EXTRUDED SORGHUM AS A BREWING RAW MATERIAL

Small scale mashes (50 g total grist) with grists containing up to 50% by weight of extruded whole sorghum produced worts of high extract yield and low viscosity. Increasing the proportion of extruded sorghum in the grist resulted in decreasing wort filtration volume, total nitrogen and free amino nitrogen content. The wort filtration behaviour of mashes containing sorghum extruded at 175°C was superior to that of mashes containing sorghum extruded at 165°C or 185°C. The results from such small scale mashing experiments suggested that extruded sorghum compared favourably to extruded barley and extruded wheat as a brewing adjunct. Worts and beers were produced on a pilot brewery scale (100 1) from grists comprising 70% malt + 30% extruded sorghum and 100% malt under isothermal infusion mashing conditions. Mashes containing sorghum extruded at 175°C showed comparable wort filtration behaviour to that of the all malt control mash whereas mashes containing sorghum extruded at 165°C or 185°C showed poor wort filtration behaviour. Worts produced from grists containing extruded sorghum fermented more quickly than the control wort and attained lower values of final gravity. The resulting beers were filtered without difficulty. Beers produced from grists containing extruded sorghum contained lower levels of total nitrogen and free amino nitrogen compared to the control beer consistent with extruded sorghum contributing little or no nitrogenous material to the wort and beer. Beers brewed from grists containing extruded sorghum were of sound flavour and showed reasonable foam stability behaviour.     

Pilot Scale Production of a Lager Beer from a Grist Containing 50% Unmalted Sorghum

Pilot scale (1000 L) brews were carried out with a grist comprising of unmalted sorghum (50% of total wet weight of grain) (South African variety) and malted barley (50% of total wet weight of grain) grist using a mashing program with rests at 50°C, 95°C and 60°C. Mashes were supplemented with a high heat stable bacterial α‐amylase, a bacterial neutral protease and a fungal α‐amylase. A control brew containing 100% malted barley was also carried out. Saccharification difficulties were encountered during mashing, and extraction of the grist was lower for the sorghum mashes. The sorghum mashes showed comparable lautering behaviour to that of the control mash. At mashing off the sorghum worts were starch positive. Apparent degree of fermentation of the sorghum gyles were less than the control gyles. Green beer filtration proved unproblematic. The sorghum beers compared quite closely with the control beer with regard to colour, pH and colloidal stability. Foam stability deficiencies were apparent with the sorghum beer. However, the fermentability of the sorghum worts were lower. Hence the sorghum beers were lower in total alcohol. Sensory analysis indicated that no significant differences existed between the sorghum beer and both the control beer and a commercial malted barley beer with regard to aroma, mouth‐feel, after‐taste and clarity. However, the sorghum beer was found to be significantly different to both of the other beers with regard to colour, initial taste and foam stability.     

Determination of the influence of starch sources and mashing procedures on the range of the molecular weight distribution of beer using field‐flow fractionation

To produce experimental beers, different mash mixtures (barley malt, barley malt + 30% pre‐cooked maize, barley malt + 30% nonmalted spelt) and distinct mashing procedures (infusion and decoction) with variations of the rest time and initial temperatures were evaluated. The range of molecular weight distribution (MWD) of the resulting beers was determined using asymmetrical flow field flow fractionation coupled to multiangle laser light scattering and refractive index. There were no differences on the range of MWD among the beers, according to infusion or decoction, using similar raw materials and initial temperatures (45 and 55°C). However the range of MWD was higher (p < 0.005) when using infusion at an initial temperature of 63°C, regardless of the raw material. The use of maize did not alter structural properties of the beer, while mash containing nonmalting spelt caused an elevation on the MWD (p < 0.001) and a lower (p < 0.05) apparent degree of fermentation. Therefore the range of the MWD of the beers was influenced by the quality of the raw material and the initial mashing temperature, whereas apparent degree of fermentation values were affected only by the type of starch source. Thus the determination of the MWD is an important tool for monitoring the production of beer. Copyright © 2013 The Institute of Brewing & Distilling     

