The structure of barley endosperm – an important determinant of malt modification

Structural differences in barley grains have been classified as either mealy or steely and their relative proportions have been determined using a light transflectance method in three barley samples varying in the degree of steeliness, Target being the most steely and Chariot most mealy with Blenheim being intermediate. These structural differences were found to be associated with differences in the concentration of endosperm components, particularly proteins and β‐glucan. Analysis of nitrogen within the endosperm showed that protein was mainly concentrated in the embryo and distal regions with the inner, mid‐endosperm containing lowest levels. As the total nitrogen (TN) of the grain increased, the mealier samples accumulated nitrogen mainly in the embryo whereas the steely sample had higher levels in the central endosperm. SDS‐PAGE showed no differences in the protein banding pattern at different TN levels. Electron microscopy using immuno‐gold labelling demonstrated that γ‐hordeins were present in sub‐aleurone and outer endosperm whereas the C‐hordeins were found throughout the central endosperm. However, steely areas of central endosperm contained γ‐hordeins. During malting, protein modification in Chariot was more extensive than in Target with 34kD and 97kD hordeins being completely degraded. In Chariot and Blenheim, level of β‐glucan was low and it was evenly distributed throughout the endosperm. In the steelier Target, however, the amount of β‐glucan was higher and was concentrated in the proximal and distal areas of the endosperm. Steely grains (containing high concentrations of protein and β‐glucan) displayed slower water distribution during steeping and later development and distribution of β‐glucanase during germination. As a consequence, the steely sample achieved a lower degree of modification during malting. The structure of the endosperm, therefore, has a prime influence on the evenness of distribution of moisture and enzymes which is crucial for homogeneous modification during malting. © 1999 Society of Chemical Industry     

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.     

Effects of Grain and Malt â‐Glucan on Distilling Quality in a Population of Hull‐less Barley

A population of barley lines, derived by mutation in the hull‐less variety, Penthouse, was included in a replicated trial, along with Penthouse and the hulled malting cultivar, Optic. Samples were assessed for a range of grain quality traits, then malted, with germination for either 4 or 5 days, prior to kilning. Most lines had grain β‐glucan contents lower than that of Penthouse, but there was no significant correlation between grain and malt β‐glucan content. Malt β‐glucan levels were indicative of differences in cell wall breakdown between 4 and 5 days germination, but negative associations with distilling parameters Extract and Alcohol Yield, were not statistically significant. It was concluded that the lines differed in the rate and extent of cell wall breakdown and that grain shape may influence modification in distal parts of the grain. However, a malting regime, optimised to suit Optic may be less suited to discriminating between hull‐less lines of reasonable quality.     

Performance of Husked,Acid Dehusked and Hull‐less Barley and Malt in Relation to Alcohol Production

Studies carried out on normal husked barley, normal hull‐less (naked) barley, acid dehusked barley and acid dehusked hull‐less barley, as well as the malts derived from them, showed that when acid dehusked barley samples (obtained from either husked or hull‐less barley), were processed using commercial enzyme preparations, they produced more alcohol when compared with the alcohol yield obtained from the barley samples from which the acid dehusked samples were derived. When the husked (Optic) control, acid dehusked and hull‐less barley samples were malted, Optic control barley produced malt that gave higher dextrinising units (DU) and diastatic power (DP), whilst acid dehusked Optic and hull‐less barley produced malts that gave similar DU results on day 5 of the germination time. When mashed, acid dehusked (Optic) barley malt produced wort that filtered faster than the wort obtained from the malt made from hull‐less barley. This observation is very important because it shows that the husk of the barley is not the only factor that determines the filtration performance of the malted barley, since both the malt samples made from husked and acid dehusked barley had similar filtration rates on day 5 of the germination time. The slow filtration rate observed for the wort made from hull‐less barley suggests that other factors play some role during the filtration of the mash made from hull‐less barley malt. Although hull‐less malt appeared to develop lower DU and DP enzyme activities, when compared with the values obtained for the Optic control, hull‐less barley malted faster and produced optimum predicted spirit yield (PSY) at day 4 of the germination time. In contrast, the control husked Optic barley malt that had higher DU and DP produced equivalent (optimum) predicted spirit yield one day later at 5 days germination time. This is an advantage for hull‐less barley, both in terms of time and energy saving during the malting of barley. Although the acid dehusked Optic barley produced more alcohol than the husked control when commercial enzyme preparation was used to process barley, it was surprising that when the derived malt was assessed, it gave a lower predicted spirit yield than the husked control, even though it produced a higher amount of hot water extract (HWE). The higher extract yield and lower predicted spirit yield obtained from the malt made from acid dehusked malt confirmed that high extract yield is not necessarily associated with high fermentable extract.     

