Effect of unmalted oats (Avena sativa L.) on the quality of high-gravity mashes and worts without or with exogenous enzyme addition

Barley malt is the preferred brewing material these days because of its high extract content and high enzyme activities. However, when substituting malted barley with oats to create a unique beer flavor and aroma, endogenous malt enzymes become the limiting factor. Therefore, the objectives of this study were to evaluate the effect of 10–40 % unmalted oats on the quality of high-gravity mashes/worts and to investigate the limitations of endogenous malt enzymes as well as the benefits of the application of industrial enzymes. The enzyme mix Ondea^® Pro was found to be particularly suitable for mashing with unmalted oats and was therefore used in the present rheological tests and laboratory-scale mashing trials. In order to gain detailed information about the biochemical processes occurring during mashing, the quality of mashes was comprehensively analyzed after each mash rest using standard methods described by Mitteleuropäische Brautechnische Analysenkommission and Lab-on-a-Chip capillary electrophoresis. Mashing with up to 40 % oats resulted in increased mash consistencies, color/pH (20 °C) values, β-glucan concentrations, wort viscosities 12.0 %, and filtration times as well as decreased FAN and extract contents. The application of Ondea^® Pro enormously increased the color of worts despite lower pH values but considerably improved the quality and processability of 30 or 40 % oat-containing mashes/worts. However, the substitution of up to 20 % barley malt with unmalted oats can easily be realized without the addition of exogenous enzymes.     

Malted and unmalted oats in brewing

Using oats as a raw material in brewing has recently become the focus of increased interest. This is due to research findings that have shown that oats can be consumed safely by coeliac sufferers. It is also a response to consumer demand for products with novel sensory properties. In this study, beer was produced entirely from oat malt, from barley malt and from oat and barley malts mixed with various quantities of unmalted oats. Compared with barley wort, wort made from malted oats provided a lower extract content and had a higher protein content, but a lower free amino nitrogen content (FAN). The oat wort also showed increased viscosity and haze. The addition of unmalted oats during wort production produced significant changes in the physico‐chemical parameters of both oat and barley worts and beers. Unmalted oats caused an increase in wort viscosity and haze, and a reduction in total soluble nitrogen and FAN. Unmalted oats also contributed to lowering the concentration of higher alcohols and esters. Beer made from 100% oat and barley malts exhibited a similar alcohol content. The use of an oat adjunct in both cases resulted in a lower ethanol content. The introduction of enzyme preparations during the production of wort with oat adjunct had many benefits: increased extract content and FAN; a higher volume of wort; and a lower viscosity that led to faster wort filtration. This research suggests that the use of enzymes is necessary to make production using a high proportion of oats in the grist profitable. Copyright © 2014 The Institute of Brewing & Distilling     

A comparative study of oat (Avena sativa) cultivars as brewing adjuncts

Brewing with high levels of unmalted oats (Avena sativa) has proven to be successful despite their high contents of β-glucan, protein, and fat. However, little is known about the effect of different oat cultivars on the quality and processability of mashes and worts. Therefore, the aim of this study was to compare the mashing performance of eight oat cultivars, selected because of their low contents of β-glucan, protein, fat, and/or high starch content, when substituting 20 or 40 % barley malt. For this purpose, seven husked (A. sativa L. ‘Lutz’, ‘Buggy’, ‘Galaxy’, ‘Scorpion’, ‘Typhon’, ‘Ivory’, ‘Curly’) and one naked oat cultivar (A. sativa var. nuda ‘NORD 07/711’) were fully characterized using standard methods, Lab-on-a-Chip capillary electrophoresis, and scanning electron microscopy. The rheological behavior of mashes containing up to 40 % of each oat cultivar was measured during mashing by applying a Physica MCR rheometer. In addition, the quality of worts obtained from laboratory-scale mashing trials was analyzed particularly with regard to their cytolytic, proteolytic, and amylolytic properties. The substitution of up to 40 % barley malt with husked or naked oats resulted in significantly higher pH values, β-glucan contents, and viscosities as well as significantly lower soluble nitrogen and polyphenol contents, color values, filtration rates, and apparent attenuation limits. Naked oats contained significantly less β-glucan as well as more protein and starch than the seven husked oat cultivars. The replacement of barley malt with naked oats resulted in a constant extract yield, whereas the use of husked oats caused significant extract losses.     

