A review of malting and malt processing for whisky distillation

This paper encompasses a re‐evaluation of published literature and data regarding wort attenuation in malt distilleries raising questions and discussing how the conventional wisdom has changed over time and what questions still need to be answered. Current knowledge is summarized in the following four points: (a) Under normal malting conditions, starch granules are partially degraded by a combination of α‐amylase and α‐glucosidase. This complex can open up the granule at specific sites on the surface and create characteristic ‘pin‐hole’ lesions, which may be widened by secondary hydrolysis by α‐ and β‐amylase, limit dextrinase and α‐glucosidase (maltase). (b) All of these diastatic enzymes can survive mild kilning, probably by forming heat stable complexes on and within the starch granules and can continue a complete degradation of starch when mashed at ambient temperatures with glucose as the end product. (c) At normal mashing temperatures, starch granules gelatinize and dissolve with a concomitant rapid degradation to glucose, maltose, maltotriose and dextrins ranging from degree of polymerization (DP) 4 to > DP20. If there is immediate wort boiling after run‐off, this is the final composition of starch derived carbohydrates according to the conventional paradigm. (d) All malt worts also contain a small amount of panose, isopanose as well as glucosyl maltodextrins, based on a core of 6₂‐α‐glucosyl maltose (panose) or 6‐α‐maltosyl glucose (isopanose), which are remnants of the α‐amylase/glucosidase degradation of granular starch. These dextrins are resistant to the action of debranching enzymes and their concentration may vary between 4 and 8% of the malt extract, depending on the degree of modification of the host starch granules. They may be created at the active sites of this enzyme complex when the granule is gelatinized. In a conventional mash of unboiled distilling wort, the spectrum of wort dextrins produced from gelatinized starch is reduced to true ‘limit’ dextrins of DP4–8 by continued α‐amylolysis during early fermentation. These dextrins will contain side chains of either maltose or maltotriose residues surrounding the α‐1,6‐glucosidic linkage and can be debranched by limit dextrinase during late fermentation, leaving only the above glucosyl maltodextrins dextrins in the spent wash. Copyright © 2016 The Institute of Brewing & Distilling     

Validation and application of osmolyte concentration as an indicator to evaluate fermentability of wort and malt

The objective was to develop a new simple and quick approach to predict fermentability, based on osmolyte concentration (OC). Eight malts were assayed for diastatic power, starch‐degrading enzymes [α ‐amylase, β ‐amylase and limit dextrinase (LD)] and malt OC (MOC). All malts were mashed to determine wort OC (WOC), real degree of fermentation (RDF) and sugar contents in a small‐scale mashing protocol. The results showed that MOC was correlated with malt α ‐amylase, LD, the resultant WOC, RDF and fermentable sugar (r  = 0.813, 0.762, 0.795, 0.867, 0.744, respectively), suggesting that MOC was discriminating in predicting levels of malt amylolytic enzymes, wort sugar and RDF without the mashing and fermentation process. Moreover, WOC showed stronger correlations with malt α ‐amylase, LD, RDF and fermentable sugars (r  = 0.796, 0.841, 0.884, 0.982, respectively), suggesting that WOC can be used to quickly predict wort sugar contents and RDF without a fermentation step. Furthermore, the effects of mashing temperature and duration on WOC, RDF and sugar contents are discussed. Adjusting mash temperature to 65°C or extending the mash duration dramatically increased RDF and WOC, whereas malt extract was relatively stable. Similarly, WOC showed significant correlations with RDF and fermentable sugars (r  = 0.912 and 0.942, respectively), suggesting that WOC provides a simple and reliable tool to assist brewers to optimize mash parameters towards the production of ideal wort fermentability. In conclusion, the ability of OC to predict malt fermentability and sugar content allows brewers to keep better control of fermentability in the face of variation of malt quality, and to quickly adjust mashing conditions for the consistency of wort fermentability. Copyright © 2017 The Institute of Brewing & Distilling     

Relationships between the index of protein modification (Kolbach index) and hydrolytic enzyme production in a wheat malt

