Well this post was all about Brunwater... Brunwater is made to read with a room temp sample. That sample is correlated to mash temp. If Brunwater says 5.3 mash pH, its expects you to read 5.3 on your cooled sample because it does/did the guess work(pH temp shifts) for you. I think you are thinking if Brunwater reads 5.3 at mash you need to read 5.6 at room, right?
Bru'n Water is not reading anything. Bru'n Water is telling me how much adjustment I need to make to my water supply based on the grist in order to hit a specific room temperature pH. The sample was read at room temperature.
I have always targeted a pH of 5.5 to 5.6 at room temperature because I am targeting a mash temp pH of approximately 5.2 to 5.3. Targeting a mash pH of 5.2 to 5.3 at room temperature places the mash pH at mash temperature at the bottom end or below that at which limit dextrinase is most effective, and far below that at which alpha-amylase and beta amylase are most effective. My standard single-infusion mash temperature is 148F, which is just below the temperature at which limit dextrinase is starting to be denatured.
Limit dextrinase Optimum pH 5.1 Optimum Temp ~57°C Denatured 65°C
Beta-Amylase Optimum pH 5.4-5.6 Optimum Temp ~62°C Denatured 68°C
Alfa-Amylase Optimum pH 5.6-5.8 Optimum Temp ~72°C Denatured 80°C
Also in looking at your sample picture, you have WAY to much grain in that sample. You should really have a nice clear (free of particles) sample.
What you are seeing is the top of the tumbler where grain managed to sneak over the lip. The sample was for the most part was clear of grain particles where the actual sensor was submerged. The sample was taken immediately after mash-in, not after conversion was partially or fully complete and the wort was for the most part clear of starch. I am testing for the pH at which enzymatic hydrolysis is occurring.
* shakes head, shrugs shoulders* Ok, *and walks away*