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.     

Phytate content is reduced and β‐glucanase activity suppressed in malted barley steeped with lactic acid at high temperature

The effect of different steeping conditions on phytate, β‐glucan and vitamin E in barley during malting was studied by a full factorial experiment with three variables (steeping temperature, barley variety and steeping additions). Addition of lactic acid to the steeping water induced a reduction of phytate during steeping and germination, especially in combination with the high steeping temperature (48 °C). Furthermore, lactic acid and high temperature steeping inhibited β‐glucanase development, resulting in a well‐preserved β‐glucan content after germination. When steeping was conducted without addition of lactic acid, the low steeping temperature (15 °C) promoted development of both phytase and β‐glucanase activity during germination. A slightly higher level of tocopherols and tocotrienols was observed in samples steeped at 15 °C than in samples steeped at 48 °C. However, addition of lactic acid reduced the amount for both temperatures. When lactic acid bacteria were added to the steeping water none of the parameters studied differed from samples steeped with water only. The results show the possibility of combining phytate degradation with a preserved β‐glucan content during malting and can thus be of interest for development of cereal products with improved nutritional value. Copyright © 2004 Society of Chemical Industry     

Effects of Pulses of Higher Temperature on the Development of Enzyme Activity During Malting

The increase of temperature at the beginning, in the middle and at the end of malting has been evaluated in terms of quality parameters (malting losses, index of acrospire development, friability, HWE, viscosity, SNR) and enzyme (β‐glucanase and α‐amylase) development, in a good quality malting barley (Otis) and a higher protein‐higher β‐glucan content barley used for feed (Extra). A shift from 15 to 20°C at the beginning of malting was shown to increase acrospire development, friability, HWE and SNR and to reduce viscosity, without significantly affecting malting losses. This effect was related to higher β‐glucanase and α‐amylase activities within each variety. However, the same enzyme activities were not directly related to a better malting quality when the two genotypes were compared. This confirms previous indications that diversity in malting performance between genotypes cannot simply be traced back to differences in enzyme activities; but, indeed, it suggests that, for a defined barley lot, changes in the levels of enzyme activities following different malting procedures may have a direct effect on malt quality.     

A Reappraisal of the Differences Between Scandinavian and Spanish Barleys: Effect of β‐Glucan Content and Degradation on Malt Extract Yield in the cv. Scarlett

Forty one samples of the malting barley cultivar Scarlett were collected from both Scandinavia (15 from Finland and 10 from Denmark) and the Iberian Peninsula (15 from Spain and 1 from Portugal), during the harvest years of 1998 and 1999. These samples were subjected to grain analyses, comprising protein content, hordein fractions by high performance liquid chromatography (HPLC) and β‐glucan content. The samples were micro‐malted and the malts were analysed to determine different patterns in the influence of grain composition on malt extract development linked to the two contrasting environments. The most obvious difference found between the Scandinavian and Iberian barleys was the effect of the total and insoluble barley β‐glucans. They were an effective barrier of malt extract in the North, but appeared to increase extract in the South. A conclusion was that the positive effect of β‐glucans in the Iberian barleys was a consequence of their greater capacity to synthesise and release β‐glucan hydrolases during germination.     

