Limit dextrinase in barley cultivars of differing malting quality: activity, inhibitors and limit dextrin profiles

Free and total limit dextrinase (LD) activity was measured in four barley varieties of differing malting quality. LD activity was not detected until 2 days after completion of steeping, at which point, total LD activity was 4–5 fold higher in Static and Chariot than in Optic or Hart. Free LD rose to higher levels in Static and Chariot than in Optic and Hart during malting. In addition, the proportion of free to total LD approached 35% in Static and Chariot whereas it did not reach 15% for Optic and Hart. Lower free LD activity was not reflected in a higher total content of branched dextrins in hot water extracts of the different varieties, but may have contributed to the persistence of branched dextrins of higher degree of polymerisation persisting in the hot water extracts of Hart and Optic.The variation in the proportion of free to total LD activity between varieties was not explained by differences in total LD activity and may be related to the presence of inhibitors of LD. Protein extracts made from the malts following steeping inhibited exogenous partially purified LD activity by >80%. After 3 days germination, Chariot, Optic and Static lost much of their inhibitory activity whereas it was retained in Hart. The increase in free LD activities during malting appeared to mirror the disappearance in inhibitory activity.Inhibitors of LD activity were also present in hot water extracts of Chariot and Hart malts. Chariot lost inhibitory activity after 3 days malting and hot water extracts from Chariot after 4 days malting caused apparent activation of LD. By contrast, hot water extracts from Hart retained inhibitory activity up to 5 days malting. These findings are discussed with reference to the availability and effectiveness of LD during malting.     

Effects of sulphur on yield and malting quality of barley

Eight field experiments were conducted at four sites in the UK in 2003 and 2004 to investigate the effects of sulphur (S) application on yield and malting quality of barley. Significant yield responses to S additions were obtained in five out of the eight experiments, with yield increases ranging from 0.2 to 1.2 t/ha (4.7–22.5%). At the two most S-deficient sites, S application significantly increased malt diastatic power, alpha-amylase activity, friability and homogeneity, and decreased (1→3,1→4)-β-glucan concentration in the wort, indicating an improved endosperm modification during malting. Sulphur applications also significantly increased the concentration of S-methylmethionine (the precursor of dimethylsulphide) in kilned malt, which could impact on beer flavour. When the supply of N was limiting, S applications decreased grain N concentration due to a dilution effect as a result of increased grain yield. In some cases, S applications resulted in decreased grain size. At sites non-deficient or marginally deficient in S, applications of S had little effect on grain or malting quality parameters. The need to maintain an adequate S supply to barley for both yield and malting quality was demonstrated.     

Individual and combined effects of pre- and post-anthesis temperature on protein composition of two malting barley cultivars

The present study has investigated the individual and combined influence of pre- and post-anthesis temperatures and cultivars on the protein composition in barley grains. Two barley cultivars were grown in soil and hydroponic systems in daylight chambers with different pre- and post-anthesis temperatures. Size exclusion (SE)-HPLC was used to evaluate the protein composition in mature barley grains. The results showed that individual and interactive effects of pre- and post-anthesis temperatures and cultivar variations influenced protein composition in the barley grains. Pre-anthesis temperature greatly affected the amounts of total sodium dodecyl sulphate (SDS) extractable proteins (TOTE) and explained 30% of the variation in TOTE. The barley cultivars accounted for 20% of the variation in TOTE. Variation in malting barley cultivars was found to influence the SDS extractable small monomers (41% of the variation). Percentage of SDS un-extractable polymeric proteins in total amount of polymeric proteins (%UPP) was governed by post-anthesis temperature, accounting for 11% of the variation and cultivar differences accounted for 7% of the variation. Thus, the climatic conditions during the specific growing period and a choice of cultivars played a major role in determining the protein composition and ultimately the malting quality of spring barley.     

