Time required for making a starter

[Brewer Gerard]

Why is it that when people make starters they only seem to ferment for a few days and then refrigerate as opposed to leaving it go for a week or more so that it completely ferments out?

 

[Yankeepride15]

Because it's only a liter or 2 and it ferments completely (and does all that good stuff for the yeast) in much less time than 5 gal of wort.

 

[GilSwillBasementBrews]

Besides fermenting quicker. Most like to pitch while the ferment is at high krausen preferably. Generally why most make starters 24hrs ahead of time. Try to catch the yeasts at their most active point.

 

[cluckk]

Besides, if you pitched a vial or smack pack in a full 5 gallon batch of beer you are underpitching, but pitching the same into a starter you are way overpitching--so it takes less time for it to reproduce to the level it can reach in the starter. The goal of a starter is not fermentation, but reproduction. There is no benefit to letting the starter go beyond the reproduction stage--you want it to do the work of fermentation in your beer. Finally, the yeast take in oxygen during reproduction, but during fermentation they use up the oxygen that they have stored. By the end of fermentation they are oxygen depleted. If you waited until fermentation of the starter was finished you would be pitching the yeast in a low oxygen state.

 

[Brewer Gerard]

Fair enough, but a lot of texts i have read havesaid that you can refrigerate your starter and use it within x amount of days.

If this is the case, how can the yeast be in reproduction stage when brought back from this refridgerated state?

 

[AnOldUR]

You're not trying to pitch them during the reproductive stage; you want them to have reproduced so that you have more viable cells to pitch.

 

[cluckk]

They don't need to be reproducing when pitched. Like asexual rabbits they'll take care of that. You are trying to pitch a batch of yeast that is healthy, and ready to work in a large enough batch that they can quickly reproduce to the volume needed for the fermentation. Part of being healthy and ready to work includes not being oxygen depleted.

 

[JLem]

Refrigerating also allows the yeast to drop out so you can decant off the starter "beer" and just pitch the yeast slurry - the starter "beer" is not exactly high quality stuff and is best left out of the fermenter.