Effect of malting and brewing processes on the microorganisms associated with sorghum grains and malt.

Ilori, M.O., Fessehatzion, B., Olajuyigbe, O.A., Babalola, G.O. and Ogundiwin, J.O.

Abstract
In Nigeria, as in other tropical countries where the use of traditional European brewing ingredients, which cannot be produced locally, has been abandoned because of the excessive cost of importation, local cereals, especially sorghum, are used in both raw and malted form as substitutes for barley malt. Like barley, sorghum can be infected by a variety of microorganisms, some of which are potentially harmful if they or their metabolic products find their way into beer. The microorganism populations of grain from two Nigerian malting sorghum varieties were cultured, the individual genera and species identified and their respective fates during malting and brewing studied. Of the 9 bacteria and 7 mould fungi found, all survived malting but were killed off by wort boiling, although fresh contamination with some of the species concerned was found in unpasteurised beers. The authors therefore recommend that sorghum grain be treated to reduce the microbiological contamination rate before malting. A tropical plant, known as "bitter leaf" and regarded as a potential substitute for hops, was studied in relation to possible adverse effects on brewers' yeast during fermentation, but no such effects were found to occur.
Keywords : bacteria brewing contamination fungi malting mould sorghum