In this study, the relationships between protein degradation, enzyme activities and quality of EBC (European Brewery Convention) wort were investigated. The Kolbach index of wheat malt at 37.6–42.7% was found to be suitable for acquiring higher enzyme activities. A globulin increase was the main factor that promoted the activities of the degradation enzymes. Strong synergistic activity was observed among the polysaccharide degradation activities of enzymes [α‐amylase, β‐amylase, β‐glucanase, β‐d ‐xylosidase and β‐(1,4)‐endoxylanase]. Increased protease production improved the Kolbach index of a wheat malt, that is, promoted the degradation of gliadins into albumins and globulins. Increased albumins and globulins resulted in increased enzyme activity for polysaccharide degradation. Increased enzyme activities demonstrated synergistic actions that ultimately promoted the quality indices of an EBC wort, including extract yield, α‐amino nitrogen, acidity and chromaticity. Copyright © 2014 The Institute of Brewing & Distilling     

Effect of malting time,mashing temperature and added commercial enzymes on extract recovery from a Nigerian malted yellow sorghum variety

Preliminary microbiological studies carried out on sorghum grains showed that the major microorganisms found were mainly bacteria and that aflatoxin‐producing fungi were not found. The effect of added commercial enzyme preparations and different infusion mashing temperatures on extract yield, from sorghum malted at 30 °C, was studied. The infusion mashing method (65 °C) developed for mashing well‐modified barley malt produces poor extract yields with sorghum malt. The extract yield from the sorghum malt in this study was very low with infusion mashing at 65 °C, without the addition of commercial enzyme preparations. A higher extract yield was obtained from the sorghum malt, without the commercial enzyme addition, when using infusion mashing at 85 °C. Both infusion mashing temperatures (65 and 85 °C) showed an improved extract yield over the control malt when commercial enzyme preparations were used during mashing of the sorghum malt. The added enzyme preparations resulted in a higher extract yield from the germinated sorghum when infusion mashing was performed at 65 °C over mashing at 85 °C. The use of individual commercial enzymes (α‐amylase, β‐glucanase, protease, xylanase, saccharifying enzyme and combinations of some hydrolytic enzyme) increased extract yields, when complemented with the enzymes that had developed in the sorghum malt. Copyright © 2016 The Institute of Brewing & Distilling     

The impact of barley nitrogen fertilization rate on barley brewing using a commercial enzyme (Ondea Pro)

Two Australian (Buloke and Commander) and two Canadian (CDC Meredith and Bentley) barley varieties were grown under four levels of nitrogen fertilization (0, 20, 40 and 80 kg ha^?1). Barley samples were assessed by barley brewing with the Ondea Pro enzyme cocktail for mashing analysis and were compared with typical malt brewing quality specifications. The study observed that increased nitrogen fertilization resulted in increased barley kernel nitrogen content which significantly impacted a range of wort quality parameters including increased soluble nitrogen, free amino nitrogen and barley beta‐amylase level, but also reduced extract, barley Kolbach index, β‐glucan and colour. Increased grain nitrogen had relatively little effect on apparent attenuation limit, lautering and barley limit dextrinase level. Knowledge of the effects of interactions between barley of different qualities (e.g. nitrogen content) and the Ondea Pro enzymes on wort quality will result in enhanced barley to directly and efficiently brew good quality beer, to better satisfy the quality expectations of brewers. Copyright © 2018 The Institute of Brewing & Distilling     

Time Course for the Development of Enzymes in Barley1

Barley (Hordeum distichon var. Harrington) was steeped, germinated and extracted to observe the order of enzyme development. Different parts of the barley kernel were extracted to observe the order of enzyme development during the malting process. Five enzymes were investigated: carboxypeptidase (EC 3.4.16.1), endo‐β1–3, 1–4‐glucanase (EC 3.2.1.73), endo‐B1‐4‐xylanase (EC 3.2.1.136), arabinofuranosidase (EC 3.2.1.55), and α‐amylase (EC 3.2.1.1). Early development of carboxypepti‐dase, followed by later development of β‐glucanase, then α‐amy‐lase, confirmed earlier reports concerning the sequence of synthesis for these activities. However, xylanase developed during the steeping of barley and early in germination, whereas other authors found this enzyme to develop much later in the malting process. Enzyme activities developed to higher levels in the proximal end of kernels for all enzymes except xylanase, which was evenly distributed throughout the kernel. Enzyme development was tested in sterile barley annuli [embryo‐less cross sections taken through the grain, and thus comprising rings of tissue with husk outermost and starchy endosperm innermost] under four effector conditions. Water controls mirrored the development pattern observed in whole barley kernels. Gibberellic acid (GA₃) promoted higher total enzyme activity and development of all enzymes at the same time. Abscisic acid (ABA) promoted earlier development of late developing enzymes (xylanase, arabinofuranosidase and α‐amylase) and significantly higher levels of xylanase than when treatment was with water alone. Mixtures of GA and ABA showed a non‐exclusive, combined response of higher activity levels and a shifting of the initiation of enzyme development. Treatment with a combination of GA and calcium chloride triggered signifycantly higher carboxy‐peptidase activity and significantly lower xylanase activity as compared to treatment with GA or with GA/ABA mixtures.     

