DEVELOPMENT OF A MASHING PROFILE FOR THE USE OF MICROBIAL ENZYMES IN BREWING WITH RAW SORGHUM (80%) AND MALTED BARLEY OR SORGHUM MALT (20%)

Different time and temperature programmes were used to evaluate the production of hot water extract (HWE) and free amino nitrogen (FAN) from mashes containing raw sorghum and either malted sorghum or malted barley in the presence of microbial enzymes. Two malted varieties of sorghum (SK 5912 and Zaria) were used. The former gave higher HWE but lower FAN than the latter. Sorghum malts were unable to provide enzyme activity for starch extraction and exogenous enzymes were always needed. Seventeen commercially available enzyme preparations were assessed. A double-mash process was developed. Inclusion of calcium ions (200 ppm) was beneficial but adjustment of mash pH had little effect. Raw sorghum was gelatinised at 100°C for 30–40 min in the presence of a heat-stable α-amylase followed by mixing with a malt mash (started at B0°C) to give a temperature of 65°C with a total mash time of 167 min (127 min from mixing the mashes). The inclusion of a single commercial enzyme preparation (containing both proteolytic and amylolytic activities) was sufficient to achieve satisfactory HWE and FAN. Addition of different activities or combinations of activities gave no significant advantages. To obtain levels of FAN of 100–140 mg/l however excessive amounts of enzymes were required.     

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.     

A Study on the Suitability of Unmalted Sorghum as a Brewing Adjunct

Grain samples of thirteen sorghum cultivars with diverse chemical composition were assessed for their suitability as brewing adjuncts based on proximate analysis. Sieving analysis of the grain as well as hot water extractables (HWE), hot water extractable protein (HWEP) and free amino nitrogen (FAN) were also determined. Cultivars with high starch and amylose contents together with low protein and fat percent are better suited as adjuncts depending on their hot water extracts and hot water extractable protein yields. Large variations in the uniformity of grain size were found, two of these cultivars (CSV‐14R and M 35‐1) had highest grain size. Cultivars CSH‐5, CSV‐11 and CSV‐13 among the released cultivars were identified as better adjuncts which could be used along with barley malt for brewing lager beers.     

THE PROPERTIES,COMPOSITION AND FERMENTABILITIES OF WORTS MADE FROM 100% RAW SORGHUM AND COMMERCIAL ENZYMES

A mashing regime was developed using 100% raw sorghum which enabled commercially acceptable hot water extracts to be obtained in 85 minutes with minimal use of a heat stable α-amylase and proteolytic enzymes. This gave worts of HWE 295 1°/kg, with FAN levels of about 40 mg/l and ammonium ion concentration of about 60 mg/l. Higher, but commercially unacceptable, levels of proteolytic enzymes gave worts with FAN from 84.5 to 95 (mg/l). Addition of an amyloglucosidase as the commercial preparation Amylo300L, was required to convert the HWE to fermentable extract. The addition of Amylo300L, increased the DP1, DP2 and DP3 carbohydrate fractions of the worts from 22% to more than 90% of the total, compared to about 80% for a wort made from malted barley without the use of enzymes. Two different proteolytic enzymes gave different extracts and FAN contents presumably reflecting either differences in susceptibilities of the sorghum to the two enzymes or the presence of different additional enzyme activities in the different preparations. The level of ammonium ions in malted barley worts was 86 mg/l and up to 88 mg/l in worts produced from sorghum and enzymes. Enzyme addition produced increased levels of ammonia. The content of Group A (the most readily assimilated) amino acids was proportionally higher in sorghum worts compared to malted barley wort. Worts made from raw sorghum and enzymes, containing as little as 40 mg/l FAN, were fully attenuated. The yeast consumed about 35 mg/l FAN and 45 mg/l ammonium ions. Under identical fermentation conditions, the same yeast, fermenting a malted barley wort of comparable extract consumed 104 mg/l FAN and 37 mg/l ammonium ions.     

膨化大米辅料酿造啤酒中糖化工艺参数对啤酒色度的影响

在100L规模上，通过五因素五水平二次旋转正交组合试验设计，探讨了挤压膨化大米辅料酿造啤酒的外加酶糖化工艺参数对啤酒色度的影响规律，得出最佳的糖化工艺参数。     

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.     

