Effect of alkaline steep and air-rest cycle on the development of sorghum peroxidase activity during malting

Thesis Abstract

The effect of alkaline steep and air-rest cycle on the development of peroxidase activity during malting was investigated in sorghum variety, KSV8. Preliminary experiment showed that alkaline steep (test) and the distilled water steep (control) had germinative energy of 92± 2.87 % and 89± 0.57 % respectively. In regime II (sorghum grains steeped in distilled water for 24h), both the test experiment and the control had germinative energy of 95± 1.41 %. Germignative capacity was high in both regimes. The two regimes were not water sensitive, however malting loss were high in alkaline (20.1± 0.93 %) and in distilled water steep (20.0± 1.28 %).Malting loss for distilled water in regime II (sorghum grains steeped in distilled water for 24h) was 5.6± 1.28 % and it is relatively comparable to that of barley. Malting loss was also high in distilled water steep (control) (15.84± 0.19 %). From the results, there was an appreciable increase in peroxidase activity from day 1 through day 3 of germination for distilled water steep in regime I (control) when compared to the test with regression in peroxidase activity. There was a positive gradual increase in peroxidase activity influence by air-rest cycle from day 1 through day 3 in regime II (distilled water steep for 24h). At the end of kilning at 60 ͦ C for 7 h, peroxidase activity dropped sharply in both regimes. Consequently, the introduction of air-rest cycle as malting condition will be beneficiary to brewers. It reduces malting loss associated with sorghum beers, increases the germinative energy and the defensive role of peroxidase against lipid peroxidation during malting. Conversely, the alkaline steep with final warm steep had an inhibitory effect on the development of peroxidase during malting.