Malt Performance is More Related to Inhomogeneity of Protein and β‐Glucan Breakdown than to Standard Malt Analyses

Nitrogen analyses of the grains of samples of commercial malts indicate that β‐glucan breakdown and the uniformity of malt modification are influenced by uniformity of distribution of grain protein. It is proposed that for normal malting barley, variations in malt modification are related to the different percentages of grains which contain high levels and different types of proteins which resist enzymic modification during malting. This kind of inhomogeneity of malt modification can cause brewhouse problems but cannot be detected with precision by standard malt analyses.     

Application of Biological Acidification to Improve the Quality and Processability of Wort Produced from 50% Raw Barley

In this study four strains of lactic acid bacteria (LAB) were chosen to bioacidify a mash containing 50% barley and 50% malt. The strains were isolated from malted and unmalted barley and assayed for extracellular enzymatic activities (proteases, amylases, β‐glucanases). The biologically acidified mash was compared to a chemically acidified mash, 100% malt mash un‐acidified and 50% malt and 50% barley mash unacidified. Characteristics such as pH, extract, colour, viscosity, total soluble nitrogen (TSN), free amino nitrogen (FAN), apparent fermentability, β‐glucan and lautering performance of the resultant worts were determined. A model lautering system replicating one used in a brewery was designed and built in University College Cork (UCC) to measure the lautering performance of the bioacidified mashes. The new system was compared to the filtration method used in EBC method 4.5.1. Overall the addition of LAB to bioacidify a mash of 50% barley and 50% malt resulted in faster filtration times, which correlated with decreased β‐glucan levels. Proteolytic LAB had a positive influence on the quality of wort and resulted in increased FAN levels. Lighter colour worts were observed along with increased extract levels.     

The Evolution of Dextrins During the Mashing and Fermentation of All‐malt Whisky Production

The production of malt whisky involves the mashing of barley malt, followed by the fermentation of the resulting wort without further treatment. While this process has many parallels to the production of an all‐malt beer, one of the main differentiating steps during substrate preparation is the inclusion of a boiling step for the wort in the production of beer. Other than the destructive action of the boiling process on microorganisms, the boiling also destroys all malt enzyme activity. Since a typical whisky wash is not boiled it carries through a certain proportion of microbial activity associated with the malt, but more importantly it retains some enzyme activity that has been activated during the malting and mashing processes. The changes in sugars and dextrins during both mashing and fermentation of the resulting wash were investigated. Evidence of the continuous amylolytic activity during an unboiled, all‐malt wash fermentation is shown; while no ongoing amylolytic activity could be deduced during the fermentation of a boiled all‐malt wort. Furthermore, the data suggests that the amylolytic activity during mashing and fermentation are different with regards to α‐amylase action linked to its multiple‐attack action pattern as a function of substrate conformation, temperature, and effectiveness of potential hydrolytic events.     

Effect of the Malting Barley Variety (Hordeum vulgare L) on Fermentability1

The influence of the malting barley genotype on the apparent attenuation limit (AAL) was investigated. The AAL level correlated closely with the maltose concentration in the wort but was not affected by other fermentable sugars or by the total carbohydrate content. The chemical composition, modification, amylolytic enzyme activities and several starch properties of selected malts were studied in detail. Variations in the maltose concentration could almost solely be traced back to genotype‐dependent disparities of β‐amylase thermostability. These differences are due to interallelic polymorphisms of the β‐amylase gene and are easily detected by PCR. Hence, PCR primers offer remarkable prospects for breeding barley on the basis of a marker‐assisted selection (MAS).     

Malting Behaviour of Barleys Grown in Canada and Spain as Related to Hordein and Enzyme Content

To continue our effort to analyse the genetic (varietal) and environmental (sites and years) effects on malting quality of barley, we have field‐tested four barley varieties, two‐ and six‐rowed, European and North American, in Spain and Canada in 1998 and 1999. The Spanish trials were autumn‐sown whereas the Canadian ones were spring‐sown. Barley grain was analysed for total protein and hordein contents and micromalted. Canadian‐grown barleys had significantly lower contents of grain protein and all‐three hordein fractions than the Spanish ones. They also had lower malt respiratory losses, wort β‐glucan and viscosity but lower fine‐ and coarse‐ground malt extract yield, friability, free amino nitrogen, Kolbach index, α‐amylase and diastatic power. In other words, the Canadian‐grown barleys, despite showing lower protein and hordein contents, produced malt of inferior quality than their Spanish counterparts, which, overall, produced higher quantities of degrading enzymes (amylolytic, proteolytic and cytolytic) during germination, thus being able to attain higher extract yield levels.     