Impact of water content on the solubilisation of arabinoxylan during xylanase treatment of wheat bran

Arabinoxylan (AX) has a major impact on the functional properties of wheat bran, and it has been shown that technological properties of bran can be improved by using endoxylanases. Enzymatic treatments are typically conducted at high water content. However, in industrial applications, low water content may be advantageous, especially when targeting dry end products. The aim of the study was to examine the impact of water content, ranging from 20 to 90%, on the efficiency of endoxylanase treatment of wheat bran. Interestingly, AX solubilisation was highest at the water contents of 40 and 90%. At water contents 50–80%, AX solubilisation was lower than at 40 and 90%. Furthermore, at low water content, less depolymerisation was detected. At water content of 40%, the bran-water mixture was transformed from powder-like into compact mass. Probably the compact consistency of the material enhanced AX solubilisation by increased breakdown of bran cell walls due to shear forces or via enhanced enzyme binding to the substrate. The results show that solubilisation of bran AX can also be efficiently performed at low water content.     

The effects of malting and mashing on barley protein extractability

Proteins in unmalted and malted barley and in brewers’ spent grain (BSG) obtained after mashing were fractionated on the basis of their differential extractability in different media and characterised by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and high-performance liquid chromatography (HPLC). Albumins and globulins were first extracted with 5.0% NaCl and hordeins (barley prolamins) were extracted with 55.0% 1-propanol in the presence, or absence, of 1.0% DTT. Glutelins were then extracted with 2.0% SDS/6.0 M urea/1.0% DTT or with 55.0% 1-propanol/6.0 M urea/1.0% DTT/0.036 M Tris-HCl (pH 8.4). Under non-reducing conditions, monomeric C hordeins and some B hordeins were extracted from unmalted barley, whereas most if not all B, C and D hordeins were extracted under reducing conditions. During malting, disulfide bonds are reduced and B and D hordeins are broken down by proteolysis. No D hordeins were extracted from malt and nearly the same levels of malt B hordeins were extracted both under non-reducing and reducing conditions. B hordeins present in BSG proteins were only extractable under reducing conditions. Whereas most of the C hordeins were extracted from BSG under non-reducing conditions, more C hordeins were extracted under reducing conditions. Mashing probably induced disulfide bond formation resulting in aggregation. Although earlier literature suggested the formation of an aggregate composed of B and D hordein (and glutelin) during mashing, the present work suggests the formation of an aggregate composed of B hordeins in which C hordeins are entrapped.     

Evaluation of malting barley quality using exploratory data analysis. I. Extraction of information from micro-malting data of spring and winter barley

This paper presents an exploratory multivariate approach for analysis of malting barley quality data. By using principal component analysis (PCA) and partial least squares regression (PLSR) complex malting quality data are combined into functional factors which are used for malting barley quality characterisation. Fifty barley samples were used in this investigation, representing 15 spring barley and 10 winter barley varieties grown at two locations in Denmark. The samples were micro-malted and mashed and analysed for 13 quality parameters according to official methods of the European Brewery Convention. These data were combined and reduced into a few latent (functional) factors using PCA by which it is demonstrated that the modification of β-glucan plays a major role in both spring and winter barleys. Additionally, the spring barley and winter barley samples display different covariate latent structures, mainly in the nitrogen and diastatic power patterns. It is furthermore shown that graphic display as facilitated by exploratory data analysis, can be utilized in order to evaluate genotype-environmental interactions by considering the position and movements of the individual objects (genotypes in this instance) in the score plots. Thus, in contrast to the classical analysis of variance, the samples can be individually evaluated and the corresponding loadings can be used to validate the genetic and environmental effect of a given sample in a quality perspective.Several of the investigated malting quality parameters are highly intercorrelated. This fact is utilized by applying PLSR to barley and malt data for the prediction of wort quality in order to exclude the mashing step. This approach was successful for the modification-dependent wort parameters, extract, wort β-glucan and viscosity.     

