Mechanisms of Malt Extract Development in Barleys from Different European Regions: II. Effect of Barley Hordein Fractions on Malt Extract Yield

To examine environmental differences between southern and northern European malting barleys, particularly relating to protein and hordein influences on malt extract development, samples of the malting barley cultivar Alexis, from the Nordic countries and from the Iberian Peninsula, were used. Fractionation of hordeins was carried out on barley grams, prior to micromalting and malt analyses, using high performance liquid chromatography (HPLC). Different mechanisms for extract development, in malting barleys from the North and South of Europe, have been demonstrated. Barley protein content determined a significantly greater decrease in malt extract in the Nordic samples, compared with those from the Iberian Peninsula, while apparent final attenuation showed a more pronounced positive association with extract in the South than in the North. B‐hordein was associated with a significanlty greater decrease in malt extract in the Nordic compared to the Mediterranean samples.     

Genetic and environmental impact on protein profiles in barley and malt

Canadian barleys have higher protein content and better protein modification than Australian barleys. Protein and protein modification was investigated in two Australian and two Canadian barley varieties under different levels of nitrogen fertilisation. Mass spectrometry was used to analyse protein profiles in grain and malt to assess how genetic and environmental factors modified the proteins in grain and malt. The differences in grain protein between the Australian and Canadian varieties were mainly in the high molecular weight proteins, less in water soluble proteins and rarely in salt‐soluble proteins, while malt protein variations were observed in all three groups. Generally, Canadian varieties contained more proteins in grain, but less water soluble and salt soluble proteins in malt. Monitoring the protein modification during the malting indicated that more proteins were digested in Canadian varieties. Genetic factors were dominant for protein variation, although environment also affected the protein composition. Barley varieties growing in Canada generally contained slightly higher protein content, and nitrogen fertiliser influenced proteins in grain that ranged from 43,000 to 47,000 Da. The protein pattern of high fermentability and lower fermentability varieties mainly varied from 30,000 to 40,000 Da. © 2018 The Institute of Brewing & Distilling     

Effects of seeding rate, nitrogen rate and cultivar on barley malt quality

BACKGROUND: Crop management tools have been shown to affect barley kernel size and grain protein content, but the direct effect on malt quality is not well understood. The present study investigated the effect of seeding rate, nitrogen fertilisation and cultivar on malt quality. RESULTS: Higher seeding rates produced barley with less grain protein and smaller, more uniformly sized kernels. The small, uniformly sized kernels modified more completely, leading to malt with higher extract and lower wort β‐glucan than malt from low‐seeding‐rate barley. Increasing rates of nitrogen fertilisation caused grain protein levels to increase, which limited endosperm modification and reduced malt extract levels. AC Metcalfe showed better modification and higher malt extract than CDC Copeland, but CDC Copeland had better protein modification at higher fertilisation rates, which resulted in less reduction of malt extract as nitrogen rate increased. CONCLUSION: Higher seeding rates reduced kernel size and grain protein levels without compromising malt extract owing to better endosperm modification of the more uniformly sized kernels. Negative effects of higher nitrogen rates on malt quality can be reduced through development of cultivars with improved ability to modify protein during malting. © 2012 Her Majesty the Queen in Right of Canada     

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.     

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.     

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY OF BARLEY PROTEINS: RELATIVE QUANTITIES OF HORDEIN FRACTIONS CORRELATE WITH MALT EXTRACT