Optimisation of the Mashing Procedure for 100% Malted Proso Millet (Panicum miliaceum L.) as a Raw Material for Gluten‐free Beverages and Beers

Proso millet is a gluten‐free cereal and is therefore considered a suitable raw material for the manufacturing of foods and beverages for people suffering from celiac disease. The objective of this study was to develop an optimal mashing procedure for 100% proso millet malt with a specific emphasis on high amylolytic activity. Therefore, the influence of temperature and pH on the amylolytic enzyme activity during mashing was investigated. Size exclusion chromatography was used to extract different amylolytic enzyme fractions from proso millet malt. These enzymes were added into a pH‐adjusted, cold water extract of proso millet malt and an isothermal mashing procedure was applied. The temperatures and pH optima for amylolytic enzyme activities were determined. The α‐amylase enzyme showed highest activity at a temperature of 60°C and at pH 5.0, whereas the β‐amylase activity was optimum at 40°C and pH 5.3. The limit dextrinase enzyme reached maximum activity at 50°C and pH 5.3. In the subsequent mashing regimen, the mash was separated and 40% was held for 10 min at 68°C to achieve gelatinisation. The next step in the mashing procedure was the mixture of the part mashes. The combined mash was then subjected to an infusion mashing regimen, taking the temperature optima of the various amylolytic enzymes into account. It was possible to obtain full saccharification of the wort with this mashing regimen. The analytical data obtained with the optimised proso millet mash were comparable to barley wort, which served as a control.     

The Advantages of Using Natural Substrate‐Based Methods in Assessing the Roles and Synergistic and Competitive Interactions of Barley Malt Starch‐Degrading Enzymes

Existing methods of assay of malt starch‐degrading enzymes were critically appraised. New methods based on natural substrates, namely starch and its natural intermediate‐derivative, were developed for all the enzymes, except limit dextrinase for which pullulan was used. Thermostability, optimal temperatures and pHs were established. α‐Amylase and limit dextrinase were the most thermostable and β‐amylase, α‐glucosidase and maltase were the least stable while diastase occupied an intermediate position. The optimal temperatures were congruent with thermostability, β‐ amylase having the lowest (50°C) and α‐amylase the highest (65°C) with the remaining enzymes, including diastase, falling in between. In contrast, α‐amylase has the lowest optimal pH (pH 4.5) and β amylase the highest (pH 5.5) while the others have pHs in between the two values. The roles of the enzymes were evaluated taking into account the level of activity, thermostability, optimum pH, the nature of the product(s), and the relevance to brewing. β‐Amylase production of maltose was synergistically enhanced, mostly by α‐amylase but also limit dextrinase. α‐Glucosidase and maltase are unimportant for brewing, because of their low activity and the negative impact on β‐amylase activity and the negative effect of glucose on maltose uptake by yeast. The starch‐degrading enzymes (diastase) in a gram of malt were able to degrade more than 8 g boiled starch into reducing sugars in 10 min at 65°C. The latter, suggests that it will be possible to gelatinise most of the malt starch at a higher temperature and ensure its hydrolysis to fermentable sugars by mixing with smaller portions of malt and mashing at lower temperatures e.g. 50–60°C.     

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.     

Refining the Prediction of Potential Malt Fermentability by Including an Assessment of Limit Dextrinase Thermostability and Additional Measures of Malt Modification,Using Two Different Methods for Multivariate Model Development

