A Comparison of White Nigerian and Red Italian Sorghum (Sorghum Bicolor) as Brewing Adjuncts Based on Optimized Enzyme Additions

Abstract

Sorghum has been used for thousands of years in human food products. In Western countries, however, it is primarily used as bird and animal feed, although there is considerable interest in its use as gluten-free alternative to wheat, barley, and rye. The aim of this study was to compare the mashing performance of white Nigerian and red Italian sorghum based on optimized enzyme additions. For this purpose, both sorghum types were fully characterized using standard methods, Lab-on-a-Chip capillary electrophoresis, and scanning electron microscopy. The application of exogenous enzymes was optimized by monitoring changes in mash consistency during mashing using a Physica MCR rheometer. Furthermore, laboratory-scale mashing trials were carried out to compare the quality of worts produced with up to 40% white or red sorghum and optimized enzyme levels. Both sorghum types are characterized by higher starch and lower protein/β-glucan contents in comparison to barley malt. The addition of protease/β-glucanase as recommended had no significant effect on mash consistency and wort quality. Besides, 50% of the recommended heat-stable α-amylase dose was sufficient for 40% sorghum adjunct. Worts produced with 40% white or red sorghum had significantly lower TSN/FAN contents and viscosities than the reference wort (100% barley malt). However, white sorghum provided significantly more TSN/FAN compared to red sorghum. Its use as a substitute for barley malt also resulted in significantly higher extract contents.