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Why no o2 for dry yeast?

I though the Lag Phase of fermentation were the o2 is used by the yeast cells to build reserves for a complete fermentation. Also much of the yeast flavor and chemical path ways are developed.
So the reason dry yeast does not need o2 is has so many yeast cells so it can skip the Lag Phase. Won’t this tend to be less yeast character?

[quote=“DUNNGOOD”]I though the Lag Phase of fermentation were the o2 is used by the yeast cells to build reserves for a complete fermentation. Also much of the yeast flavor and chemical path ways are developed.
So the reason dry yeast does not need o2 is has so many yeast cells so it can skip the Lag Phase. Won’t this tend to be less yeast character?[/quote]

Nope.

So dry yeast doesn’t need any additional O2? If so, I guess you never stop learning new things. :oops:

Think about the purpose of adding O2. It’s so yeast can use it to synthesize sterols to use for new cell walls. Dry yeast has so many more cells than liquid yeast that the need for growth is minimal to none. So, there’s no need for O2.

Plus in addition to the high count, the dry yeast are produced with much higher sterols.
Here is a quote I made in a older thread discussing this topic.

" growth is one of the very least concerns and then we move onto the main reasons outside of growth into why starters, O2 etc… is essential with liquid as these yeast are low in sterol count also if not treated correctly will ferment with sick symptoms as outlined briefly below.

In Dry yeast not alone is it the high pitch count the sterol reserve is way higher than you would ever have in a slurry/liquid pitch of any sort. I have said this time and again but dry yeast is prepacked with up to 5% sterol reserves and a properly prepared slurry of any type will hold maybe >1% sterol content before starting the anaerobic fermentation phase. All this means to the layman is at the end of brewing cycles or before making a starter liquid yeast are sterol difficent. IE:<1.0% they then need O2 to build sterols during the aerobic phase which then leaves them replete with >1% sterols in which to see proper cell growth and healthy anaerobic fermentation. Yeast can and will ferment a beer with low <1% sterols but you will have higher incident of dead/ non viable cells and petite mutants and budding is a haphazard operation so fusel production and other ester production can be exaggerated also which is all byproducts of sickly yeast.

Here is a good FAQ that has been covered before in a conversation between Shadetree and myself he found coming directly from one of the dry producers website.

http://www.danstaryeast.com/frequently-asked-questions

I always aerate my wort when using liquid yeast. Do I need to aerate the wort before pitching dry yeast?

No, there is no need to aerate the wort but it does not harm the yeast either. During its aerobic production, dry yeast accumulates sufficient amounts of unsaturated fatty acids and sterols to produce enough biomass in the first stage of fermentation. The only reason to aerate the wort when using wet yeast is to provide the yeast with oxygen so that it can produce sterols and unsaturated fatty acids which are important parts of the cell membrane and therefore essential for biomass production.
If the slurry from dry yeast fermentation is re-pitched from one batch of beer to another, the wort has to be aerated as with any liquid yeast."

[quote=“DUNNGOOD”]I though the Lag Phase of fermentation were the o2 is used by the yeast cells to build reserves for a complete fermentation. Also much of the yeast flavor and chemical path ways are developed.
So the reason dry yeast does not need o2 is has so many yeast cells so it can skip the Lag Phase. Won’t this tend to be less yeast character?[/quote]

Part of your understanding is correct though in regards to liquid slurries.
If pitching a dry yeast its sterols are sky high and if pitched at correct count they will go right into Anaerobic fermentation.

If pitching a liquid starter you will still want O2 in the wort as the slurry will be sterol deficient after the respiration cycle seen in the starter. Unless you pitch the yeast at high krausen they will need Wort O2 to create higher sterols across the very high count you created prior, so this aerobic/ lag phase will still happen although faster than if pitched with low count slurries.

If pitching a low count/ 1 pack slurry it will be a much longer lag phase/ aerobic fermentation time as you have to grow the needed cells and those cells all need to create the same needed glycogen/ sterols that a starter slurry requires. It is only dry yeast that will never require wort O2. Although it hurts nothing if its there too.

Thanks. I guess that’s what happens when we brew without thinking about the why’s of what we are doing.

Great information. I can see that part of my problem was thinking liquid and dry yeast ferment the same way. Thanks everyone for the replies.

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