What constitutes over pitching?

[sareinhart]

I'm looking into yeast calculations on this page. http://www.yeastcalculator.com

It's pretty cool. Anyway... I found that a while labs vial can contain between 75-150 billion yeast cells. That's a pretty wide margin. Depending on what number you pick, it can really change your results in the calculator. That leads me to the question of over pitching...

I've read enough to understand that over pitching is not a huge concern unless you go really crazy. But... at what point does is become an issue leading to fermentation problems and/or off flavors? at 2x the calculated rate? 3X? 4x? 10x?

 

[Queequeg]

I don't like that calculator because you can't seem to change the pitching rate.

Optimized pitching rates are not fixed in stone and depend on the yeast supply, strain and beer style. The calculation then factors in the gravity and volume to estimate the cells needed from your target pitching rate.

So for example assuming a pure culture from Wyeast or Whitelabs you might want a pitching rate of 0.5 million cells/ml/*plato for a English Bitter, whilst you might want 1M/ml/P for a clean tasting american pale.

When pitch rates are higher fewer esters are produced, so overpitching is relative to what you want to get from the yeast. Pitching 1M/ml/P for a bitter will be an over pitch but not so for a American pale.

Over pitching to the point of producing off flavors is pretty difficult, because your more likely get a stalled fermentation before that happens.

 

[sareinhart]

I don't like that calculator because you can't seem to change the pitching rate.

Optimized pitching rates are not fixed in stone and depend on the yeast supply, strain and beer style. The calculation then factors in the gravity and volume to estimate the cells needed from your target pitching rate.

So for example assuming a pure culture from Wyeast or Whitelabs you might want a pitching rate of 0.5 million cells/ml/*plato for a English Bitter, whilst you might want 1M/ml/P for a clean tasting american pale.

When pitch rates are higher fewer esters are produced, so overpitching is relative to what you want to get from the yeast. Pitching 1M/ml/P for a bitter will be an over pitch but not so for a American pale.

Over pitching to the point of producing off flavors is pretty difficult, because your more likely get a stalled fermentation before that happens.

Thanks, Queequeg. I'm surprised to see you on Home Brew Talk. I thought the white whale took down your ship with Ishmael being the only survivor.

You're telling me that pitching different numbers of yeast cells can yield a different tasting beer - even with the same strain of yeast?

 

[DurtyChemist]

I believe the general consensus is over pitching is harder to do than under pitching. Without taking an accurate cell count you'll never know if you're over or under pitching because calculating yeast vitality isn't linear. You should probably do your best to over pitch and see what happens.

 

[Owly055]

I'd like to know how you would get a stalled fermentation from over pitching?? That seems like an extremely improbable scenario. I frequently grossly over pitch, and have even pitched a batch on top of nearly all the yeast cake / trub from a previous brew. Of course with a "neutral" yeast.

The real issue with over pitching is what you want out of the yeast...... I don't see "off flavors" being even remotely probable.......Unless you look at lack of flavor development as an "off flavor". How much of the yeast's distinctive flavor are you looking for?

I've frequently manipulated temperature to get what I want in terms of flavor, but I have to admit that I have not tried to manipulate pitch rate to get there, and I'm not convinced that we can as home brewers judge pitch rate as far as the number of viable yeat cells with much accuracy.

H.W.

I don't like that calculator because you can't seem to change the pitching rate.

Optimized pitching rates are not fixed in stone and depend on the yeast supply, strain and beer style. The calculation then factors in the gravity and volume to estimate the cells needed from your target pitching rate.

So for example assuming a pure culture from Wyeast or Whitelabs you might want a pitching rate of 0.5 million cells/ml/*plato for a English Bitter, whilst you might want 1M/ml/P for a clean tasting american pale.

When pitch rates are higher fewer esters are produced, so overpitching is relative to what you want to get from the yeast. Pitching 1M/ml/P for a bitter will be an over pitch but not so for a American pale.

Over pitching to the point of producing off flavors is pretty difficult, because your more likely get a stalled fermentation before that happens.

 

[Queequeg]

I have never had a stalled fermentation from over pitching but supposedly its to do with the limited life span of mother cells. When you over pitch the growth phase is diminished and so there are few daughter cells.

I agree about not knowing your pitch rate exactly but you can make provisions for each end of the spectrum. Or invest in a microscope if you are really serious into pitch rates.