Predicting fermentation dynamics of concrete egg fermenters

Background and Aims Concrete egg fermenters are of increasing interest to winemakers interested in expanding the range of sensory properties that emerge during fermentation. Winemakers and concrete egg fermenter vendors have made a priori assumptions about the liquid mixing efficacy and heat transfer in egg fermenters, which have not been explored in the literature. These assumptions were therefore examined using a computational fluid dynamics approach, along with a model for fermentation dynamics, to compare a concrete egg fermenter with a jacketed cylindrical tank typically used for winemaking. Methods and Results The liquid temperature, external concrete surface temperature and sugar concentration in a concrete egg fermenter were monitored, and compared with values predicted from a reactor engineering model designed to simulate the fermentation dynamics of a concrete egg fermenter, to good agreement. Simulated mixing and temperature control were then compared in concrete eggs and cylindrical tanks. Finally, the impact of wall thickness and air velocity on fermentation dynamics was explored, with both variables found to have a significant impact on fermentation temperature and kinetics. Conclusions Superior mixing and temperature control was predicted in the jacketed cylindrical tank with the concrete shell found to function more as an insulator than a heat sink during fermentation. Significance of the Study This work represents the first quantitative exploration of concrete egg fermenters, and in doing so will act as a tool for winemakers interested in using concrete eggs as part of their winemaking practices.