Fate of polyphenols and antioxidant activity of barley throughout malting and brewing

Phenolic contents of barley and malt extracts and their corresponding antioxidant activities were investigated using a chromatographic online antioxidant detection system. Ethyl acetate extracts of barley and malt were separated using reverse phase HPLC and compounds eluting from the column were submitted to two UV–visible detections: one for the phenolic compounds; and the other for the reduced form of the radical cation 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS^•+) after the compounds were allowed to react online with it. Prodelphinidin B3 and procyanidin B3 were identified as two major contributors in the antioxidant activity of barley, in addition to catechin. Malting had a dramatic impact on these three compounds by resulting in a sharp decrease in their detected amounts and the associated antioxidant activities. Two other antioxidants, ferulic and sinapic acids, showed a better ability to withstand not only malting but also brewing steps. As for the overall phenolic content and antioxidant capacity, the study showed that malting allowed a better release and/or extraction of phenolic compounds, while the first brewing step caused the most significant damage by drastically decreasing the total polyphenols and their activity. Hopping however did not significantly affect neither the phenolic content nor the antioxidant activity.     

The endogenous endoprotease inhibitors of barley and malt and their roles in malting and brewing

Endoproteases play an important role in barley germination by controlling the hydrolysis of the grain's storage proteins into peptides and amino acids that are needed by the young plant. During malting, the commercial version of this process, many high M_r barley biopolymers are converted into malt nutrients that can be utilized by yeasts during brewing. However, barley and malt both contain endogenous proteins that inhibit the enzymatic activities of these proteases. High levels of these inhibitors can cause brewing problems by preventing the proteases from producing optimal levels of soluble proteins and amino acids. Both high and low M_r inhibitors of cysteine proteases occur in barley and malt. Two of the high M_r inhibitors, lipid transfer protein 1 (LTP1) and LTP2, have been purified and studied. Recently, members of the trypsin/alpha-amylase inhibitor protein family (CM proteins) have been shown to inhibit the activity of SEP-1, a purified serine class barley protease. No inhibitors of aspartic proteases or metalloproteases have yet been purified, but it has been reported that endogenous metalloprotease inhibitors do exist. The inhibitors of the cysteine proteases and metalloproteases are probably the ones most important for brewing, because members of these two protease classes apparently catalyse most of the protein hydrolysis that occurs during malt mashing and, presumably, also during malting. More biochemical studies are needed to clarify how these proteins interact with the proteases to control protein hydrolysis during germination.     

The endogenous endoprotease inhibitors of barley and malt and their roles in malting and brewing

Endoproteases play an important role in barley germination by controlling the hydrolysis of the grain's storage proteins into peptides and amino acids that are needed by the young plant. During malting, the commercial version of this process, many high M_r barley biopolymers are converted into malt nutrients that can be utilized by yeasts during brewing. However, barley and malt both contain endogenous proteins that inhibit the enzymatic activities of these proteases. High levels of these inhibitors can cause brewing problems by preventing the proteases from producing optimal levels of soluble proteins and amino acids. Both high and low M_r inhibitors of cysteine proteases occur in barley and malt. Two of the high M_r inhibitors, lipid transfer protein 1 (LTP1) and LTP2, have been purified and studied. Recently, members of the trypsin/alpha-amylase inhibitor protein family (CM proteins) have been shown to inhibit the activity of SEP-1, a purified serine class barley protease. No inhibitors of aspartic proteases or metalloproteases have yet been purified, but it has been reported that endogenous metalloprotease inhibitors do exist. The inhibitors of the cysteine proteases and metalloproteases are probably the ones most important for brewing, because members of these two protease classes apparently catalyse most of the protein hydrolysis that occurs during malt mashing and, presumably, also during malting. More biochemical studies are needed to clarify how these proteins interact with the proteases to control protein hydrolysis during germination.     

