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.     

TESTS FOR SELECTION OF MALTING QUALITY USING UNMODIFIED BARLEY

Various tests for malting potential based on unmodified barley were evaluated. These were based on NearInfraRed Reflectance Spectrophotometry (NIR), sedimentation of meals in cold alcohol or Lactic Acid/Sodium dodecyl sulphate solution, the content of total β glucan as measured by the viscosity of acidic extracts. NIR and sedimentation in Lactic Acid/SDS were found to be the most applicable to the breeding programme at this Institute, whereas the methods based on total β glucan or sedimentation in cold alcohol were unsuitable. The method based on soluble β glucan was only suitable to a breeding programme in which parents with known high β glucan content were used. An hypothesis for the contribution of total β glucan to malting quality is presented. None of the tests investigated were affected by declining dormancy or water sensitivity in the grain.     

GENETIC AND ENVIRONMENTAL VARIATION OF GUM CONTENT IN BARLEY

The influence of genetic vs environmental factors on the gum content of the barley grain has been studied by growing 4 varieties of barley, at 4 locations in the South of Spain, with 6 sowing dates at each location. The genetic factors proved to be the more important, accounting for 89% of the variation over locations and 71·5% of the variation among locations and sowing dates. Of the environmental factors studied, the sowing date was the most important. The variety × sowing date interaction was also statistically significant. Furthermore, the later the sowing date the higher the gum content of the grain. There was no variety × location interaction and, therefore, the varieties ranked in the same order at each location. It was also demonstrated that there was a different pattern of response for the varieties when grown in environments which were able to induce high or low gum content, suggesting that low gum content-low response varieties should be grown if the grain is to be used as an adjunct in brewing.     

Relationship Between Flour Turbidity,Malting and Endosperm Structure

Turbidity values of Chariot, Optic and Decanter barley varieties showed that Optic had the highest turbidity and Decanter the lowest. However, Optic malted slower than Chariot although they are both considered as good quality barley varieties and also slower than Decanter, a low graded barley variety. Scanning electron microscopy results suggested that high turbidity scores are influenced by the “open” barley endosperm structure, while localized compaction may result in resistance to milling as well as undermodification and poor malting performance in terms of friability, β‐glucan and protein breakdown.     

Influence of barley variety, timing of nitrogen fertilisation and sunn pest infestation on malting and brewing

BACKGROUND: This paper presents a multivariate approach to investigate the influence of barley variety, timing of nitrogen fertilisation and sunn pest infestation on malting and brewing. Four spring and two winter barley varieties were grown in one location in southern Europe. Moreover, one of the spring varieties was infested with sunn pest, in order to study the effects of this pest on malting quality, and subjected to different nitrogen fertilisation timing regimes. The samples were micromalted, mashed, brewed and analysed. RESULTS: The data showed that even though the two winter barleys seemed to be the best regarding their physical appearance (sieving fraction I + II > 82%), this superiority was not confirmed in the malt samples, which showed low values of Hartong extract (27.1%) and high values of pH (6.07–6.11) and β‐glucan content (12.5–13.2 g kg^?1), resulting in low‐quality beers. The barley sample subjected to postponed fertilisation had a total nitrogen content (19.5 g kg^?1 dry matter) exceeding the specification for malting barley and gave a beer with a low content of free amino nitrogen (47 mg L^?1) and high values of viscosity (1.99 cP) and β‐glucan content (533 mg L^?1). The beer obtained from the barley sample subjected to pest attack had good quality parameters. CONCLUSION: All spring barleys gave well‐modified malts and consequently beers of higher quality than the winter barleys. Moreover, postponed fertilisation was negatively related to the quality of the final beer, and sunn pest infestation did not induce important economic losses in the beer production chain. Copyright © 2010 Society of Chemical Industry     

Quantification of uncertainty using Bayesian and bootstrap models to simulate the impact of nitrogen fertilisation on β‐glucan levels in barley

BACKGROUND: β‐Glucans have enjoyed renewed interest as a functional food ingredient, with current attention focused on optimising β‐glucan levels in finished products without compromising final product quality. In order to measure the uncertainty about the level of β‐glucans in barley, two different statistical methods (Bayesian inference and Bootstrap technique) were applied to measured levels of β‐glucan in three different varieties of barley grain (n = 83). RESULTS: The resulting probability density distributions were similar for the full data set and also when applied to smaller sample sizes, highlighting the potential for either method in quantifying the total uncertainty in β‐glucan levels. Bayesian inference was used to model the effect of nitrogen treatment on β‐glucan and protein contents in barley. The model found that a low level of fertilisation (50 kg N ha^?1) did not have a significant effect on β‐glucan or protein content. However, fertilisation above this level did result in an increase in β‐glucan and protein levels, the effect seeming to plateau at 100 kg N ha^?1. In addition, the uncertainty distributions were significantly different for two consecutive years of data, highlighting the potential environmental influence on β‐glucan content. CONCLUSION: The model developed in this study could be a useful tool for processors to quantify the uncertainty about the initial level of β‐glucan in barley and to evaluate the influence of environmental factors, thus enabling them to formulate their ingredient base to optimise levels of β‐glucan without compromising final product quality. Copyright © 2009 Society of Chemical Industry     

