Effect of Germination Time, Temperature and Moisture on Malting of Sorghum

Abstract

The effect of germination conditions on sorghum malt quality and malting loss was studied by germinat ing sorghum for different periods of time up to 6 days over a range of temperatures (24 to approximately 36°C) and moisture conditions. The moistureconditions varied fromthatsufficientto 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 a-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 a-amino nitrogen, extract, and malting loss all increased with germination time. Germination tempera tures of 24°and 28°C were both equally good for the development of diastatic power, free a-amino nitrogen and extract but higher temperatures were progressively worse. Distatic power, free a-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.Key words: Sorghum, malting, diastatic power, free amino nitrogen, extract, malting loss. IntroductionMalted sorghum {Sorghum bicolor (L.) Moench) is used in the brewing of the traditional alcoholic beverage of Southern Africa, known as sorghum beer.13'14 In sorghum beer brewing, unlike lager brewing, diastatic power is a much more important criterion of malt quality than extract.10 This is because the diastatic power of sorghum malt is intrinsically rather low14 and because the malt has to act on twice its own weight of starchy adjunct during mash ing.12'14 Another important parameter of malt quality in sorghum beer brewing is free a-amino nitrogen content. This is again due to the fact that the relative percentage of malt in the mash is low. Furthermore-, sorghum malt pro duces only a small additional amount of free a-amino nitro gen during mashing19 and the starchy adjunct (maize grits or sorghum grain1 ) contributes very little to the final free a-amino nitrogen content of the wort.6Recently, there has been some interest in the feasibility of using malted sorghum for the brewing of lager becr.8>15i '7 This topic is of interest to brewers in countries where the climate is suitable for the cultivation of sorghum but not barley.l>Sl17 However, Nout and Davies8 considered that sorghum malt was not even adequate as an extender for barley malt, because of its low extract and poor filterability.Research into the effects of malting conditions on the quality of sorghum malt has been limited.7*10'1'116 Their effects on free a-amino nitrogen content having until now received no attention whatsoever. This paper describes an investigation into the effect of germination time, tempera ture and moisture on the developme...

Effect of Malting Conditions on Pearl Millet Malt Quality

“…These findings are in agreement with those of other authors working with sorghum 12,13,14,15,17,18,20,22 and millets 13,14,20,26 . Recently, Muoria and Bechtel 13 suggested that a germination temperature > 22°C would be more desirable for sorghum and pearl millet, than for barley, in order to obtain higher values of α-amylase.…”

“…The pearl millet malt DP values found in this research work are generally similar to those found by Gomez et al 6 for pearl millet and slightly lower than those found by Morrall et al 12 for sorghum. The effects of germination time, temperature and variety on α-amylase activity are shown in Figure 3.…”

“…Where stated, these were separated from the pearl millet malt kernels by rubbing the grain in a nylon bag of coarse mesh size, which allowed the roots and shoots to escape while retaining the kernels, as described by Morrall et al 12 The weights of roots and shoots are expressed as a percentage of the total weight.…”

Purification and Some Properties of a Protease from Sorghum Malt Variety KSV8-11

“…A 200 g aliquot of the grains was surface-sterilized by immersion for 40 min in sodium hypochlorite solution having 1.0% (v/v) available chlorine, washed repeatedly in tap water and malted as described by Morrall et al 21 .…”

Modification of the Methods for the Extraction of Carboxypeptidase and Proteinase Activities from Sorghum Malts

“…Thereafter, sorted samples, in triplicate of 200 g batches, were surface-sterilized by immersion for 40 min in sodium hypochlorite solution having 1% (v/v) available chlorine. Subsequently, the grains were drained and washed four times in tap water as described by Morrall et al 32 .…”