Calculation Confusion! Effiency & Ibu Calcs

[piraterum]

Ive trying to get my head around calculating the efficiency of my mini mash procedure and determining the IBU of the batch to no avail. Any pointers would be greatly appreciated!


Firstly calculating the mini mash efficiency:

The mini mash procedure produced 7L of 1.040 gravity wort using 2.5kg of grain. The wort was boiled and 1.5kg of LME was added to the wort. The final volume after 1 hour of boil time was 5.5L. This was mixed with water to create a final volume of 20.5L.

Using Palmers (http://www.howtobrew.com/section2/chapter12-5.html) I get the following figures

1.5 kg (3.31 lbs) Ale Malt
1 kg (2.2 lbs) Wheat Malt

2.5kg (5.51 lbs) malt to produce 7L (1.54 gallons) of 1.040 gravity wort.

Malts OG based on Max PPG
3.31 lbs of 2 row malt 37 x 3.31 / 1.54 = 79.52
2.2 lbs of wheat malt 30 x 2.2 / 1.54 = 42.85

Total = 122.38 points

The mash extraction of 1.040 means the percent efficiency is 40/122.38 = 32.68% Is this correct?? It seems very low! :huh:

Calculating the IBU of the batch details of brew:


Malts

1.5kg Pale malt
1kg wheat malt
2.5kg grain total

Extract
1.5kg Morgans Pale Malt


Hops

EK Goldings 4.8%AAU 13g 60 min
US Cascade 6.3%AAU 12g for 60 min
US Cascade 6.3%AAU 25g for 10 min


Yeast

Wyeast 1056 American Ale

Initial strike attempt to make 2.5kg grain to 7L water ratio
Only enough room in mash tun for 6.3L water, temp = 74c
Mash temp ~64c after mixing grain with strike water

1st runnings = 3.5L (2.8L lost to grain)

Sparge intended to add 6 L only enough room for 3.75 L, temp 84c

2nd runnings = 3.5 L (0.25L lost to grain)

Before boil Total runnings = 7L (total 10.05 L added, lost 3.05L to grain)

Pre boil gravity = 1040

1.5kg Extract added at 40min, boil returned, whirfloc for last 15 mins

After 60min boil total = 5.5L (1.5 L lost to evaporation)

Water added = 15L to make final volume 21.5L
Initial gravity before pitching = 1.048

Ive tried several formulas and I seem to get conflicting results. Using the hop bitterness tool in Beersmith I get IBUs ranging from 9.7-17. Clearly Im making a mistake somewhere. It was suggested an IBU of around 35 would be appropriate for this beer style.

Any help would be greatly appreciated! :icon_cheers:

Cheers,

piraterum

 

[Stuster]

A couple of things spring to mind. First, did you cool the sample before taking your hydrometer reading? It doesn't seem that that reading can be right. Your calculation seem about right and using that 35% efficiency and adding the malt extract, there's no way you'd get close to 1048 for 21.5L. So one of the readings must be out.

Your bitterness level does seem as though it's going to be very low. It's hard to say since you added the LME part way through the boil, but with a concentrated boil like this it's probably going to be only around 10IBUs according to Beersmith.

 

[piraterum]

A couple of things spring to mind. First, did you cool the sample before taking your hydrometer reading? It doesn't seem that that reading can be right. Your calculation seem about right and using that 35% efficiency and adding the malt extract, there's no way you'd get close to 1048 for 21.5L. So one of the readings must be out.

Your bitterness level does seem as though it's going to be very low. It's hard to say since you added the LME part way through the boil, but with a concentrated boil like this it's probably going to be only around 10IBUs according to Beersmith.

Ahhh thanks for your help. I don't recall cooling the sample before the boil, so the high temp would result in an inaccurate low reading.

I found some details from a previous brew which yielded a pre boil gravity of 1.080. That kind of figure makes more sense and yields an efficiency around 65% which sounds more feasible.

For the hop schedule I based it on Grumpy's recipe (http://www.grumpys.com.au/r1.php3?recipeid=9) which now having run the numbers through Beersmith seems to yield a very low IBU for an American Pale Ale style. If i'm calculating it correctly I should have added something like 60g EK Goldings and 56g Cascade for 1 hour, especially given the high gravity of the wort and the relatively small boil volume