Determination of Prolamins in Beers by ELISA and SDS‐PAGE

Coeliac disease is triggered by exposure to the prolamin protein fraction of wheat, barley, or rye. The prolamin content of five lager beers and one wheat beer were analyzed by sodium dodecyl sulfate—polyacrylamide gel electrophoresis (SDS‐PAGE) and immunoblotting and seven lager beers and three wheat beers were analyzed by enzyme‐linked immunosorbent assay (ELISA). Most of the lager beers were made from barley and some had varying amounts of rice or corn as adjuncts. One of the beers was “gluten‐free”, having been produced from corn and buckwheat without barley. The lager beer samples were gel‐filtered before ELISA or SDS‐PAGE analysis. Prolamin proteins were found in all but one beer which was made of corn, rice and barley and which was not the “gluten‐free” beer. ELISA analysis was done using a commercially available gluten assay kit. For lager beers, a barley prolamin standard for ELISA was propanol‐extracted from barley malt instead of using the prolamin standard of the gluten assay kit. As expected, the wheat beers contained much higher amounts of prolamins than the lager beers. The samples were studied by SDS‐PAGE to identify different prolamin fractions. Proteins having a relative molecular mass in the range of 8000–17,000 and 38,000 and above were detected in immunoblotting by the prolamin sensitive antibody in the lager beers.     

Analysis of flavour compounds in beer with extruded sorghum as an adjunct using headspace solid‐phase micro‐extraction and gas chromatography–mass spectrometry

Sorghum is a widely used adjunct that is used in the production of beer and increasingly affects beer flavour as the amount added increases. The aim of this work was to establish a simple, solvent‐free technique, without derivatization, to analyse flavours and typical volatile compounds present in extruded and unextruded sorghum beer, and to compare the flavour differences of the two types of beer. Headspace solid‐phase micro‐extraction gas chromatography–mass spectrometry was used to determine the flavours in the two beers and eight typical volatile compounds were quantified using GC. Forty‐five flavour compounds were identified and quantified in extruded white sorghum beer, while 31 flavour compounds were identified in unextruded white sorghum beer. Extruded or unextruded white sorghum can be used to produce ale beer, but the primary flavour content in the extruded white sorghum beer was higher than in the unextruded white sorghum beer. Copyright © 2016 The Institute of Brewing & Distilling     

AMINO ACID ANALYSIS OF BEER POLYPEPTIDES

The principles of amino acid analysis of proteins and polypeptides are reviewed. Analysis of the amino acid composition of dialysed beer material prepared from a wide variety of commercial and pilot brewery beers showed that the principal amino acids comprised glutamic acid/glutamine, proline, glycine and aspartic acid/asparagine. The results from the analysis of a series of pilot brewery beers brewed under standardised conditions showed that the composition of the grist may influence the amino acid composition of beer polypeptide fractions. Dialysed beer material prepared from beer brewed from grists containing torrified wheat, wheat flour and malted wheat contained greater proportions of glutamic acid/glutamine compared to material prepared from all malt beers. Further fractionation and analysis of dialysed beer material prepared from pilot brewery beers suggested that fractions MW>60000 contained polypeptide material derived from yeast mannan-protein. In addition fractions MW>60000 prepared from beer brewed from grists containing torrified wheat, wheat flour or all malted wheat may contain high molecular weight polypeptide material derived from wheat proteins. The results from the analysis of fraction MW 40,000–60000 prepared from beers brewed from grists containing all malt, 80% malt and 20% torrified wheat and 50% malt and 50% malted wheat are consistent with the presence of polypeptide material derived from cereal albumins and globulins whereas fractions MW 40,000–60000 prepared from beers brewed from 80% malt and 20% wheat flour and 100% malted wheat may contain polypeptide material derived from wheat prolamins and glutelins. The amino acid composition of fraction MW 20,000–40,000 from all pilot brewery beers investigated is consistent with the presence of polypeptide material derived from cereal prolamins and glutelins. The amino acid composition of beer polypeptide fractions may be used to detect the use of wheat adjuncts in beer brewing.     