Mashing Studies with Unmalted Sorghum and Malted Barley

The effects on wort quality when mashing with unmalted sorghum (0–100%) and malted barley (100–0%) in combination with industrial enzymes were evaluated. A mashing program with temperature stands at 50°C, 95°C and 60°C was used. Different combinations of commercial enzymes were evaluated. A heat stable α‐amylase was found to be essential for efficient saccharification. The inclusion of a fungal α‐amylase in mashes with a high sorghum content improved filtration rates to that of 100% malted barley mashes. Addition of a bacterial protease increased the amount of nitrogen solubilisation and peptide degradation. An increase of the relative proportion of sorghum in the grist resulted in decreases in wort filtration, colour, viscosity, attenuation limit, free amino nitrogen, high molecular weight nitrogen, and a corresponding increase in pH (p < 0.01). Overall the addition of malted barley in small proportions to unmalted sorghum mashes together with commercial enzymes was found to improve the potential for brewing a high quality lager beer from unmalted sorghum.     

Influence of High Protein Digestibility Sorghums on Free Amino Nitrogen (FAN) Production during Malting and Mashing

In sorghum brewing, obtaining sufficient Free Amino Nitrogen (FAN) for rapid and complete fermentation remains a problem due to the high proportions of unmalted sorghum used and the poor digestibility of wet‐heat treated sorghum protein. Sorghum mutant lines with high protein digestibility have been developed through breeding. These high protein digestibility sorghums (HPDS) have protein bodies with villi‐like borders that apparently facilitate protease access. This work investigated FAN production from HPDS when malted and mashed, to assess their potential for use in sorghum brewing to improve wort FAN levels. When malted, HPDS contained substantially higher levels of FAN than normal protein digestibility sorghums (NPDS), 32 mg/100 g malt more. However, when the HPDS were mashed either as malt, or as grain or malt plus exogenous proteases, FAN production during mashing was not substantially higher than with NPDS subjected to the same treatments, only 6, 6–18 and 9–13 mg/100 g grain or malt, respectively. This is probably due to wet‐heat induced cross‐linking of the kafirin proteins reducing their susceptibility to proteolysis. Notwithstanding this, HPDS could be very useful for improving FAN levels in sorghum brewing if they are malted.     

Influence of malted barley and exogenous enzymes on the glucose/maltose balance of worts with sorghum or barley as an adjunct

The sugar profile of wort from laboratory malted barley, malted sorghum, unmalted barley and unmalted sorghum grains mashed with commercial enzyme preparations were studied. Similar levels of glucose to maltose (1:7) were observed in wort of malted barley and malted sorghum. Mashing barley or sorghum grains with commercial enzymes changed the glucose to maltose ratio in both worts, with a greater change in wort from sorghum grains. Although hydrolysis with commercial enzymes released more glucose from maltose in sorghum wort, the same treatment retained more maltose in barley wort. Adding malted barley to sorghum grains mashed with commercial enzymes restored the glucose to maltose ratio in sorghum mash. Fermentation of wort produced from all barley malt (ABM) mash and commercial enzyme/barley malt/sorghum adjunct (CEBMSA) mash of similar wort gravity was also studied. ABM and CEBMSA worts exhibited similar glucose to maltose ratios and similar amino acid spectra. However, ABM released more individual amino acids and five times more proline than wort from commercial enzyme/barley malt/sorghum adjunct. ABM produced 27% more glucose and 7% more maltose than CEBMSA. After fermentation, ABM mash produced 9.45% ABV whilst commercial enzyme/barley malt/sorghum adjunct mash produced 9.06% ABV. Restoration of the glucose/maltose ratio in the CEBMSA mash produced wort with a sugar balance required for high gravity brewing. © 2020 The Institute of Brewing & Distilling     

