beersydoesit
Well-Known Member
I spent some time over the weekend researching yeast and pitching rates and thought I'd share what I found.
Wyeast Activator smack packs contain a minimum of 100 billion cells plus nutrient, and according to Wyeast, is ready and able to inoculate directly 5 gallons of wort with a specific gravity up to 1.060, at "the pitching rate recommended by professional brewers."
Wyeast also makes a smaller Propogator pack that has 25 billion cells that is designed for making starters.
White Labs offers vials. Their web site states:
"We package each vial with 70 to 140 billion yeast cells, which corresponds approximately to a 1-2 liter size starter."
White Labs' web site states a vial is designed to ferment a 5 gallon batch.
Further they indicate a starter should be used:
"if the gravity is over 1.070, if the yeast is past its "best before" date, or if a faster start is desired."
So both White Labs and Wyeast suggest 100 billion cells or so for OGs of 1.070 and 1.060 respectively
MrMalty indicates that for a 1.060 OG you need 208 billion cells. wtf?
Doing a little quick math, Wyeast's 100 billion cells divided by 18,927 ml in 5 gallons = 5.28 million cells per ml.
Dividing that by 15 degrees plato (60/4 for a 1.060 gravity) yields 352,000 cells/ml/degree Plato.
MrMalty assumes about 750,000 cells/ ml/ degree Plato.
750,000 * 15 degrees plato * 18927 ml = 213 billion cells.
There seems to be a broad consensus that beer should be inoculated with .75 million cells/ ml/degree Plato for ales and 1.5 million cells/ml/degree Plato for lagers.
There is a lot of background here that I don't mean to go into now. However there seems to me to be an assumption that yeast has been harvested and will be repitched as in a commercial brewery.
So, what is going on?
Both Wyeast and White Labs indicate that their yeast is propagated under ideal sterile conditions and is therefore in better shape than what is expected by MrMalty. Further they argue the .75 million to 1.5 million cell/ml/degree Plato values are really pitch rates for repitched yeast as described above.
What to do?
Let us start with the easy ones.
With White Labs OGs over 1.070 should have a starter for sure. ( Except I believe they market some yeasts specifically for high OG beers. Those are outside the scope of this post).
Similarly Wyeast with OGs over 1.060, make a starter.
If your yeast is old, or if you suspect it has had a rough shipment, make a starter.
As to the rest, I don't know. I'm inclined to trust White Labs and Wyeast, and I seem to get fresh yeast at my LHBS but I haven't been brewing that long.
I've seen some suggest that while a starter may not necessarily be needed below 1.060, they get more consistently good results by using a starter.
I haven't been brewing long enough to argue with that.
I've brewed big beers (OG 1.080) with one Activator with tasty results. The yeast was fresh, and perhaps I got lucky. I wouldn't bet on that working again.
But for OG 1.060 with fresh White Labs or Wyeast I might.
I've also pitched two Activator packs in one batch. Kinda pricey.
Making a starter isn't hard but there are downsides
1) You have to start it days ahead.
2) For a noob, everything can be a little overwhelming so if a starter isn't strictly necessary it might not be worth it. (Or it might be better to spend a little more and pitch two Activators or Vials)
3) It approximately doubles your risk of infection. Essentially you brew two beers, (one small) and each carries a risk of infection. If your sanitizing practice is good this risk remains small but non-zero.
MrMalty has a pitch rate calculator here
Mr Malty Pitching Rate Calculator
I like Wyeast's better here
Wyeast Laboratories : Home Enthusiasts : Brewers : Pitch Rate Calculator
because it tells me how many cells/ml I am getting. Even if I accept the higher pitching requirements this calculator is nice. It also has nice starter making instructions.
That is liquid yeast, what about dry?
Danstar's Nottingham yeast has about 5 billion cells per gram and comes in 11 gram packets. That is 55 billion cells per packet.
So two packets would compare in cell count to an Activator pack.
Indeed from Danstar's website the rehydration and usage tips seems to suggest 1g/L, or 20 grams in 5 gallons.
Danstar Premium Beer Yeasts - The Dry Yeast Advantage
I haven't used dry yeast so I don't know how many packets people use.
I've found no evidence that anyone feels there is a risk of a homebrewer over pitching yeast.
