HEAT SENSITIVITY, OPTIMUM pH AND CHANGES IN ACTIVITY OF SORGHUM PEROXIDASE DURING MALTING AND MASHING

Abstract

Peroxidase activity was demonstrated in dry and germinating sorghum seeds. The specific activity increased about 14-fold during malting for a 96-hour period. On the average about 41% of peroxidase activity was located in the endosperm, and the remaining 56% in the acrospire and rootlet of sorghum malt. The crude enzyme extract retained 77%, 17.5% and 7.6% of activity after heating at 60°, 70°and 80°C, respectively. More than 50% of the peroxidase activity in the finished malt survived mashing at 65°C. Optimum activity was recorded at pH 5.5 which falls within the observed pH range of sorghum worts. The level of residual peroxidase activity in the wort differed with sorghum species.

Changes in catalase activities during malting of some improved Nigerian sorghum grain varieties

“…In this work we demonstrated the presence and relative incidence of the antioxidant enzyme catalase in ten improved sorghum grains at the different malting and brewing stages of steeping and germination. Several workers have demonstrated the presence of catalase and many other antioxidant enzymes such as peroxidases and superoxide dismutase in many important industrial and brewery cereals (Kruger, 1977;Nwanguma and Eze, 1995;Bakalova et al, 2004;Dicko et al, 2006;Ishibashi et al, 2008). As a rule, these important antioxidant enzymes play such vital roles as combating the many excesses caused by free oxygen radical usually generated during the many metabolic activities of these plants or other organisms concerned, by reducing the energy of free radical groups.…”

“…Not surprisingly therefore, biological systems protect themselves against these deleterious oxygen free radicals using the above-mentioned scavenging enzymes: superoxide dismutase, peroxidase and catalase. The occurrence of these critical enzymes has been indicated in important brewery and allied industrial grains as wheat, barley and sorghum (Kruger, 1977;Nwanguma and Eze, 1995;Bakalova et al, 2004;Dicko et al, 2006;Ishibashi et al, 2008). Additionally, these enzymes are known to influence important brewing properties such as lipid peroxidation and flavour instability among others (Nwanguma and Eze, 1995;Bamforth, 2009).…”

“…The occurrence of these critical enzymes has been indicated in important brewery and allied industrial grains as wheat, barley and sorghum (Kruger, 1977;Nwanguma and Eze, 1995;Bakalova et al, 2004;Dicko et al, 2006;Ishibashi et al, 2008). Additionally, these enzymes are known to influence important brewing properties such as lipid peroxidation and flavour instability among others (Nwanguma and Eze, 1995;Bamforth, 2009). The cereal we are concerned with in the present work is sorghum, the the fifth most important cereal in total world production, after wheat, rice, corn and barley (Wong et al 2009;USDA, 2011).…”

“…Different workers had tried to determine the course of these enzymes at the different stages of brewing with sorghum (Nwanguma and Eze, 1995;Dicko et al, 2002;Nnamchi et al, 2013). Unfortunately, the quest for the role of these antioxidant enzymes in malting and breweryrelated works have been mostly restricted to works with peroxidase.…”

Effects of germination on the activities of amylases and phenolic enzymes in sorghum varieties grouped according to food end‐use properties

“…1,2 These germination-related properties are dependent on the sorghum variety. 3,4 Among the important reasons for germinating sorghum is the activation of starch-degrading enzymes. During sorghum germination, α-amylase (α-1,4-D-glucan 4-glucanohydrolase, EC 3.2.1.1) isoenzymes are de novo synthesised, 5 whereas β-amylase (α-1,4-D-glucan maltohydrolase, E.C 3.2.1.2) isoenzymes may not be synthesised.…”