yeast confusion

[buzbey]

so I understand the pitching rate .(.75 million cells) x (milliliters of wort) X ( degrees plato of the wort). For ales. Why then does white labs and wyeast say that there 100 billion yeast cells in a smack pack or vial is good for 5 gallons of wort up to 1.060 when it should really be more around 1.030? In the book yeast they say " keep in mind these suggested pitching rates are for repitching harvested yeast, when pitching a fresh, laboratory culture grown with aeration and good nutrition, a brewer can use up to a 50 percent lower pitching rate". Which I thought wcas the answer to this. But whenever I hear jamil zainasheff talk about pitching rates on the jamil show he always says to make a starter for this gravity of wort and also the mr malty calculator says to make a starter or pitch two packs. why then does a vial say its good for 5 gallons 1.060 wort and why do they say that in the book yeast?

 

[ShootsNRoots]

The viability declines with age. By making a starter you are boosting that viability back to 100%.

Using one of the calculators, try entering a date several months prior to the date you bought your yeast.

IMHO, no one really understands this stuff, some of these calculators were made out of observed results of experiment and some of the calculators use simple curves.

Generally speaking it's very hard to overpitch and easy to underpitch, so it never really hurts to make a starter.

 

[BigFloyd]

The viability declines with age. By making a starter you are boosting that viability back to 100%.

Using one of the calculators, try entering a date several months prior to the date you bought your yeast.

IMHO, no one really understands this stuff, some of these calculators were made out of observed results of experiment and some of the calculators use simple curves.

Generally speaking it's very hard to overpitch and easy to underpitch, so it never really hurts to make a starter.

+1.

Remember, by the time the pack/vial gets to you and you get around to brewing/pitching, a good portion of those 100 billion cells have gone to yeasty heaven.

For most folks, the only time you'll encounter a problem with over-pitching is when you pour a batch of average gravity beer on a whole yeast cake from a batch that just finished fermenting.

If I'm using liquid yeast that's not recently-harvested slurry, I'm going to get a starter going on the stirplate.

 

[Nomad]

I was asking myself the same thing as the OP about a year ago, and after having a slow, estery fermentation on a *three gallon* batch pitched with a fresh Wyeast 550 culture, I decided I would always make a starter. I don't think the two big liquid yeast companies have any reason to stick us on viable yeast, but I do think its tough to keep even a fresh culture healthy for long.

 

[buzbey]

Even if a vial of white labs is 100 percent viable its still only 100 billion cells. Which is not enough for 5 gallons of 1.060 wort. I will be making starters to increase the counts for normal pitching rates but am still confused

 

[ShootsNRoots]

Even if a vial of white labs is 100 percent viable its still only 100 billion cells. Which is not enough for 5 gallons of 1.060 wort. I will be making starters to increase the counts for normal pitching rates but am still confused

Yeast are always multiplying. The 100 billion cells in that vial will multiply according to some growth rate (which I'd guess Wyeast and White Labs have calculated based on ideal conditions) up to or even beyond the number of cells required for fermentation. The problem comes in because of what I alluded to earlier when the viability of the yeast in the vial decline, or they don't have enough nutrients or oxygen or what have you.

Think of your wort as a huge starter where that little vial multiplies into a huge yeast cake. In fact you can re-use the yeast from your fermentation, though, as opposed to an actual starter, you'll have a lot of trub and dead yeast that needs to be washed from the good yeast.

I believe both White Labs and Wyeast say 1 vial/smack pack is good for ales < 1.060 and fermented @70F. You therefore know they are using that as the baseline for their estimated yeast growth in your wort.

The fact is that 1 vial or smack pack does ferment 5 gallons of wort, however, it may not be able to do the best job that can be done due to the conditions imposed on it (cold lager, not enough nutrients, hot fermentation temp, a lot of trub, etc...). Those conditions outside of the recommended 5 gallons of < 1.060 @ 70F.

Wyeast

6. Do I need to make a starter for an Activator?

No. The Activator is designed to deliver professional pitch rates (6 million cells/ ml.) when directly added to 5 gallons of wort. ( <1.060 at 70 degrees). However, if a package is slow to swell, suspected of being mishandled, or if the date is approaching the six month shelf life it is a good idea to build the culture up with a starter. High gravity or low temperature fermentations require higher pitch rates. This can be achieved with inoculating with additional packages or making a starter.

 

[buzbey]

Thanks! It finally makes some sense now. So in reality you could use a 50 percent lower pitching rate if it is very fresh yeast. And the mr malty calculator says to make a starter assuming you have dated product? now I'm understanding why there's different information from the same sources, there leaving out the small details that should (for the most part) be overlooked. That being said I will still be making starters.