Yesterday, after I mentioned the Oregon State article, I decided to conduct the flour moisture bake test as described in that article. For the test, I decided to use the King Arthur bread flour (KABF). Since my bag of that flour is a fairly fresh one, I wanted to see how close to 14% the results would come. A moisture content of 14% is standard for most white flours, and is also the value I have been using for all of my calculations in reverse engineering projects. So, for the test I used 3 grams of KABF and baked it in my countertop toaster oven at 266 degrees F for one hour. At the end of that time, the flour had turned a light brown color. The numbers suggested a moisture content of almost 17%. I let the sample bake longer but the numbers were erratic. I think part of the problem was that the sample was too small and my scale is accurate to only 0.1 gram. That meant being off by only 0.1 gram changed the numbers by several percent. So, I decided to conduct a second test along the lines that I recommended to you and that you used. I had used that test with flour before when we were conducting hydration bake tests at the Mellow Mushroom thread, and similar tests with molasses products, so I thought that maybe that test method was more reliable for our purposes in a home setting.
For the second test, I used a 5-gram sample of the KABF and heated it in my toaster oven at about 212 degrees F until the weight stabilized. It took about three hours for the weight loss to stabilize. From the final weight value, I calculated that the moisture content of the KABF was 14%. The actual value might have been a bit higher or bit lower because of my scale limitations but the larger sample size reduced the error rate. Also, the color of the flour was only slightly changed. Like you, I then decided to leave the KABF sample uncovered to see if it would regain any of the moisture that it had lost because of the bake test. I left the sample overnight on my kitchen counter. I checked its weight a few times before going to bed and I saw that its value was gradually increasing, suggesting that it was taking moisture out of the air. By this morning, all of the moisture that had been lost through the bake test was completely regained. The weight of the flour sample was exactly the same as when I started the test. This was all quite fascinating to me since I had not thought before how flour left at room temperature can attract moisture from its environment and at what rate. I had read before that that sort of thing can happen quite quickly, which was the reason I suggested to you that you let your sample cool off for only a brief period, but I did not think that the flour could absorb the ambient moisture so quickly.
Of course, the above tests, and yours as well, beg the question about the effect of flour moisture on the gluten mass test results. I guess in your case you would need a fresh sample of the Caputo Extra/Blue 00 flour to see if the gluten mass test results are different. I guess the best we can say is that we learned something new.