EFFECTS OF CULTIVAR AND ENVIRONMENT ON β-GLUCAN CONTENT AND MALTING QUALITY OF TURKISH BARLEYS

Eight barley cultivars grown under the same agronomic conditions and samples of Tokak cultivar grown at six different sites of Turkey were used in this study. There were significant differences among the barley cultivars and growing locations in terms of β-glucan content (p<0.05). Among malt quality criteria tested for the 8 barley cultivars; friability, viscosity, Kolbach index and extract difference showed significant correlations (p<0.05) with the total β-glucan content. Similar correlations were also observed between the malt quality criteria (Kolbach index and extract difference) and β-glucan contents for the Tokak samples grown at different sites.     

Barleys Grown as Cultivar Mixtures Compared with Blends Made Before and After Malting,for Effects on Malting Performance

Four barley cultivars were grown in replicated trials at three sites in Scotland in 2000, both as pure stands and in all four possible three‐component mixtures. After harvest, some grain from the pure stands was used to synthesise four blends of three component varieties. Grain from the pure stands, the mixtures and the blends was malted and all samples were assessed for total β‐glucan content. At two of the sites, field grown mixtures were shown to have lower malt β‐glucan than blends made prior to malting, although their grain β‐glucan contents had not been significantly different from the means of the component varieties. At the other site, the mixtures had higher levels of soluble nitrogen than the blends or the means of their component cultivars although, significant differences had not occurred in grain nitrogen contents. Three component blends were also made from the malted grain of the pure stands and hot water extracts were measured on all samples including the blends made before and after malting. There were considerable differences between sites and also between mixtures, blends and the mean of the mixture components when assessed separately. At all sites and for all varietal combinations, field grown mixtures were shown to be equal or superior to blends made after harvesting, in addition to frequently exceeding the mean of their components. It was concluded that the advantages, in β‐glucan or protein modification, associated with mixtures resulted from interactions between components in the growing environment and that interactions in the malting and mashing environments had little if any effect.     

Lofty Nijo: A High Quality Malting Barley Variety Released from an Australian‐Japanese Collaboration

A new malting barley variety, Lofty Nijo, was bred in Australia through a collaborative breeding program between a Japanese brewing company and Adelaide University. The variety is early flowering and maturing, with similar yield potential to Schooner except in lower rainfall areas, and is not zinc efficient. It produces plump grains with low screenings similar to Schooner and more uniform and plumper grains than Franklin. Lofty Nijo has a well‐balanced malting quality profile. It shows high values in malt extract, diastatic power, apparent attenuation limit and Hartong index (VZ45) and low values in wort beta‐glucan and viscosity. The Kolbach index of this variety is lower than Schooner and Sloop, however, it is higher than Franklin. A pilot‐scale brewing trial indicated that Lofty Nijo is as suitable for Japanese brewing as the world's leading varieties, such as Franklin. Lofty Nijo should therefore offer a premium malting barley variety in Australia for export markets. The breeding, agronomic performance and quality profile of the variety is described in this paper.     

RELATIONSHIPS BETWEEN PEARLING RESISTANCES OF BARLEYS AND THE EXTRACT POTENTIAL OF THE SUBSEQUENT MALTS

A modified pearling instrument was used to determine the hardness of samples of barley and the results correlated with the extracts achieved by the malts made from those barleys. The influence of variety was such that the procedure could not be applied to selection of progeny from a breeding programme. However, the method could be used to accurately predict the malting potential of samples of varieties of malting barley if the relationship for the particular variety were known.     