THE BREWING POTENTIAL OF “ACHA” (DIGITARIA EXILIS) MALT COMPARED WITH PEARL MILLET (PENNISETUM TYPHOIDES) MALTS AND SORGHUM (SORGHUM BICOLOR) MALTS

The malting and brewing characteristics of millets (Pennisetum typhoides and Digitaria exilis) and sorghum (Sorghum bicolor) were compared. Diastase, α-amylase, amyloglucosidase and proteases increased with malting time and the increase was associated with the modification. Development of hydrolytic enzymes was significantly higher in pearl millet and Digitaria exilis (“acha”) than in sorghum at P ≥ 0.01. The major starch degrading enzyme in the three varieties of pearl millet (SE composite, SE.13 and SE 2124) was α-amylase. On the other hand, β-amylase was the major starch degrading enzyme in “acha” (Digitaria exilis) which is similar to the pattern in barley. Gibberellic acid had a stimulating effect on the diastatic activity of pearl millets, Digitaria exilis (“acha”) and sorghum (KSV-4), but inhibited the diastatic activities of sorghum (Farafara). Gibbereltic acid inhibited the proteolytic activities in all the pearl millet varieties, Digitaria exilis and sorghum varieties. Potassium bromate had little or no effect in the reduction of malting losses. Although “acha” (Digitaria exilis) had a high β-amylase content, a high malting loss makes it uneconomical to brew with “acha” mart. A blend of “acha” malt with pearl millet malt or sorghum malt (composite malt) will produce a malt of the same profile as barley malt and this will enhance the quality of sorghum and pearl millet malt during the mashing process. Wort quality of all the samples was suitable for brewing conventional beer.     

ENZYMIC BREAKDOWN OF ENDOSPERM PROTEINS OF SORGHUM AT DIFFERENT MALTING TEMPERATURES

Enzymic breakdown of endosperm proteins of sorghum was more effective at 20°C than at 25°C and 30°C, as regards total protein solubilization, α-amino nitrogen and peptide production. Although the embryos (axes and scutella), of the three temperature treatments contained similar quantities of protein, it appeared that less proteins, in terms of amino acids and peptides, were transferred to the roots during malting at 30°C than at 25°C and 20°C. During mashing, higher levels of peptides but lower levels of α-amino nitrogen and total soluble nitrogen were released in an infusion mash at 65°C than in a decantation mash where enzymically active wort was decanted and used to mash gelatinized sorghum starch at 65°C. Although more of the maltose-producing enzyme—β—amylase was found in sorghum malts made at 25°C and 30°C than at 20°C, it would seem that, for sorghum, malting temperature of 20°C to 25°C were optimal as regards protein breakdown during malting. The protein breakdown produced when sorghum is malted at 20°C is comparable to that found in barley malt and should support similar levels of adjuncts and yeast growth during brewing.     

Brewing with Rice Malt — A Gluten‐free Alternative

The preparation of beer‐like beverages with rice malt as the only raw material is reported. Several tests were performed on a laboratory scale and in a 25 L‐capacity pilot plant. Both the decoction and the infusion procedure were tested; malt and water were mixed in a ratio 1:3.5 for both methods and the mash was brewed without adding exogenous enzymes. The obtained worts were fermented using bottom fermenting yeasts, while “beers” were re‐fermented utilizing top fermenting yeasts and adding either sterile wort or sugar. A maximum ethanol of 4.5% vol. was obtained after the primary fermentation from an initial wort with an original gravity of 11.8°Plato. All parameters of the beer were found to be acceptable using a standard beer analysis. Owing to a suitable hop addition, an aroma very similar to that of a normal beer was obtained.     

