Starch Conversion

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

Help Support Homebrew Talk:

jakegreen58

Well-Known Member
Joined
Mar 23, 2012
Messages
45
Reaction score
3
Location
Almería
Last night I made a Lagunitas IPA Clone, I had issues fully converting the starches. After one hour of mashing (grain bill below) at 156F I performed an iodine test. I got a color change to black. So I left it for 15 minutes more, still black, I left it for 20 minutes more, still black. At this point the temp dropped to 153. I left it in for 2 hrs and 15 minutes total and it was still black. I just couldn't stand it and into the brew kettle it went. I have never performed an iodine test and have always just waited the standard hour. So, is there a reason the sugar conversion never fully occurred? Should I have just waited and waited for the conversion to occur, maintaining temp by adding hot water? Or is there a reason my full conversion wasn't going to happen?


Grain Bill:
12 lbs 2-row
1 lb White wheat malt (Rahr)
14 oz. Crystal 10L
14 oz. light Munich malt
8 oz. Crystal 60L

5.2 pH adjuster added (1 Tbl.)
Gypsum added (1.25 tsp.)

Mash was 155F for 2.25 hrs. ; O.G. : 1.074
Mash water volume was 3.5 gal.
 

Vagrant

Well-Known Member
Lifetime Supporter
Joined
Jun 25, 2006
Messages
131
Reaction score
1
Location
A Marriott near you
Check your thermometer against another thermometer. Maybe your mash temp wasn't where you thought it was. If your OG was 1.074, I'd say you probably shouldn't worry about your conversion with that grain bill.

Edited to add: Another consideration is your mash thickness. That seems a bit on the thick side. Try a 1.25:1 - 1.5:1 next time and see if that affects your results.
 

BigEd

Well-Known Member
Joined
Nov 5, 2004
Messages
2,935
Reaction score
449
So, is there a reason the sugar conversion never fully occurred?

It converted. I guarantee you were getting a false negative reading. Iodine tests for homebrewers using modern malts are a waste of time IMO and from posts like this which appear almost daily on the various boards they seem to cause more problems than they solve.
 

bja

Well-Known Member
Joined
Nov 24, 2007
Messages
2,079
Reaction score
186
Location
Pittsburgh
O.G. : 1.074[/B]
It did convert.

If you never had a problem before, why start testing now?

Back when I first started brewing I bought iodine for this test. Never did use it. Never had a reason to.
 

progmac

Well-Known Member
Joined
Mar 26, 2012
Messages
1,878
Reaction score
283
Location
Cincy
to make sure you are reading the result right, it is helpful to do two controls -- take a paper towel and put your wort in one spot, a bit of flour in another, and another spot with a drip of water. drip iodine in all three, then you can compare your wort with pure starch (flour) and with water, no starch.
 

oakbarn

Well-Known Member
Lifetime Supporter
Joined
Jun 23, 2011
Messages
1,628
Reaction score
300
Location
Bartonville
If you had grain residue in the tested Wort you will get false results. The iodine test should be done a clean white plate and the sample dropped in the plate. The edges may still turn black. The paper towel method is also a great idea and should work well. Try the test before you convert as well. I.e. Test about 15 minutes in to see what unconverted looks like. The real reason to do the test is to see if you have converted after 60 minutes and if it needs more time, go to 90. I almost always to go 90 minute. If your temp is correct (I regularly have to adjust thermometers), you will have conversion. You can also check for conversion based upon expected efficiency. BTW, you will get conversion from the low 140s to high 150s, so only a highly inaccurate one would you fail to convert. You want to control the temp for the specific profile you are making as different attributes come with Mash temperature.
 

brewmadness

Well-Known Member
Joined
Jan 24, 2011
Messages
167
Reaction score
11
Location
Ionia, Michigan
I tend to just stick my finger in it. If it tastes sweet, it converted. My gravities have always fallen right in the close ballpark of what the recipes expects so I have never worried about it enough to do an iodine test or anything. If I had come up with 1.030 or 1.040 with that grain bill, them maybe I worry about it. But I'm not a professional, nor to I intend to be. I make beer and I enjoy what I make.
 
OP
jakegreen58

jakegreen58

Well-Known Member
Joined
Mar 23, 2012
Messages
45
Reaction score
3
Location
Almería
Thanks guys, I performed the iodine test just to prove it works and just give me some peace of mind. Clearly had the opposite effect. The wort tasted just fine and sweet with a good hops bite, so I am not worried. This beer should be badass and the yeast is churning away vigorously as I type. I will check the iodine test with the negative and positive controls next time, but I will give it 90 minutes or so at the correct temp. and cut it off.
 

Vagrant

Well-Known Member
Lifetime Supporter
Joined
Jun 25, 2006
Messages
131
Reaction score
1
Location
A Marriott near you
I would add to the discussion that iodine tests are done for a reason. Even at breweries where the malt bill is in the 1000#'s. During every mash. It turns black for a reason. So there IS a reason for it or a production brewery wouldn't waste time on it, even if some people are happy with it turning black for magical reasons or not checking at all. To each their own.
 

diS

Well-Known Member
Joined
Apr 9, 2011
Messages
1,024
Reaction score
52
Location
Croatia
Maybe its not case here, but some papers contain starches and if you drop iodine on it it will turn black no matter if wort contains starches.
 

HopOnHops

Well-Known Member
Joined
May 23, 2012
Messages
200
Reaction score
7
Location
Inglewood
Refractometer FTW! Very good investment when going to AG brewing IMO because I'm PARANOID
 
Top