Implementation of commercial oat and sorghum flours in brewing

Brewing with commercial flours has the potential to reduce mashing times and improve brewhouse efficiency. At present, however, no studies are available assessing the application of commercial oat and sorghum flours as brewing adjuncts. Therefore, the objectives of this study were to evaluate the quality and processability of mashes/worts produced with 10–90 % oat or sorghum flour as well as to reveal the advantages and limitations of their use as a substitute for barley malt. For these purposes, both flour types were fully analyzed in terms of brewing-relevant characteristics using standard methods, Lab-on-a-Chip capillary electrophoresis, and scanning electron microscopy. Laboratory-scale mashing trials were performed to assess the effect of up to 90 % flour adjunct on mash/wort quality. Equivalent factors were introduced to determine the performance efficiency of different oat/sorghum flour concentrations. Commercial oat flour sourced in Ireland exhibited significantly more protein, β-glucan, and fat, less starch, ash, and polyphenols, as well as a lower starch gelatinization temperature than commercial sorghum flour obtained from the USA. Worts produced with 10–90 % oat or sorghum flour had lighter colors, higher pH values, and lower concentrations of foam-positive proteins as well as free amino nitrogen compared to 100 % barley malt worts. In terms of extract yields, the use of up to 70 % oat flour and 50 % sorghum flour, respectively, has proven economically beneficial. Worts containing up to 70 % oat flour showed a very good or good fermentability, those containing 30–50 % sorghum flour resulted, however, in a lower alcohol production.     

Brewing with 100% Oat Malt

Oats are a cereal with beneficial nutritional properties and also unrealized brewing potential. Furthermore, oats can be tolerated by the majority of people who suffer from celiac disease. Malting of oats produced a malt, which was found suitable for brewing a 100% oat malt beer. The mashing regime, designed by using mathematical modelling, was successfully transferred to a pilot scale plant. The improved lautering performance of oat malt was due to its higher husk content, which also led to a lower extract content in oat wort when compared to barley wort. The protein profile of oat wort, as measured by using Lab‐on‐a‐Chip analysis, revealed that there was no significant difference in the protein profile between oat and barley wort. The fermentation of oat and barley worts followed the same trend; differences could only be seen in the higher pH and lower alcohol content of the oat beer. The flavour analysis of oat beer revealed some special characteristics such as a strong berry flavour and a lower amount of staling compounds when forced aged. This study revealed that it was possible to brew a 100% oat malt beer and that the produced beer was comparable to a barley malt beer.     

Influence of ammonia and lysine supplementation on yeast growth and fermentation with respect to gluten-free type brewing using unmalted sorghum grain

Because gluten-free type brewing with unmalted sorghum does not provide adequate nitrogen for complete fermentation, wort supplementation with ammonia (as diammonium phosphate, DAP) or lysine on yeast performance was investigated. By Phenotype Microarray, under aerobic conditions, greater yeast growth was indicated with DAP than lysine both as a single source and combined with sorghum wort amino acids. With sorghum fermentation, both DAP and lysine improved maltose and maltotriose uptake. However, DAP supplementation also maintained yeast numbers (24.0–21.3 × 10⁶ cells mL⁻¹), whereas there was a decline with lysine supplementation. Lysine supplementation also resulted in adverse effects on yeast cell morphology. Neither DAP nor lysine supplementation resulted in evident genetic change to the yeast, but the change in substrate from barley malt wort to unmalted sorghum wort slightly altered the yeast genetically. Therefore, ammonia as DAP has potential as a nitrogen supplement for improving yeast fermentation performance in sorghum gluten-free brewing.     