SMALL SCALE MASHING EXPERIMENTS WITH GRISTS CONTAINING HIGH PROPORTIONS OF RAW SORGHUM

Small scale mashes (50 g total grist) with grists containing high proportions of raw sorghum (50%–80% malt replacement) showed high values of extract recovery and produced worts of lower total nitrogen, free amino nitrogen, viscosity and colour but higher values of pH compared to worts produced from all malt mashes. Increasing the proportion of raw sorghum in the grist relative to malt resulted in a decline in extract recovery, wort total nitrogen, free amino nitrogen and an increase in wort pH. Addition of industrial enzyme preparations to mashes containing raw sorghum resulted in higher values of extract recovery (enzyme preparations containing α amylase and β glucanase), higher values of wort total nitrogen and free amino nitrogen (enzyme preparations containing a neutral proteinase) and decreased wort viscosity (enzyme preparations containing β glucanase or cellulases) compared to worts produced from untreated mashes. Worts and beers were produced on a pilot brewery scale from 50% malt and 50% polished (whole) sorghum (single decoction mashing regime) and 20% malt and 80% raw sorghum supplemented with an industrial enzyme preparation (double mashing regime). Mashes comprising 50% malt and 50% polished sorghum showed comparable wort filtration behaviour (lautering) to that of control mashes (70% malt and 30% maize grists) whereas wort produced from 20% malt and 80% raw sorghum filtered slowly. Worts produced from grists containing sorghum were of high fermentability and showed lower levels of total nitrogen and free amino nitrogen compared to control worts. Analysis of worts produced from small scale mashes containing raw sorghum and a pilot brewery scale mash comprising 20% malt and 80% raw sorghum demonstrated that the levels of total nitrogen and free amino nitrogen were higher than expected from the reduction in the malt content of the mash, consistent with the release of nitrogenous components (polypeptides, peptides and amino acids) derived from sorghum into the wort. Beers produced from 50% malt and 50% polished sorghum and 20% malt and 80% raw sorghum were filtered without difficulty and were of sound flavour. Beers produced from 50% malt and 50% polished sorghum contained lower levels of isobutanol, 2-methylbutanol, dimethylsulphide and higher levels of n propanol and diacetyl compared to control beers.     

Corn grist adjunct – application and influence on the brewing process and beer quality

In the brewing industry, barley malt is often partially replaced with adjuncts (unmalted barley, wheat, rice, sorghum and corn in different forms). It is crucial, however, to preserve constant quality in the beer to meet the expectations of consumers. In this work, how the addition of corn grist (10 and 20%) influences the quality of wort and beer was examined. The following parameters were analysed: wort colour, dimethyl sulphide (DMS) and protein content, non‐fermentable extract, extract drop during fermentation, alcohol content and the attenuation level of the beer, together with filtration performance. The samples (all‐malt, and adjunct at 10 and 20% corn grist) were industrial worts and the beers produced in a commercial brewery (3000 hL fermentation tanks). The application of 10 and 20% corn grist had an effect on the wort colour, making it slightly lighter (11.1 and 10.5°EBC, respectively) than the reference barley malt wort (12.2°EBC). The free amino nitrogen level, DMS and non‐fermentable extract were significantly lower in the worts produced with the adjunct; the alcohol content and attenuation levels were higher in the beers produced with adjunct. The use of corn grist, at the level of up to 20% of total load, appears to affect some of the technological aspects of wort and beer production, but it does not significantly influence the final product characteristics. Copyright © 2014 The Institute of Brewing & Distilling     