Prediction of malt fermentability (apparent attenuation limit — AAL) by measurement of the diastatic power enzymes (DPE), α‐amylase, total limit dextrinase, total β‐amylase, β‐amylase thermostability, and the Kolbach index (KI or free amino nitrogen — FAN) is superior to the conventional use of diastatic power (DP) alone. The thermostability of β‐amylase is known to be an important factor in determining fermentability, thus the thermostability of the other relatively thermolabile enzyme, limit dextrinase, was investigated to determine if it was also useful in predicting fermentability. To facilitate this aim, methods were developed for a rapid and cost efficient assay of both β‐amylase and limit dextrinase thermostability. Internationally important Australian and international malting varieties were compared for their total limit dextrinase and β‐amylase activity and thermostability. Interestingly, the level of limit dextrinase thermostability was observed to be inversely correlated with total limit dextrinase activity. The prediction of malt fermentability was achieved by both forward step‐wise multi‐linear regression (MLR) and the partial least squares (PLS) multivariate model development methods. Both methods produced similar identifications of the parameters predicting wort fermentability at similar levels of predictive power. Both models were substantially better at predicting fermentability than the traditional use of DP on its own. The emphasis of this study was on the identification of predictive factors that can be consistently used in models to predict fermentability, because the model parameter estimates will subtly vary depending on mashing conditions, yeast strain/fermentation conditions and malt source. The application of these multivariate model development methods (PLS and MLR) enabled the identification of further potential fermentability predicting factors. The analyses divided the predictive parameters into those defined by DP enzymes and those associated with modification (KI, FAN, fine/coarse difference, wort β‐glucan and friability). Surprisingly, limit dextrinase thermostability was not a substantial predictor of fermentability, presumably due to its negative correlation with total limit dextrinase activity. The application of these insights in the malting and brewing industries is expected to result in substantial improvements in brewing consistency and enable more specific quality targets for barley breeder's progeny selection cut‐off limits to be more precisely defined.     

Effect of varying starch properties and mashing conditions on wort sugar profiles

The aim of this research was to investigate the relationship between starch composition in barley and its malted counterpart alongside malt enzyme activity and determine how these factors contribute to the fermentable sugar profile of wort. Two Australian malting barley varieties, Commander and Gairdner, were sourced from eight growing locations alongside a commercial sample of each. For barley and malt, total starch and gelatinisation temperature were taken, and for malt, α‐ and β‐amylase activities were measured. Samples were mashed using two mashing profiles (infusion and Congress) and the subsequent wort sugar composition and other quality measures (colour, original gravity, soluble nitrogen) were tested. Variety had no significant (<0.05) effect on any barley, malt, enzyme or wort characteristics. However, growing location impacted gelatinisation temperature, colour, malt protein content and original gravity. The gelatinisation temperature in malt samples was higher, by ~0.8°C, than in the equivalent barley sample. Several malt samples, even with protein contents <12.0%, had gelatinisation temperature >65°C. The fermentable sugars measured in the malt prior to mashing showed a higher proportion of maltose than glucose or maltotriose. In addition, there were significant differences in the amount of sugar produced by each mashing method with the high temperature infusion producing a higher amount of sugar and proportionally more maltose. There is scope for further research on the effect of genetics and growing environment on gelatinisation temperature, mash performance and fermentable sugar development. Routinely measuring gelatinisation temperature and providing this information on malt specification sheets could help brewers optimise performance. © 2019 The Institute of Brewing & Distilling     

Effect of teff (Eragrostis tef) variety and storage on malt quality attributes

Varieties of a cereal may have a considerable influence on malting qualities owing to variations in the physicochemical properties of the grains. This research was aimed at assessing the influence of five teff varieties on malt quality attributes. The teff samples were malted using previously optimized malting conditions and mashed with the congress mashing procedure. In this research, the Kuncho teff variety was malted in a one year period after harvesting, whereas the other four varieties were malted after three years of storage. Alpha‐ and β‐amylase, and limit dextrinase activity, were in the ranges 14–68, 10–440 and 375–1072 U/kg, respectively. Extracts ranged from 54% for Dessie to 74% for Ivory teff. Free amino nitrogen, protein content, soluble nitrogen, Kolbach index, viscosity and wort colour were in the ranges 160–364 mg/L, 8.6–13.6%, 532–1048 mg/100 g, 24–50%, 1.441–1.629 mPa s and 5.9–9.0 EBC units, respectively. High‐performance liquid chromatographic analysis for individual fermentable sugars revealed that the highest value in all varieties was recorded for glucose followed by maltose. The concentration of glucose ranged from 9.49 g/L in Brown teff, to 19.42 g/L in Ivory teff, whereas maltose ranged from 2.95 g/L in Dessie teff to 16.1 g/L in Kuncho teff. All of the malt quality attributes considered in this study were markedly influenced (p < 0.05) by the type of teff cultivar. It was concluded that the use of different teff varieties yielded malts with significantly different malt quality attributes. Copyright © 2013 The Institute of Brewing & Distilling     