青稞品种对青稞发酵酒营养与感官品质的影响

本研究以7种西藏特有的青稞品种及相应发酵青稞酒为对象,基于理化性质、营养、风味和感官等指标,采用典范对应分析（canonical correspondence analysis,CCA）和主成分分析（principal component analysis,PCA）等探究青稞品种与其发酵酒品质的关系。研究表明,与青稞原粮相比,青稞酒体氨基酸中必需氨基酸占比增加,可能是酿造过程中非必需氨基酸转化形成了必需氨基酸。CCA结果显示不同品种青稞原粮在总氨基酸、γ-氨基丁酸、β-葡聚糖和总多酚含量等方面具有一定相似性,但其营养结构的差异经微生物生物化学转化得以放大,为筛选青稞酒的优质品种提供了可能。通过青稞原粮及相应青稞酒中的蛋白质、氨基酸、γ-氨基丁酸和总多酚水平等营养指标分析初步优选出‘藏青2000’为酿酒青稞品种,其次是‘隆子黑’‘芶芝黑’‘藏青25’。结合青稞酒营养、风味和感官等多维度指标,最终确定‘藏青2000’为最佳酿酒青稞品种,其次为各具特色风味的‘芶芝黑’‘隆子黑’‘藏青25’。本研究可为我国青稞酒领域的发展提供参考。     

THE ACTION OF ENDO-β-1,3-GLUCANASES ON BARLEY AND MALT β-GLUCANS

The β-glucan extracted from ungerminated barley with water at 40 °C has a much lower specific viscosity than the corresponding material isolated from a wort prepared at 65 °C from a two-day germinated barley malt. Both glucans are similar in that they are polymers of β-D-glucose, with approximately 74% of the linkages in the β-1,4 configuration and 26% in the β-1,3 configuration. However, the two glucans are not hydrolysed to the same extent either by a partially purified bacterial endo-β-1,3-glucanase or by a homogeneous endo-β-1,3-glucanase from malted barley. The malt glucan is readily hydrolysed, causing a rapid decrease in specific viscosity but with no measurable increase in reducing power, whereas barley glucan undergoes only limited hydrolysis under similar conditions. Thus, different β-glucan preparations from barley or malt may be identical in the proportion of β-1,3 to β-1,4-linkages but the overall arrangement of linkages, and hence susceptibility to enzyme attack, differs according to the source and the method of extraction of the glucan. The molecular weights of both β-glucan preparations and the products of their enzyme hydrolysis have been determined by agarose gel permeation chromatography. A simple model which illustrates the underlying structural relationships of the β-glucans from barley and malt is suggested.     

QUANTITATIVE CHANGES IN THE CONCENTRATIONS OF THE MAJOR COMPONENTS OF FOUR GENOTYPES OF BARLEY GRAINS DURING MALTING AND MASHING

Four genotypes of barley, including good and poor malting varieties, were sampled as grain, green malt, kilned malt and spent grains. Each of these samples were analysed for total protein, aggregated protein, total and soluble β-glucan, starch and husk contents. Protein sub-units were separated using sodium dodecyl sulphate polyacrylamide electrophoresis. Activities of β-glucanase, endopeptidase and α-amylase were measured and starch from each sample was purified and separated into large and small granules, and analysed for total protein and sub-unit protein content. Results calculated as % of dry weight and as a proportion of the weight of dry grain showed quantitatively the changes which occurred in the components of the grain during malting and mashing. Comparisons of the composition of the genotypes at the various stages showed that the best malting variety studied, Ark Royal, was better because of moderate superiority in several characters rather than a fundamental difference in a single attribute and supports the thesis that to further improve malting quality plant breeders should select for several characters which are independently inherited.     

DIFFERENTIATION OF PERFECTION, ALSWEET AND ALASKA VARIETIES BY TOTAL STARCH AND AMYLOSE CONTENT

The USDA grading system assigns different quality attributes according to two types of peas, wrinkled and smooth skinned. Since crosses between these types exist which exhibit characteristics of both types, a method of identification between types is needed to apply the correct grading standards. Perfection, Alsweet and Alaska varieties were evaluated for percent starch and amylose content in starch within sieve size classification or tenderometer value grouping. Perfection peas are easily differentiated from Alsweet and Alaska peas of similar sieve size or tenderometer values by their high amylose content. Alsweet has the lowest percent amylose in starch; however, there exists an overlap in content between Alaska and Alsweet varieties making differentiation uncertain. Results indicated that differentiation was possible between Alaska and Alsweet within sieve size or tenderometer values on the basis of total starch content. The Alaska variety has a higher total starch content compared to the Alsweet variety.     

SCREENING OF BARLEY VARIETIES FOR ALPHA-AMYLASE CONTENT

Abrasion of barley induces accelerated water uptake and malt production and a higher hot water extract is obtained. These improvements are largely due to an increased rate of germination and faster α-amylase production. If a barley that behaved as though it were naturally abraded were available it could be of advantage economically. A world collection of barley varieties has been screened for α-amylase content using abraded and unabraded Proctor as controls. Field grown barley and varieties grown under controlled conditions in a glasshouse have been compared. The environmental effect on field-grown material seems to be consistent for all varieties and does not appear to affect which part of the α-amylase distribution curve that variety occupies. Of the 1362 varieties examined, some 13% exceeded the α-amylase activity of abraded Proctor, but only about 1% were two-row husked varieties. There is the possibility that some of these two-row husked barleys might be suitable for introducing the genetic factor for high α-amylase into a high-yielding, disease-resistant barley.     