Effects of malting on β‐glucanase and phytase activity in barley grain

The effects of malting on β‐glucan and phytate were investigated in one naked and one covered barley by a full factorial experiment with three factors (steeping temperature, moisture content and germination temperature) each with two levels. Analysis of total content of β‐glucan in the malted samples showed small changes after steeping at the high temperature (48 °C), while steeping at the lower temperature (15 °C) gave a significantly lower content. This trend was even stronger for β‐glucan unextractable at 38 °C. Analysis of the activity of β‐glucanase for the samples steeped at 15 °C showed a strong increase over the time of germination, while those steeped at 48 °C had a much slower development. The other two factors influenced the outcome to a small extent, mainly because the steeping temperature was the most important factor overall where any changes in β‐glucan and β‐glucanase were observed. When β‐glucan was extracted at 100 °C, a larger yield was obtained, and this was influenced by the steeping temperature in a much stronger way than for β‐glucan extracted at 38 °C. Determination of average molecular weight for β‐glucan extracted at 100 °C gave a lower value for samples steeped at 15 than at 48 °C. The design did not have any large effects on phytate degradation and phytase activity. However, it indicated that selective control of the enzymes might be possible, since phytase activity was barely affected by the parameters studied, while β‐glucanase was heavily affected. © 2002 Society of Chemical Industry     

The Influence of Lactic Acid Bacteria on the Quality of Malt

In this study three strains of lactic acid bacteria were applied during the malting process to evaluate the impact on malt and wort quality. The trials were performed in a micromalting plant simulating an industrial malting programme. The samples were compared to chemically acidified as well as non‐acidified malt. Bacterial cultures were chosen with reference to their enzymatic (proteolytic/amylolytic) activity, or their good acidifying properties. The effects of lactic acid bacteria on wort characteristics were investigated and compared to wort produced from 100% unacidified malt. A chemical food grade lactic acid was also used to acidify the barley for comparison purposes. Characteristics such as pH, extract, colour, viscosity, total soluble nitrogen, free amino nitrogen, apparent fermentability, β‐glucan and lautering performance of the resultant worts were determined. Results showed improved levels of β‐glucanase in the malt although reduced malt friability was observed where LAB was employed. An improved lautering performance, lower wort viscosity and elevated TSN levels were also reported where LAB exhibiting protease activity were applied.     

Sorghum β‐Amylase Production: Relationship With Grain Cultivar,Steep Regime,Steep Liquor Composition and Kilning Temperature

Steep regime, nature of alkaline liquor, and kilning conditions were studied for their effects on sorghum malt β‐amylase development in four Nigerian sorghum cultivars. Malt β‐amylase activity was markedly (p < .001) influenced by all the four factors as well as their various interactions. Overall, malts from KSV 8 variety were the most β‐amylolytic followed in sequence by those from Local Red (LR), SK 5912, and Local white (LW) respectively. The presence or absence of air rests in steep regimes was a significant (p < .001) determinant of sorghum β‐amylase response to final warm steeping, steep liquor and kilning condition. The nature of the alkaline steep liquor was also a major determinant of the pattern of malt β‐amylase response to the kilning condition. Steeping in Ca(OH)₂ enhanced malt β‐amylase activity at the higher temperature of kilning, while KOH produced the opposite effect. Ca(OH)₂ enhancement of β‐amylase development, at a kilning temperature of 50°C, was variety‐dependent suggesting that different sorghum cultivars may employ different biosynthesis models for β‐amylase synthesis. The regime‐dependence of β‐amylase response to kiln temperature suggests that this was an important modulator of sorghum germination physiology.     

