### Day 24, Engineering review and Brewing Calculations

I would like to apologize in advance for all the techno-jargon.

Engineering currently seems rather easy, I sure hope it stays that way. On Thursdays we usually have a free period in the morning, but today we had a bonus lecture on brewing calculations by our future lab instructor. Other than it being kind of long, about 2 1/2 hours, I enjoyed it and I think I will use the information a lot in the future.

Here is one of the many equations we learned today.

The hop utilization (%) equals (the output times 100) divided by the input. In other words, the hop utilization % = [(iso-alpha-acids present in beer or IBU's)(1 mg/liter)(100)]/[(kg of hops/hl of brew)(1,000,000 mg/kg)(1 hl/100 liters)]

to explain, the:

(1 mg/liter) is the conversion for 1 IBU to reach consistent units (though this conversion is not completely precise according to the ASBC, but it should be more than sufficient for everything that I will need to compute)

(100) turns the number into a percentage

(1,000,000 mg/kg) and (1 hl/100 liters), both of these numbers convert into the desired units

It is funny to me that this is one of many things that I must memorize for tomorrow, since this equation means didly without an equation for determining IBU's. We also learned that one, but we are not expected to memorize it.

In case any nerds exist that wish to do a calculation, here is an example:

A brewer adds 5 kg of alpha acids to a 1000 hl brew. The lab tests the beer and reports it to have 15 IBU's. What was the hop utilization %.

## 6 Comments:

Oh I so want to crunch the numbers but I have a ton of stuff to work on this morning....maybe later!

? for you though...

Why do you guys use hectaliters (hL), its such an odd unit prefix, and by that I mean not that many people use it. Seems like kilo would be more common place and isn't that far off of hecta (kilo = hecta/10)? Is it just because of tradition or something? Just curious.

8:22 AM

This comment has been removed by a blog administrator.

8:35 AM

What are the units on IBU's? or is it like pH and is unit less? you state "(1 mg/liter) is the conversion for 1 IBU to reach consistent units" but if IBU's has units then the units in the equation don't cancel out?

Well ok I couldn't resist (and yes I am that much of a nerd), I did the calculation and got 300% but that doesn't seem right.

Also doesn't hop utilization depend on the SG of the wort as well?

10:29 AM

I knew you'd fall into my trap. The answer is 30%, check your zero's, you might have forgotten one of them in the denominator. I guess I should have explain IBU's more fully, 1 IBU is the percieved bitterness from a solution of 1 mg of iso-alpha acids in 1 liter of beer.

You make a good point about the role of the original gravity. We were told that the hop utilization % does decrease as the original gravity increases. But it changes on other factors as well, mainly brewhouse efficiency. So it is best to calculate this number after every batch.

As for hectaliters, they are used everywhere except the U.S. for quantifying beer output. I believe the reason is because it is so similar to barrels. 1 barrel = 1.1734 hl = 31 gallons

2:00 PM

I knew I had something off but had to get back to work so I didn't have time to double check, oh well!

Anyway thanks for the info about the IBU's and hL, just thought that was a little odd.

2:11 PM

It would be bad news for hop growers if you could get 300% utilization. I suppose that would be impossible, but people are always telling me to give 110%.

9:14 PM

Post a Comment

<< Home