Quality Assessment of a Sorghum Variety Malted Commercially under Tropical Conditions and Controlled Tropical Temperatures in the Laboratory

Abstract

A sorghum variety was supplied as commercial malt and as an unmalted cereal by a maltster. The commercial sample had been malted in a tropical country. Sub-samples of the unmalted cereal were malted in the laboratory under controlled germination temperatures of 28°C and 30°C. Laboratory and commercially malted sorghum were studied for their brewing qualities. The α-amylase development in sorghum malt was enhanced when germination was carried out at the higher temperature of 30°C rather than at 28°C. Hot water extract (HWE) was more variable. With infusion mashing, results showed a significant difference for germination time (3–6 days), but no significant difference relating to germination temperature. With the decantation mashing method the reverse was observed. The low numerical values of HWE obtained from sorghum malt in the infusion mashing process confirmed that this process is not suitable to produce optimal extract development from malted sorghum. The 28°C germinated sorghum released more FAN products into the worts than the 30°C malt, using both the infusion and decantation methods. With regard to the parameters tested, commercially malted sorghum gave lower analytical values than laboratory malted sorghum. It was also observed that variations in malting temperatures and mashing processes can cause unexpected variations in the analyses of sorghum malt. These findings suggest that careful process control is required during the malting and mashing of sorghum.