MALTING QUALITY OF SRI LANKAN VARIETIES OF SORGHUM

The malting quality of Sri Lankan sorghum was studied using seventeen varieties. These varieties represented four colour categories (brown, yellow, pink and white) of sorghum found in Sri Lanka. The main criteria used for the assessment of malting quality in this study were the malting loss, diastatic power, liquefying power and the quantity of extract. Malting losses of these varieties were somewhat higher than those encountered in malting barley. However, they appeared to depend partly on the malting conditions. The diastatic powers and liquefying powers observed in this study were inferior to those observed with barley malt. However, with some varieties they appeared to be adequate for the purpose of mashing, as indicated by the high extract values obtained, which were comparable with those of some barley malts. Extract values of the four colour categories varied considerably and the best values were observed with the yellow and pink varieties and some varieties of white. Brown varieties in spite of their comparatively high diastatic powers and liquefying powers gave very little or no extract on mashing.     

ROLE OF ALPHA-GLUCOSIDASE IN THE FERMENTABLE SUGAR COMPOSITION OF SORGHUM MALT MASHES*

The cause of the high glucose to maltose ratio in sorghum malt worts was studied. Mashing temperature and pH strongly affected both the amount of glucose and the proportion of glucose relative to total fermentable sugars. The relative proportion of glucose was higher when mashing was performed. at pH 4.0, close to the pH optimum for sorghum alpha-glucosidase, than at the natural pH of the mash (pH 6.0–5.5). Mashing according to the EBC procedure using an enzymic malt extract with pre-cooked malt insoluble solids producing a wort containing maltose and glucose in an approximately 4:1 ratio, whereas mashing with a malt extract without pre-cooking the malt insoluble solids resulted in a wort with approximately equal amounts of maltose and glucose. Both treatments gave the same quantity of total fermentable sugars and amount of wort extract. Sorghum alpha-glucosidase was confirmed to be highly insoluble in water. All or virtually all activity was associated with the insoluble solids. Hence, it appears that the high amount of glucose formed when sorghum malt is mashed conventionally is due to alpha-glucosidase activity. Pre-cooking the malt insoluble solids inactivates the alpha-glucosidase, preventing the hydrolysis of maltose to glucose.     

DURATION OF FINAL WARM STEEP AS A CRUCIAL FACTOR IN PROTEIN MODIFICATION IN SORGHUM MALTS

Cold water soluble protein (CWS-protein), cold water soluble protein modification index, total non-protein nitrogen (TNPN), small peptide accumulation, free alpha amino nitrogen, carboxy-peptidase and proteinase activities, all protein modification indicators in malts from two improved Nigerian sorghum cultivars were estimated after six days of malting. Grains were steeped in distilled water for a total of 48 h under four different final warm steep (40°C) treatment periods. Cultivar and duration of final warm water steep, plus their pair-wise interactions highly significantly influenced all these protein modification indices. Sorghum ICSV 400 generally exhibited higher FAN, CWS-protein solubilising activity and accumulation, superior amylolytic potential over proteolysis and better protein modification potential over KSV 8. Lower TNPN and TNPN-FAN difference exhibited by ICSV 400 in spite of its higher FAN suggests superior anabolic protein turnover probably due to more efficient peptide translocation process. Proteolytic activities recorded for both cultivars were inconsistent with levels of N-substances obtained suggesting roles for factors other than proteolysis in grain protein modification.     

FERMENTATION OF WORTS MADE FROM 100% RAW SORGHUM AND ENZYMES

Worts made from raw sorghum and enzymes were successfully fermented even though the level of FAN present (51 mg/l) is well below that essential for fermentation of wort made from malted barley. Changes in typical fermentation parameters such as specific gravity, pH uptake of free amino nitrogen (FAN) and ammonium ions mirrored the increase in yeast cell concentration. Yeast viability remained high throughout the fermentation. Under identical fermentation conditions, malted barley worts showed typical fermentation profiles. However, malted barley worts with specific gravity maintained by the addition of D-glucose, but in which the FAN was diluted to a level similar to that found in a wort made from sorghum and enzymes, fermented more slowly and failed to attenuate fully. Five consecutive fermentations, using yeast cropped from the preceding to pitch the current fermentation were conducted. The specific gravity profiles were essentially the same in all five fermentations. Final values of pH, yeast in suspension, yeast viability and FAN were also indistinguishable. The yeast crop taken from fermentations of worts made from raw sorghum and enzymes represented a 5-fold increase over the initial pitching rate. When compared to commercial beers, the beers derived from fermentation of worts made from raw sorghum and enzymes contained lower levels of ethyl acetate, and higher levels of both 2- and 3-methyl butanol. In the beers derived from sorghum, isobutanol was always less than 20% of the total higher alcohol concentration.     

