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 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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Within This Chapter: Brewers Yeast
- Introduction to Brewers Yeast
- Ale Yeast
- Lager Yeast
- Yeast Life Cycle During the Beer Brewing Process
- Yeast Nutritional Requirements in Brewing Beer
- Yeast Byproducts in Brewing Beer
- Yeast Strain Selection in Brewing Beer
- Pure Culture Maintenance
- Yeast Propagation and Scale-Up
- Culture Contamination
- Yeast Washing
- Yeast Viability and Replacement
- Yeast Storage