Acidification and pH

[cnorth3]

Hi everyone,

This is my first post (!) so please be patient.  Being a wine and beer maker, I have of acid measuring equipment, including a decent pH meter.  I was making a cheddar this weekend, and decided to look at pH values during the process.  This led to a few questions:

• Where can I find pH markers for various cheeses?  Is there a consolidated list somewhere?
• I used a DS meso culture in supermarket organic hom/past milk with a starting pH of 6.6 (I calibrated my pH meter before starting).  After 45 minutes, there was no drop in pH.  In fact, I didn't start seeing a drop until the point at which I drained the whey, at which point it was 6.0.  Is this normal?  I expected to see a drop earlier in the acidification process.
• The curd seemed a bit soft at cutting.  Could this be due to insufficient acidification?
• Finally, how do you test the pH of curds?  My meter (a Milwaukee pH 600) seems better suited to liquids.

Thanks!

[linuxboy]

Where can I find pH markers for various cheeses?

Here, mostly. Also on my site. Peter Dixon has some as well. If you're stuck, ask.

  Is there a consolidated list somewhere?

Yes, but not public. I'm working on releasing my recipe collection this year.

I didn't start seeing a drop until the point at which I drained the whey, at which point it was 6.0.  Is this normal?

No, pH with DVI lyophilized culture should show a .01-.05 drop within ~45 minutes. I suspect your meter was coated with milk protein or somehow did not properly read the pH.

The curd seemed a bit soft at cutting.  Could this be due to insufficient acidification?

In a roundabout way. Curd strength is determined by

- PF ratio of milk
- Rennet amount
- Set time before cutting
- Milk quality and acidity at point of adding rennet.

Finally, how do you test the pH of curds?

Puree/homogenize and test, or test the whey that curds release. Yes, probes make a difference. Flat probes are easier to use, so are ISFET probes.

[cnorth3]

Thanks for the quick response!  As to the pH drop, my meter only has 0.1 display resolution, so perhaps I was getting an appropriate drop and not seeing it?  (I rinsed the probes with tap water between tests, and it seemed to read the water correctly.  So I'm not sure milk residue was the issue.  Also, the meter was working/reading correctly during the calibration process).

[linuxboy]

Okay, so you tested repeatedly and there were no in-between changes from the initial one to the whey drain pH? Like halfway through, when you cut the curd, the pH was still the same at 6.6?

If so, it's your meter.

[cnorth3]

Okay, so you tested repeatedly and there were no in-between changes from the initial one to the whey drain pH? Like halfway through, when you cut the curd, the pH was still the same at 6.6?

If so, it's your meter.

Or a bad culture? Mine was freshly bought New England Cheese Co. from Midwest (in store, right from the freezer).  Is culture viability a frequent/infrequent issue with DS cultures?

[linuxboy]

No, honestly with modern DVI cultures, they'll survive for a decade when refrigerated. If you tested halfway through the make (when you cut the curds) and the pH was the same as the beginning of the make, and then in another 30-60 minutes it was 6.0, it's your pH meter.

45 minutes into the make, your meter is not sensitive enough to detect changes. It takes about 2 hours to see a change with .1 sensitivity.

Now if you tested at the beginning and did not test in between, and then finally tested at whey drain, then there's not enough data. You didn't specify your testing interval, time of cook, temps, etc.

[cnorth3]

Thanks.  This cheddar is now air drying, and its consistency and cheesy smell are really pretty good.  So, it's possible that things went right even if there was something wrong with my pH readings.  I'll know for sure in a few months!  I'll try the pH readings again on my next cheese, now that I have a better idea of what to expect.

p.s., I was following the basic banded cheddar recipe in Tim Smith's book, and using his techniques, timing, etc.  I was pretty much on the numbers.

[Boofer]

The curd seemed a bit soft at cutting.  Could this be due to insufficient acidification?

In a roundabout way. Curd strength is determined by

- PF ratio of milk
- Rennet amount
- Set time before cutting
- Milk quality and acidity at point of adding rennet.

If you're using pasteurized/homogenized milk you should also be adding CACL2. Not sure what Tim Smith's recipe calls for.

-Boofer-

[cnorth3]

Thanks Boofer, I did indeed use CaCL2.