How does one measure the pH of a curd? Make a water extract or push the probe right into the curd?
Answered in the other thread.
And how can you slow the progression of the bacteria once you get to a good pH? Refrigeration?
I've posted some common methods before, but to recap, this is in order of efficacy: temperature rise or drop from the optimal for the bacteria type (meso or thermo have different thresholds), and salting. Salting has less of an effect. You want to kill bacteria or stop metabolysis to stop acid production.
Could a person soak the curd in a solution of baking soda to increase the pH?
Yes, but pH is not some magical indicator. I mean, if you increase pH, it does help with stretching, but the stretching has to do with the micelle ability to slide over each other. Let's recap some science of coagulation. First, rennet cleaves k-casein, exposing the underlying micelle, and with the help of Ca++ ions, the micelles bond to each other, and you get a matrix, which then expels whey. Cool, you have curd, heat that, acidity drops. Now with the acidity development, you have another complex dynamic, which is the conversion of di to mono calcium paracaseinate. This conversion is where you get the stretch. Here's an interesting tidbit, if you used a very slow acidifier, and aged mozz curd at 60-70 F for a few days, the pH would be somewhere around 5.8, and it would stretch. Why? Because the lactic acid aided the conversion.
What you mean I think is that if the conversion happened, but pH was so low, say 4.8, that the micelles could not bond well. Yes, if you neutralized the acid and brought the pH up, it would help.
Finally, does a mozzarella made with the citric acid method, change pH? I would think not.
What do you mean? Citric acid is acid... when you add it, it puts citric acid ions into solution, which decreases the pH. [edit] Oh, do you mean after you add the acid, is it stable at that pH because there are no bacteria? Yes, if there are no contaminants, it will be stable.