A good weekend for me.:rockin:
Wyeast Activator smack packs contain a minimum of 100 billion cells plus nutrient, and according to Wyeast, is ready and able to inoculate directly 5 gallons of wort with a specific gravity up to 1.060, at "the pitching rate recommended by professional brewers."
Wyeast also makes a smaller Propogator pack that has 25 billion cells that is designed for making starters.
White Labs offers vials. Their web site states:
"We package each vial with 70 to 140 billion yeast cells, which corresponds approximately to a 1-2 liter size starter."
White Labs' web site states a vial is designed to ferment a 5 gallon batch.
Further they indicate a starter should be used:
"if the gravity is over 1.070, if the yeast is past its "best before" date, or if a faster start is desired."
So both White Labs and Wyeast suggest 100 billion cells or so for OGs of 1.070 and 1.060 respectively
MrMalty indicates that for a 1.060 OG you need 208 billion cells. wtf?
Doing a little quick math, Wyeast's 100 billion cells divided by 18,927 ml in 5 gallons = 5.28 million cells per ml.
Dividing that by 15 degrees plato (60/4 for a 1.060 gravity) yields 352,000 cells/ml/degree Plato.
MrMalty assumes about 750,000 cells/ ml/ degree Plato.
750,000 * 15 degrees plato * 18927 ml = 213 billion cells.
There seems to be a broad consensus that beer should be inoculated with .75 million cells/ ml/degree Plato for ales and 1.5 million cells/ml/degree Plato for lagers.
There is a lot of background here that I don't mean to go into now. However there seems to me to be an assumption that yeast has been harvested and will be repitched as in a commercial brewery.
So, what is going on?
Both Wyeast and White Labs indicate that their yeast is propagated under ideal sterile conditions and is therefore in better shape than what is expected by MrMalty. Further they argue the .75 million to 1.5 million cell/ml/degree Plato values are really pitch rates for repitched yeast as described above.
What to do?
Let us start with the easy ones.
With White Labs OGs over 1.070 should have a starter for sure. ( Except I believe they market some yeasts specifically for high OG beers. Those are outside the scope of this post).
Similarly Wyeast with OGs over 1.060, make a starter.
If your yeast is old, or if you suspect it has had a rough shipment, make a starter.
As to the rest, I don't know. I'm inclined to trust White Labs and Wyeast, and I seem to get fresh yeast at my LHBS but I haven't been brewing that long.
I've seen some suggest that while a starter may not necessarily be needed below 1.060, they get more consistently good results by using a starter.
I haven't been brewing long enough to argue with that.
I've brewed big beers (OG 1.080) with one Activator with tasty results. The yeast was fresh, and perhaps I got lucky. I wouldn't bet on that working again.
But for OG 1.060 with fresh White Labs or Wyeast I might.
I've also pitched two Activator packs in one batch. Kinda pricey.
Making a starter isn't hard but there are downsides
1) You have to start it days ahead.
2) For a noob, everything can be a little overwhelming so if a starter isn't strictly necessary it might not be worth it. (Or it might be better to spend a little more and pitch two Activators or Vials)
3) It approximately doubles your risk of infection. Essentially you brew two beers, (one small) and each carries a risk of infection. If your sanitizing practice is good this risk remains small but non-zero.
MrMalty has a pitch rate calculator here
Mr Malty Pitching Rate Calculator
I like Wyeast's better here
Wyeast Laboratories : Home Enthusiasts : Brewers : Pitch Rate Calculator
because it tells me how many cells/ml I am getting. Even if I accept the higher pitching requirements this calculator is nice. It also has nice starter making instructions.
That is liquid yeast, what about dry?
Danstar's Nottingham yeast has about 5 billion cells per gram and comes in 11 gram packets. That is 55 billion cells per packet.
So two packets would compare in cell count to an Activator pack.
Indeed from Danstar's website the rehydration and usage tips seems to suggest 1g/L, or 20 grams in 5 gallons.
Danstar Premium Beer Yeasts - The Dry Yeast Advantage
I haven't used dry yeast so I don't know how many packets people use.
I've found no evidence that anyone feels there is a risk of a homebrewer over pitching yeast.
A good weekend for me.:rockin: