Liquid Yeast Activation

Is there a time limit as to how long a liquid yeast will be good after activating. Im using a smack pack for the first time and want to make sure I have everything up and running in time.

Why not take the question out of the equation all together and make a starter. That way, 1) you know your yeast are viable; 2) you give the yeast time to multiply which reduces risk of underpitching; 3) it fully wakes them up and gets them ready for the big game; 4) you can pitch at anytime after making the starter. Ideally you would wait till high krausen, but you could pitch earlier or later if needed.

If you insist on just using the smack pack... some guys have smacked em and not bothered pitching for 2 days. At the very least I would leave the smack pack in the fridge until at least the morning you plan on brewing. It only takes an hour or two for it to warm up to room temp, but up to several hours for the yeast to fully activate. I've had some smack packs not expand at all, but had ferocious fermentation just the same.

From Wyeasts FAQ

7. I popped the inner nutrient pouch and the package swelled tight but I can’t use it right away. What do I do?

If you have activated a package but can’t use it right away, simply allow the package to swell and then refrigerate the package. The yeast will survive for extended periods if refrigerated. Before using, take the package out of the refrigerator and allow it to come up to room temperature before using. It is best to use the yeast as soon as possible.

Click to expand...

So let it swell and if you are not ready to brew put it in the fridge. As these are presumably healthy yeast you should pitch within about a week, any longer and the viability is going down and I would definitely make a starter at that point.

GT