At the completion of fermentation, yeast is recovered either for disposal (commonly to animal feed or production of yeast extracts) or for repitching. For open fermenters, ale yeast is skimmed from the surface of the vessel, but for closed cylindroconical vessels the yeast is harvested from the cone. The population of yeast
cells differs in the cone, with stratification such that older cells are located beneath the younger, more vital ones.
Harvested yeast may either be pumped to the next fermenterfilling with fresh wort (cone-to-cone pitching) or stored in either a pressed or slurry form. It may receive acid washing to kill any bacteria that may have developed in the slurry. Its collection from fermenters is often through the use of centrifuges, creating damage that has implications for subsequent performance. The impact of serial repitching was addressed by Jenkins et al,who showed that extents of deterioration vary between yeast cells.