Custom attenuation

[Marc ook]

Hello,
I'm running into problems trying to tune my profile to past brewing sessions. I've noticed that the F.G prediction is very high relative to what I generally get. So I've tried to get the F.G. prediction correct by using a custom attenuation as per FAQ. That is where the results get weird:
I have for instance an Dusseldorfer Alt batch that fermented from 1.046 to 1.010, just as expected for my usual Wyeast #1007 high end attenuation (78%). The recipe builder however gives a F.G of 1.017 with the default settings (alledgedly 75% attenuation, but I would think (46-17)/46 is about 63%). If I want the prediction to match my brewing (and the BJCP style guide) I need to fill in a custom attenuation of 93%. That sounds highly unlikely. Stranger yet: if I use 100% attenuation the beer supposedly ends at 1.007. That's even more unexpected...
Is this a bug or am I missing something?

I'm using the on-line recipe editor on Win7/32+Firefox 41.0.1

 

[Ozarks Mountain Brewery]

unfortunately your not alone, I see this a lot when it comes to converting recipes from another software or even spreadsheet to here, the only thing I advise is to go through your profile, general and equipment settings and go back the drawing board and find all your losses then set up your equipment properly and pick it in the recipe builder under the more button, also the size of your batch, kettle and brew house efficiency is very important to get a correct beginning and final gravity, I rarely have to change the attenuation more than a couple of points my self

 

[Taitoko]

Hi guys. The custom attenuation function is definitely throwing weird numbers. I use it all the time and have only had
a problem in the last couple of days.

 

[PZ]

This issue is important because apparent attenuation is a good way of comparing different batches and even different styles. Even if there are differing opinions on how to calculate the number or how useful it is, it should be consistent across the site. The brew log and stand-alone calculator give slightly different results which could be due to rounding, but the recipe builder is way, way off. Inconsistencies like this (and the calcium chloride weight to volume calculation) make the software appear amateurish.

Another beef is that no one (Austin???) acknowledges these issues, much less making an attempt to fix them.

Thanks, PZ

 

[Ozarks Mountain Brewery]

I'm not positive but I'm pretty sure its from opening their new store and programing has been moved to that site, I think it will return once they get things running smoothly
http://www.homebrewsupply.com

 

[Josh (Brewer's Friend)]

Hi guys,
Firstly I really want to apologize for the lack of communication on this. Unfortunately Austin has had to move on, so we're scrambling to get caught up with what he was managing, including the forum. I'm hoping to get fully up to speed soon and will be on point going forward. If you notice something that isn't getting traction or that you think I've missed, please feel free to email me here, which may get my attention faster:
http://www.brewersfriend.com/feedback-welcome/

Now, on to the brewing related things. I've done some investigation on this, and I think I have an answer. Earlier this year, we added a feature to adjust attenuation based on mash temperature. The way this works is it looks at your mash guidelines and picks the one that it thinks is the saccharification step, using that temperature to adjust the attenuation, and FG. The issue here is that it's picking the wrong mash step to use. I looked at your Alt recipe, and it appears that your final decoction step of 45min is being used since it's the longest hold in the reasonable saccharification temp range. (to verify this, try changing the temp of that step and see if the FG adjusts).

Now the fix, we have a few options:
1. Refine the way we select the step used for temp. This is tough since that step looks like the primary step, unless you're a human smart enough to know better
2. Change the range of temps that we look for - right now we look for steps between 145 and 163, but that might be a little large.
3. Instead of choosing the step by time, we choose by closest step to the middle of that range, e.g. 153 or so.

I'm leaning toward #3, maybe with the caveat that the step needs to be a minimum of 30 minutes or something like that. What do you guys think?

 

[PZ]

Thanks very much for answering, Josh. I can't speak for anyone else, but when I type in a custom attenuation, I have already taken into consideration the fermentability of the wort. My preference would be to let the attenuation (be it custom or average for the yeast) dictate the FG. If people want to allow a set of algorithms to determine the FG/attenuation that could be an additional option but I prefer not to have a bunch of logic under the covers that I can't see. Also, the direct calculation would make the recipe builder consistent with the brew log and basic calculator.

I have to say that trying to predict the FG based on the mash schedule is ambitious. I would think that the variability of equipment would make it impossible, but it is interesting. Good luck with it!

Brew on, PZ

 

[Josh (Brewer's Friend)]

Thanks for the thoughts PZ. Definitely understand where you're coming from. I suppose our thinking was that we'd treat the yeast attenuation property as a constant across recipes. Then we'd scale that attenuation based on the composition and mash statistics of each individual recipe. Either way, I think you're right that it would be helpful to have a toggle for this behavior. I'll work on building that in as soon as I can.