Extract -v- Partial Mash IBU's

[billym99]

Quick question... created a recipe in Beersmith and chose Partial Mash as the type and noticed that the IBU's of the recipe significantly change if the type is changed to Extract and was wondering the reasoning behind this. I was surprised to see that the IBU's are nearly cut in half for PM as opposed to Extract (26.3 down to 15).

I believe that I've read the amount of sugars and enzymes affect the amount of alpha acids that are extracted from the hops. I guess Beersmith figures if you choose Extract you are only steeping grains, although there is not that much grain in the recipe (2#).

 

[Haputanlas]

Well, check to make sure that the gravities are the same. It would be hard for the software to assume anything about your beer process (Unless the gravities are different).

 

[billym99]

The gravity's are different, extract is lower and i'm assuming that is because of the difference between mashing and steeping the grains that are included in the bill, mashing of course extract more fermentables.

I'm just confused on why the IBU's would have a significant change if the boil volume/length and amount of hops are not changed.

My only thought is that *maybe* beer smith ignores the late addition of extract when using partial mash and considers it to be in the entire 60 minute boil?

 

[ayoungrad]

Is your extract recipe a late extract addition and therefore you would have significantly lower gravity during the majority of the boil? Many formulas take gravity (right or wrong) into account when calculating IBU's. With those types of calculations, higher gravity wort means decreased hop utilization.

 

[billym99]

Is your extract recipe a late extract addition and therefore you would have significantly lower gravity during the majority of the boil? Many formulas take gravity (right or wrong) into account when calculating IBU's. With those types of calculations, higher gravity wort means decreased hop utilization.

Makes sense, and yes, the recipe uses primarily late addition extract. It's still marked late addition for PM, but I'm assuming Beersmith ignores this.

 

[ayoungrad]

The PM may also have a late extract addition but I'd be willing to bet that the PM recipe has a higher SG than the extract recipe (presumably with steeping grains) prior to the late additions.