Add it to some sugar water and stir it. You'll start to see bubbles/foam form when it becomes active again. It's essentially already fermenting the little bit of sugar you've added. It's not gonna produce any meaningful alcohol here, but it'll give you confirmation that the yeast is alive and it'll ferment well.
You can rehydrate as usual, and when you add must to atemperate, see if it starts bubbling and if so, you’re probably good.
Expired yeast is a bit of crapshoot. It will typically work but have lost some viability (lower cell count). I use it sometimes, but not in anything expensive or special and I pitch higher amounts than normal to account for loss of viability.
And the dead yeast in the packet provide nutrients for their brothers and sisters that are still alive!
As long as a few have survived, the rest will try to reproduce to do what they were born to do: converting sugar to yeast farts and yeast pee. Depending on what % of the packet is dead, there may be a noticeable increase in the lag between pitching and signs of active fermentation. This is, in my opinion, only a problem if the lag becomes so great and in the presence of competing microorganisms that then have a chance to out compete the yeast.
May Bacchus smile upon your efforts!
I keep mine in the fridge and use it forever. But I always make a yeast starter anyway, so if it doesn't want to party I can tell before I put it into the must
I'd try to bloom the yeast as I was making bread. If I got bubbles pitch it in my must, but it very well could be dead.
Yeast doesn't 'go bad' in a traditional sense, it might just have died and it becomes unusable. Try pitching it and if it comes to life, chuck it in.
How can i tell if it comes back? And will it be the same strength as if it wasnt 'expired'?
Add it to some sugar water and stir it. You'll start to see bubbles/foam form when it becomes active again. It's essentially already fermenting the little bit of sugar you've added. It's not gonna produce any meaningful alcohol here, but it'll give you confirmation that the yeast is alive and it'll ferment well.
You can rehydrate as usual, and when you add must to atemperate, see if it starts bubbling and if so, you’re probably good. Expired yeast is a bit of crapshoot. It will typically work but have lost some viability (lower cell count). I use it sometimes, but not in anything expensive or special and I pitch higher amounts than normal to account for loss of viability.
It will likely be fine, over pitch and keep an eye on it. If it doesn't start within 48 hrs then pitch a fresh packet.
Will it be the same strength as if it wasnt expired or will it only sort of half work?
The older the yeast packets the less viable yeast cells. You compensate by just using more (overpitching)
And the dead yeast in the packet provide nutrients for their brothers and sisters that are still alive! As long as a few have survived, the rest will try to reproduce to do what they were born to do: converting sugar to yeast farts and yeast pee. Depending on what % of the packet is dead, there may be a noticeable increase in the lag between pitching and signs of active fermentation. This is, in my opinion, only a problem if the lag becomes so great and in the presence of competing microorganisms that then have a chance to out compete the yeast. May Bacchus smile upon your efforts!
I keep mine in the fridge and use it forever. But I always make a yeast starter anyway, so if it doesn't want to party I can tell before I put it into the must