Fermentation Symposium—Part II Yeast Handling Studies. II. Temperature of Storage of Pitching Yeast.
McCaig, R. and Bendiak, D.S.
The methods employed in handling production yeast
before pitching are important. Fermentations pitched with improperly
handled yeast could experience problems such as hanging fermentations or
poor attenuation or both. The temperature of yeast storage is a major
factor when considering handling procedures. Yeast stored 6 days at 1°C
showed a 5% drop in glycogen content and a 7% drop in viability. The
same yeast stored at 5°C decreased 22% in glycogen content and 14% in
viability. At storage temperatures of 10, 15, 20, and 25°C, significant
reductions in glycogen content (up to 79%) and viability (up to 68%)
occurred. Fermentations pitched with yeast stored at 1 and 5°C showed
little difference in numbers of yeast in suspension; rate or
attenuation; final attenuation; diacetyl, alcohol, and dimethyl sulfide
concentrations; or final pH. Fermentations pitched with yeast stored at
10°C exhibited higher final diacetyl and dimethyl sulfide
concentrations. The fermentations pitched with yeast stored at 15, 20,
and 25°C did not ferment normally; rate and extent or attenuation were
poor; the number of yeast in suspension was abnormal; subsequent yeast
crops were less; diacetyl, alcohol, and dimethyl sulfide concentrations
were less; and final pH was much higher.
Keywords: Attenuation, Beer quality,
Temperature, Yeast viability