Suitability of Oat, Millet and Sorghum in Breadmaking

Challenges and opportunities of minor cereals with poor viscoelastic value deserve a special attention in breadmaking applications due to their unique nutritional components. In a preliminary stage, the suitability of oat, millet and sorghum in breadmaking was assessed in simple binary wheat flour matrices in which wheat flour was replaced from 0% to 60%. The research allowed the quantification of grains (up to 30% for millet and sorghum and up to 50% for oat of wheat flour replacement) to be incorporated into the binary blended matrices providing minimization of techno-functional impairment and sensory depreciation of breads. Combinations of gluten, vegetable fat and a commercial mix of surfactants, ascorbic acid and antistaling enzymes were used to make breads with 10% increased level of wheat flour replacement by single oat, millet and sorghum in binary mixed samples. The quality profile of binary mixtures of oat–wheat (60:40 w/w), millet–wheat (40:60 w/w) and sorghum–wheat (40:60 w/w) was significantly improved in terms of keepability during storage, mainly for oat–wheat blends which stale at a similar rate than 100% wheat breads. Overall acceptability of highly replaced wheat breads deserved higher scores for oat and sorghum composite breads (7/10) than control wheat breads (6/10). Oat, millet and sorghum represent a viable alternative to make aerated breads with mitigated technological and sensory constraints based on non-viscoelastic cereals.     

The composition and ultrastructure of sorghum spent grains

The present study aimed to investigate the composition and structure of sorghum spent grains (SSG) as a pre‐requisite for evaluating potential applications of this brewery co‐product. SSG samples sourced from African breweries employing a grist with a proportion of a hammer milled‐unmalted sorghum (Sorghum vulgare cv. Fara Fara) were found to be heterogeneous materials containing remnants of intact grains, and with particles ranging in size from <0.1 to >2 mm. Samples contained a considerable amount of residual starch (4.6–10.0% d.b.), much higher than typically reported for barley‐derived spent grains. This probably arises from the use of grists high in unmalted sorghum, but indicates that improvements in brewing process efficiency could be achieved with improvements, for example, in milling and mashing protocols. The crude protein content of the SSG samples was unexpectedly high (38.0–41.2% d.b.), indicating that this material would have potential value as an animal feed or source of refined protein. Potential reasons for this higher than expected residual protein content are discussed. The remainder of SSG gross composition (mean of five samples) was cellulose (11.4% d.b.), hemicellulose (17.3% d.b.), lipid (8.5% d.b.), lignin (9.4% d.b.) and ash (4.46% d.b.), with a total mass recovery of close to 98% represented by all analysed components. Copyright © 2013 The Institute of Brewing & Distilling     

Quality Assessment of a Sorghum Variety Malted Commercially under Tropical Conditions and Controlled Tropical Temperatures in the Laboratory

A sorghum variety was supplied as commercial malt and as an unmalted cereal by a maltster. The commercial sample had been malted in a tropical country. Sub‐samples of the unmalted cereal were malted in the laboratory under controlled germination temperatures of 28°C and 30°C. Laboratory and commercially malted sorghum were studied for their brewing qualities. The α‐amylase development in sorghum malt was enhanced when germination was carried out at the higher temperature of 30°C rather than at 28°C. Hot water extract (HWE) was more variable. With infusion mashing, results showed a significant difference for germination time (3–6 days), but no significant difference relating to germination temperature. With the decantation mashing method the reverse was observed. The low numerical values of HWE obtained from sorghum malt in the infusion mashing process confirmed that this process is not suitable to produce optimal extract development from malted sorghum. The 28°C germinated sorghum released more FAN products into the worts than the 30°C malt, using both the infusion and decantation methods. With regard to the parameters tested, commercially malted sorghum gave lower analytical values than laboratory malted sorghum. It was also observed that variations in malting temperatures and mashing processes can cause unexpected variations in the analyses of sorghum malt. These findings suggest that careful process control is required during the malting and mashing of sorghum.     

Phenols in spikelets and leaves of field‐grown oats (Avena sativa) with different inherent resistance to crown rust (Puccinia coronata f. sp. avenae)

BACKGROUND: Avenanthramides, health‐beneficial phenols in oats, are produced in response to incompatible races of the crown rust fungus, Puccinia coronata, in seedlings of greenhouse‐grown oats. This study aimed to elucidate whether avenanthramides and/or other phenolic compounds, together with the activities of phenylalanine ammonia lyase (PAL), phenoloxidase (PO) and the avenanthramide biosynthetic enzyme hydroxycinnamoyl‐CoA:hydroxyanthranilate‐N‐hydroxycinnamoyl transferase (HHT), are associated with crown rust infection in mature field‐grown oats. Nine oat (Avena sativa L.) genotypes with wide variation in crown rust resistance were exposed to naturally occurring fungal spores during the growth period. RESULTS: In the spikelets avenanthramides as well as HHT activities were more abundant in the crown rust resistant genotypes, whereas p‐coumaric and caffeic acids were more abundant in the susceptible ones. In the leaves avenanthramides were not associated with resistance. Instead two unknown compounds correlated negatively with the rust score. Phenols released by alkaline hydrolysis and PAL and PO activities were not related to rust infection, either in spikelets or in the leaves. CONCLUSION: Because grains of crown rust‐resistant oat genotypes seemed to have higher endogenous levels of health‐promoting avenanthramides, use of resistant oats may contribute to a food raw material with health‐beneficial effects. Copyright © 2009 Society of Chemical Industry     