THE INSTITUTE OF BREWING ANALYSIS COMMITTEE REVISED METHODS OF EXTRACT DETERMINATION

Following a Brewer's Society request to consider a change from a standard Miag Disc Mill setting of 0·5 mm to one of 0·7 mm the Analysis Committee has re-evaluated the determination of hot water extract. It is recommended that from 1st December 1979–1. A Miag Disc Mill setting of 0·7 mm be adopted for grinding malt for the determination of hot water extract. 2. Where an estimate of the fine/coarse grind hot water extract difference is required, mill settings of 0·2 mm and 0·7 mm respectively should be used. The reproducibility of this procedure is adequate to separate malts into classes with high and low values but analytical tolerances cannot be recommended for commercial transactions. Revised methods for setting the Miag Disc Mill and for determining the hot water extract of fine and coarse ground malts are given in Appendix I. It is proposed that all mashes should be made in stainless steel beakers, the use of the standard brewers' mash flask being limited to making the mash to the correct volume at the end of the determination. It is recommended that, from 1st December 1979, the 0·7 mm Miag Disc Mill setting should replace also the 0·5 mm setting in all Recommended Methods for coloured malts, dark malts, roasted barley and unmalted grain. It is further recommended that from 1st December 1979 all specific gravity determinations for laboratory extracts of malt, coloured malt, dark malt, roasted barley, unmalted grain, sugars, syrup, caramel and spent grains should be made at 20°C.     

糖化工艺参数对膨化大米辅料麦汁收得率的影响

在100L规模上,通过五因素五水平二次旋转正交组合试验设计,探讨了膨化大米辅料酿造啤酒的外加酶糖化工艺参数对麦汁收得率的影响规律.最佳糖化工艺参数为:辅料含量为46.77%,料水比为1∶4.88,50℃蛋白质休止时间为60 min,63℃糖化时间为60 min,70℃糖化时间为30.35 min.     

RAW MATERIALS OF BREWING*

The main cost implications of the principal brewing materials as they relate to identifiable, compositional and transformational formulations are elaborated. The relationship of plant design in regard to these considerations is discussed.     

THE INSTITUTE OF BREWING ANALYSIS COMMITTEE EXTRACT OF UNTREATED GRAIN GRITS AND OTHER RAW GRAIN

A half-and-half method for determining the potential extract of untreated grits and raw grain is recommended: it replaces the cold water extract method.     

GRAIN AND MALT MILLING ENERGIES IN SORGHUM AND THEIR RELATIONSHIPS WITH EXTRACT AND DIASTATIC POWER

Twenty three sorghum genotypes were shown to vary widely for a range of grain and malt quality characters. Grain milling energy did not give an indication of the likely malting performance of sorghum samples. There were, however, close relationships between malt milling energy and both % extract and diastatic power, if samples with unusually high or low grain nitrogen contents were excluded from the population under study. Rapid screening of very small malt samples for milling energy and diastatic power could form the basis for malting quality selection in early generations of sorghum breeding programmes.     

EFFECT OF GERMINATION TIME,TEMPERATURE AND MOISTURE ON MALTING OF SORGHUM

The effect of germination conditions on sorghum malt quality and malting loss was studied by germinating sorghum for different periods of time up to 6 days over a range of temperatures (24 to approximately 36°C) and moisture conditions. The moisture conditions varied from that sufficient to maintain green malt weight to that where surface moisture remained on the malt throughout germination. Germination time, temperature, moisture and the three possible pairwise interactions all had a highly significant effect on malt diastatic power, free α-amino nitrogen and extract. Malting loss was highly significantly affected by germination time and moisture and their pair-wise interaction. However, over the range examined, germination temperature had no significant effect on malting loss. In general diastatic power, free α-amino nitrogen, extract, and malting loss all increased with germination time. Germination temperatures of 24° and 28°C were both equally good for the development of diastatic power, free α-amino nitrogen and extract but higher temperatures were progressively worse. Distatic power, free α-amino nitrogen, extract and malting loss were, in general, all increased by high moisture during germination. However, high moisture and a negative effect on diastatic power towards the end of the germination period.     