Several high performance liquid chromatography (HPLC) approaches have been used to study the relationships between amounts of particular groups of grain storage proteins (hordeins) and malt extract, using two sets of barley samples. The areas of several chromatogram peaks varied between samples in a manner that correlated with malt extract. Size-exclusion HPLC of protein aggregates extracted by sonication gave negative correlations of the relative areas of the three largest chromatogram peaks with malt extract in a set of 39 samples of the one variety, but not in a set of samples of 8 varieties grown at 4–5 sites. Under reducing conditions, disulphide-bonded hordeins were quantitatively extracted and the proportion of hordein in the largest peak, comprised of D- and B-hordeins, correlated well with malt extract in both sets of samples. The hordeins sequentially extracted into 50% (v/v) 1-propanol and 50% (v/v) 1-propanol-50 mM dithiothreitol (DTT) were also analysed by reversed-phase HPLC, and could be resolved into several peaks of B-, C- and D- hordeins. Relationships between the amount of certain C- hordeins in the propanol extract, and certain B- hordeins in the propanol-DTT extract and malt extract were seen. As well as providing a better understanding of the relationship between barley grain protein composition and malting quality, these HPLC methods are useful additional methods to enable partial prediction of malt extract using un-malted barley.     

Barley and Malt Proteins and Proteinases: III. A Simple Method for Estimating the Combined Actions of Malt Proteinases and the Extent of Protein Degradation during Malting

The activities of barley and malt proteinases have been measured using haemoglobin and the highly degradable barley protein fraction (HDBPF) in malting and feed barley varieties. In conjunction, the barley and malt total protein and its components: hordein, glutelin, soluble proteins and free amino nitrogen (FAN) as well as Kolbach index were investigated. The comparative analysis of results revealed that the general grain modification index of Kolbach (KI), which was higher in malting varieties, was much more strongly associated with the levels of hordein degraded during malting than any other parameter investigated. The KI levels were also correlated with the increase in the levels of FAN, but not with the increase in the levels of soluble protein or changes in the glutelin component. The changes in total proteinase activity were low and cannot account for the increase in KI or the degraded hordein. The levels of total proteinase activity in both feed and malting barley varieties were similar. The results suggest that estimation of the levels of degraded hordein, during malting, is a sensitive indicator of the total proteolytic action of proteinases as well as the degradability of the reserve proteins. Therefore, we recommend measuring the amounts of hordein degraded during malting for the assessment of the impacts of grain protein and proteinases on malting barley quality of different varieties, in addition to KI and FAN.     

Multiple Linear Regression Calibrations for Barley and Malt Protein Based on the Spectra of Hordein

The feasibility of using NIR spectral information from barley and malt hordein was assessed as to the suitability of developing improved NIR calibrations to predict protein in barley and malt. Using extracted hordein it was possible to gain more information on wavelengths relevant to predict protein with reduced errors. Strong correlations for grain protein and NIR wavelengths were found at 1,116, 1,268, 2,040, 2,068, 2,188 and 2,300 nm. Multiple linear regression equations provided improved predicting power for barley and malt protein with a standard error of prediction of 0.15 and 0.17%, respectively, whereas partial least squares regression gave a standard error of prediction of 0.22 and 0.27% for barley and malt, respectively. The use of NIR becomes more pronounced in breeding programs as NIR is a rapid and non‐destructive technique allowing the screening of early generation lines with limited grain quantities. Also, the spectral analysis of native components from resting grain components will assist in building calibrations that provide qualitative values rather than just ranking breeding lines.     

Some Relationships Between Malted Barleys of Different Nitrogen Levels and the Wort Properties

Barleys containing different levels of total nitrogen seem to have similar initial patterns for endosperm modification during malting. The higher nitrogen barley had a slower rate of endosperm modification, whilst the lower nitrogen barley had a faster rate of endosperm modification as germination progressed. Although the higher nitrogen barley had slower rate of endosperm modification, it transferred more nitrogen materials to the roots and shoots, whilst the lower nitrogen barley transferred less nitrogen materials to the roots and shoots. The higher nitrogen barley produced a lower yield of extract, but released higher levels of soluble nitrogen, free amino nitrogen (FAN) and peptides in the extract. The lower nitrogen barley produced a higher yield of extract and higher levels of carbohydrates (reducing sugars) in the extract. These results suggest that other important relationships exist between barleys of different nitrogen content. A drop in peptide nitrogen occurred on the same day of germination in both barley samples.     

