Effect of Mashing Regime on Fermentability of Malted Sorghum

Abstract

The use of sorghum malt in fermentability studies is scarce. This study was carried out to investigate the fermentability potential of sorghum malt. The sorghum variety used in this study was malted commercially in a tropical country and in the laboratory at 28�C. Infusion mashing was poor in obtaining extractable materials from both commercially and laboratory malted sorghum. Conversely, the difference in total soluble nitrogen (TSN) results obtained when sorghum malt was mashed using either the infusion or decantation method was marginal between the two mashing systems. Also, production of free amino nitrogen (FAN) from the TSN released when both mashing systems were used to extract sorghum malt was similar. Fermentability results obtained from sorghum malt were more complex and difficult to understand and interpret. A similar correlation was also found between low predicted spirit yield (LPSY) obtained from infusion-mashed sorghum malt versus higher predicted spirit yield (HPSY) obtained from decantation-mashed sorghum malt. Furthermore, when correlation analysis was performed between HFE obtained from decantation-mashed sorghum malt versus HPSY obtained from decantation-mashed sorghum malt, the result was also similar to that found when similar correlation analysis was performed between LFE obtained from infusion-mashed sorghum malt versus LPSY obtained from infusion-mashed sorghum malt. While these correlation results clearly show that fermentable extracts are strongly linked to predicted spirit yield (PSY) obtained from malted sorghum can also give misleading information. A researcher working on sorghum malt but using the standard infusion mashing method developed to extract well-modified barley malt would erroneously tend to conclude that the infusion method was as effective as decantation mashing in extracting materials from sorghum malt. This highlights the importance of development and use of suitable analytical methods for sorghum and malt. Notwithstanding, the results of this study show that sorghum malt can produce good PSY results, but like other cereals, suitable sorghum variety, adequate malting and mashing conditions are pre-requisites.