Yeast Pitching Dilemma

You'll get various opinions on the best pitch rates, but one thing is universally true. Whatever rate you decide on should be present at pitching, not made in the beer wort. One reason is that the concentrations of compounds (desirable and undesirable) present at the end of the process will be different depending on the initial pitch rate. Another reason is that for a given amount of oxygen and nutrients, cells can only divide some number of times before their cells walls can't be further divided. (They literally don't have enough material left.)

Think of it this way...
With a yeast starter, the goal is to make yeast.
With a batch of beer, the goal is to make beer.

 

“This is the simplest example from Mrmalty.com that I've recently read and it showed that 180 billion would be needed to ensure proper fermentation.

Is this cell count needed at the beginning or is it the total cell count for the entire fermentation period?”

The Mr. Malty ‘result’ of 180 billion cells represents what that tool recommends for the amount of yeast pitched; the cell count at the beginning of fermentation.

“My question is how much yeast do you really need to actually pitch in a 5.25 gallon of wort with a OG of 1.048.”

Wyeast would ‘say’ that a single smack-pack of their yeast is needed for this volume/original gravity.

I personally pitch per the yeast vendor’s recommendations and I achieve great results. There are other considerations for having a healthy fermentation beyond yeast cell count: proper oxygenation/aeration, proper nutrients in the wort, proper fermentation temperature, etc.

As a homebrewer you should pitch a yeast cell count that works for your brewhouse per your homebrewing practice.

Cheers!

 

From a practical standpoint, overpitching is more forgiving than underpitching. 200B cells vs. 180B cells isn't going to hurt anything. And don't forget that the number of viable cells in a pack or vial decreases with age.

This is what I almost always do. But not only to target a specific cell count. The viable cells at the end of a properly conducted starter should also be more vital (healthy enough to do fermentation) than an equal number of older (but still viable, i.e. living) cells.

 

One thing you will read a lot about is people stating their beer turns out just great using XXXX technique. And in their mind this is true. What you want to determine is which technique really works.

As Vikeman says, your pitch rate is your goal. This is what gives the best chance for the yeast to do their job correctly. You will find professional brewers like the ale pitch rates of 0.75 million yeast cells per milliliter of wort per degree Plato. Okay, the math gets really sticky here, that's why we have yeast calculators. Mr. Malty is telling you to pitch 180 billion cells where your friend is saying just pitch what's in the packet.

First, take a look at the date on the packet. There is degradation of yeast population based on age (assuming good storage). The calculators will use different assumptions, but expect lower yeast count for the older packets. After a couple of months this really adds up. Consider if you want to think all yeast packets are the same (Mr. Malty will tell you they degrade with time, your friend ignores age).

You friend is asking 100 billion yeast (less what dies off with time) to consume all the sugars in the wort and that's independent on how much sugar is available (OG). Mr. Malty will tell you to get more yeast ready for the higher OG beers. The yeast do try and eat as much as they can, but do you think <100 billion can do as good a job on 1.060 wort as 1.040 wort?

Your pitch rate determines the cell growth rate and that is what influences flavor compounds. It's going to be hard to say when the yeast have doubled, but try and get away from how many cells you produce and focus on initial pitch rate. Underpitching will hurt your flavor compounds (along with slower fermentation). Overpitching can reduce ester formation and other problems. Ideally you want to get it just right . . . that is what makes the best beer.

A 20L batch of wort can grow up to 600 billion cells, but much of this is well after the yeast has influenced the character of the beer. Remember, the first 3-4 days of fermentation largely determines the quality of your brew. Your goal isn't number of yeast cells produced, rather a pitch rate that gives you a chance for the healthiest of yeast to growth at the best possible rate and produce the anticipated flavor. Mr. Malty will ask you to pitch more cells into higher OG batches. Always pitching a single packet (like your friend) will definitely make beer, but ask if you think fermentation is a static problem or dynamic.

There are probably another 100+ factors that go into making the yeast cooperate, but I think you can see which way I lean with yeast calculators. If interested in starters, if you understand this you've got it made.

 

“You will find professional brewers like the ale pitch rates of 0.75 million yeast cells per milliliter of wort per degree Plato.” A pitch rate of 0.75 million yeast cells per milliliter of wort per degree Plato is appropriate for commercial brewers since that value is consistent with re-pitching yeast (which is what commercial brewers typically do). The value of 0.75 million yeast cells per milliliter of wort per degree Plato is much larger than what is needed for fresh liquid yeast (i.e., a Wyeast smack-pack or a White Labs vile).

Cheers!

 

So, in your opinion, what is the appropriate pitch rate, in cells per ml per degree plato, for non-repitched yeast? If 0.75 is too high, what's the better number?

