Optimization of Malting Conditions of Sorghum (Sorghum bicolor)

Abstract

A study was carried out to known about the effects of malting on physical, chemical and functional properties of sorghum. Design expert (Central composite rotatable design) was used to design the experiment for different temperature (20-30°C), relative humidity (70-95%) and time (3-6 days) for germination period for all three factors. Grains were steeped for 24 h at 28°C, at last grains were dipped in KMS solution for 10 min to prevent the mold growth during germination. After steeping the grains were germinated for pre-determined malting condition. Then, the germinated grains were dried in cabinet dryer at 50°C for 24 h to obtain desired moisture content. The dried malt samples were then taken for analysis. Analysis of physical, chemical and functional properties of both grain and malt samples were performed and malting condition was optimized on the basis of reducing sugar, starch content and amylase activity. The 1000 kernel wt., bulk density and particle density were found to decrease after malting from 29.91 g to 18.52 g, 82.33 kg/HL to 66 kg/HL and 1.23 g/ml to 0.94 g/ml respectively. While porosity of grain varies after malting from 0.26 to 0.35. Protein, starch, crude fiber, crude fat and moisture content were found to decrease after malting from 12.8% to 10.05%, 69.77% to 51.16%, 1.13% to 0.95%, 4.71% to 2.25% and 10.37% to 6.93% respectively. While Ash content, reducing sugar and amylase activity were increased after malting from 1.45% to 2.96%, 1.04% to 5.14% and 0.00193 mg/g sample/15 min to 41.33 mg/g sample/ 15 min. The water absorption capacity, foam stability and swelling power increased after malting from 1.22 g/g sample to 1.80 g/g sample, 10.39% to 18% and 0.87 g/g sample to 3.08 g/g sample respectively while gelatinization concentration decreased after malting from 12% to 6%. Optimization of malting condition was carried out on the basis of amylase activity, reducing sugar and starch content by keeping maximum reducing sugar and amylase activity and minimum starch content. The optimum malting condition was found as 20°C, 95% RH for 5 days.