Effect of Germination Moisture and Time on Pearl Millet Malt Quality — With Respect to Its Opaque and Lager Beer Brewing Potential

The effect of germination moisture and time on pearl millet malt quality was investigated. Two pearl millet varieties SDMV 89004 and 91018 were germinated at 25°C under three different watering regimes for 5 days. As with sorghum malting, diastatic power, beta‐amylase activity, free α‐amino nitrogen (FAN), hot water extract and malting loss all increased with level of watering. However, pearl millet malt had a much higher level of beta‐amylase and higher FAN than sorghum malt and a similar level of extract. Malting losses were similar or lower than with sorghum. Thus, it appears that pearl millet malt has perhaps even better potential than sorghum malt in lager beer brewing, at least as a barley malt extender, especially in areas where these grains are cultivated and barley cannot be economically cultivated. Also, its increased use in commercial opaque beer brewing, where sorghum malt is currently used, could be beneficial.     

Variety and germination time effect on total β‐glucan,water‐insoluble β‐glucan,water‐soluble β‐glucan components and β‐glucanase levels in improved sorghum varieties SK5912, KSV8 and ICSV400 before and after malting and their relationships to wort viscosity

The effects of variety and germination time on β‐glucan components – total β‐glucan (TBG), water insoluble β‐glucan (WIBG) and water soluble β‐glucan (WSBG) and β‐glucanase (BG) levels – before and after malting in improved sorghum varieties SK5912, KSV8 and ICSV400 and their relationships to wort specific viscosity (SV) were studied. This study was part of efforts to aid local malting and brewing industries in the application of sorghum varieties that are abundantly available to reduce costs. At the fifth day of germination, variety ICSV400 had the lowest TBG, WIBG and WSBG levels in its raw and malt samples. Variety SK5912 had the highest TBG, WIBG and WSBG levels in its raw samples, while variety KSV8 had the highest levels of TBG, WIBG and WSBG in its malt samples. Similarly, variety ICSV400 malts developed the highest BG levels, while the KSV8 malts gave the lowest level. The effect of variety, germination time and variety × germination time interaction was significant (p < 0.05) on the TBG, WIBG and BG levels and was not significant on the WSBG levels. Weak and significant correlation of TBG levels with SV (0.25, p < 0.05 for SK5912; 0.24, p < 0.05 for KSV8; and 0.31, p < 0.05 for ICSV400) was observed in all the samples, suggesting that the low β‐glucan levels may not be primarily and solely responsible for any viscosity impediments associated with sorghum worts during run‐off. With improvement in the effective utilization of sorghum, ICSV400 appeared the most suitable variety for malting and brewing in Nigeria.Copyright © 2016 The Institute of Brewing & Distilling     

Barley Products of Different Fiber Composition Selectively Change Microbiota Composition in Rats

1 Scope

Several dietary fiber properties are suggested to be important for the profiling of the microbiota composition, but those characteristics are rather unclear. Whether different physico‐chemical properties of barley dietary fiber influence the gut microbiota composition is investigated.

2 Methods and results

Seven diets containing equal amounts of dietary fiber from barley malts, brewer's spent grain (BSG), and barley extracts, resulting in varying amounts of β‐glucan, soluble arabinoxylan, and insoluble arabinoxylan in the diets were given to conventional rats. Malts increased microbiota alpha diversity more than BSG and the extracts. The intake of soluble arabinoxylan was related to Akkermansia and propionic acid formation in the cecum of rats, whereas β‐glucan and/or insoluble arabinoxylan were attributed to some potentially butyrate‐producing bacteria (e.g., Lactobacillus, Blautia, and Allobaculum).

3 Conclusion

This study demonstrates that there is a potential to stimulate butyrate‐ and propionate‐producing bacteria in the cecum of rats with malt products of specific fiber properties. Moreover, BSG, a by product from beer production, added to malt can possibly be used to further modulate the microbiota composition, toward a higher butyric acid formation. A complex mixture of fiber as in the malts is of greater importance for microbiota diversity than purer fiber extracts.     

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.