I know it's an old thread, but this might be relevant to some folks looking.
I made my first mozz the other day and had some issues. I bought Mountain Dairy, the cheaper of the two house brands at Kroger (a.k.a. Food 4 Less in SoCal), thinking that if Kroger brand made the list, and both are listed as just "Pasteurized," that it might work and I'd save 40 cents per gallon. Also on my mind was the store's advertising about "new practices" that keep their milk fresher, so I was skeptical all around that maybe they had switched to Ultra and not labelled it.
My first mozz with Mountain Dairy appeared to fail, and I was afraid I had confirmed my suspicions. It wouldn't form a smooth ball at the end, despite hitting the internal temp of 135 - it stayed grainy no matter how hard I worked it. So I chilled it, went out and bought a Kroger brand gallon, and tried again.
This part is where I screwed up - I also changed the process a bit. At the same point where I said that the Mountain Dairy brand failed, the Kroger brand came together a little better, so I kept heating it up higher. I had to heat it up higher than 135 (I didn't temp it though), but it ultimately formed a smooth ball and made a great pizza, and later a great lasagna, too.
A few days later, I took the Mountain Dairy brand mush, and after cooling it had formed a smooth surface in its container! So now I'm not sure if it would have worked better had I only kept working it.
But I do know one thing: Even though Kroger advertises their "Stays fresher longer" in the stores, their house brand milk still makes a good cheese.