Trying to determain the caffeine content of Recipie

[maverick_Ace69]

This is my Sweet Espresso Stout. I was wondering how I could determine the caffeine content of it and any thoughts about it. I used 12 oz of dry ground espresso (Cafe Bustelo) and pitched the yeast today. Any comments are welcome!


% LB OZ
73% 8 0 American Two-row Pale
9% 1 0 Honey Malt
9% 1 0 Flaked Oats
7% 0 12 Chocolate Wheat Malt
2% 0 4 Black Patent Malt
10 0
Batch size: 5.0 gallons


Original Gravity
1.060 measured
hops

boil 60 mins 1.5 Goldings info leaf 5.0
boil 15 mins 0.75 Cluster info leaf 7.0

yeast
English Ale
ale yeast in liquid form with very high flocculation

use time amount ingredient
boil 0 min 12 ounces Coffee, Espresso info
boil 10 min 0.25 ounces Irish Moss in

 

[DavidHawman]

Well coffee is about 125mg of caffeine per cup, a pound of coffee yields about 45 cups.

So 12/16 x 45 = 33.75 cups
33.75 cups x 125mg = 4218mg of caffeine in your 5 gallon batch. So that will get you about 80mg of caffeine per 12oz beer.

This of course assumes that caffeine is extracted at the same percentage as in brewing coffee and that 12 ounces of ground espresso beans yields about 34 cups of coffee. These assumptions especially the extraction assumption could be a bit off, I imagine you'd get higher extraction due to the alcohol and longer soak time.