Do Unconverted Starches Affect SG?

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk:

Evan!

Well-Known Member
Joined
Aug 9, 2006
Messages
11,835
Reaction score
104
Location
Charlottesville, VA
I attempted my first decoction on Saturday, and after a grueling 4-hour mash process, and 60 minutes of the final conversion rest at 159f, I was still testing positive for starches in my mash. I decided to proceed with the boil anyway, and my efficiency was great---85%. But I'm wondering: since there were still unconverted starches left in the beer, is it possible that at least some of my gravity points are coming from unfermentable starches?
 

ColoradoXJ13

Well-Known Member
Joined
Dec 9, 2006
Messages
1,257
Reaction score
26
Location
Somerville
yes, and your resulting FG will be higher...this is the problem I have with decoction mashing, you are effectively killing a lot of the amylases when you boil grains, yes, I know, you take the thicker part of the mash and most of the enzymes stay in the liquid portion, you are still deactivating a lot of them...so your conversion will not go as fast.
 

sudbuster

This ain't my first rodeo....
Lifetime Supporter
Joined
Jul 14, 2007
Messages
4,028
Reaction score
288
Location
Western Arkansas
Evan! said:
I attempted my first decoction on Saturday, and after a grueling 4-hour mash process, and 60 minutes of the final conversion rest at 159f, I was still testing positive for starches in my mash. I decided to proceed with the boil anyway, and my efficiency was great---85%. But I'm wondering: since there were still unconverted starches left in the beer, is it possible that at least some of my gravity points are coming from unfermentable starches?
HI! Evan,
Just wondering, how do you know for sure you have unfermentable starches? Did you use an iodine test? Iodine tests for us homebrew boys are notoriously inaccurate. Cellulose will react exactly like starch in the test. Husks are cellulose. The standard tincture of iodine we get from the pharmacy is inappropriate for brewing, as is idophore etc. I think the iodine test was began by homebrewers because the "big boys" do it. But we don't have access to brewer's iodine nor have we had the personalized training to be able to make the correct analysis of results. One way to know for sure your wort is starchy is to just wait it out. When secondary is over, your green beer will not be clear.

With any choice of procedures, there will always be proponents of one or the other. The major breweries are no different. They have the decoction believers and the stepmash believers. Several of the traditional decoction breweries have dropped it for economic reasons. With all due respect to the previous post, I will have to dissagree. I have had great success with decoction. I wouldn't put in an 8 1/2 hour day if the results were worse and the taste was not better. I have done th same recipe by step-mash and decoction, and with the help of my wife, blinfolded, i pick the decoction brew. It's subtle full depth of flavour is unmistakable. Decoction brewing is not for everyone, just as AG is not for everyone, or for that matter homebrewing itself.

I know many will not agree, and i fully appreciate thier views and opinions, but IMHO, decoction makes the best beer.

Congrats on the effiency! One hour at 159 f , in all probability, got you full conversion.
RDWHAHB :D
 
OP
Evan!

Evan!

Well-Known Member
Joined
Aug 9, 2006
Messages
11,835
Reaction score
104
Location
Charlottesville, VA
Yeah, I use iodine tincture. Maybe you're right, and it's cellulose. I've never had this problem with stepped mashing, though...which is why I ask. You'd think that if it were the husks, I'd have run into the problem before on my countless mashes...or does decoction do something to the husks that might cause them to react to the iodine that stepped mashing does not?
 

boo boo

Well-Known Member
Joined
Jun 6, 2005
Messages
4,164
Reaction score
46
Location
Hearts's Delight, Newfoundland
Iodine will change colour when exposed to husk material.

Also when you are decocting, are you rising up to sacc temps and resting before
boiling the decoction? If not you are in effect killing off some of the enzymes before they have a chance to convert, Even if you are boiling a thick decoction
and most of the enzymes are still in the liquid portion of the mash.

IIRC

OK read your other post. You did do the rest. Sorry.
 

sudbuster

This ain't my first rodeo....
Lifetime Supporter
Joined
Jul 14, 2007
Messages
4,028
Reaction score
288
Location
Western Arkansas
Evan! said:
Yeah, I use iodine tincture. Maybe you're right, and it's cellulose. I've never had this problem with stepped mashing, though...which is why I ask. You'd think that if it were the husks, I'd have run into the problem before on my countless mashes...or does decoction do something to the husks that might cause them to react to the iodine that stepped mashing does not?
FROM http://en.allexperts.com/q/Beer-2269/starch-sugar-conversion.htm : >>Another possibility is that you are not doing the iodine test correctly. You should take only clear liquid for the iodine test. Any husk fragments or particles of malt *will* turn dark in the test, and fool you into thinking starch conversion has not finished. (See http://howtobrew.com/section3/chapter14-5.html). As a quick check, you can taste the liquid. Is it sweet or does it taste "flat" and starchy? If it is sweet and clear, mashing has finished despite the iodine result.<<


When doing a decoction, the mash is boiled violently for several minutes, this does put minute husk particles into solution from abrasive interaction. Since alpha amylase has a "lifespan" of about 2 hrs at 156f, i much prefer a timed sacc rest over the iodine test.

SKOL ! :mug:
 
Top