Did my pH affect my conversion?

[rich8932]

I'm brewing a pilsner and it's my first partial mash, with 5 lbs of pilsen malt. I stabilized the water (5 qts reverse osmosis) at a temp of about 152 on my glasstop stove then added the malt split into two muslin bags. After 45 minutes I checked the for starch conversion with iodine and I wasn't getting anything. So I checked the pH and according to the test strips my mash was at about 4.8. I added Calcium Carbonate in 1/2 tsp increments and waited about 10 minutes between each addition and sufficient mixing but after 3 tsp. and 60 minutes I had no change in pH...according to the strips. After several hours of maintaining my low 150's temp I couldn't get conversion as per the iodine. I'm hoping I got some sugar out of the malt but finally pulled it, rinsed/sparged and added my bag of DME. I would like to continue doing partial mash and eventually all grain but what the heck am I doing wrong? Thanks for the help!

 

[Bensiff]

Off the top of my head that is not a low enough pH to be of any great negative impact. You want to figure your mash temp with grains added, not before grains...there are online mash temp calculators that will get you really close. The cooler temperature resultant of adding cool grains to target temp water will slow down conversion; however, bringing it back up again will make it a minimal impact. I'm guessing your no change in pH has more to do with the poor quality of measurement than reality. I'm also guessing your titration is at fault and you had a near full conversion at 30 minutes.

Oh yeah, you did crush the grains right?

 

[rich8932]

I ran the grains through a mill at the HBS so I think I was okay there. I also factored in a 16-18 degree loss of temp when adding the grains so I was pretty on when I added. I'm not sure what you mean by titration? Also, if I had conversion wouldn't the iodine disperse in the sample? I hope you're right otherwise I'm going to have a very light pilsner.

 

[wyzazz]

Iodine turns purple/black when starch is present, how did you perform your test? Did you have any grain husk floaties in the solution you used? That will give you a false positive.

 

[rich8932]

There were chunks of hull and other debris in my solution. I didn't realize that would cause problems. Is it possible to pull a solution without the debris? How do you test? Thanks for all the help by the way...

 

[wyzazz]

That'll do it! You need to pull a little sample of mash liquid on a white dinner plate, no chunks/hulls. Put a drop of iodine on there and streak it in to the liquid, if it blackens there is starch (you need to mash longer) if it stays rusty colored then you're good!

 

[remilard]

The pH strips were wrong. We know that pilsner malt only mashes have a pH around 5.8 in distilled water so the best interpretation of your reading is that it is wrong. Adding calcium carbonate would have raised the pH further. Yes, this may have negatively affected conversion.