Hop amount question

[Bulls Beers]

I have a recipe that calls for:
.44 g alpha acids
.29 g alpha acids
.2 g alpha acids

Does this mean .44 grams?

 

[Nugent]

Presumably, but this doesn't make much sense.

First, those proportions of hops in grams are beyond miniscule.

Second, what do you mean by 'alpha acids' - there needs to be a value in a percentage with alpha acids. It's a unit of measurement.

Please clarify.

 

[Bulls Beers]

I know. The recipe is out of a book on Kolsch. Some of the recipes are in oz, and others are in this fashion.

 

[Nugent]

Hmm ... those could be decimal forms for alpha acid percentages. Maybe they're recommending looking for specific alpha acid amounts.

Strange one.

 

[ajf]

What I understand by .44 g alpha acids is .44 g divided by the alpha acid percentage expressed as a decimal.
i.e. if your hops are 5% (0.05) alpha acids, then you need 0.44 g / 0.05 = 8.8 g hops.

-a.

 

[Bulls Beers]

How should I calculate the amount for my hops schedule? Any idea?

 

[Bulls Beers]

Ok thanks.

 

[Bulls Beers]

Doesn't seem to be much hops in this batch.

My calculations are
Perle 8% -.44 g alpha acids = .19oz
Perle 8% -.29 g alpha acids = .13oz
Hersbrucker 3% - .2 g alpha acids = .23oz

Is this right? Seems real low.

 

[david_42]

It's a Kolsh == low IBUs

 

[ajf]

What's the size of the brew?
If you can post the whole recipe, we can check it against the style guidelines, and make recommendations for changes if necessary.

-a.

 

[Bulls Beers]

7lbs Pilsner
.75 Wheat

Hops schedule:
Perle .44 g alpha acids ( boil begin)
Perle .29 g alpha acids ( 40 minutes in)
Hersbrucker .2 g alpha acids ( aroma )

Single infusion @ 149 for 60 minutes.
Boil for 90 minutes.

 

[ajf]

The one critical thing that is missing from the recipe is the batch size.
Assuming it is a 5g batch, with that grain bill, assuming 70% efficiency, and using my equipment, which loses a bit of wort to equipment, you would end up with an OG of 1.040, and 11 IBU's (as predicted by Tinseth)
The BJCP guidelines say OG should be 1.040 - 1.050, and IBU's 20 - 30.
If you reduced the batch size to 4g, you would increase the OG to 1.050, but the IBU's would still be very low at 12.8.
For a 5g batch, I would at least double the Perle hop additions which would get you into the low end of the suggested IBU's, and possibly increase the grain bill a small amount, depending on your efficiency.

-a.

 

[chrisbr]

My apologies for bumping an ancient thread but I had this exact same question about the exact same recipe. I believe I have found the answer and hope this helps future searchers. The numbers all show up as expected when plugged into beersmith with minimal differences due to rounding.

Assumptions:

1.045 OG
22 IBUs

1st addition at 60 minutes, 24% hop utilization, 47.3% of overall IBUs
2nd addition at 20 minutes, 14.65% hop utilization, 31.2% of overall IBUs
3rd addition at 10 minutes, 8.75% hop utilization, 21.5% of overall IBUs

5 gallons = 18.9 liters
1 gram = 0.035 ounces

8.5% alpha acid perle hops for 1st and 2nd additions
2.0% alpha acid hersbrucker hops for 3rd addition

Total g of alpha acid in recipe:

22 IBUs = 22 mg alpha acid / L * 18.9 L = 415.8 mg alpha acid = 0.4158 g alpha acid total

Addition 1:

47.3% of 0.4158 g aa = 0.2 g aa / 24% utilization = 0.82 g aa / 8.5% aa hops = 9.6g hops * 0.035 oz/g = 0.34 oz total for 60 minute hop addition

Addition 2:

31.2% of 0.4158 g aa = 0.13 g aa / 14.65% utilization = 0.89 g aa / 8.5% aa hops = 10.4 g hops * 0.035 oz/g = 0.36 oz total for 20 minute hop addition

Addition 3:

21.5% of 0.4158 g aa = 0.09 g a a / 8.75% utilization = 1.01 g aa / 2.0% aa hops = 51.1 g hops * 0.035 oz/g = 1.79 oz total for 10 minute hop addition