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     

SOME RELATIONSHIPS BETWEEN THE PROTEIN NITROGEN OF BARLEY AND THE PRODUCTION OF AMYLOLYTIC ENZYMES DURING MALTING

Barleys studied (Chariot and Delibes) contained different levels of extractable β-amylase enzymes. The potential levels of β-amylase enzymes of the two varieties studied were similar at 1.4 to 1.7% total nitrogen. Higher values of potential β-amylase enzyme were observed in the Delibes barley of higher total nitrogen of 1.9%. The higher level of β-amylase found in the barleys with the highest total nitrogen was not reflected in the protein banding patterns as revealed by SDS-PAGE protein fractionation. Extraction of barley proteins was largely influenced by the different extractants used. The alcohol soluble proteins, M_r 97 kDa (D-hordeins), were only extracted when mercaptoethanol was included in the extracting solution. Although barleys with the highest nitrogen (1.9%) had the highest apparent potential to develop β-amylase enzymes, the better modified low nitrogen barleys produced higher levels of β-amylase and α-amylase when malted. Dehusking revealed that the high nitrogen barleys contained more steely grains. In contrast, the low nitrogen barleys contained more mealy grains. Steely grains contained more nitrogen than mealy grains and had the greater potential to develop β-amylase. Notwithstanding, the results of this study suggested that the proteins of the lower nitrogen barleys (1.4–1.7%) were capable of producing higher levels of β-amylase and α-amylase than the higher nitrogen barleys (1.9%) over comparable periods of malting. The high apparent β-amylase potential of the barley was linked to high nitrogen levels and associated high levels of steeliness, whilst the corresponding high β-amylase levels of malt were linked to the efficiency of endosperm modification of the malted grain.     

Genotypic and environmental variation in phytic acid content and its relation to protein content and malt quality in barley

Phytic acid or phytate is a chelating agent, which is involved in binding minerals (such as K⁺, Ca²⁺, Zn²⁺, Fe²⁺, etc.) and making them unavailable for dietary absorption. It is also involved in forming complexes with protein, making protein less soluble, and affecting enzymatic degradation, gastric absorption, and malting processes. The phytic acid and protein contents of barley grains are influenced by genetic and environmental factors. This study investigated differences in phytic acid and protein contents in grains of 100 barley (Hordeum vulgare L.) genotypes or cultivars. Eight barley cultivars were selected and grown at seven locations for two years to study the effects of genotypic and environmental factors on phytic acid content (PAC) and its relation to malt quality. The phytic acid contents of 100 barley genotypes ranged from 3.85 mg g⁻¹ to 9.85 mg g⁻¹, with a mean of 7.01 mg g⁻¹. The effects of cultivars, locations, time and their interactions were highly significant, but the variation was mainly attributed to the environment (location and time). The correlation between grains phytic acid and protein content was significant and positive. Whereas, the correlation between grain phytic acid content and malt extract was significant and negative. The relationship between phytic acid and protein contents of barley is important as it affects the malting process, malt yield and quality, and final beer quality. Barley grain for malting and feed uses should have low phytic acid content.     

萌发大麦种子内肽酶活力、醇溶蛋白及氨基酸含量变化

以两个大麦品种垦啤8号和Harrington为材料研究了大麦种子萌发过程中体内醇溶性蛋白质、游离氨基酸和内肽酶活力的变化。垦啤8号大麦种子的醇溶蛋白含量高,但其降解量比Harrington多。垦啤8号游离氨基酸增长量略高于Harrington。整个大麦种子发芽期间,国产品种内肽酶活力始终高于进口品种。以上表明,与Harrington相比,虽然国产品种垦啤8号含氮量高,但其内肽酶活力升高快,最大酶活力高,醇溶蛋白降解、转化为可输出氮的进程快,有制造优质麦芽的潜力。     

