He's my very unscientific theory on pH and some of the problems I've been having at times. I've been following the times in recipes very closely, yet looking at the site that John posted above, http://www.dairyfoodsconsulting.com/recipes.shtml
and many other small farm type cheese making sites, they make their cheeses in large, open vats. Many recipes call for the starter to mature for 45 minutes to an hour and this is in our small pots, normally with the lid closed. The larger makers seem to have that time around the same or longer, and granted, there is a larger amount of milk, but there is a correspondingly greater amount of starter.
Surrounding that large vat, there has to be a fair amount of ambient bacteria in the air (which has been discussed here before) and even though the conditions I'm sure are very clean, there is still bacteria. Much more can enter that vat than our relatively small, closed pots. I would think that open air space would have an effect on the bacteria growing in the pot. I assume the starters we use are aerobic bacteria and not anaerobic...I am sure they have to be. Perhaps my (our) starters are starving for oxygen?
Then this morning I hear this on the radio http://www.npr.org/templates/story/story.php?storyId=91448837
The twentieth anniversary of "The Most Important Microbe You've Never Heard Of." I found it interesting that 20% of our oxygen comes from this tiny microbe, but again, I digress. I am trying to use up time before adding the rennet, however.
So, this evening I am letting my starter sit a while longer while making John's Manchego Cheese Recipe. Hopefully I will get the pH a little lower or more importantly, correct.
That's my theory and until I invest in a pH meter, I'm sticking to it.