Influence of sulphur application on hordein composition and malting quality of barley (Hordeum vulgare L.) in northern European growing conditions

The influence of sulphur (S) application on yield formation, hordein composition and malting quality of 2-rowed spring barley (Hordeum vulgare L.) was studied in Nordic conditions for the first time. In a greenhouse experiment, S deficiency was indicated when 10 mg S/kg soil or less was available, by an increase in the malate:sulphate ratio in leaves. The contents of aspartic acid and cystine in grains increased and decreased, respectively. Also a substantial decrease of total hordein and the proportion of B hordein, and an increase in the proportion of C hordein were associated with S deficiency. The effect of S was further assessed in field experiments by applying N and S in four different combinations prior to sowing. No apparent S deficiency occurred in the field conditions based on the malate:sulphate and grain N:S ratio. However, in a site where the grain S content was slightly but significantly increased by S application, a change in hordein composition and malting quality was observed. Thus even in S-sufficient conditions, the end use quality of malting barley may be affected by S application.     

啤用二棱大麦产量构成因素的表型相关分析与应用

应用简单相关、回归分析、偏相关、通径分析方法对沪麦4号等10个啤用二棱大麦品种（系）的产量构成因素进行统计分析和研究,结果表明,3个产量构成因素对单株产量均有正向效应,其中以每株穗数的贡献最大,每穗粒数次之,千粒重贡献最小。因此,提出了高产优质啤用二棱大麦的育种模式：以增加每株穗数“多穗型”为主要选择目标,兼顾每穗粒重,增加千粒重为配合选择指标,并适当协调好千粒重与穗粒数的关系。     

啤酒大麦新品种新啤4号的选育及栽培要点

1选育经过 新啤4号是新疆农科院奇台麦类试验站1994年采用日本引进品种红日啤麦作母本,耶费欧作父本,经系统选择,2000年成为稳定品系,2001年进行产量鉴定,2002至2003年在本站进行品系比较试验,两年平均6 190.5/hm 2,比对照法瓦维特增产9.7%,2004至2007年在不同生态区进行生产示范,2006至2007年参加自治区啤酒大麦区域试验,2007年同时参加了自治区生产试验.     

Evidence for the presence of arabinoxylan hydrolysing enzymes in European wheat flours

Water extracts of flour samples prepared from six sound European wheat varieties hydrolyse p-nitrophenyl-β-d-xylopyranoside and p-nitrophenyl-α-l-arabino-furanoside and, in addition, release soluble, dyed fragments from azurine crosslinked xylan. Incubation of water soluble wheat arabinoxylan with water extracts of flour results in the release of low molecular weight fractions consisting mainly of arabinose and xylose and small proportions of oligosaccharides as detected by high performance anion exchange chromatography. Gel permeation profiles of the incubation mixtures show a clear breakdown of the arabinoxylan.     

Application of an orcinol-ferric chloride colorimetric assay in barley and wheat accessions for water-extractable and total arabinoxylan

Arabinoxylan is an important hemicellulose potentially affecting wheat baking qualities, barley malt quality, and may impart prebiotic benefits. Water-extractable (WEAX) and total arabinoxylan (TOAX) were characterized in 204 wheat and barley accessions, respectively, using an orcinol-ferric chloride assay. WEAX measurement accuracy was optimum when glucose concentration was greater than 12–13 times pentose concentration. The modified method removed enough excess glucose spectral absorbance to make the corrected and uncorrected lines different, but still significantly correlated (p = 0.009, R = 0.94). Mean WEAX (expressed as percentage WEAX of TOAX) for the wheat accessions was 15.90%, ranging from 8.82% to 24.87%, and for barley accessions WEAX the mean was 7.10%, and ranged from 2.98% to 13.86%. Conclusions are 1) the assay is useful for a breeding program because of its semi-high throughput design for the simultaneous analysis of 16 (WEAX) to 40 (TOAX) barley lines or 24 (WEAX) to 40 (TOAX) wheat lines, 2) the trichromatic measurement reduces the impact of glucose, and 3) the broad range of WEAX measured showed that barley and wheat accessions vary in their extractable and unextractable components.     

