How does one measure the ph of sourdough
I would be interested in helping Kelley with his starter experiment if I could. I already have a pH meter and NaOH, if someone could guide me how to use them.
That article gives good high level directions on how to determine TTA. To elaborate on them:
1) Identify the exact concentration of your NaOH and dilute as necessary to create a 0.1N solution.
2) Acquire a burette of proper size, stirrer (magnetic works well), and lab stand to hold the burette.
3) Prepare the sample by thoroughly dissolving the weighed starter and water in a beaker.
4) Stick the pH meter probe and stirrer magnet into the beaker. Put the beaker under the burette and on top of the stirrer so its constantly mixing.
5) Start adding the NaOH solution, plotting volume added vs. pH value as you go. The volume of titrant added at the inflection point of that curve is your TTA. Note: you will need to add a lot initially to get the pH to budge, but as you approach the TTA value the amount needed will shrink to a single drop.
You'll need to do repeated titrations of a batch of starter at fixed intervals of time (e.g. every 15 or 30 minutes) so you can draw a TTA vs. time curve. The slope of this curve at any point is a proxy for overall starter metabolism at that time.
Of course to get meaningful results, you'll need to do this under specific, controlled, consistent conditions of starter composition, starting state, and temperature.