Are there "killer strains" of beer yeast as there are in wine yeasts?

-Al

RESPONSE:

Yes. There are killer strains in every genus and specie of yeast. Yeast are divided into three categories regarding the killer factor:

1. Killer positive--this strain produces a killer factor and cannot be effected by another yeast that produces a killer factor.
2. Killer sensitive--this strain does not produce a killer factor and is effected by a strain that does.
3. Neutral-- this strain do not produce a killer factor nor are they effected by a yeast with a killer factor.

It is important to know that a killer factor from one specie cannot kill a yeast from another specie. All three categories are in common use in the wine industry with out any problems with cross contamination when good sanitary practices and proper inoculating volumes are used. Extended re-pitching where killer yeast plus neutral and sensitive yeast in the same plant are used would not be advisable. Killer yeast may be used more often that suspected, since beer yeast strains are not always screened for the killer factor.

Dr. Clayton Cone