Low alcohol opaque beer quality : influence of malt, mashing conditions and wort dilution

Abstract

Research was carried out to determine the effect of high temperature mashing, use of short time germinated malt and low gravity fermentation on the quality of sorghum beer. The objective was to produce an acceptable low alcohol opaque beer. Mashing at high temperatures of 65-80°C resulted in lower generation of fermentable sugars with the least being obtained at 80°C leading to production of low alcohol. The main reason being that although beta- and alpha- amylase enzymes are inactivated at high temperatures beta-amylase is less temperature resistant than alpha-amylase. Thus the reduction in beta-amylase activity leads to reduction in the amount of fermentable sugar in the wort. The best low alcohol product was produced at 75°C. At 80°C although low alcohol was achieved than at 75°C there was the problem of poor body of the beer. On the other hand malt germinated for shorter period of time produced beers almost as good as those of the control brew. Only malt germinated for one day gave alcohol slightly lower than control. This shows that malt irrespective of having been germinated for 1, 2 or 3 days can produce an excellent product as long as the germination reached required levels during malting process so as to have a malt with sufficient diastatic power. Low gravity fermentation revealed that very low alcohol could be achieved by this method but dilution of wort meant also dilution of other beer characteristics resulting in a product which was watery and had no flavour. The major effect of diluting wort was that the content of fermentable sugars was reduced proportionally. However, the product of a 30% dilution was still acceptable since although alcohol was low, texture and flavour of the product were still reasonable. Thus mashing at 75°C, use of malt germinated for one day and method of 30% dilution can be recommended for the production of low alcohol opaque beers.