Modulation of steeping conditions influence the diastatic enzymes and protein profile in pearl millet malt

Adejoke Naomi KOLAWOLE, Ikoojo Blessing EBILOMA

Abstract


Malting is targeted at getting the optimum point of enzymatic induction without losing much energy during the embryo metabolism and growth. Successful production of malt includes production of various hydrolytic enzymes and controlled degradation of the grain endosperm structure. Attention is at the centre stage of using Pearl millet as a substitute for barley, wheat and sorghum due to the cost of importation of barley and wheat to tropical countries. This study seeks to understand the effect of different steeping conditions with respect to varying pH, temperature and time on key enzymes associated with malting processes. Activities of α-amylase, β-amylase, β-glucanase, β-glucan content, protein profiles were monitored with respect to the varying steeping conditons. There was a steady increase (from 0 to 96 h) in the α-amylase activity at 30ᵒC under all the pH stress conditions with the exception of acidic pH malted pearl millet where the enzyme activity decreased from 191.04 ± 1.5 U/g to 142.50 ± 2.20 U/g between the 72nd and 96th hour. Optimal activity (248.04 ± 0.20 U/g) was observed at 96 h for alkaline pH steeped pearl grains germinated at 30 ᵒC. However activity decreases as germination days prolong. Optimal activity was recorded at the 96th hour for malted pearl millet grains subjected to alkaline stress (2.73 ± 0.20 U/g) as compared with the control. β-glucanase activities of the malted pearl millet grains were high especially under the 30 ᵒC heat stress. Peak activity was observed at the 96th hour for the pearl millet grains subjected to alkaline pH stress (892.34 ± 0.20 U/kg). β-glucan content under the alkaline pH stress, acidic pH stress and control conditions at 30 ᵒC were within the same range of approximately 4-8 % w/w malt flour.

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