Yeast starter temperatures

Question

What temp guidlines apply to doing a yeast starter?

Should the starter be at the intended fermentation temp?
Should it be higher for good growth/activity?
Should it be lower to keep it clean flavored?

Answer 1

What temp guidlines apply to doing a yeast starter?

Yeast Starters are used to boost the starting population of yeast before pitching it into the wort. This is best accomplished by creating an ideal environment for the yeast to bud, rather than simulating the wort into which you will pitch. Keep the starting wort gravity around 1.040, don't add hops, aerate well and ferment warm. The December 22nd, 2008 episode of Brew Strong a good resource

Should the starter be at the intended fermentation temp?

Not necessarily. For ales, target the ideal temperature for the yeast as advertised by the supplier. For lagers, somewhere in the 70's F is acceptable.

Should it be higher for good growth/activity?

This is reasonable, but do not go above the ideal temperature range.

Should it be lower to keep it clean flavored?

The volume of yeast slurry you pitch will probably not impact the beer's flavor. If you are making a delicate style such as pilsner or kölsch you can allow the starter to settle and decant.

Answer 2

I like to run my starters at about 75F because its a constant temp in the room with my furnace year round. I don't think fermentation temps are critically relevant to the starter because starters are not fermenting (fermentation is an aerobic process, yeast growth happens aerobically). So the idea is to get optimum growth and most all yeast grow best warm. In fact warm, means closer to 85F than 75F, but that's what I do.

I use a stirplate which maximizes the growth in the culture by keeping good contact with the air in the flask.