Whenever possible, look for a local brand. This is because long, cold storage and transportation is problematic for milk. The closer the milk is to the source (cows, goats, etc.) the better for cheese making.
Another factor is the heat at which the milk has been pasteurized. If the milk clearly states that it is ultra-pasteurized (UP), do not purchase it. It has basically been stripped of friendly bacteria. More importantly, the alteration of the proteins is so severe that the milk will not form a proper curd. Fresh milk from a healthy animal is about as good as it gets. It contains its own system of cultures and enzymes that make it well suited for cheese making.
Ultra-pasteurized (UP) is milk that has been heated at a temperature range of 191-212F for varying times. This temperature and time combination is lethal to bacteria, killing virtually all that would be beneficial in cheese making. Milk processors are required by law to state on the label that the milk is ultra-pasteurized.
Unfortunately, even if your milk is not labeled UP, it may have been heated to just short of ultra-pasteurization. When milk has been pasteurized at a high temperature (anything over 172F), it is problematic for cheese making. The only way to know how high a processor has heated their milk is to call them. We encourage you to do this because we believe it will let the large processing plants know where we stand.