Pitch Rates

[Dr Malt]

I just read a thread under Yeast & Fermentation where there was so discussion about pitch rates in beers and what is optimal. I thought a discussion here in Brewing Science would be appropriate. So to start the discussion off here are a few questions:

1. What are your target pitch rates for a standard 12 P beer and why?
2. How do you know you are hitting you desired pitch rates?
3. Can you over pitch as well as under pitch a beer?
4. What about yeast viability, its determination and pitch rates?

So who can provide some insight here?

Dr Malt

 

[hercher]

1. I think an ideal pitch rate is about 1 million cells per ml per degree Plato. (Fix suggest 1.5 million cells). But from a practical point of view, about a 1 gallon starter is ideal for a 5 gallon patch. That said, I've never pitched anywhere near that much. Typically, my ideal starter is built this way: a basic smack pack pitched into 1 pint of wort at or near my desired gravity. Then I double that 2 more times -- next day I add 2 pints, then 4 pints.

2. I don't count yeast cells as I don't have a microscope, a hemocytometer, or the patience. So I guess I don't know, but I've always had pretty good luck doing it this way.

3. Yes, it is possible to overpitch, but it is much harder to overpitch than underpitch, and the negative consequences are nowhere near as significant. It can lead to reduced yeast growth. This means the yeast you pitch will be the yeast cells responsible for fermentation. If the viability of your yeast is too low (90%), you could wind up with yeast/sulfur flavors, that will take longer to mature away. It is pretty hard to do.

4. I'll leave it to more scientific minded people to address viability. Generally speaking, if you build a starter as I mention in step one, you have no problem. As I understand it, you don't want to repitch yeast too many times, although there is much debate as to what is too many times. I've gotten 10-15 generations out of one batch of yeast, without any noticeable effect.

 

[nolabelbrewing]

1. What are your target pitch rates for a standard 12 P beer and why?
2. How do you know you are hitting you desired pitch rates?
3. Can you over pitch as well as under pitch a beer?
4. What about yeast viability, its determination and pitch rates?

Dr Malt

1. Pitching rates are all over the board, both in bottling and in fermentation.
In "Brew like a Monk" for refermentation in the bottle here are some of the rates that are listed.

Duvel - 1 million cells per milliliter
Orval - 3 million cells per milliliter
Rochefort- 1-plus million cells
Westmalle - 2 million cells
Allagash - .75 to 2 million cells

For pitching rates .. listed in the same material these are some of the numbers I found interesting.

Ommegang pitches 18.5 million cells per milliliter for (1.076) 18.5 degree P
Moortgat pitches 7.5 million per milliliter for (1.069) 16.9 degree P
Orval and Rochefort pitch 15 million per milliliter regardless of strength (1.072 to 1.096) 17.5 to 23 degrees P

Chris white owner of white labs basically says that there is a balance. I quote from page 187 "By pitching a little less, if your yeast is healthy, flavor is going to be spit out during growth." " Of course if you don't pitch enough, you get solventy."

On a personal level. I only ever build starters for big beers, and more likely I pitch on top of a cake if its a big beer. Otherwise, if i'm trying out a new yeast, I use a single vial, and I have yet to have a problem.

2. Microscopes and counting. 250$ plus. Otherwise, a good yeast slurry will be about 40-50 percent yeast, and should contain 1 billion cells per milliliter.

3. I gave the most professional answer I could find in section one of my response. Flavor tends to come out during yeast growth. Grow it in good stuff, like beer, and get good flavor. Grow it in DME starter, and get less flavor. Temp makes a huge difference. The hotter the temp, the faster the multiplication, the more off flavors... ... but it truly is yeast dependent. Read more.. pick your yeasts carefully. The maxim is, Brewers make wort, but yeast makes beer.

4. My experience is that all brewers have the potential to re use their yeast. Harvesting is a choice left up to you. Open fermentations and white plastic buckets for all their bad rap, can be harvested off easily, and I have read about many brewers using their yeast up to 10 times in open fermentations. In my closed fermentations, I have reached my limit at 4 before I notice definite problems with the yeast cake at the bottom, and frequently , my second beer is the best, which could perhaps relate to the use of a single vial for pitching. Belgians often use their yeast vertically to brew small, medium, large, and then trash the yeast. Professionally here in America, I think it primarily depends on the availability of yeast to the brewer. Many smaller craft breweries get their yeast from larger breweries, and re use three or fewer times because fresh yeast is always available. Larger breweries of course, grow their own, and maintain labs to keep their supplies healthy. Contract breweries such as Sam Adams, receive regular shipments of yeast from banks to keep their supplies healthy.

gl brewing

~J~

 

[passedpawn]

Passedpawn's rule: Pitch Rate = OG / 5.

That's it, that is all you need to know.

I.e., 1.060 beer: 60/5 = 12 million cells per ml.

19000 ml in 5 gal, so for a 5g batch 228b cells. That's 2 smack packs, or 1 smack pack into a 1L starter.

 

[MrSaLTy]

I usually see as is stated above ... about 1-1.5 mil per ml per degree plato for ALES, but you probably want double that for lagers.

Jamil has an awesome pitch rate calculator that you can check out here...

http://www.mrmalty.com/calc/calc.html

Cell growth rates and starter size calcs are taken from data that he has amassed over years of testing and data that he has worked with people from white labs to verify.