Multiplying yeast

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InTheBasement

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When we use liquid yeast we always talk about oxegenation so that the yeast can multiply. But when we use dry yeast we say there is no need to add oxygen to the wort. Why is this? Do we not need for the dry yeast to multiply? Does the dry yeast multiply?
 

JONNYROTTEN

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Theres way more yeast in dry packet than liquid. Plenty to get it going with no help. I thought I heard there are yeast nutrients in the dry packet also, but don't quote me on that.
 

seatazzz

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The dry yeast packets have more cells than the liquid yeasts. Yes, they can get going with no help (i.e., just sprinkling on top of your wort) but they will do better with rehydration. Always check the date on the packet. To be safe, your best bet is to always rehydrate. For the same reason you always rehydrate bread yeast, it will give the cells a jump start on reproduction, but unlike bread yeast you don't need to add sugar. Just rehydrate with about 2oz of room temperature (not hot or warm) water about 30 minutes prior to pitching. By the time they hit your full-of-maltose wort they'll have started to reproduce and will take off running.

One of the biggest problems brewers face is the lag time from pitching yeast to actual fermentation starting; infections or wild yeast can take hold quickly with no active healthy yeast to compete with. With rehydration, you reduce that risk by a lot.
 

Smellyglove

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When we use liquid yeast we always talk about oxegenation so that the yeast can multiply. But when we use dry yeast we say there is no need to add oxygen to the wort. Why is this? Do we not need for the dry yeast to multiply? Does the dry yeast multiply?

Dry yeast from a good lab/manufacturer has all, or most of what it needs built into the yeast cells. A snack-pack.

Liquid yeast is not dried for storage so it will use up its reserves in the vial over time. Dry yeast is sort of hibernated so it wil not consume the food it has until you hydrate it.
 

kh54s10

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Dry yeast packages, as already noted contain more that twice the cells as liquid yeast. When they get rehydrated, they will reproduce if necessary. It is also engineered with nutrients etc that make a starter unnecessary or even detrimental. It is said that whatever they add in nutrients, etc. make oxygenating the wort unnecessary. But, oxygenating the wort won't hurt and may help. I always oxygenate!
 
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