21 June 2017

Possibilities for Optimising Wort Preparation – Part 3

The third part of this series of articles addresses the question in greater detail of the best process for driving off DMS from wort. Part 2 described that external boiling permits better re-formation than kettle boiling and that, in return, kettle boiling achieves superior evaporation. These processes, having opposite effects, were calculated independently. In this article, the question of which system is superior is examined, when jointly and simultaneously investigating evaporation and hot holding.

nd proved in many articles that formation of DMS in the brewhouse can be calculated [1-4]. These considerations thus form the basis for mapping and comparing processes. Comparisons are subsequently calculated both for external and kettle boiling. For the sake of simplicity, it is assumed that both boiling methods are the same or are similar in terms of wort volume, wort composition, energy input and boiling times. Wort circulation rate, also referred to as wort flow or pumping rate, through the external boiler is the only variable in the calculations below. Why should this parameter be investigated and what can be its influence, if any?

Influence of Circulation Rate

The volume of the circulation rate is important [1]. On the assumption that the external boiler is operated with constant heat input, the circulation rate determines temperature in the boiler. When a high wort volume flow is circulated, temperature in the boiler will be almost 100 °C. When a very low wort volume flow is circulated, temperature will be elevated reaching 101 to 106 °C in the boiler. As a result of a low volume flow, heat supplied from the heating steam is given off to a low wort volume. As a consequence, temperature in the boiler will be considerably higher. In contrast, a very high wort volume flow will lower temperature quite considerably as heat is given off to a larger volume. Varying circulation rate thus results in changes in boiler temperature and, hence, in differences in wort treatment.