THE EFFECTS OF MASHING TEMPERATURE AND MASH THICKNESS ON WORT CARBOHYDRATE COMPOSITION

Temperature and mash thickness are shown to affect both mash performance and enzyme activity. Alpha amylase was found to be considerably more resistant to heat inactivation than was beta amylase. This difference was reflected by changes in wort fermentability that were manifest at temperatures below those which affected levels of extract. Increasing the mashing temperature from 65°C to 80°C had only a slight effect on extract but reduced wort fermentability from over 70% to less than 30%. At 85°C and over, when temperature had a significant effect on alpha amylase, as well as on beta-amylase, extract was lost and starch was present in the wort. Diluting the mash with liquor had a similar effect to that of increasing temperature on both the amylolytic enzymes and on the mash performance. Thin mashes contained more starch and fewer fermentable sugars than did thick mashes at the same temperature. These changes can be related to the stability of the amylolytic enzymes.     

Application of high‐pressure treatment in the mashing of white malt in the elaboration process of beer

In this study, high‐pressure treatment (HPT) was applied to the mashing stage of beer production, which involves drying and milling of white malt and subsequent mixing with water. The following parameters were evaluated after pressurisation: β‐glucanase activity, starch gelatinisation and sugar extraction. Evaluation of starch hydrolysis from the malted barley endosperm after HPT was performed by measuring β‐glucanase activity after pressurisation; this enzyme breaks down gums and β‐glucans in wort and is desirable to obtain a good‐quality beer. Soaked malt samples pressurised at 200–600 MPa showed no increase in this activity compared with controls. Conversion of milled malt was evaluated indirectly by measuring the gelatinisation of starch, which began at 400 MPa. Soluble sugars were also measured in pressurised samples from the mashed liquid to investigate saccharification during the mashing stage. After 400 or 600 MPa treatment for 20 min, both the sucrose (g per 100 ml) and extract (l ° kg^?1) values were the same as those found in mashed samples following the standard procedure used in the brewing industry (65 °C,90 min). Starch gelatinisation was analysed at different high pressures (200–600 MPa) and it was shown that gelatinisation began at 400 MPa. The HPT time would have to be shorter to make the process commercially attractive. © 2002 Society of Chemical Industry     

Impact of buffering capacity on the acidification of wort by brewing‐relevant lactic acid bacteria

Acidified wort produced biologically using lactic acid bacteria (LAB) has application during sour beer production and in breweries adhering to the German purity law (Reinheitsgebot ). LAB cultures, however, suffer from end product inhibition and low pH, leading to inefficient lactic acid (LA) yields. Three brewing‐relevant LAB (Pediococcus acidilactici AB39, Lactobacillus amylovorus FST2.11 and Lactobacillus plantarum FST1.7) were examined during batch fermentation of wort possessing increasing buffering capacities (BC). Bacterial growth was progressively impaired when exposed to higher LA concentrations, ceasing in the pH range of 2.9–3.4. The proteolytic rest (50°C) during mashing was found to be a major factor improving the BC of wort. Both a longer mashing profile and the addition of an external protease increased the BC (1.21 and 1.24, respectively) compared with a control wort (1.18), and a positive, linear correlation (R ² = 0.957) between free amino nitrogen and BC was established. Higher levels of BC led to significant greater LA concentration (up to +24%) after 48 h of fermentation, reaching a maximal value of 11.3 g/L. Even higher LA (maximum 12.8 g/L) could be obtained when external buffers were added to wort, while depletion of micronutrient(s) (monosaccharides, amino acids and/or other unidentified compounds) was suggested as the cause of LAB growth cessation. Overall, a significant improvement in LA production during batch fermentation of wort is possible when BC is improved through mashing and/or inclusion of additives (protease and/or external buffers), with further potential for optimization when strain‐dependent nutritional requirements, e.g. sugar and amino acids, are considered. Copyright © 2017 The Institute of Brewing & Distilling     

Unmalted triticale cultivars as brewing adjuncts: effects of enzyme activities and composition on beer wort quality

The applicability of three selected triticale cultivars (Trinidad, Lamberto, Fidelio) for use as brewing adjuncts was investigated in comparison with wheat adjunct and barley malt. Fermentable substance, crude protein and arabinoxylan levels of starchy materials were determined as well as their native potencies (amylolytic, proteolytic, pentosolytic) to solubilise and degrade grain components during mashing. Laboratory‐scale experiments were performed to evaluate the influence of the adjuncts (composition, enzyme potency) on beer wort quality by mashing mixed (1:1) grists of malt and adjunct. Barley malt was rated as the superior raw material, possessing considerably higher enzyme activities and yielding the lowest wort viscosity. Among the triticale cultivars cv Trinidad was identified as the most suitable to serve as a brewing adjunct due to its improved starch solubilisation properties and its ability to generate low wort viscosities. Compared with the potent malt enzymes, the enzyme activities of unmalted triticale (such as amylases, pentosanases and proteases) had little affect on the composition of the sweet worts. In contrast, the contents of crude protein and fermentable substance of the triticale varieties greatly affected wort quality. Furthermore, the adjunct moiety determined the level of wort viscosity when mashing a combination of malt and triticale. In general, the brewing properties of triticale cv Trinidad were comparable with those of wheat. Copyright © 2004 Society of Chemical Industry     

