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Home Brew Forums > Home Brewing Beer > All Grain & Partial Mash Brewing > Incomplete Conversion
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Old 11-05-2012, 07:08 PM   #1
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Default Incomplete Conversion

Here's one I haven't had happen before.

I brewed my maibock this weekend. This is the 5th or 6th time I've brewed the recipe and it has been pretty consistent up until this point.

The first thing I noticed and this happened with the last light colored beer I brewed in that the pH was just above 5 at mash in. Usually I'm above 5.5 and add calcium cloride to lower the mash pH. I use colorphast strips which have tended to be very accurate for me. My batch of strips is about 7 years old. 1st question, do pH strips "go bad" with time?

My 1st decoction went 45 minutes and it took me a while to get there. The main mash stayed pretty consistent over 90 minutes at 144 Fahrenheit, but still seemed cloudy/milky at the end. I added enough of the 1st decoction to raise it to 154. After more than 45 minutes it still tested positive for starch. I added two fresh pounds of pilsener malt hoping to add enough enzymes to convert it but it didn't seem to move it at all. I sparged and moved on with the boil and was surprised to see I obtained my normal conversion percentage of 75% with this recipe. The wort is definitely cloudy though.

Anyone have any ideas why this would be so?

I'm thinking it could be a pH issue (being too low). Is anyone aware of a recent change to lake Michigan water? My pH has always been a little high on mash in without any darker malts. The other thing I'm thinking is that the enzymes denatured before I was done with them. I didn't go over 144 degrees though. Would the higher temp enzymes (i.e. the beta amylase) be denatured at this temp range?

Well, I'm going to soldier on and see how this tastes when it is done. It does look pretty cloudy at this point though.

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Old 11-05-2012, 08:22 PM   #2
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1. Yes, they can.
2. Incomplete conversion would lend me to think that A.) your PH is really jacked, B.) You decocted too thin of a mash and left too few enzymes in the main mash, C.) Your thermometer is reading way high, or D.) (unlikely) you got some really poorly modified malt. The cloudiness I wouldn't worry about - you get a lot of proteins with a decoction. It will likely clear out in no time.

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