william_shakes_beer

Recipes 

Mr Malty gives figures for how many healthy yeast cells to pitch for a given OG wart. It is also possible, but not advisable, to ignore pitching rates and pour one vial of yeast culture directly into the cooled aerated wart without a starter. This practice is not recommended because underpitching can stress the yeast and increase lagh times.

Given that the purpose of aeration is to promote cell reproduction, Is it the intent of Mr. Malty to produce a pitching starter with ALL the cells required to finish the job, (IE no aeration of wart is necessary), or only produce a colony sufficient to establish a beachhead and assure other bacteria do not have a viable chance of colonizing the wart (aeration required) I intend to aerate regardless, so this is really an academic question.

samc

Recipes 

The calculator has a pull down menu for choices such as simple starter, shaking, aeration, etc. So the intent is whichever method you choose.

seabass07

Recipes 

It is to make sure you have enough yeast so that they don't have to reproduce excessively. If you follow his pitching calculator, the yeast are still going to multiply but you will end up with healthier less stressed yeast. You still need to aerate.

__________________
Fermenter 1: Strong Scotch Ale
Fermenter 2: Hot dog Imperial Stout?

Bottled: English IPA, Dark Candi Cider, RyePA
Aging: Belgian Dark Strong, English Barleywine
Next RIS

solavirtus

Recipes 

I think Mr Malty calculator is for calculating the size of starter (of whatever type). I don't think it makes any assumptions about aeration of the full wort you're pitching the starter into. That being said, you should aerate your wort to ensure the healthiest fermentation possible!

PoppinCaps

Recipes 

I think the OP was asking theoretically if Mr Malty calculates the final amount of cells needed to ferment, or just a proper healthy amount for pitching. I think the answer is the latter. If you think about it, yeast divide and conquer, making enough of themselves to get the job done. They like to grow to a density before really tackling the job, and of course use some sugar along the way.

A typical starter will grow to a density of around 200 million cells per ml wort, and Mr Malty calculates you will need around 11 million/ml wort final pitching concentration. This means that you are actually adding about 5-10% of the number of cells that will be in your finished beer. Healthy yeast like a normal lag, exponential, and stationary phase for growth and fermentation, so that's what you're giving them. This is also why it's a bad idea to pitch directly onto a full batch's yeast cake. Way too many yeast.

jfr1111

Recipes 

Mr Malty simply uses Fix's recommended pitching rates: it checks how much yeast is needed according to the formula, taking into account the OG and type of yeast/fermentation (ale, lager, hybrid), and then figures out how big of a starter you need from your starting cell count and the particulars of your setup.

Fix's numbers do provide for a lag phase and yeast reproduction and I think they are derived from commercial practices. I don't know of any commercial brewery that doesn't aerate the wort prior to fermentation. Thus, you need to aerate too. There's a big debate about wether pitching on a cake is good or not on another thread, but the general consensus seems to be that you need some form of lag phase because desirable flavour compounds are created during this phase. Getting fermentation in an hour isn't necessarily positive, but it depends on what you want to achieve.

Long story short: Mr Malty gives you an approximation on the size of the starter you need for proper pitching rates, accounting for some multiplication before fermentation actually begins.

william_shakes_beer

Recipes 

K. Thanks. Something I was idly pondering in the shower yesteday.

arg

Recipes 

I'm glad you asked this because I've been asked the same question and could only give a half-hearted answer. My understanding is in line with what jfr1111 said.