Incomplete starch conversion with infusion mashing

sboyer85 · April 30, 2013, 7:40am

I’ve tried TWO TIMES to do a 122F protein rest with Bohemian Floor-malted Pilsner malt followed by an infusion of boiling water to 155F. At the end of the 90 min hold at 155F, I still don’t get complete starch conversion. Waiting longer does not fix it. The runoff is like oatmeal water and the sparge eventually slows to almost a halt.

Did the infusion of boiling water inactivate the amylase enzymes? I tried to carefully add the water ladle by ladle and stir.

This malt should only be SLIGHTLY modified and is suitable for single infusion mashing, but I thought I’d try to do a protein rest as a learning experience.

Anyone else experience haze issues with a protein rest? I thought it was supposed to HELP with haze, but I guess that’s referring to protein, not carbs.

tom_sawyer · April 30, 2013, 2:59pm

If its only slightly modified then it may need a decoction mash. Infusion mashes work best on well-modified malt.

The other thing I’d check if I were you, is my thermometer.

Mash pH could be way off and this can affect conversion.

Finally, adding boiling water won’t inactivate enzymes any more than decoction so I doubt this is the problem.

sboyer85 · April 30, 2013, 5:09pm

Why would decoction yield different results over infusion in terms of enzyme action, besides all the fuss about yield and flavor? I’ve also tried decoction, and got the same starchy gum up problem. I figured it was because the mash was just sitting at protein rest too long while the first decoction rose to 155F for 15, then was brought to a boil for 10 min. Even after a long boil and lagering, beer was still hazy. Had to leave tons of trub behind in the kettle. Any lower temp rest has been such a headache for me, regardless of how modified the malt.

The profile for the malt (as in the link below) appears to contain sufficient enzyme activity, and I’ve heard people at MoreBeer that a single infusion for 90 min gives a clear beer.

http://www.weyermann.de/downloads/pdf/V ... 202010.pdf

Due to my distrust of machines, I use a glass floating thermometer, but I have a spare I could use to get a “second opinion”.

I have pH strips (with the pH range for mashing) to give a rough estimate, I’ll give that a try. I’m using 1/2 distilled water and 1/2 spring water … ya, I even splurged on the water for this one.

Thanks for the help

tom_sawyer · April 30, 2013, 6:21pm

They are doing a decoction mash in the article you linked. The boiling will help the starch granules to unwind/gelatinize and become more available to what might be a more limited amount of enzyme. I sometimes have issues with chill haze, mostsly in British floor malted malts. I haven’t done much in the way of protein rests, although for a pils it might be a good idea. It is a PITA I agree. I think your issue might be starch rather than protein anyway.

Are you using supermoss or irish moss? If so, then I’d focus on water.

You’ll be needing to add some acidifying salts (Ca Cl2 or CaSO4) and/or some lactic or phosphoric acid to get the pH down in a good range. Its possible that your water mix lacked enough calcium too, that affects conversion since amylase needs calcium as a cofactor or something. At the very least I’d add a teaspoon of calcium chloride to the water next time. You can get it at Walmart in the canning section.

I tend to trust glass thermometers but even they can be off, check with a second thermo of some kind.

sboyer85 · May 1, 2013, 5:35am

Thanks for your help sawyer, you were right on with the pH. I tried a single infusion, then measured pH. It was somewhere around 6.0!!! I’ve heard the Floor-malted Pils is lighter in color than the regular, so maybe a higher starting pH (unadjusted) is even more of an issue with the floor malted pils.

CaCl2 brought it down immediately and I got conversion, as confirmed by an iodine test. Feels good to “move past” a brew problem. Sucks for the lost $$$, time, and gallons of magic sunshine.

tom_sawyer · May 1, 2013, 1:10pm

Post back on how you like that Weyermann floor malted pils malt, I was tempted to buy a sack myself but I really don’t make that many German lagers and its kind of pricey. Then again I love my floor malted British Maris Otter so maybe I should spring for this.

sboyer85 · May 1, 2013, 3:01pm

I’ve heard nothing but good things … mostly increased complexity and maltiness (I don’t like that description “malty” … wine people don’t say this wine tastes “grape-y”. I would describe a good light pilsner as “doughy”. Munich is “malty”). But it also seems to require increased boiling times, as the DMS, or whatever, smell was pretty strong in the mash and early in the boil.

Is the floor-malted maris otter sufficient for single infusion? Or does it benefit from multiple rests?

I’m going for a long lager period, but I will post back.

tom_sawyer · May 1, 2013, 3:10pm

The MO is supposed to be fine for single infusions but of course the British typically make well-modified malts since single infusion is thier usual method. On the other hand I and others have had intermittent haze issues with MO so maybe its a conversion thing more than a protein issue.