On Jun 29, 3:46 pm, Sam > wrote:
> What is the pH of the flours you use? That would be your baseline and
> when you add some acid with the starters, it would go down.
> That would be an interesting number to see the effect of 10 % of starter.

The white flour when mixed without any starter at 100% hydration
yields a pH of 5.91, but this is a point measurement and I did not let
it sit and repeat it for the same batch over time. I will do that
next weekend and we will see what it does.

Each data point is the minimum of at least three measurements. The
ISFET sensor was calibrated (2-point) at the beginning and at the end
of the series (and just prior to the second calibration it was reading
4.08 in the 4.01 buffer so it had not drifted too far).
I agree that it looks like a small amount of something (a buffer of
some kind) is slowly dissolving.
I suppose it could be something leaching out of the bran as it
hydrates, but the phenomena is not limited to whole wheat flour.

I have two other time series on larger batch sizes (but with longer
intervals between data points) that show the same behavior, an
increase in pH over the first hour, then a monotonic decrease.
Of the four data sets, two were collected from samples in glass jars
and two from samples in stainless steel bowls.
Today I did a batch that started with starter at pH 4.1; added water
and dispersed the starter - pH stayed at 4.1; added salt and high
gluten white flour and mixed - pH 5.07 at end of mix; an hour later
the pH was 5.82; after another hour 4.55.

Doc