White labs yeast ruined by room temp?

[412CiderGuy]

My girlfriend didn’t know my package containing a few white lab yeasts needed refrigerated so she threw in the garage and I didn’t catch for 2 days. Is it worth even pitching?

 

[Qhrumphf]

Depends on the temps. As long as it didn't get above 100 or below freezing, should still be alive (but hotter or cold enough to freeze and the yeast could be outright dead). If it stayed consistently cool/cold but didn't freeze, shouldn't make much a difference. But steady warmer temps (room temp+) or fluctuating, viability may have suffered a bit so i would prop that yeast up with a (bigger) starter.

Given the section and user name I assume you're using it for cider. Not sure what that means in terms of propagation. DME will get the job done, not sure if cider must has nutrition enough for ideal propagation if something malt based won't work for you. I know there's stuff like GoFerm I don't know much about, but my impression was that's for rehydration of dry yeast, not propping up liquid yeast.

 

[IslandLizard]

You should always make starters with liquid yeast to prove viability and ramp up cell count. There's no way to know what condition it's in, especially when shipped or sent through the mail. The ice pack had likely already melted before the shipment left the warehouse, it acts as a mere buffer.

Use regular DME for the starters, cold crash after successful propagation, decant the clear starter beer, and pitch your yeast slurry or ramp up for more.

On a side note, most yeast is propagated in yeast labs with apple juice and a blend of nutrients.

 

[412CiderGuy]

I never made starters but I guess I should start. I just never really had issues in the past with just dumping it in and aeriating fully.

 

[kh54s10]

I never made starters but I guess I should start. I just never really had issues in the past with just dumping it in and aeriating fully.

This is totally do-able. But you are not using the optimum amount of yeast and you really don't know much about how healthy the yeast is.

Even if there are only a few live yeast cells, they will probably ferment the beer - eventually. A long lag time could allow a contaminate to take hold and dominate over the selected yeast. The few cells will also be stressed - possibly causing off flavors.

Whenever I use liquid yeast, I ALWAYS make a starter, even with low gravity beers.

 

[wasully]

Even if there are only a few live yeast cells, they will probably ferment the beer - eventually. A long lag time could allow a contaminate to take hold and dominate over the selected yeast. The few cells will also be stressed - possibly causing off flavors.

Why does underpitching result in stressed yeast?

A dose of sulfite should give the pitched yeast time to establish itself.

 

[TheMadKing]

Why does underpitching result in stressed yeast?

A dose of sulfite should give the pitched yeast time to establish itself.

The number of yeast is limited by 3 factors - food, nutrients, and oxygen. The yeast will multiply until the competition for food prevents them from multiplying. Every time a yeast cell buds (multiplies) it gives up a bit of its cell wall (glycogen reserves) and internal proteins. The yeast use oxygen to rebuild those in nature.

Now in your beer oxygen is a limited resource. So if yeast need to multiply too much to use the available food source, their cell walls become weaker and they are less healthy overall.

You need to pitch enough yeast so that they can multiply up to the final cell count in fewer generations so that their cell walls remain sturdy and they are not limited by the lack of oxygen or nutrients.

Now in a starter you intentionally introduce oxygen the whole time on a stir plate or by shaking it. You should also never increase the yeast by more than a factor of 10 in a single starter. When they run out of food, they begin the process of going dormant again which involves building their glycogen reserves back up.

This all has to do with this principal of maintaining healthy cells by not limiting their oxygen and reducing the number of generations that they have to create before going dormant and replenishing their glycogen reserves.

Then when you pitch a starter into your beer you have a high number of healthy cells with full glycogen reserves ready to go.


Dosing wort with sulfite isn't a great idea I IMO. It will certainly inhibit bacterial growth, but if it's not all consumed before the yeast is pitched it will also inhibit yeast growth. The only way to get rid of sulfite is to oxygenation your worth thoroughly.

 

[kh54s10]

Why does underpitching result in stressed yeast?

A dose of sulfite should give the pitched yeast time to establish itself.

I am talking of a serious underpitch. Then my idea (not a biologist) is that the yeast spend most of their energy reproducing rather than just fermenting the wort. Thus, stressed...

 

[wasully]

Now in your beer oxygen is a limited resource. So if yeast need to multiply too much to use the available food source, their cell walls become weaker and they are less healthy overall.

You need to pitch enough yeast so that they can multiply up to the final cell count in fewer generations so that their cell walls remain sturdy and they are not limited by the lack of oxygen or nutrients.

Dosing wort with sulfite isn't a great idea I IMO. It will certainly inhibit bacterial growth, but if it's not all consumed before the yeast is pitched it will also inhibit yeast growth. The only way to get rid of sulfite is to oxygenation your worth thoroughly.

Ah, I hadn't put it together with the oxygen. That makes more sense. Thanks.

As for sulfite-yeah, don't need to in wort because you just pasteurized it. But cider is likely to have plenty of wild yeasts & bacteria in it.