Goat milk with low pH

[scasnerkay]

I milked the Nubian goat and transferred the milk to a container from home and put it in the frig at "work", then brought it home (chilled) and put it in the frig for a couple of hours. Now heating it to 90 degrees, and the pH says 6.2. That seems very low to me. Is it possible the goat has mastitis? Is the milk safe to go ahead and make mozzarella for home?

[chevre au lait]

Scasnerkay, I can't speak for the suitability of the milk for mozzarella, but when you milked the goat, was her udder swollen or hot, or did it have any lumps in it?  Is her milk the normal colour and consistency, or is it lumpy or clotted, or tinged pink?  If any of these apply, further investigation into the possibility of mastitis would be in order.

[ArnaudForestier]

I milked the Nubian goat and transferred the milk to a container from home and put it in the frig at "work", then brought it home (chilled) and put it in the frig for a couple of hours. Now heating it to 90 degrees, and the pH says 6.2. That seems very low to me. Is it possible the goat has mastitis? Is the milk safe to go ahead and make mozzarella for home?

Susan, mastitis actually raises milk pH, not lowers it.  It also can make for an extremely slow acidification, and lengthy (and poor) coagulation.  Your lower pH suggests to me, LAB acidification.  Without knowing more about the initial pH, difficult to say precisely what's going on, but perhaps Sailor or another more skilled in microbial diagnosis can chime in.

[Sailor Con Queso]

I agree. Mastitis or other infections will raise the pH. Low pH could be from a number of things but is probably from acidification by bacteria. I don't work with goat milk, however our lower limit on cows milk is 6.55. Below that we toss the milk. HOW are you testing the pH? I would double check the calibration.

[scasnerkay]

I am not entirely satisfied with the accuracy of the pH meter. But when I re-check in the 4.0 and 7.0 solutions, it is reading correctly. It is now about 24 hours after adding the Thermo C starter to the milk, with the milk pH reading 6.2 at that time. The milk rested at temp 90 mins. The flocculation was 11 mins, which seems long to me given the low pH. Curd as cut and intermittently moved around for about 4 hours. I seemed to be getting a 6.0 measurement, so drained it and into the frig overnight. Now the curd has been resting at (warm) room temp, and the pH is rising.
The most recent measurement of whey draining off is 6.5. And yes I did recheck the calibration in the 4.0 and 7.0 solutions. So any explanation?  I am thinking I do not want to eat this!

[John@PC]

Susan, a two-point pH check with the 4.0 and 7.0 buffer solutions should assure accuracy.  You can also do a check with white vinegar - a 5% acetic acid vinegar should be close to 2.4 pH, but the buffers are the best check.  This leads me to a question: Some recipes call for measuring whey and some say the curd.  Curd's no problem when soft but how do you measure a firmer curd (say in the case of the mozzerella)?  I've seen some spear-types like this one but your talking over $300 .  Or is checking the draining whey just as good using a $80 checker?

[Sailor Con Queso]

Susan,

IF your initial pH was low because of bacterial acidification, that most likely happened with spoilage bacteria, not pathogens. (that's what happens when milk spoils in your refrigerator). So, while I could not sell it commercially, I would taste the cheese and see what you think. If it doesn't taste too sour, I would eat it or use it as a cooking ingredient.