The effect of germination time on malt quality of six sorghum (Sorghum bicolor) varieties grown at Melkassa, Ethiopia

Abstract

The effect of germination time (48, 96 and 144 h) on malt quality of six sorghum varieties was investigated to determine the potential of grain sorghum cultivars in the local brewery industry. Six sorghum varieties (Gambella 1107, Macia, Meko, Red-Swazi, Teshale and 76 T1#23) were evaluated in a randomized complete block design with three replications. The results showed that both germination time and variety had a significant effect (p ≤ 0.05) on sorghum malt quality. The hectolitre weight (kg hL À1 at 12.5% moisture), germination energy (%), crude protein (%) and flour starch amylose content (%) were: 75. 8-82.9, 96-99, 7.0 À 11.9 and 16.0 À 23.0, respectively. The sorghum malt diastatic power (DP, L), free amino nitrogen (FAN, mg L À1 ), hot water extract (HWE, %) and malting loss (%) were: 18.96 À 31. 39, 185.67 À 343.29, 41.85 À 85.08 and 8.68 À 27.56, respectively. Malting loss, HWE and FAN increased with germination time. The DP increased as the germination duration increased from 48 to 96 h, but the difference between 96 and 144 h was not significant. Considering the excessive malting loss and marginal increase in HWE beyond 96 h, this study suggests that the optimum malting duration would be around 96 h. Among the varieties tested, Teshale and Gambella 1107 produced the better malt quality. Copyright © 2012 The Institute of Brewing & Distilling Keywords: diastatic power; extract; fan; germination; sorghum malt IntroductionSorghum evolved in semi-arid tropical Africa where it is still used as a major food grain, and it remains one of the most important cereal crops grown in arid and semi-arid parts of the world. In Eastern Africa, more than 70% of the sorghum crop is cultivated in the dry and hot lowlands, where serious water deficits prevail (1). In Ethiopia, sorghum is grown in diverse agro-ecologies, but it is predominantly cultivated in the dry lowland areas that account for nearly 66% of the country (2). Sorghum is one of the major staple crops, serving as the major source of energy and protein for millions of people (3).In Ethiopia and elsewhere, barley is the preferred grain for malting in modern brewing industries. However, intensive cultivation of barley in tropical areas, including Ethiopia, is limited. Most of the cultivated areas in Ethiopia are characterized by a warm and dry climate and are not suitable for barley production. Pockets of areas in the highlands where barley is normally grown have frequently suffered from infestations by biotic agents that have limited the production of this crop (4). As a result, local brewery industries have increased the import of malt barley and at present 67% of the barley used by local breweries is imported (5). This trend has negative consequences, not only in that it competes for the meager national foreign currency earnings, but also in the inability to utilize locally available alternative sources. Sorghum is increasingly becoming popular for lager beer production (6,7). In Ethiopia, sorghum is the third most widely grown cereal after tef and maize, ...

Grain and malt quality properties of some improved Nigerian sorghum varieties

“…The malting losses reported here (Table ), with values of >30% in some cases (White Kaura, SK5912 and Nafelen 6 ), agree with similar findings in respect to sorghum . Malting losses in sorghum grains are measures of the losses recorded as a result of metabolic processes associated with grain germination, which manifests in rootlet and plumule growth and development .…”

“…However, the FAN values were mostly lower than those previously obtained by Ezeogu and Okolo and Bekele et al . . Seasonal variations in raw materials owing to a multiplicity of reasons – environmental, varietal changes, pest infestation and even factors that can be ascribed to humans, and also differences in grist composition – could be responsible for some of these differences .…”

Suitability of the Weibull four-parameters model to predict the induction phase ofα-amylase production during red sorghum malting when a steep in dilute NaOH is used prior to a re-steep in aBacillus subtilis-S499 based treatment

“…Malt enzymes activities during the sorghum malting process may be affected by several factors, including the following: the nature of the steeping liquor ; the steeping temperature and time; aeration during steeping ; the final warm water steep and air rest cycles ; the steep‐out moisture ; the use of microbial starters such as lactic acid bacteria and yeasts , and B . subtilis ; germination temperature ; and germination time . Therefore, in this study the following steeping conditions were set: aeration, temperature, time and nature of the steeping solution for the initial 8 h steeping.…”

Variety and germination time effect on total β-glucan, water-insoluble β-glucan, water-soluble β-glucan components and β-glucanase levels in improved sorghum varieties SK5912, KSV8 and ICSV400 before and after malting and their relationships to wort visco

“…The size index has been reported to correlate significantly with germination energy and capacity . Similarly, diastatic power (up to a germination duration of 96 h), free amino nitrogen, hot water extract and malting loss have also been reported to increase with increasing time of germination .…”

“…These structural and NSPs are linear homopolymers of β ‐ d ‐glucopyranosyl residues linked mostly via two or three consecutive β ‐ linkages that are separated by a single β ‐ linkage . The β ‐glucans have been associated with increased wort viscosity, poor filtration performance, impaired pumping, reduced extract yield and gelatinous precipitates in matured beer, resulting in chill haze and poor shelf .…”