Development of proteolytic activities during barley malting and their localization in the green malt kernel

The water-insoluble storage proteins of barley seeds reside in the starchy endosperm tissue. This tissue, when expressed from germinating barley, has a pH of 4·8. The hydrolysis of storage proteins during germination (malting) occurs mainly in the endosperm, so proteinases that are located in endosperm and are active at pH 4·8 are probably important to the storage protein hydrolytic process. This study reports our continued investigations of the endoproteinases of germinating barley (Hordeum vulgare L., cv. Morex) with a two-dimensional gel separation method that uses isoelectric focusing (IEF) and non-denaturing polyacrylamide gel electrophoresis (PAGE) in gels containing incorporated substrate protein. We identified the endoproteinases that were active at pH 4·8 and determined when they appeared during germination and where they were located in 4-day germinated barley (green malt). A total of nine cysteine, four aspartic, and two serine class proteolytic activities that were active at pH 4·8 were extracted from the endosperm tissue of green malt. It seems probable that some or all of these endosperm endoproteinases, especially proteinases C7, C8, C11, D3, E3 and E4, are the ones most intimately involved in hydrolyzing the storage proteins during malting.     

Evaluation of malting barley quality using exploratory data analysis. II. The use of kernel hardness and image analysis as screening methods

This paper presents an exploratory investigation of the use of image analysis and hardness analysis of barley kernels for characterisation and prediction of malting quality. A sample set of fifty barley samples representing 15 spring barley and 10 winter barley varieties grown at two locations in Denmark was used. The samples were micro-malted and mashed and analysed for 13 quality parameters according to the official methods of the European Brewery Convention. A sub-sample of the barley samples was analysed on two different single kernel instruments: (1) Foss Tecator GrainCheck was applied for non-destructive recording of single kernel size and shape (width, length, roundness, area, volume and total light reflectance) and (2) Perten Single Kernel Characterization System 4100 was applied for single kernel hardness and weight determinations. The eight variables from these single seed analyses have been used in two different ways, either as means and standard deviations, or as appended histogram spectra representing 250 kernels from each bulk sample. By the two methods, it has been possible to obtain reasonable Partial Least Squares Regression (PLSR) models for the structural and physical part of the malting quality complex associated to malt modification, but it was as expected impossible to predict the biochemical parameters associated with nitrogen chemistry and enzymatic power. The best model was achieved for (1→3, 1→4)-β-D-glucan in barley. The hardness of the barley kernels is by far the most important variable for describing malting performance. The additional use of the morphological data as acquired by fast non-destructive image analysis, however, also reveals some malting quality information by improving the calibration models based on hardness alone. The brightness of the kernels is by far the most important GrainCheck variable but also kernel size and shape is associated to malting performance. In general, the utilisation of the single kernel readings (used as histogram spectra), compared to sample mean and standard deviation, did not provide additional information for an improved prediction of the malting quality parameters.     

Evaluation of protein nutritive value in barley and wheat cultivars usingAspergillus flavus

The fungusAspergillus flavus was used to evaluate the protein nutritive value of barley and wheat cultivars with a wide range in protein and amino acid concentrations. The biomass yield, after 72h incubation on isonitrogenous diets, also varied widely among barley or wheat cultivars. However, biomass was more closely associated with sample weight or glucose supplementation of the medium than with amino acid concentrations. Only threonine, serine and histidine in barley proteins gave low positive correlations with biomass yield at all energy levels in the diets, and no consistent correlations were found in the wheat experiment. Also biomass mycelium varied in nitrogen concentration, depending on diet, and biomass weight was not a consistent measure of nitrogen retention by the mycelum. It was concluded thatA. flavus was not a satisfactory organism for rapid screening of barley or wheat cultivars for concentration of available amino acids, essential for human nutrition.