I am so very interested in several points of this conversation, that I would like to relate some of my own experiences related to the subject, as well as ask a few questions that have been lurking in my head for several years now. I have been using milk from several farmsteads, each with a bit of a different management/feeding system. My questions/issues stem mostly from those managing as "grass fed" milk, keeping calves on half of the day, removing them half the day then milking once a day.
The milk pH is HIGH, I am testing 6.8 to 7.05.
Progression of pH drop during make is very slow initially, and then in the press too fast!
I have been consistently having this problem. So much so, I have sort of come up with a work-around. During the initial ripening, if the pH doesn't drop, I just proceed as if it has. I know darned well in the end I'll be chasing the pH so it doesn't get too low anyhow. (It's interesting to note the farmstead that is feeding grass, alfalfa, and grain mix with once a day milking has a pH consistently at 6.5-6.6, while the "grass fed" cows have pH's more at 6.7-6.9, sometimes close to 7.)
The SCC can be elevated for many reasons - mastitis, stress, udder injury, stale milk from incomplete milking, late lactation/low production, etc - and can really impact milk quality/cheesemaking (in the ways you described).
Wow. This is a revelation to me, especially the "stale milk from incomplete milking" and "low production". I will have to check and see exactly what some of the milking protocols are on these farmsteads. Could it be that they are only milking 2 quarters and leaving 2 quarters for the calf and that can result in "stale milk"? Since I'm not the person milking the cow, I have no idea.
Right now I'm dealing with "grass fed" milk where the cow has low production...I'm guessing she needs more nutrition to produce higher quality milk, but for right now the milk has very low solids, not much cream and what is there seems to have low solids too. It makes for runny yogurt and very low yield, high moisture cream cheese with curds that do not set up well. But the flavor is nice and clean and makes for good drinking milk!
On the other end of the spectrum, milk I've used from a Jersey cow on the more traditional dairy diet with grain, etc. has so much milk solids and heavy, yellow cream that I have to back off on the rennet amount in a cheese recipe, otherwise the curds get way too firm, too fast.
So it has been fascinating to try all these different milks, but it does steepen the cheese making learning curve quite a bit. I may go to using Straus milk to make cheese for a while so I can have more of a consistent baseline to start the process out with and go from there.
The remaining question is, can a good cheese making quality milk be produced from a primarily grass-based (no or very little grain) diet? Or does it depend on the breed of cow, etc.?