Enhancing yeast alcohol production during red sorghum (Sorghum bicolor L. Moench) wort fermentation

Abstract

The fermentation of sorghum wort is one of the fundamental steps that determine the quality of this beer. It is influenced by several parameters, among others: temperature, pH, sugar content, amino acid profile, phenolic compound content, and redox potential. Controlling these parameters will therefore make it possible to optimize the production of alcohol and the growth of the yeast during fermentation. The aim of this work is to show that the extraction of polyphenols, the main inhibitors of sorghum enzyme activity, prior to malting increases enzyme activity in the malt, thereby producing high levels of reducing sugars. This is reflected in the high alcohol content at the end of the fermentation process. Three parameters were considered in this work, namely: The polyphenol content in the grain (Discolored and non-discolored sorghum), temperature (12 and 25 °C) and fermentation time (in hours). The choice of fermentation temperature was made depending on the specific characteristics of the yeast used and taking into account the range used by artisan breweries producing sorghum beer in DR Congo. These breweries ferment their beers at room temperature. The results obtained give a better alcohol content of 7.53% for the E1T1 sample (Discolored sorghum, fermentation at 12 °C). The comparison of the results confirms that the extraction of the phenolic compounds before malting as well as the fermentation temperature had a significant effect on the production of alcohol and the growth of the yeast. The results of this work open the door to many other studies to provide to the industrial and artisanal brewers with scientific data that will allow them to better integrate red sorghum malt as raw material into brewing.