COMPARATIVE MALTING PERFORMANCE OF OLD AND NEW BARLEY VARIETIES

A comparison was made of the malting behaviour of eight barley varieties representing a range from ancient to modern types. Plants were grown under controlled conditions in a glasshouse with two different nitrogen treatments and the grain obtained was subjected to a factorial micro-malting analysis. Under the conditions of this experiment there was little evidence of an improvement in malting ability between Plumage Archer and Ark Royal and there is limited scope for further increases in potential hot water extract. It would therefore appear that emphasis should now be given to the production of varieties with good agronomic characteristics which maintain this potential and modify rapidly without the need for abrasion and exogenous GA₃.     

MALTING TECHNOLOGY AND THE PROPERTIES OF MALT: A CLUSTER ANALYSIS STUDY

A cluster analysis study of 72 malts produced from four varieties of barley malted under varying conditions has demonstrated the relative importance of the degree of steeping, germination time and temperature and kilning on the chemical and physical analysis of the malt. Seventy-two malt samples were produced from four barley varieties malted at two different degrees of steeping, two germination temperatures, two germination times, and two kilning temperatures. The malt samples were divided into 2 or 3 groups (clusters) by means of the Fuzzy Cluster Variety family of algorithms, applied to nine chemical or physical malt analyses. Each cluster could be characterized by certain mean values for the laboratory analyses and also by a particular set of technological parameters. The degree of steeping was the most important of these parameters. Laboratory analyses such as fine/coarse difference and friability were able to discriminate between a high or low degree of steeping. The cluster with a high degree of steeping could be further divided into two subclusters, with different kilning temperature. The DMS-precursor discriminated between these two kilning temperatures.     

Variation across environments in patterns of water uptake and endosperm modification in barley varieties and variety mixtures

The malting barley varieties Chalice, Chariot, Optic and Prisma and all four three‐component mixtures derived from them were grown at three sites in eastern Scotland in 2000. Following harvest, malting samples were obtained for each trial entry from grain retained by a 2.5 mm sieve. Water uptake during the steeping phase of malting was determined on all samples at two of the sites. Of the varieties, Chariot was shown to have more extensive and also, at one site, more even hydration than the other varieties, whereas the mixtures were generally similar to the other three varieties in water uptake. Malt samples were tested for cell wall modification using a fluorescence method that assessed individual grains, so enabling both homogeneity and extent of modification to be calculated. There were significant differences between genotypes and between sites, with Chariot and Chalice showing poor modification at one site, which led to reduced levels of hot water extract. The variety Prisma had a lower level of predicted spirit yield at another site, possibly owing to over‐modification, and Optic was the only variety to give consistently high spirit yield at all three sites, despite considerable variations in levels of modification. The mixtures had better consistency in their malting results than the varieties, with the exception of Optic, and also performed well at sites where modification was sub‐optimal. Differences in spirit yield were greater between sites than between varieties, indicating that genotypic constitution may not always be a reliable predictor of phenotypic expression of malting quality. Copyright © 2006 Society of Chemical Industry     

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.     

Re‐Assessment of the Half‐Grain Modification Method for Assessing Malt Modification

The half‐grain mashing (modification) method proposed by Palmer (J. Inst. Brew., 1975, 81: 408) was reassessed. The intention was to quantify the differences in malt modification in terms of β‐glucan breakdown and clarify the relationship between β‐glucan breakdown and overall modification of the endosperm during malting. This was carried out at 45°C as well as at 65°C, the percentage of weight loss was recorded and the endosperm residue was analysed for β‐glucan content. In general, weight loss was related to modification. Samples, which were modified at higher levels, lost significantly more material during the half‐grain mashing procedure than those which were under‐modified. At a malting process time of 96 h all the varieties had similar weight loss. After mashing the half grains, the β‐glucan contents of the grain residues showed an apparent increase because of loss of non‐β‐glucan materials. However, over the malting period β‐glucan decreased. Chariot malted faster than the other varieties studied. The β‐glucan levels of this variety were reduced by 78% between 48 and 72 h of germination. Significant levels of β‐glucan were degraded and large quantities of starch and protein were released. During the same period of germination, the corresponding samples of Decanter did not show a significant reduction in β‐glucan levels. In contrast, Brazilian variety MN698 lost endosperm material and β‐glucan rapidly by 48 h. These early results suggest that during malting, extract solubilization may or may not accompany β‐glucan breakdown. Therefore, β‐glucan levels in malt cannot be used as an overall index of modification of the endosperm.