Grain/Malt Conditioning & Absorption Rate

[cactusgarrett]

I just did my first brew on my new AIO system, and am conducting a post mortem to determine what to tweak in my personal spreadsheet and BeerSmith profile. As my pre-boil volume was about 0.5 gal higher than expected, the only thing seemingly affecting that is that the grain absorption rate has decreased. To hedge my bets and prevent a clogged pump, I used a handful of rice hulls (rinsed/pre-soaked) for the and conditioned my grain (~11 lbs). I've never had an issue with rice hulls in the past in this regard, so the only thing left is the absorption.

Mill my own grain (and haven't changed the gap), and I've previously used an absorption rate of 0.50 qt/lb (0.125 gal/lb) with accurate and predictable results. However, with 0.5 gal extra pre-boil volume on my AIO, this adjusted rate is 0.38 qt/lb (0.095 gal/lb). Logic would dictate changing to an AIO and all else being equal, absorption shouldn't change. Does anyone that conditions their grain experience this decrease in absorption? I haven't found any references to this happening or why it would.

 

[DonT]

I don't condition grain, but I can't see it changing the absorption rate in any measurable way.

 

[cactusgarrett]

I can't see it changing the absorption rate in any measurable way.

Right. I wouldn't think so either, but it's practically the only factor affecting my pre-boil volume and the difference I've seen from my previous brew days. I really don't think the changeover to an AIO system using a malt pipe affected it.

 

[DonT]

Using an All-In-One type system won't affect grain absorption but figuring out your deadspace can be a hassle. I always struggled with water volumes on my Grainfather...

 

[cactusgarrett]

I believe I've got all the other factors dialed in: recoverable dead space under the false bottom, dead space on pump transfer, etc. However, none of that should really matter since this is essentially between the mash and pre-boil. Absorption seems to be the only wildcard.

 

[DonT]

I just re-read your first post and you state you ended up with .5 gal. too much which brings down the absorption rate. That can't happen as far as I know. Maybe you're confusing mash thickness with absorption?

 

[doug293cz]

I just re-read your first post and you state you ended up with .5 gal. too much which brings down the absorption rate. That can't happen as far as I know. Maybe you're confusing mash thickness with absorption?

Why do you think that can't happen? Reducing the grain absorption rate will give you a higher pre-boil volume, if you use the same strike and sparge volumes. After all, the formula for calculating grain absorption rate is:

Absorption Rate = ((Strike Volume + Sparge Volume) - Pre-Boil Volume) / Grain Weight​

or​

Pre-Boil Volume = (Strike Volume + Sparge Volume) - Absorption Rate * Grain Weight​

For best accuracy, all volumes should be temperature expansion adjusted to the same temp.

Brew on

 

[cactusgarrett]

Why do you think that can't happen? Reducing the grain absorption rate will give you a higher pre-boil volume, if you use the same strike and sparge volumes. After all, the formula for calculating grain absorption rate is:

Absorption Rate = ((Strike Volume + Sparge Volume) - Pre-Boil Volume) / Grain Weight​

or​

Pre-Boil Volume = (Strike Volume + Sparge Volume) - Absorption Rate * Grain Weight​

For best accuracy, all volumes should be temperature expansion adjusted to the same temp.

Brew on

Not to mention: this was full volume/no sparge. Not many variables to fudge here.

 

[DonT]

Why do you think that can't happen? Reducing the grain absorption rate will give you a higher pre-boil volume, if you use the same strike and sparge volumes. After all, the formula for calculating grain absorption rate is:

Absorption Rate = ((Strike Volume + Sparge Volume) - Pre-Boil Volume) / Grain Weight​

or​

Pre-Boil Volume = (Strike Volume + Sparge Volume) - Absorption Rate * Grain Weight​

For best accuracy, all volumes should be temperature expansion adjusted to the same temp.

Brew on

I was taking that literally, because actual grain absorbs water. But you can fudge the numbers.... and it appears the OP is using full volume

 

[DuncB]

Maybe the rice hulls have let your no sparge drain a bit more than usual?
Do you have different figures for different grain bills surely the absorption will change if more wheat, oats etc.
You mention more volume pre boil but what about the gravity pre boil temp corrected how was that?
as @doug293cz mentions correction for temp / expansion is very important, I don't use beersmith just collect all my data and am slowly building some consistency but with system changes nearly every brew ( I'm nearly finished modding) and different hops etc it is a variable feast.
I have always conditioned my grains, not wheat, flaked adjuncts or roasted grains or naked oats, so can't say re your original comment. But 2% of 5kg is very little water.
Final query in the ramble how big was your batch, if it was a 50 litre plus no sparge then 0.5 gallon might be within a margin of the many errors.

 

[cactusgarrett]

Do you have different figures for different grain bills

I don't, as I typically don't utilize wheat or dehusked grains in a considerable amount.

what about the gravity pre boil temp corrected how was that

Despite the volume being 0.5 gal higher than originally projected, my pre-boil gravity was 0.007 higher than BeerSmith predicted (refractometer read, cooled), so my mash efficiency was much higher than BeerSmith predicted. I used a Hochkurz temp schedule, btw.

as @doug293cz mentions correction for temp / expansion is very important

All my volume measurements (aside from volume into the fermenter) are done hot/at temp.

But 2% of 5kg is very little water

EVERYthing I've read re: conditioning states to use 2% water by weight. With a 10.3 lb grainbill, I used 3 oz of water (by weight).

how big was your batch

10.3 lb (4.7 kg) grainbill with preboil of 8.0 gal (30.3 L). Shooting for 5.5 gal into the fermenter.

 

[DuncB]

Sorry I meant 100ml is not much water. But it is the right amount, I use 2% as well.

I've found better efficiency with more mash water. I do give the mash a really good squeeze though at the end. I'll look up my numbers from last brewday.

 

[Witherby]

Not to mention: this was full volume/no sparge. Not many variables to fudge here.

This may or may not help, but it I thought I'd throw it out there anyway...

I do no sparge in my Foundry and use a modified BIAB mash profile in Beersmith. The one Beersmith setting that I would never have seen or heard of is the "BIAB Grain Absorb" in the advanced setting. There is a Brulosophy Beersmith tutorial that talks about this and they recommend changing that from the default to .96 because normal BIAB presumes squeezing and no sparge doesn't.

The tutorial is here and the section I am talking about starts about 2:30 into the video:
No Sparge Brewing: How-To + BeerSmith Tutorial