 

Fresh is the key term here. Yeast vendors mean less than a week old when they say fresh. When a commercial brewery orders yeast it is propagated to order and then overnight end from the lab, this is done (at a significant cost) because the age of the yeast significantly effects it's viability. I don't know about you but I don't ever remember seeing yeast that was a week old in my LHBS. Most of the time it is closer to the end of its six month shelf life than the beginning, in which case you need a starter. Same thing applies to smack packs (which are a fucking gimmick anyway).

 

Personally don't like MrMalty, I use BeerSmith to tell me what I need.

 

These conversations always make me wonder how relevant the information is that we opine and pass back and forth when no one is actually counting their cell #. There maybe significant variance homebrewer to homebrewer and viability pack to pack. Many of these conversations are spot on accurate from a theoretical side and based on good research and information. But if you don't know the true starting concentration of viable cells in that smack pack no calculator is going to help you. You may be off by 2%, maybe 20%.

I think this is where the science of brewing must yield to the art of brewing (especially true on the homebrew scale). You literally need to get a consistent 'feel' for how that yeast pack will perform from your LHBS. Learn how long to let your starter go, how big and what temp. You need to experiment with some empirical way of adding O2 to the wort, what temp regime to ferment with, etc etc.

Not knocking any of the answers or peoples methods. I agree with them 100%. I am a hardcore scientist type by trade and love sticking to the #s. (In fact, I work with microbes and other cells, growing and counting regularly.)

This reply is just more of a philosophical exhale.

 

I agree with everything you wrote except the above. For some styles underpitching can improve performance, ie flavor, as more esters are generated. For other styles, a conservative overpitch will make better beer. Furthermore, some folks might like their beers in general better when underpitched, ie a bit estery.

This I certainly agree with.

 

Below is something I posted previously:

David Logsdon (who founded Wyeast Labs) prefers to slightly underpitch since this will result in a beer that is more flavorful and it benefits the yeast health. Below is a quote from an article of Yeast Starters authored by Jamil Zainasheff:

“There is also an upper limit to how much yeast you should add. Logsdon says, “I try to stay within 20 percent of my ideal pitch rate and I prefer to slightly under pitch rather than over pitch. This causes more cell growth, more esters and better yeast health. Over pitching causes other problems with beer flavor, such as a lack of esters.
Changes in the flavor profile are noticeable when the pitch rates are as little as 20 percent over the recommended amount.”

Cheers!

 

So let it be written, so let it be done.

Agree absolutely . . . but you saw how long my original post was, had to stop somewhere.

 

A stir plate for starters will also save you money in the long run if you plan on making large batches or lagers.

 

See, here's a problem... someone told you that 0.75 million cells per ml per degree plato is more than you need, but they can't or won't give you a better number. I will say that 0.75 is a very good default and that many, many award winning ales have been made using that target. Probably more than any other target. But as I said before, IMO it's important to know what rate you are going for, whatever that rate may be (and it may be different for different styles). But *if* you believe that there is some best general pitch rate and/or specific best rate for a style (regardless of what that rate is), then one-size-fits-all type recommendations like "1 pack for 5 gallons of wort up to 1.0XX gravity" or "don't make a starter below 1.0XX gravity, but make a X.XX Liter starter if above" are IMO silly, because the effective target rate coming out of that binary logic will be different every time.

Having said all that, yes you can use the binary advice, or you can use a low pitch rate. And you might make good beer with it.

By the way, Jack wasn't saying to go with a higher pitch rate if you intend to repitch from the result. He was saying that the higher pitch rate is appropriate if you're pitching from already used yeast.

 

“I can actually go with a lower approach of say 0.50 million cells per ml of wort. This seems to work for OGs <48..”

The proper units for pitch rate are “million yeast cells per milliliter of wort per degree Plato. Therefore you would adjust the amount of yeast pitched based upon original gravity. There is no need to caveat “seems to work for OGs <48”.

You appear to have selected a value of 0.50 which is less than the 0.75 value which corresponds to reusing yeast.

Cheers!

P.S. For the case of a 1.048 (12P) OG ale and 20 liter volume, the needed number of yeast cells for a pitch rate of 0.5 will be 120 billion yeast cells (0.5 x 20,000 ml x 12). This is the amount of yeast cells in a brand new Wyeast smack-pack. As I posted previously, Dave Logsdon would suggest you pitch up to 20% lower than this: 96 billion yeast cells.

 

The thing I have been struggling with lately is wrapping my head around harvesting yeast from a yeast cake to brew another batch. I think it is probably best to do a starter to wake things up, but do you think you need to if its only been 2 or 3 weeks in the fridge? The big problem though is how do you know how much to pitch with and without a starter? Does that make sense?