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

Abstract

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.

Grain and malt quality properties of some improved Nigerian sorghum varieties

“…Glennie‐Holmes also refers to CWE as extracts formed in malts when enzyme activities have been inhibited. Values for CWE obtained here do not differ much from those previously reported for some species of sorghum , but they are slightly lower than those reported by Ogu et al . .…”

“…One key consideration among grains is size: bigger grains or kernels are often preferred because they contain proportionately less husk and therefore a higher starch content than smaller ones . The largest grains were SK5912 and KSV 8, which have been proven to have other important germinative and grain qualities in abundance . Indeed these two sorghum varieties, together with the smaller‐sized ICSV 400, have in several previous studies carried out in our laboratory shown tremendous proficiency in malting and brewery‐related capacities .…”

“…Several authors have shown how these different grain properties can satisfy both food and non-food purposes (19)(20)(21). Of particular importance is the evaluation of the malting and brewing qualities of the sorghum varieties (9,11,(22)(23)(24)(25)(26)(27)(28)(29). Extensive pioneer and follow-up research studies have resulted in the successful use of sorghum malt in the brewing of continental beers in Nigeria and other countries, including Mexico, Cuba, Israel, the USA and South Africa (30).…”

Bioconversion of degraded husked sorghum grains to ethanol

“…These results are similar to observed ethanol concentration of 379 L/t for KSV3 substrate reported in this study. However, previous studies have reported a favourable ethanol yield of 460-490 L/t with clean, sound and malted sorghum grains [8,[34][35][36][37], which are higher values than those reported here for de-husked and un-malted KSV8 sorghum grain (421 L/t).…”

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

“…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 .…”