How long can I let a yeast starter go?

I have 2 yeast starters (Wyeast) that I had planned to use for brewing on Sunday. They have been going for 18 hours and I found out we have to be gone tomorrow. Thus, The earliest I can use these will be Monday morning which will give the starters about 50-55 hours of activity. Should I refrigerate these prior to brewing (and if so at what point do I refrigerate them?) or just let them go? These starters are for ales in the 1.050 OG range. If I do refrigerate them then how early should I pull them out of the fridge prior to use? I don't have much prior experience using yeast starters.

Thanks,

Mick

They should be fine for a few days. I refrigerate mine overnight to settle the yeast so I can pour off some of the beer before I pitch. Plenty of people don't do this and get great results pitching the whole thing. You don't need to warm it up after taking it out of the refrigerator.

thanks for letting me know.

I made a starter for my saison and then I had to postpone brew day. I put it in the fridge for a week and then took it out and let it warm up and added a small amount of fresh wort. Took right off and pitched it 12 hours later. Only thing I would suggest is letting it come up to near pitching temp before you actually pitch it. Any thermal shock, whether it's warmer or colder, could stress the yeast. I know others have had success with pitching right from the fridge, but why take the chance. Besides, if you were taken from a frozen river the medics wouldn't drop you into a warm bath. The thermal shock would kill you.

As the others have said, you're fine to let a starter sit for a few days as long as everything was sanitized and all that. My last batch I had a few brewing delays and had to keep my starter for about a week in the fridge before I could get around to brewing. Everything turned out fine.

I typically keep my starters on the stir plate for 48 hours and have no problems at all.

A yeast starter will get yeasties to max in about 15-20 hours. You can go ahead and chill for 24 hours, then decant to wort on top, then pitch only the yeast. Did this on the weekend with Wyeast 2112 and had fermentation in about 12 hours.

Sithdad said:

Only thing I would suggest is letting it come up to near pitching temp before you actually pitch it. Any thermal shock, whether it's warmer or colder, could stress the yeast.

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There is at least anecdotal evidence that pitching cold could be beneficial, and a plausible hypothesis as to why. http://www.danstaryeast.com/library/pitching-temperature-and-nutrients

I would go as long as two weeks with a starter. After 2 weeks it will still take right off.