Effects of Vessel Geometry, Fermenting Volume and Yeast Repitching on Fermenting Beer

This paper statistically examines the effect of tank shape and size, fermenting volume and yeast pitching number on fermentation parameters routinely monitored in a series of industrial fermentations. With the fermenter tanks employed in this pilot study, little effect of tank shape existed between any of the parameters. The number of brews fermented or fermenting volume had a significant difference (p<0.05) on the apparent extract at 48 h, the final pH and the apparent degree of fermentation (ADF). Interestingly, the number of yeast repitchings (up to 13) did not show any effect on any of the parameters. We conclude, as have other studies, that the automatic practise of discarding the yeast crop after 10 fermentations (and the related expense of early yeast repropagation) could be questioned and is worthy of further study.