No abstract

Enzymic breakdown of endosperm proteins of sorghum was more effective at 20°C than at 25°C and 30°C, as regards total protein solubilization, a-amino nitrogen and peptide production. Although the embryos (axes and scutella), of the three temperature treatments contained similar quantities of protein, it appeared that less proteins, in terms of amino acids and peptides, were transferred to the roots during malting at 30°C than at 25°C and 20°C. During mashing, higher levels of peptides but lower levels of a-amino nitrogen and total soluble nitrogen were released in an infusion mash at 65°C than in a decantation mash where enzymically active wort was decanted and used to mash gelatinized sorghum starch at 65°C. Although more of the maltose-producing enzyme-p-amylase was found in sorghum malts made at 25°C and 30°C than at 20°C, it would seem that, for sorghum, malting temperature of 20°C to 25°C were optimal as regards protein breakdown during malting. The protein breakdown produced when sorghum is malted at 20°C is comparable to that found in barley malt and should support similar levels of adjuncts and yeast growth during brewing.

No abstract

The endosperm cell walls of barley are degraded extensively during malting whilst those of sorghum are not. Malting barley produced endo-β-1,3:1,4-glucanase, endo-β-1,3-glucanase and pentosanase in large quantities. In contrast, malting sorghum developed mainly endo-β-1,3-glucanase and pentosanase. Although the limited break-down of the endosperm cell walls of sorghum may reflect sub-optimal activities of β-glucanases, such as endo-β-1,3:1,4-glucanases, it is possible that the highly intractable nature of the cell walls and their high protein content (approx. 60%) may contribute to the low susceptibility of sorghum endosperm cell walls to enzymic degradation during malting.

No abstract

Four sorghum varieties (SK 5912, KSV 4, KSV 8, ICSV 400) were malted and extracted under similar conditions to assess their quality for brewing. The results showed that, in general, the sorghum varieties had high malting loss which was attributed to the high germination temperature used. The sorghum varieties also developed low levels of amylolytic activity (␣-amylase and ␤-amylase), and with similar ratios. When the sorghum malts were mashed at different temperatures with the aid of commercial enzyme preparations, it was observed that mashing temperatures were more important in sugar release than additions of commercial enzymes. This was because at the lower mashing temperature, sorghum starch was not adequately gelatinised. However, when commercial enzyme preparations were added, low levels of enzymes were very effective in reducing wort viscosity and producing free amino nitrogen (FAN). Although, both commercial enzyme preparation and mashing temperature influenced sugar production, the malts produced glucose and maltose at similar ratios. Therefore good quality malts can be produced from sorghum, however mashing will employ commercial enzymes and mashing regimes are not yet optimised.

Nitrogen analyses of the grains of samples of commercial malts indicate that fi-glucan breakdown and the uniformity of malt modification are influenced by uniformity of distribution of grain protein. It is proposed that for normal malting barley, variations in malt modification are related to the different percentages of grains which contain high levels and different types of proteins which resist enzymic modification during malting. This kind of inhomogeneity of malt modification can cause brewhouse problems but cannot be detected with precision by standard malt analyses.

The malting characteristics of high and low nitrogen barleys were compared. Results confirmed that low nitrogen facilitates malting rate and extract development. Modification rate was not related to (3-glucan content. In general, these low nitrogen barleys and high nitrogen barleys had similar levels of a-amylase but high nitrogen barleys tend to have higher levels of fi-amylase.Since barleys of similar nitrogens had different levels of a-amylase and p-amylase, nitrogen may not be a reliable indicator of the potential of the grain to develop amylolytic enzymes.