Fermentis and Lallemand say no wort aeration necessary

[Rugby Fan.]

Apparently the info has been out for a while. I never knew this.

This only applies to their dry yeast out if the pack. Recycled yeast still needs aerated wort.

Thoughts?

 

[MashBag]

 

[Agentgonzo]

Apparently the info has been out for a while. I never knew this.

This only applies to their dry yeast out if the pack. Recycled yeast still needs aerated wort.

Thoughts?

Fermentis and lallemand know more about their yeast than all of us on this forum ever will. I trust them.

 

[dad_of_jon]

Fermentis and lallemand know more about their yeast than all of us on this forum ever will. I trust them.

+1 as I use dme it needs a damn good stirring with a paddle neways.

 

[Rugby Fan.]

Fermentis and lallemand know more about their yeast than all of us on this forum ever will. I trust them.

2 less jobs on brew day :-)

 

[JockyBrewer]

Yeast doesn't need oxygen like we do - it's only used to produce sterols and certain unsaturated fatty acids necessary for cell growth in the presence of oxygen. Yeast cells can store a certain amount of these so they are ready to replicate in the presence of sugar (they can store enough to replicate 5-10x).

Fermentis and Lallemand grow their yeast with oxygen being continuously added, meaning that when the yeast is dried their stores are full. Drying the yeast cells out then stops any function, meaning the stores are preserved and there's no need for more oxygen.

 

[DocAnna]

Yeast doesn't need oxygen like we do - it's only used to produce sterols and certain unsaturated fatty acids necessary for cell growth in the presence of oxygen. Yeast cells can store a certain amount of these so they are ready to replicate in the presence of sugar (they can store enough to replicate 5-10x).

Fermentis and Lallemand grow their yeast with oxygen being continuously added, meaning that when the yeast is dried their stores are full. Drying the yeast cells out then stops any function, meaning the stores are preserved and there's no need for more oxygen.

Yes and....
Yeast has specific metabolic pathways for aerobic (with oxygen) and anaeorbic (without oxygen) function, and cannot be in both states at the same time, it takes energy and resource to switch between the two, with aerobic function allowing faster growth in numbers. If a yeast has been grown then dried in the presence of oxygen then it is in its aerobic state - and is still in this state when rehydrated. If yeast has been harvested and recycled then it is in its anaerobic state, so needs a period of oxygen exposure to reset the metabolism to aerobic to support initial growth expansion in the wort.

 

[MashBag]

Yes and... (can I steal that Anna? )

This is also why you whisk a yeast (to oxygenate) and raise the temp if you want to restart a stuck ferment. It changes state to get growing again.

 

[JockyBrewer]

Yes and....
Yeast has specific metabolic pathways for aerobic (with oxygen) and anaeorbic (without oxygen) function, and cannot be in both states at the same time, it takes energy and resource to switch between the two, with aerobic function allowing faster growth in numbers. If a yeast has been grown then dried in the presence of oxygen then it is in its aerobic state - and is still in this state when rehydrated. If yeast has been harvested and recycled then it is in its anaerobic state, so needs a period of oxygen exposure to reset the metabolism to aerobic to support initial growth expansion in the wort.

Thanks Anna.

Do you know why liquid yeast from a manufacturer does require oxygen?

I'm assuming it's grown in the presence of continual oxygen so should have sterol reserves at packaging, which are then depleted somehow?

I see that White Labs newest 'PurePitch Next Generation' packaging has very high viability for months (over 90% after 6 months), so I'm wondering if they'll also eventually say that there's no need to provide additional oxygen on 1st use.

 

[Agentgonzo]

Do you know why liquid yeast from a manufacturer does require oxygen?

Anna will no doubtedly answer better than I can, but from what I understand, when the yeast runs out of sugars to feed on (when it's packaged up), it starts converting into a dormant state to store energy. When it is repitched into a growth medium (wort), it begins needs to move from its dormant state and into a growth state. Lots of complicated metabolic stuff happens here, but it needs oxygen to do this.

However (and this is where there is less detail, as the manufacturing process is complex and a trade secret), when making dried yeast, the manufacturers don't let it go into the dormant state - instead they dry it out rapidly when it's still in its growth phase. Essentially freezing (metaphorically, not in the temperature sense) it whilst it still full of sterols that are required for growth. When you pitch dried yeast, it rehydrates but is then already in a state ready to grow - no extra oxygen required.