MALT CYTOLYTIC ACTIVITY OF BARLEYS OF DIVERSE ORIGINS AND ITS RELATION TO MALTABILITY*

The inter-relations of malt cytolytic activity, barley β-glucan (gum) content and two wort properties were studied for 12 two-row varieties. Although barley gum contents differed considerably, these differences were not correlated with wort viscosity of green malt, and the positive association with extract yield of green malt was only significant (r =0·83**) if one variety was omitted from the calculation. Cytolytic activity was directly correlated with extract yield (r = 0·77**) if another anomalous variety was excluded. The inverse relation (r =-0·57) between cytolytic activity and wort viscosity was not quite significant at the 5% level. The present study provides additional evidence of the importance of cytolytic activity in malting and it is suggested that testing for this character could be of importance in selection for potential malt extract and general maltability in breeding programmes involving barleys of diverse origins.     

RELATIONSHIPS BETWEEN MILLING ENERGY AND HOT WATER EXTRACT VALUES OF MALTS FROM SOME MODERN BARLEYS AND THEIR PARENTAL CULTIVARS

Determinations of hot water extract values of malts of some modern barleys and their parental cultivars correlated well (r = ?0.71) with milling energy estimates made on ungerminated grain. This confirms previous findings that these grain attributes are negatively correlated over different sites and growing seasons. Three types of barley endosperm can be distinguished on the basis of milling energy determinations. Most barley cultivars that are difficult to malt or are classified as feed barleys have high milling energy values (ranging from 370 to > 400 mg trace weight). This includes a number of currently recommended cultivars with Hordeum laevitigum in their pedigree. A second endosperm type has significantly lower milling energy values than the feed barley group (ranging from 330 to 355 mg, trace weight); barleys in this category also produce malts with high hot water extract values, e.g. Wing, Proctor and Berac. All of these barleys have one of the sister lines, Kenia—Opal—Maja in their ancestry. The third endosperm type with a loosely-structured ‘mealy’ endosperm has very low milling energy values (280 to 315 mg, trace weight) and includes the cultivars Ark Royal, Triumph and Keg, which give very high hot water extracts from their malts. All of the barleys in this group have the European malting barley Kneifel (also with a very low milling energy) in their pedigree. The results strongly indicate that hot water extract values of malts of current European cultivars are mainly due to the milling energy attribute of the endosperm, or are closely linked to it. This endosperm attribute has been selected through pedigree crossing or in barley collections, from just a few older malting quality cultivars. Evidence that this attribute is not linked to Hordein protein patterns controlled by the hor 1 and hor 2 loci on chromosome 5, is also presented .     

Reduced Phytate Barley Malt to Improve Fermentation Efficiency

Brewery fermentations require continuous yeast growth to efficiently convert fermentable sugars to ethanol. Yeast growth is dependent on an adequate supply of nutrients, including minerals. Minerals are generally assured in the brewery with addition of nutrient supplements but reduced phytate barley malts could reduce the need for supplements. The present study used bulked segregant analysis to determine effects of the reduced phytate trait in barley on field performance, barley quality, malting quality and brewing performance. Two bulks from a doubled haploid population, along with a series of normal and reduced phytate controls, were grown at 3 to 5 western Canadian sites in 2006, 2007 and 2008. The normal and reduced phytate barley bulks had similar yields, but the reduced phytate barley had significantly lower test weight. Rates of endosperm modification were similar between the two phytate types, although, reduced phytate malt was significantly more friable. Malt extract and α‐amylase levels were significantly lower in the reduced phytate bulk. Zinc and magnesium levels were significantly higher in reduced phytate worts and these worts produced better yeast growth as indicated by greater amino acid use during fermentation. Brewing performance tended to be better with reduced phytate worts, but not consistently so, likely due to the lower levels of malt extract and α‐amylase. Results supported the incorporation of the reduced phytate trait into malting barley varieties, but with attention to breeding for improved test weight and levels of α‐amylase.     

