I saved some yeast from my last batch of beer, but that was in December . The yeast has been kept in the fridge in a mason jar. My question is, do you think the yeast is still good? I also plan to make a starter for the yeast using my stir plate. I plan on brewing this Saturday. Thanks in advance.
didn't you just answer your own question? make a starter and see what happens. guarantee you that you'll get fermentation.
Sorry I'm a newbie at this, how do I know for sure that I will get a healthy fermentation? I will have the stir plate going on the whole time. Do you still get a krausen while on the stir plate?
My understanding is that you should not get krausen on the stir plate because of the abundance of oxygen, you are only multiplying heathy yeast not fermenting at that point.
boil up 100 ml of water and 10g DME, oxygenate and stir into the slurry. let it sit at room temp with a cover. if all is well, your yeast will wake up and get back to work. if you get no activity, use fresh yeast. you will have to pay attention though, because the krausen will come and go quickly. then you can step up to a full starter from there. your yeast has been hibernating, but it will almost certainly get back to work if the conditions are favorable. yeast can hibernate for a thousand years, wake up and go to work like it was yesterday. Cheers.
if you get activity, then you have at least some healthy yeast that are ready to ferment. if it is ready to pitch depends on if you have a large enough colony though. you might want to step up to be sure. otherwise you could be underpitching which seems pointless if you are going through the trouble of making a starter. Cheers.
made a starter Friday afternoon. put it on the stirplate at 6 pm. yesterday, looked at it at noon. nice krausen on it. foamier and more loose than a typical carboy krausen, but i've always had a krausen or crema on my starters.
I think that there will almost certainly be some good yeast cells left. The question is how many, and how to know when you've reached a good pitch rate? I suppose these things can be calculated, given the volume of the slurry you have, and an average attrition rate, and the amount of time the yeast was stored, or something like that. Maybe somebody can chime in on that? Anyway, I would plan on doing a step starter to be sure.
the question about a healthy fermentation is interesting. what is considered healthy? not stalling? mutating and tasting strange? gravity will dictate if it has fully fermented. but yeah, checking gravity on a starter? guessing some people do that. i'd just smell it.
Yeast is cheap. Grain and hop bills are not. Why risk under-pitching and end up drain-pouring 5Gs? Buy some fresh yeast and be done with it.
The reason for less Krausen on a Stirplate is that the agitation tends to keep the yeast in suspension as compared to a non-stirred starter.
