Home Education Brewing Microbiology Current Research, Omics and Microbial Ecology
Consequences of failure
Propagation of brewery yeast sets the tone of subsequent fermentations generation by generation. The ‘traditional' propagation approach is without focus on cell yield. The addition of oxygen to the propagator via the periodic bubbling of air via a ‘lance' achieved little if any gas transfer so that propagation was effectively anaerobic. Yields were poor (ca 50 x 106/ml) and little attempt was made to match the required yeast pitching rate. At best the fermentation vessel would be partly filled and then topped up some days later with fresh wort. Typically, the performance of such yeast would be woeful, such that the fermentation charts tracking gravity fall would extend from the usual single page to two or even three pages. Such extended fermentations result in poor-quality yeast of compromised viability. On pitching on, this extends fermentation vessel cycle times, and at best a number of fermentation generations are required before the yeast achieves the required and repeatable cycle times and associated product quality.
The above is the readily visual ‘tip of the iceberg'. Cutting corners in terms of hygiene or step-up volumes can add further woe in terms of product
Table 3.3 Yeast propagation from laboratory to the brewery
quality and consistency, which is potentially amplified further with successive generations of use.
|< Prev||CONTENTS||Next >|