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

Abstract

The effects of two extractants on the activities of carboxypeptidase and proteinase enzymes from three sorghum varieties germinated for 3 and 5 days were studied. In all three varieties, cysteine hydrochloride (Cyst. HCl) proved a better extractant than 2-mercaptoethanol (2-ME) as shown by the increase in carboxypeptidase and proteinase activities with 5-day malts. A three-way analysis of variance (ANOVA) on the effect of germination time, extractant and variety on the carboxypeptidase activities of the three malts showed that all the factors plus their possible fourway interactions highly significantly (P < 0.001) affected the extractability/activity of the enzyme. However, while the three factors had a highly significant (P < 0.001) effect on the proteinase activity, one of their four-way interactions, specifically, extractant/variety, had no significant effect. This suggests that, unlike the carboxypeptidase enzyme, the effectiveness of the extractants in enhancing the extractability/activity of the proteinase enzyme in all the sorghum malt samples was amongst other factors, not variety-dependent.

125thAnniversary Review: The science of the tropical cereals sorghum, maize and rice in relation to lager beer brewing

“…Both the metallo‐ and cysteine‐type proteases have been purified from sorghum malt. The sorghum malt proteases, like those of barley malt, are insoluble in simple aqueous solvents . This presumably means that enzymatic sorghum malt extracts, as have been proposed in lager brewing , would be very deficient in protease activity.…”

“…Such prolyl carboxypeptidases have been found in germinated barley (141) and there are indications that that they are present in maize, rice and sorghum (60). It has also been shown that there is carboxypeptidase activity in sorghum malt at brewing type acidic pH (138,139) and importantly that the activity releases FAN from endopeptidase hydrolysed kafirin prolamin (139). Unlike the situation with endoprotease activity, carboxypeptidase activity in sorghum was found to increase substantially during malting (139).…”

Changes in Sorghum Malt During Storage

“…To improve the utilization of sorghum in beer brewing, a lot of studies have been carried out. Such studies however were limited to morphology and ultra-structure 2,8,9 , enzyme development and extraction 4,6,14,15 as well as mashing features 1,16,19 . The changes that develop during storage of sorghum have largely been overlooked.…”

Effect of Experimental Variables on the Malting Performance of Nigerian Maize Oba Super 2 Variety

“…Six hundred (600) grammes of the grain sample was cleaned to remove broken kernels, foreign matter and washed several times in tap. The sample was surface sterilized by immersion for 40 minutes in sodium hypochlorite (NaOCl) solution having 1% (v/v) available chlorine to check microbial contamination and washed several times in tap water [19].…”