Benefits of β-xylanase for wheat biomass conversion to bioethanol

BACKGROUND: The efficiency of bioethanol production from wheat biomass is related to the quality of end products as well as to safety criteria of co‐products such as distiller's dried grains with solubles (DDGS). The inclusion of a new biocatalyst for non‐starch polysaccharide degradation in fermentation processes could be one of the solutions. The objective of this study was to evaluate the influence of β‐xylanases in combination with traditional amylolytic enzymes on the efficiency of bioethanol production and DON detoxification during fermentation of Fusarium‐contaminated wheat biomass with high concentration of deoxynivalenol (DON; 3.95 mg kg^?1). RESULTS: The results showed that the negative effect of Fusarium spp. on yield and quality of bioethanol could be eliminated by the application of Trichoderma reesei xylanase in combination with amylolytic enzymes. This technological solution allowed to increase the concentration of ethanol in the fermented wort by 35.3% and to improve the quality of bioethanol by decreasing the concentrations of methanol, methyl acetate, isoamyl and isobutyl alcohols. Mass balance calculations showed that DDGS was the main source of DON contamination, comprising 74% of toxin found in wheat biomass. By using new enzyme combination for wheat biomass saccharification, a higher level of detoxification (41%) of DON was achieved during the fermentation process. CONCLUSION: The addition of Trichoderma reesei xylanase played a positive role in bioethanol production from Fusarium‐contaminated wheat biomass, indicating that the yeast‐growing medium was enriched during the enzymatic treatment. Copyright © 2011 Society of Chemical Industry     

Limit Dextrinase — Does Its Malt Activity Relate to Its Activity During Brewing?

Limit dextrinase (EC 3.2.1.142) hydrolyses α‐1,6 glucosidic bonds in amylopectin and branched dextrins. Measurement of limit dextrinase activity during fermentation of unboiled wort at the pH of the wort has shown that its activity increases almost 10 fold during the first 10–15 h of fermentation and this increase in activity is unaffected by the presence of leupeptin, a cysteine protease inhibitor. The increase in activity seen when assays were carried out at pH 5.5 was much smaller and was reduced by leupeptin. The activity of limit dextrinase declined slowly during the latter part of the fermentation. It was established that the optimum pH for rapid extraction and assay of malt limit dextrinase in the absence of a reducing agent is approximately 4.5, but in the presence of dithiothreitol, at pH 5.5, activities 2–3 times higher can be obtained after 5 h extraction (600–700 mU/g dry weight). Limit dextrinase activities after 1 h extraction at mashing temperatures were below 20 mU/g dry weight if the mash pH was below 5.0. It is concluded that at pHs below 5.0, where limit dextrinase activity is below its optimum for activity, limit dextrinase activity increases due to dissociation of the inhibitor/enzyme complex. The protection from mashing temperatures of 65°C afforded by the inhibitor is lost at these lower pHs.     

Studies on the mashing conditions of teff (Eragrostis tef) malt as a raw material for lactic acid‐fermented gluten‐free beverage

Formation of extracts and fermentable sugars during mashing can be limited by incomplete starch gelatinisation. The aim of this research was to develop mashing programme for 100% teff malt as a potential raw material for gluten‐free lactic acid‐fermented beverage. Isothermal mashing at temperatures ranging between 60 and 84 °C was conducted, and the highest extract (85%) was observed for the wort samples produced at temperatures higher than 76 °C. Sixty‐minute rest at 71 °C resulted in higher fermentable sugars than other tested conversion rest temperatures. Inclusion of lower mashing‐in temperature in the mashing programme also substantially improved the concentrations of free amino nitrogen (128 mg L^?1) and fermentable sugar (58 g L^?1) in the final wort. Therefore, 30‐min rest at 40 °C followed by 60‐min rest at 71 °C and 10‐min rest at 78 °C was found to be a suitable mashing programme for teff malt.