General Category > Ingredients

Correctly reading ph test strips

(1/4) > >>

Ok, I've seen all the discussion about the difference between ph at mash temp and at room temp... also the discussion of the test strips reading about 0.3 hi/lo.  And now I'm confused.

I wait at least 10 minutes after dough-in, collect a small sample that is, as much as possible, just liquid, let it cool to ambient temp, and then check it with the test strip.  Say I read 5.8.  Does that mean the mash ph was 5.5? (subtract 0.3 for temperature)...  or was it 5.2? (subtract 0.3 for temp and another 0.3 for strip inaccuracy)... or was it 5.8? (subtract 0.3 and then add 0.3)...  or am I adding when I should be subtracting or what?

Also, if ph differs at the different temperatures, when they say 5.2 is ideal, what temp is that at?

I claim no first hand knowledge but according to Kai;
"In the end it was confirmed that the colorpHast strips have a -0.3 systematic error when they are used for testing the mash pH." "I.e. the strips tend to report a pH reading that is about 0.3 pH less than what is determined with a calibrated pH meter"


--- Quote from: lupy on January 09, 2010, 11:36:54 PM ---"I.e. the strips tend to report a pH reading that is about 0.3 pH less than what is determined with a calibrated pH meter"

--- End quote ---

Ok, got that part.  So above, when I read 5.8 with the strip, that really means 6.1?  Still leaves what do I do about the temp?  The ph at mash temp is supposedly 0.3 off from the ph at ambient.  Do I add or subtract 0.3?  Ultimately, I guess I want to find out how from the magical 5.2 I am so I can see which direction to adjust things, right?

Mash pH readings are (or at least should be) reported with the assumption that the sample is cooled. So you want to read roughly 5.5 at room temp, which is about 5.2 at mash temp.

Of course, for your own measurements you can do it either way, as long as you're consistent.

To make things more confusing, the ColorpHast strips are not affected by temperature. For some reason, the will always read a room temperature pH. A strip dipped in the mash at room temperature and at mash temperature will look exactly the same. Kai noticed this, I tried it for myself and noticed the same thing.

Essentially follow this with the ColorpHast strips:

Regardless of the temperature, try to target a pH between 5.1 and 5.4 on the strip.

You can just dip the pH strip in the mash and take a reading. Adjust if it looks like it is out of this range.


[0] Message Index

[#] Next page

Go to full version