[metron-brewer]

I'm planning on a 1.048 German Pils using W-34/70 for the first time. Yeast packs dated 01-2016 so production date 01-2014 and 69% viable. BeerSmith says I need 353 billion cells and (2) packs of yeast yielding 276 billion, a bit of an under pitch as calculated by BeerSmith. Mr. Malty indicates using 2.50 packs yielding approximately 345 billion cells. The cost of the third pack is not an issue, just want to make the best beer.
So my question is, pitch 2 packs at 276 billion, or 3 packs at 414 billion?

I have not decided on the mach schedule yet, may just do a single infusion but the Recipe Specifics:
Recipe: German Pils
Brewer: Ron
Asst Brewer:
Style: German Pilsner (Pils)
TYPE: All Grain
Taste: (30.0)

Recipe Specifications
--------------------------
Boil Size: 7.98 gal
Post Boil Volume: 5.98 gal
Batch Size (fermenter): 5.25 gal   
Bottling Volume: 5.25 gal
Estimated OG: 1.0479 SG
Estimated Color: 3.0 SRM
Estimated IBU: 38.3 IBUs
Brewhouse Efficiency: 75.00 %
Est Mash Efficiency: 82.1 %
Boil Time: 60 Minutes

Ingredients:
------------
Amt                   Name                                     Type          #        %/IBU         
9.00 lb               Best Malz Pilsen Malt (2 Row) German Pil Grain         1        100.0 %       
2.00 oz               Hallertauer [3.10 %] - Boil 60.0 min     Hop           2        23.5 IBUs     
1.00 oz               Hallertauer [3.10 %] - Boil 30.0 min     Hop           3        9.0 IBUs     
1.00 oz               Hallertauer [3.10 %] - Boil 15.0 min     Hop           4        5.8 IBUs     
1.00 Items            Immersion Chiller/Pump (Boil 15.0 mins)  Other         5        -             
0.50 tsp              Yeast Nutrient (Boil 10.0 mins)          Other         6        -             
0.50 Items            Whirlfloc Tablet (Boil 5.0 mins)         Fining        7        -             
1.00 oz               Huell Melon [4.50 %] - Boil 0.0 min      Hop           8        0.0 IBUs     
2.0 pkg               Saflager Lager (DCL/Fermentis #W-34/70)  Yeast         9        -             


Mash Schedule: Single Infusion, Medium Body, Batch Sparge
Total Grain Weight: 9.00 lb
----------------------------
Name              Description                             Step Temperat Step Time     
Mash In           Add 14.00 qt of water at 154.9 F        145.0 F       45 min       
Mash Out          Add 8.00 qt of water at 189.3 F         160.0 F       45 min       

Sparge: Batch sparge with 2 steps (Drain mash tun , 3.56gal) of 185.0 F water

[morticaixavier]

you're probably fine with the two packs.

[HoosierBrew]

you're probably fine with the two packs.

+1.  Plenty for a 1.048 beer IMO.

[metron-brewer]

(2) It is. Thanks Guys!

[metron-brewer]

Maybe just a follow up here. Why would it be ok to under pitch with dry yeast but not with liquid?

[HoosierBrew]

I don't think it's ever a good idea to underpitch a lager (or any beer) in a significant way. But for a sub 1.050 lager, I've had good results (clean beer, good attenuation) rehydrating two packs. And I've seen several brewers here and elsewhere who reported good results doing the same. Worst case you could always hit it exactly and pitch the extra half pack.

[jtoots]

Worst case you could always hit it exactly and pitch the extra half pack.

That's what I was thinking, but lots of experience above saving you a few bucks.

[morticaixavier]

Maybe just a follow up here. Why would it be ok to under pitch with dry yeast but not with liquid?

three reasons,

first, at the levels of underpitch you are talking about there is just not that much to worry about even with liquid.

second, the calculators tend to be very conservative about yeast viability over time anyway.

Third, these are all just estimates and you are likley within the margin of error anway.

[metron-brewer]

Thanks guys, appreciate it.

[S. cerevisiae]

Yeast cultures are kind of like nuclear weapons in that being close to the target is more than adequate to get the the job done.  The difference between 276 billion cells and 353 billion cells is not even a full replication cycle.  The yeast biomass cell count grows roughly at a rate of 2ⁿ, where n is the number of minutes that have elapsed since the end of the lag phase divided by 90 at 25C.  The replication period lengthens as fermentation temperature decreases.

[rabeb25]

Your Pitch Rate for this particular venture is dependent on your fermentation temp... what is that going to be?

[metron-brewer]

Your Pitch Rate for this particular venture is dependent on your fermentation temp... what is that going to be?

The yeast is rated 48-59, I'm planning on running to the lower end, 48-50 degrees.

[rabeb25]

Then I strongly suggest you look at the manufacturers pitch rate for that temp.. because it GREATLY differs at that low range.

[beersk]

Yeast cultures are kind of like nuclear weapons in that being close to the target is more than adequate to get the the job done.  The difference between 276 billion cells and 353 billion cells is not even a full replication cycle.  The yeast biomass cell count grows roughly at a rate of 2ⁿ, where n is the number of minutes that have elapsed since the end of the lag phase divided by 90 at 25C.  The replication period lengthens as fermentation temperature decreases.

This is good to know. Thanks.

I've always pitched 2 packs of 34/70 (rehydrated) and it worked out just fine.

[metron-brewer]

Then I strongly suggest you look at the manufacturers pitch rate for that temp.. because it GREATLY differs at that low range.

Per the spec sheet:
"increase dosage for pitching below 12°C (53°F), up to 200 to 300 g/hl at 9°C (48°F)"

So if I'm doing the math correctly, for 5.25 gallons, say 20 liters, fermenting at 48-50 degrees, I should be pitching somewhere between 40 to 60 grams of yeast. Basically 3 to 5 11.5 gram packets. Understanding that pitching "exactly per spec" may not be required in real world home brewing applications. And while two packets may work just fine and people have had great success with that, pitching 3 or 4 packets to me may be cheap insurance.