Effect of Malting on Protein Metabolism in Two Varieties of Sorghum

The metabolism of albumin, globulin, glutelin and prolamin in two varieties of sorghum recommended as alternatives to barley malt for brewing in Nigeria has been studied. There was a continuous degradation of prolamin and glutelin (storage proteins) with a concomitant rise in albumin and globulin (enzyme proteins) resulting in a synchronous rise in free amino nitrogen (FAN) during malting of SK 5912. On the other hand, all the major proteins in farafara increased at the peak of malting without a synchronous increase in FAN. When compared to the unmalted sorghum digested with external enzymes, only a quarter to half of the groups of amino acids required for yeast nutrition were obtained with malted sorghum. The production of FAN in SK 5912 malt is higher than farafara malt. FAN produced in SK 5912 malt is high enough for lager beer production therefore its recommendation as a local substitute is supported, in part, by this study. © 1997 SCI.     

ENZYME AND ACID HYDROLYSIS OF MALTED MILLET (Pennisetum typhoidees) AND SORGHUM (Sorghum bicolor)

Malted millet and sorghum were hydrolysed by the enzymes produced during malting. Malted and unmalted millet and sorghum were acid hydrolysed. The enzyme hydrolysed carbohydrate was mostly glucose, with only traces of disaccharides, in the case of malted millet. The yield of enzyme hydrolysed carbohydrate was however low in both millet and sorghum. Acid hydrolysis of malted millet or sorghum showed that glucose of malted grains was destroyed during acid hydrolysis more than pentoses in the malted grains.     

Enzyme inhibition by polyphenols of sorghum grain and malt

Enzyme production and activity in malt produced from birdproof sorghum cultivars were unaffected by the endogenous polyphenols present in the testa and nucellar layer of the grain. When the rigid segregation of tissues and substances in the malt grain is disrupted by milling, the polyphenols inhibit the endogenous enzymes in aqueous suspensions and reduce the brewing value of the ground malt. Sorghum beer made from malt of birdproof cultivars did not taste bitter. Bird-proof sorghum cultivars differ widely in content and quality of polyphenols inhibiting enzymes. Enzymatic methods are proposed to determine the inhibiting fractions of the polyphenols in sorghum grain. The results of these methods correlate well with DMF-extractable polyphenols assayed by ferric ammonium citrate in alkaline medium. The merits of enzymatic and chemical methods to determine biologically active polyphenols are discussed. Suggestions to protect the brewing industry against unsuitable grain sorghum cultivars of the birdproof class are made.     

Current Developments in Malting and Brewing Trials with Sorghum in Nigeria: A Review

Initially, large‐scale lager beer brewing with sorghum malts proved highly intractable due to a number of biochemical problems including: high malting losses estimated at 10–30% as against 8–10% for barley; high gelatinisation temperatures which limited starch solubilisation/ hydrolysis by the amylolytic enzymes during mashing; low extract yield/low diastatic power (DP) due to inadequate hydrolytic enzyme activities especially β‐amylase; low free α‐amino nitrogen (FAN) due to inadequate proteolysis limiting yeast growth during fermentation; high wort viscosities/beer filtration problems due to low endo‐β‐1,3; 1–4‐glucanase activities on the endosperm cell walls causing the release of some β‐glucans. Strident research efforts using improved Nigerian sorghum malt varieties (SK5912, KSV8 and ICSV400) have reported some encouraging results. The knowledge of the biochemical integrity of the endo‐β‐glucanases of the sorghum malt is helping to elucidate their mode of activity in the depolymerisation of the β‐glucans. This is bound to ensure process efficiency in sorghum beer brewing, reduce beer production costs and ultimately, produce a Pilsner‐type of lager beer with 100% sorghum malt.     

A 75% reduction in herbicide use through integration with sorghum + sunflower extracts for weed management in wheat

BACKGROUND: To reduce herbicide use by 75%, integrated use of sorghum and sunflower extracts each at 18 L ha^?1 combined with 1/4^th (75% less) of label rates of four herbicides (mesosulfuron + idosulfuron, metribuzin, phenoxaprop‐p‐ethyl and isoproturon) were investigated for the management of wild oat and canary grass, the two pernicious weeds in wheat fields worldwide. RESULTS: The results revealed that sorghum + sunflower extracts combined with 1/4^th (75% less) of label rates of herbicides inhibited dry matter production of wild oat by up to 89% and canary grass by up to 92%. The wild oat and canary grass persistence index in sorghum + sunflower extracts combined with 1/4^th (75% less) of label rates of herbicides was either lower or equal to respective label rates of herbicides, except sorghum + sunflower extract + 1/4^th phenoxaprop‐p‐ethyl. Lower herbicide rates + water extracts also produced wheat grain yield statistically equal with label rates of respective herbicides. Two treatments having water extracts + lower herbicides rates were economical and sorghum + sunflower + 1/4^th mesosulfuron + idosulfuron produced the highest (4404%) marginal rate of return. CONCLUSION: Herbicides use can be reduced by 75% through integration with sorghum + sunflower extracts without compromising yield and net benefits for cost‐effective and eco‐friendly management of wild oat and canary grass in wheat. Copyright © 2010 Society of Chemical Industry     

Combining unmalted barley and pearling gives good quality brewing

Brewing with unmalted barley can reduce the use of raw materials, thereby increasing the efficiency of the brewing process. However, unmalted barley contains several undesired components for brewing and has a low enzymatic activity. Pearling, an abrasive milling method, has been proposed as a pre‐treatment for barley to remove some of its undesired components, while maintaining its β‐amylase activity. The potential of combining pearling with using barley/malt mixtures for brewing was studied. Filtration was performed either in a mash filter or in a lauter tun. The effects of the different barley/malt ratios, degree of pearling and two different filter types on compositional and quality parameters were assessed. It was concluded that a mash filter is optimal for this type of process, and a window of operation could be identified in which optimal use is made of the raw materials while maintaining the end product quality, judged on basis of four quality parameters. Copyright © 2016 The Institute of Brewing & Distilling     

Optimization and Validation of a Fluorescence Polarization Immunoassay for Rapid Detection of T-2 and HT-2 Toxins in Cereals and Cereal-Based Products

A fluorescence polarization (FP) immunoassay has been optimized and validated for rapid quantification of T-2 and HT-2 toxins in both unprocessed cereals, including oats, barley and rye, and cereal-based products for direct human consumption, such as oat flakes, oats crispbread and pasta. Samples were extracted with 90 % methanol, and the extract was filtered and diluted with water or sodium chloride solution prior to the FP immunoassay. Overall mean recoveries from spiked oats, rye, barley, oat flakes, oats crispbread and pasta ranged from 101 to 107 %, with relative standard deviations lower than 7 %. Limits of detection (LODs) of the FP immunoassay were 70 μg/kg for oats, 40 μg/kg for oat flakes and barley, 25 μg/kg for pasta and 20 μg/kg for rye and oats crispbread. The trueness of the immunoassay was assessed by using two oat and oat flake reference materials for T-2 and HT-2 toxins, showing good accuracy and precision. Good correlations (r?>?0.953) were observed between T-2 and HT-2 toxin contents in naturally and artificially contaminated samples determined by both FP immunoassay and ultra-high-performance liquid chromatography (UHPLC) with immunoaffinity column cleanup used as reference method. These results, combined with rapidity and simplicity of the assay, show that the optimized assay is suitable for high-throughput screening, as well as for reliable quantitative determination of T-2 and HT-2 toxins in cereals and cereal-based products.