AMYLOLYSIS OF SORGHUM STARCH AS INFLUENCED BY CULTIVAR,GERMINATION TIME AND GELATINISATION TEMPERATURE

The susceptibility to amylolysis of starches derived from two improved Nigerian sorghum cultivars were evaluated at assay temperatures between 50°C and 75°C. Enhancement of gelatinisation rates at temperatures up to 65°C was not significant inspite of the apparent grain modification due to germination for four days. Greater starch gelatinisation rates (20–22%) were achieved in this study compared to previously reported values, suggesting possible roles for cultivar and malting methods. There was a statistical correlation between starch gelatinisation rates over the temperature range 65°C–75°C and the duration of grain germination (r=0.91 for KSV8 and r=0.5 for SK5912 starches). Gelatinisation rate and temperature were affected significantly by assay pH. The occurrence of two pH related maxima of starch gelatinisation for both cultivera at all temperatures examined indicates the possible presence of two sets of “binding forces” within the starch granules and features of starch retrogradation .     

UNMALTED CEREAL PRODUCTS FOR BEER BREWING. PART I. THE USE OF HIGH PERCENTAGES OF EXTRUDED OR REGULAR CORN STARCH AND SORGHUM

On the basis of results obtained in micro-brews four beers were produced on a 50 litre scale with 50% of the following adjunct materials: debranned sorghum, extruded debranned sorghum, corn starch and extruded corn starch. The extruded materials were processed in an infusion mash while the regular adjuncts were submitted to a preliminary boil, followed by a cooling step (to 45°C) and a subsequent infusion mash. The results indicate a normal fermentation in all cases, no impact of extrusion upon the colloidal stability and the colour of the resulting beers although the saccharification and filtration rates are seriously impaired during the production process inter alia due to the presence of intact starch granules in the extruded products. If these problems could be overcome, it seems perfectly possible to produce beers with high percentages of extruded adjuncts containing no nitrogeneous substances. Indeed, extrusion of debranned sorghum leads to the presence in beer of nitrogen containing compounds (e.g. alkylpyrazines) responsible for highly obnoxious flavours described by a professional taste panel as giving “artificial”, “coffee”, “burnt” or “caramel” odours. These negative flavour characteristics are absent in the beer produced with 50% of extruded corn starch.     

EFFECTS OF AIR REST PERIODS ON MALTING SORGHUM RESPONSE TO FINAL WARM WATER STEEP

The effects off various lengths of air rests on response off malting sorghum main root length, malting loss, diastatic activity, α- and β-amyloytic activity and extract to final warm water steep at 40°C was investigated. Grains were steeped in distilled water for a total of 48 h at 30°C with a 6 h final warm water steep under four different cycles incorporating 1, 2, 3 or 4 h air rest periods. All malt quality properties evaluated were significantly affected by the length of air rest, the cultivar and their pair-wise interactions. Main rootlet length and malting loss reduced progressively as the length of air rest increased. Reducing power, α- and β-amylolytic activity and extract generally increased as the length of air rest was increased for both sorghum cultivars ICSV 400 and KSV 8 examined. The steep cycle incorporating 3 h length of air rest was found by experiment to give the optimum levels of malt quality indices analysed while at the same time causing considerable reduction in average main rootlet length and total malting loss for both grain cultivars.     

DEXTRINS IN SORGHUM BEER

Dextrins containing from 4 to 10 glucose units were determined in sorghum malt, wort and beer by means of HPLC. Throughout a malting period of 10 days approximately 5% fermentable sugars and only trace amounts of dextrins could be detected and the pattern remained constant. During mashing, using maize adjunct and at pH 4, there was a rapid build-up of a wide range of dextrins but their content was greatly reduced during the final stages of mashing. Both sorghum and barley beer contained similar amounts of dextrins containing 4 to 9 glucose units. The majority of these dextrins was branched as their concentration was reduced to a great extent by the action of pullulanase. Dextrins containing more than 10 glucose units were detected and their concentration was also diminished by pullulanase.