THE USE OF EXTRUDED BARLEY,WHEAT AND MAIZE AS ADJUNCTS IN MASHING

The principles of extrusion cooking are summarised. In small scale trials good extracts were obtained from extruded barley when it was mashed with industrial enzymes, using a programmed temperature cycle. Extruded barley, wheat and maize and wheat flour yielded acceptable levels of extract when mashed with lager malt (70%) using a programme with 1 hour rests at 50°C and 65°C. The extracts obtained from these grists were increased above those obtained from grists of lager malt alone and the viscosities of the worts were reduced when the mashes were supplemented by preparations of bacterial enzymes. Enzyme additions also improved extract recoveries from all-malt mashes and reduced the viscosities of the derived worts. Using a temperature programmed mashing cycle and supplementary enzymes beers were prepared from a lager malt grist and grists in which the lager malt was partly replaced, by 30%, with extruded barley or extruded wheat, or extruded maize or wheat flour pellets. In every case wort was recovered relatively easily, the worts fermented normally and the beers were all fully acceptable, although their flavours did differ. However, in contrast to results of preliminary brewing trials, the head retentions of the beers made with adjuncts were unusually low, possibly because of particular enzyme additions.     

Changes in the Starch Fraction During Extrusion-cooking of Corn

Whole ground corn was extruded at 23.7, 18.5, 15.4,13.9 and 7.6% moisture contents (EMC). Decreasing EMC resulted in increases in water solubility index (WSI), enzyme susceptibility (ES), degree of gelatinization and blue values, while water absorption index and water insoluble carbohydrates decreased. ES and WSI of several blends prepared by combining raw (R), gelatinized (G), and dextrinized (D) corn were compared to those of extruded products. Corn extrudates had properties similar to blends containing G and D corn only. The relative proportion of D corn increased from about 10 to 60%, as EMC decreased. “Dextrinization” appears to become the predominant mechanism of starch degradation during low-moisture, high-shear extrusion. Viscoamylographs, scanning electron and light photomicrographs support these findings.     

Cognitive and emotional differentiators for beer: An exploratory study focusing on “uniqueness”

The current explosion of micro-brewed beers has created a category that varies greatly in style, quality, ingredients, sensory attributes and brand images. To establish a niche in this market, brewers often differentiate their product through the tailoring of sensory characteristics of the beer or its brand image. However, many other consumer-based attitudinal and cognitive variables can be used to differentiate beers. These include perceived familiarity, novelty and situational appropriateness, as well as attitudinal and emotional product associations. In the present study, these variables were evaluated for their effectiveness in differentiating a variety of New Zealand beers. Two sets of 8 beers were evaluated by consumers (n = 203 beer enthusiasts) by: (i) classifying them for familiarity/novelty, (ii) answering attitudinal questions, (iii) assessing appropriateness for 15 common use situations and (iv) identifying emotional associations. Results showed each of the variables to be important differentiators. Although perceived familiarity and novelty were inversely related, familiarity better differentiated among the familiar beers, while novelty better differentiated the novel beers. Attitudinal data showed the most familiar beers to be “ordinary”, “boring” and “simple”, and those judged novel to be “unusual”, “intriguing”, and “complex”. In spite of this, “appealing” beers could be found among both the familiar and novel samples. Situational appropriateness data showed familiar beers to be appropriate for “casual” and “everyday” situations, while novel beers were most appropriate for “special occasions”. Lastly, emotion data showed the beers to differ along “active/passive” and “hedonic” dimensions, with familiar beers having passive emotional associations and novel beers having more active associations. In summary, this novel, consumer-based multi-faceted approach was extremely effective in differentiating among beers and provided useful insights for the identification of what may be considered “unique” beers.     

Expertise and memory for beers and beer olfactory compounds

Do beer experts have better recognition memory for beers than novices? And can recognition memory for beers be predicted on the basis of recognition memory for beer odor compounds? We compared the memory performance of “beer experts” and novices in two recognition tasks. The first task was performed ortho- and retronasally with beers, and the second orthonasally with beer odor compounds. As a control we also compared the performance of “experts” and novices on an identification task and a same/different discrimination task. “Beer experts” outperformed novices in both the identification task and the recognition memory task with both beers and odor compounds, but only for beers they had been trained on (familiar beers), and regardless of the type of odors (familiar vs. unfamiliar). “Experts” were only marginally superior in the beer discrimination task. This suggests that the experts’ advantage in recognition memory is likely to have its source in more efficient coding and retrieval in long-term memory, rather than in better perceptual ability. No significant correlation was found between odor and beer memory performance, which suggests that, during training, “experts” might develop independent memory structures for odor compounds and for beers.     