Effect of Different Steeping Conditions on Endosperm Modification and Quality of Distilling Malt

This study showed that when barley was steeped in water for either 8 h or 16 h, hydration of endosperm materials was suboptimal and modification of endosperm materials of barley malt was inadequate. The malt produced under these steeping regimes gave poor friability scores and produced a large number of whole grains. When barley was steeped for 24 h on a continuous basis, or when a regimented standard steeping method was used, the malt produced gave higher friability scores and a much lower number of whole grains. An important relationship was found between friability scores and whole grain results for the malt samples produced under these conditions. Optic barley, whose endosperm was more difficult to hydrate, gave a strong negative correlation between friability scores and number of whole grains at R² = 0.8689. Oxbridge, whose endosperm was more easily hydrated, gave a much stronger negative correlation between friability scores and number of whole grains at R² = 0.9769. Rapid visco‐analysis (RVA) results also confirmed that steeping the barley samples for only 8 h or 16 h produced malt that modified poorly as the RVA peak viscosities were very high. RVA pasting results further confirmed that when barley was steeped for 24 h on a continuous basis, or when a standard regimented steeping method was used, good quality malt was produced and no differences were found in the RVA peak viscosities of the barley malt samples produced under the two different steeping conditions. The results of protein breakdown (proteolysis) during these experiments, measured in terms of total soluble nitrogen (TSN) production, or soluble nitrogen ratio (SNR) further confirmed that optimal proteolysis was achieved when barley was steeped for either 24 h on a continuous basis, or with a standard steep. Optimal results were also found for hot water ex‐tractable materials such as hot water extract (HWE) and free amino nitrogen (FAN) when barley was steeped for 24 h or the standard steep. The 24 h continuous steep for barley produced quality malt comparable to that obtained when the standard regimented steep was used for steeping barley. For both Optic and Oxbridge barley, with a 24 h continuous steep, produced malt that gave significantly higher fermentabilities and PSY values, regardless of germination time, than those obtained using a standard regimented steep. Therefore steeping barley for 24 h on a continuous basis prior to malting will produce good quality malt for some barley samples/varieties. This will help to reduce water usage during steeping, will save steeping time thereby reducing malting time and will reduce the amount of water for effluent treatment. All of these factors result in an overall cost saving for the malting industry.     

CONTROLLING MALTING LOSSES WITH ANOXIA,CARBON DIOXIDE,AND SULPHUR DIOXIDE

Micromalting trials were used to evaluate the effectiveness of various treatments with anaeroblosis, carbon dioxide or sulphur dioxide in controlling malting losses with grain treated with gibberellic acid. Periods of increasing anoxia, with carbon dioxide accumulation as in Kropff malting, produced malt with a reduced malting loss and a lower hot water extract than control malting. Covering germinating barley with atmospheres containing various partial pressures of carbon dioxide reduced malting losses, but the resulting malts were usually inferior in quality to the controls. Sulphur dioxide gas, applied to moist germinating barley three days after casting, reduced malting losses by almost 3%, and increased the hot water extract by about 3 lb./Qr. relative to control malts. The treated malt occupied less space than the control, and the heat output was reduced. Sulphur dioxide treatment and only 4 days' germination produced a malt in high yield, with an extract identical to that of a control malt germinated for five days. The sulphur dioxide malts yielded worts with lower pH and higher soluble nitrogen values than the control and the fermentability of the worts was normal.     

Effect of sample size on the micro-malting of barley

Steep moisture, malt moisture, malt yield, malt extract and extract yield were determined when barley samples in the range 5–100 g were subjected to the same malting procedure. Smaller samples took up more water during steeping, and produced malts with a higher moisture content. This led to a lower malt yield and a higher malt extract and extract yield for small samples. The malt moisture, malt extract and extract yield determinations on 5 g samples were of similar precision to those on 100 g samples, while the steep moisture and malt yield were more variable with the small sample.