Educate me on yeast...

mciaio · 04-05-2009, 12:55 PM

Liquid yeast,2 quart/liter starter, 1 cup DME, 24 hours. Pitch.

I am wondering about aeration. Aerating your wort is only to allow enough oxygen for the yeast to reproduce, correct? A full boil will remove all of the oxygen from the wort, correct? Therefore, with a full boil and a starter, do you still need to aerate? Because of the starter you are adding double the amount of yeast that you would be just from the smackpack and you want the yeast to start fermenting not reproducing once they hit the wort. With the presence of oxygen they will reproduce, with the absence they will ferment, is that right?

**Coastarine** · 04-05-2009, 12:57 PM

Quote:

Originally Posted by mciaio

you want the yeast to start fermenting not reproducing once they hit the wort.

This is where you're wrong. The recommended pitching rate accounts for one more big yeast orgy when they get pitched.

Beerrific · 04-05-2009, 01:02 PM

Yeah, even with a starter, you should expect (and want) a 2-3 fold increase in cell count.

mciaio · 04-05-2009, 01:04 PM

So if I do a 1 gallon starter that would give me 4 billion yeast cells; according to Wyeast. In theory, that should should be enough if I didn't want to aerate.

How do you pronounce Wyeast??

Beerrific · 04-05-2009, 01:13 PM

Quote:

Originally Posted by mciaio

So if I do a 1 gallon starter that would give me 4 billion yeast cells; according to Wyeast. In theory, that should should be enough if I didn't want to aerate.

How do you pronounce Wyeast??

Yeah, I guess that would give you enough yeast so that reproduction would not be needed. But, I have heard that if you do that the beer will not come out right. The reproduction of the yeast gives certain flavors and characteristics to the beer that you expect.

Wyeast: "why yeast"

beersydoesit · 04-05-2009, 02:15 PM

The reproduction phase also produces flavor characteristics, according to Wyeast's David Hogsden. So you want reproduction.
Basic brew radio has a great podcast on this.
Hogsden says it may not be necessary to aerate wort with a sufficiently large well aerated starter becasue the yeast stores the oxygen it needs for reproduction
BUT he continues that he thinks aerating anyway is the smarter approach. At this stage you cannot over aerate. Excess oxygen is forced out by co2 as fermentation proceeds.

The ultimate population accordind to Papasian is 50 million per ml. That is a lot.

Why east

Regards

**Coastarine** · 04-05-2009, 02:20 PM

I've heard jamil talk about how he experimented with the no-reproduction pitch. He verified that the beer was missing something. Turns out you don't ever really want the beer "as clean as possible".

mciaio · 04-07-2009, 12:18 AM

Thanks, a very enlighting thread.