THE NUTRITIVE CONTENT OF AFRICAN BEERS BREWED WITH MAIZE GRITS OR SORGHUM ADJUNCT

Sorghum beer samples were brewed in a pilot plant operation using either sorghum grain or maize grits as starchy adjunct in order that the nutritive content of the beers could be compared. Significantly higher ethanol, thiamin, nicotinic acid, ash, phytate, zinc, copper, manganese, iron, magnesium, potassium and phosphorus concentrations were found in beers brewed with sorghum adjunct. Sorghum adjunct beers can therefore make a greater contribution to the nutritional requirements of the Southern African beer drinker than beers brewed with maize grits. The results obtained suggest that the use of sorghum adjunct in the brewing of sorghum beer should be encouraged for economic and dietary reasons.     

THE MEASUREMENT OF DIMETHYL SULPHIDE PRECURSOR IN MALTS,ADJUNCTS, WORTS AND BEERS

Dimethyl sulphide in beer originates from a precursor in the malt. A method is described for the measurement of this precursor in brewing raw materials, wort and beer. The precursor levels in various green malts, kilned malts, and adjuncts are given. Excess methionine inhibits precursor uptake by yeast during fermentation. Residual precursor is still present in some commercial bottled beers.     

Extrusion-Cooking of Sorghum Containing Different Amounts of Amylose

Three sorghums containing different amounts of amylose (12.2, 21.5, and 26.7%) were decorticated, ground and extruded at three extrusion moisture levels (17, 32, and 45%). Highly expanded and brittle sorghum extrudates with high degrees of starch cooking were produced at 17% extrusion moisture content. All sorghum extrudates exhibited a V-amylose x-ray diffraction pattern. Functional characteristics, such as expansion, enzyme-susceptible starch ratio, and water solubility, indicated that low amylose extrudates were more cooked than other varieties. Thin porridges prepared from extruded sorghums had an intermediate consistency, smooth texture, roasted flavor and white color. Thin porridges (atoles) from extrudates containing 21.5% amylose, were preferred by a sensory panel over those from extrudates containing 12.2 and 26.7% amylose.     

THE EFFECT OF CARBOHYDRATE ADJUNCTS ON BREWER'S WORT FERMENTATION BY SACCHAROMYCES UVARUM (CARLSBERGENSIS)*

The use of carbohydrate adjuncts such as sucrose, fructose and glucose in brewer's wort significantly modifies the initial wort sugar spectrum and also the pattern of sugar uptake during fermentation by a strain of Saccharomyces uvarum (carlsbergensis). Under these conditions, the concentration of glucose and fructose in the wort was observed to increase when compared to worts in which corn starch was employed as an adjunct and glucose was taken up at a faster rate than fructose. The increase in glucose concentration in the wort also resulted in severe repression of maltose and maltotriose utilization with significant levels of these sugars remaining in the beer produced.     

EUROPEAN BREWERY CONVENTION: HAZE AND FOAM GROUP. TOWARDS THE CHEMICAL PREDICTION OF SHELF LIFE

Rapid chemical methods are described for assesssing in beer the levels of “oxidizable polyphenols” and “sensitive proteins,” both of which influence non-biological shelf life. The method for oxidizable polyphenols depends on the formation of an insoluble complex with cinchonine sulphate. Freshly processed beers form only a slight haze on the addition of cinchonine sulphate, but the haze produced is greatly increased if the beers are previously oxidized. For beers stabilized by a process involving reduction of the polyphenol content, it is found that the rate of haze formation is then directly related to shelf life and is inversely proportional to it.