley starch granules; the pinholes typical of α‐amylase‐treated large barley starch granules could not be seen. Lipid addition during partial gelatinization decreased the formation of soluble carbohydrates during α‐amylolysis. Also free amylose remained in the granule residues and mostly amylopectin hydrolyzed into soluble carbohydrates. These findings indicate that lysophospholipid (LPL) complexation with amylose occurred either during pretreatment or after hydrolysis, and free amylose was now part of otherwise complexed molecules instead of being separate molecules. Partial gelatinization caused the granules to swell somewhat less during heating 2% starch‐water suspensions up to 90°C, and lipid addition prevented the swelling completely. α‐Amylolysis changed the microstructure of heated suspensions. No typical twisting of the granules was seen, although the extent of swelling appeared to be similar to the reference starch. The granules with added LPL were partly fragmented after hydrolysis.

Beer: An Ancient Yet Modern Biotechnology

The brewing of beer is a complex process that draws on a diversity of sciences and technology, of which chemistry is but one. This paper focuses on the chemistry of the brewing process and of the finished product. It examines each of the main classes of molecule found in beer, considers their contribution to quality and their origins in the brewing process. The study of beer and its production provides an excellent illustrative example for teaching how raw materials and the manner by which they are processed determine the acceptability of a product. Beer, whilst 90%+ water, contains a wide range of chemical species which establish its properties. Apart from ethanol (the common denominator amongst all alcoholic beverages), beer contains substances that determine its flavor, foam, and color. The flavorsome components of beer include the bitter iso-a-acids and aromatic essential oils from hops, along with esters, acids, sulfur-containing compounds and vicinal diketones from yeast. The foaminess of beer depends on the presence of carbon dioxide but also of surface-active materials like amphipathic polypeptides from malt and the bitter substances from hops. The color is due to Maillard reaction products generated largely during the kilning of malt. The malting and brewing processes (which are briefly described) are designed to maximize the extraction and digestion of barley starch and protein, yielding highly fermentable wort. The processes are also designed to eliminate materials that can have an adverse effect on beer quality, such as the haze-forming polyphenol from barley and hops and the lipids and oxygen that, together, can cause beer to stale.

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

α-Amylolysis of native granular starch represents a biochemical process, in which an enzyme in solution solubilises a highly organised, semicrystalline substrate. To study this process, which is very slow compared to the hydrolysis of gelatinised starch [1], it is necessary to use high concentrations of enzyme or very long incubation times. The solubilised dextrins are therefore easily hydrolysed further into small fragments, preventing a study of the products originally released from the granules. A method that enables a collection of the dextrins solubilised from starch granules by α-amylase was developed [1] and has made it possible to study the composition of the products at early stages of the process. In this method, the starch granules are packed as a thin layer in a two-compartment column [2] and a diluted enzyme solution is pumped through the starch. Before a secondary hydrolysis occurs, the enzyme is bound to an anionexchange matrix (DEAE-Sepharose) in the upper compartment of the column, whereas the solubilised dextrins are collected into fractions representing successive stages of the

Carbohydrate Make Up of Huskey Barley

The chemical composition of two and six-row huskey barley grown under Haryana agroclimatic conditions is reported. Two-row varieties had slightly higher percentage of reducing sugars, sucrose and lignin whereas protein, proanthocyanidins, starch, neutral detergent fibre (NDF), acid detergent fibre (ADF) and hemicellulose were higher in six-row barleys. Malting significantly decreased the starch, sucrose and protein contents, while total soluble sugars, reducing sugars and maltose increased. The concommitant decrease in proanthocyanidins level is also desirable when barley is used for malting and brewing purposes. The variety RD2560 emerged to he superior for malting and brewing. The conduction of feeding trials and investigation of physico-chemical properties of barley starch are suggested.

Molecular Structure and Some Physicochemical Properties of High‐Amylose Barley Starches

ABSTRACTThe molecular structure and some physicochemical properties of starches from two high‐amylose cultivars of barley, high‐amylose Glacier A (HAG‐A) and N (HAG‐N), were examined and compared with those of a normal cultivar, Normal Glacier (NG). The true amylose contents of HAG‐A, HAG‐N, and NG were 41.0, 33.4, and 23.0%, respectively. Iodine affinities before and after defatting of starch, and thermograms of differential scanning calorimetry, indicated that HAG‐A and HAG‐N starches had a higher proportion of amylose‐lipid complex than did NG starch. The amylopectins from HAG‐A and HAG‐N were similar to NG amylopectin in average chain length (18–19), β‐amylolysis limit (β‐AL 56–57%), number‐average degrees of polymerization (DPn 6,000–7,500) and chain length distribution. Very long chains (1–2%) were found in amylopectins from all cultivars. HAG‐A amylopectin had a larger amount of phosphorus (214 ppm) than the others. The amyloses from HAG‐A and HAG‐N resembled NG amylose in DPn (950–1,080) and β‐AL (70–74%). However, HAG‐A and HAG‐N had a larger number of chains per molecule (NC 2.4–2.7) than NG amylose (1.8) and contained the branched amylose with a higher NC (9.5–10.6) than that of NG amylose (5.8), although molar fractions of the branched amylose (15–20%) were similar.

Effect of Extrusion Cooking on the Primary Structure and Water Solubility of β‐Glucans from Regular and Waxy Barley

ABSTRACTWater‐soluble β‐glucan from native and extrusion‐cooked barley flours of two barley cultivars, Candle (a waxy starch barley) and Phoenix (a regular starch barley), was isolated and purified. The purity of β‐glucan samples was 85–93% (w/w, dry weight basis) for Candle and 77–86% (w/w, dry weight basis) for Phoenix. The water solubility of β‐glucan (at room temperature, 25°C) in the native and extruded flours (primary solubility) was different from that of the purified β‐glucan samples (secondary solubility). The solubility of β‐glucan in the native and extruded Candle flour was substantially higher than that of β‐glucan in Phoenix. For both cultivars, β‐glucan in the extruded flours had solubility (primary solubility) values higher than in their native counterparts. The solubility of β‐glucan in the purified β‐glucan samples differed depending on the barley cultivar and the extrusion conditions employed. The glycosidic linkage profiles of purified soluble β‐glucan from native and extruded barley flours were determined in order to understand the changes in the primary structure of β‐glucan and the effect of extrusion on the β‐glucan structure‐solubility relationship.