Chapter 4

Brewers Yeast

Yeast Culture Contamination

It frequently happens that brewing yeasts carry a persistent low level of contaminants such as Obesumbacterium proteus, acetic acid bacteria, and slow-growing Torula-type yeasts. These organisms are generally regarded as harmless because their numbers never reach a point where they are likely to have adverse effects on the beer. On the other hand, L. pastorianus, Z. anaerobia, and S. carlsbergensis are strains considered harmful at low levels.

Microscopic Examination

Microscopic examination of the yeast culture can be useful in assessing the overall health of the population. Abnormal-looking or irregularly shaped yeast cells are signs of cell stress, possibly indicating potential problems with wort composition, aeration, poor yeast handling, or fermentation conditions. Microscopic examination is also useful in detecting extraneous particles such as diatomaceous earth, trub, grain particles, etc. that may interfere with proper yeast performance.

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