The malting parameters: steeping, germination, withering, and kilning temperature and aeration rate as possibilities for styrene mitigation in wheat beer

Aiming at the mitigation of the toxicologically relevant styrene formed during wheat beer brewing, different malting parameters, such as steeping temperature, germination temperature, withering and kilning temperatures applied during kiln-drying, and aeration rate, were evaluated for their suitability to reduce the content of cinnamic acid, the precursor of styrene, in malts of barley and wheat, responsible for the input of the undesired precursor into the brewing process. According to the results of the present study, higher steeping temperatures, higher germination temperatures, lower aeration rates, and lower withering temperatures during malting are beneficial for the overall reduction of cinnamic acid in wort produced with barley and wheat malts. Thereby, the withering temperature showed the highest impact among the investigated parameters, able to reduce the soluble cinnamic acid content in wort by up to 72%, followed by the germination temperature in combination with the aeration rate and the steeping temperature with reduction capacities of 52 and 16%, respectively. Additionally, a kilning temperature of 200 °C led to the absence of enzyme activities in dark malts, which might also be the main reason for the low phenolic acid contents found in the corresponding wort, finally causing the low concentrations of styrene but also to a certain extent of desired vinyl aromatics in dark wheat beers.