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The specs for Lallemand BRY-97 dry yeast explain that aeration of the wort is not necessary. I've had good results following their instructions precisely, but I wonder if I'm missing out. I wonder if they are saying "technically you don't need to aerate".

...in other words, do I need to buy aerating equipment?

From the technical sheet, at the end of the REHYDRATION section:

BRY-97 yeast has been conditioned to survive rehydration. The yeast contains an adequate reservoir of carbohydrates and unsaturated fatty acids to achieve active growth. It is unnecessary to aerate wort upon first use.

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Honestly, this looks like a cut and paste and propbably doesn't differ much from thier other species of yeast that may benifiet from hard growth conditions.

Yeast needs oxygen for healthy growth. Healthy growth reduces esters. If the yeast has a clean ester profile it will, do better with oxygen. All yeast grow better with oxygen, but some yeast you actually want to stress to get them to produce desirable esters.

The lack of oxygen is the trigger for yeast to end growth phases and begin feeding.

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    Interesting, thanks! I don't know if this particular yeast is intended to be stressed, but I think I can justify aerating equipment to find out. – Stewii May 3 '18 at 3:19
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    @Stewii I would oxygenate this specific yeast. Actually I oxygenate all yeast. I prefer to control esters and stress by pitch rate. – Evil Zymurgist May 3 '18 at 13:25
  • It commonly claimed that this is bragging rights because of the increased cell count. – Martin May 5 '18 at 8:09
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There is almost never a need to aerate/oxygenate with dry yeast. The purpose if aeration is that the O2 is used by the yeast to synthesize sterols. Those keep the cell walls flexible to encourage budding. Because there are so many cells in a pack of dry yeast, there is little to need need for cell growth.

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  • Ah, ok. Yeah, the beer is tasty, and it gets down to the right gravity, so the yeast seem to be doing their job. Still, I have to try it. I'm curious what aerating will change, if anything (faster? more delicious?). Thanks! – Stewii May 4 '18 at 0:20
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It's important to note that they specifically say aeration is only unnecessary for 'first use'. This is very common for active dry yeasts, the reason being that most are grown under 'oxidative' conditions.

As Denny Conn correctly points out, the point of aeration is to provide yeast the means of synthesizing sterols and unsaturated fatty acids, which allow for cell growth/division. The oxidative growth technique used to produce dried yeasts actually helps to stabilize the cells against the dehydration process, in part by increasing the production of these compounds (by up to 5 times).

As a consequence, though, you no longer need to provide oxygen when pitching these yeasts directly because they already contain sufficient sterols and UFAs to support several rounds of cell division (the 'growth' phase). If you were to save the yeast for re-use, it would be starved for sterols and UFAs (having consumed them all during growth in the previous batch), and would therefore require oxygenation upon re-pitching in order for growth to occur (unless you were to first make an aerated starter with it). You don't need cell growth if you pitch enough, but as EvilZymurgist points out, this can have important impacts for beer flavor (esters, especially).

So should you have aeration equipment? If you plan to re-pitch the yeast, then yes. If you will use a new packet of dry yeast for each batch, I'd say don't bother, at least for now.

In a sense, oxygenation is just a means to an end (allowing synthesis of sterols and UFAs) and if they are already present in sufficient quantities, there's no point to oxygenate further. Basically, whether or not you need to oxygenate, and the effects that oxygenating will have, will depend on the physical state of the yeast and its particular nutrient reserves.

It's worth noting too that I don't think this statement is meant to apply exclusively to this strain (BRY-97), but rather to all active dry yeasts.

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  • Fantastic answer, thanks! I had no idea about those differences between first-run and harvested yeast. Thanks! – Stewii May 9 '18 at 19:44

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