Hello all.
Tonight I'm wading through making my second batch of just cheese curds. I'm trying to identify why the pH didn't seem to really want to drop, and even came back up a bit. I used this formula the first time and had no issues with getting the pH to drop. This time when the pH seemed to be taking forever ( a very scientific term I know ) I went with some of the formula from the cheesmaker on curds, and heated it to 116. https://culturecheesemag.com/diy/homemade-squeaky-cheese-curds
The pH did drop down to 6.39, then went up to 6.42 and I just got too tired to mess with in and so it's now in the cheddaring process.
I think I need some references for what the story is with how the pH works, and while I scanned and searched the forums nothing popped out at me in a clear way except "get the Caldwell book", so I'll do that. But any other suggesting would be awesome. I did clean my pH meter, and it is only the second time using it and it seems to work just fine, it measures the water pH like normal.
Thoughts and suggestions appreciated.
Any smell of ammonia in the pot? When did you add the CaCl2? If you added a lot, and late, it might push the pH up a tad. Do you use bleach as a utensil sterilizer?Any soap on your hands?
Generally speaking pH will only drop when you add the culture. That's because the bacteria eats the sugars and outputs lactic acid. This lactic acid reduces the pH.
However, that's only part of the story. Probably you have had the experience of adding baking powder to something acidic -- for example when you make pancakes. It makes lots of bubbles (which is carbon dioxide). What's happening is that the baking powder reacts with the acid and neutralises it. The end result is that some carbon dioxide gas is produced and the pancake batter becomes less acid (the pH goes up). If you have a pH meter you can try it next time you make pancakes.
The same thing happens in milk. The protein in milk that we use to make cheese is actually all bound up with a salt called calcium phosphate. When the pH of the milk goes down, the protein balls (called micelles) relax and some of the calcium phosphate can dissolve. Once that happens it reacts with the acid, neutralising it. The calcium phosphate tries to push the pH up while the acid tries to push it down. However, you can't make the pH go down until the calcium phosphate in solution is used up. This is called "buffering".
Normally the bacteria cultures are working fast enough that they produce more acid than can be buffered by the released calcium phosphate, but if it goes slowly enough it can rebound a bit.
You do need to calibrate your pH meter. I think you should have buffered solutions at pH 8 and pH 4 IIRC (usually they give you some with the meter, but you can buy it as well online) and you should measure them to see if they are correct. There should be instructions for calibrating the meter that came with it. It's been a donkey's age since I had a pH meter, so I'm afraid I can't give you any other specifics.
Montana,
I'm glad you started this subject up, as I've been meaning to myself. I do have the Caldwell book, and have recently started making cheese while checking pH along the way, and the measurements do not jive with the recipe numbers along the process. It seems there is quite a "lag time" in acidification in the vat, and only after a few hours of pressing does it come down (and then very quickly, in just a few hours). I've been hesitant to write in as for now I'm just using pH test strips which do not record measurements to the correct accuracy, but I still am seeing a definite pattern in the few recipes I've measured thus far. It's probably going to take me a long time to figure out what's happening in my case, but just wanted to let you know that you are not alone with such things happening to your cheeses! Hopefully someone with more cheesemaking experience can help you (and me) resolve this mystery.
Susan
I have heard that winter milk is often highly buffered. You may find that things work differently in the summer.
Montana, what kind of culture were you using? Usually I think of mesophilic when I hear "making cheese curds." If so ... you killed the bacteria when you went up to 116°. :(