Mozzarella ranges the gamut, from plastic-packaged shreds hanging in the grocery's dairy case to carefully tended curds made fresh daily in picky Italian delicatessens. This cheese was first made from water buffalo milk and is still the most prized among choosy eaters, but the majority is now made from cow's milk.
Mozzarella results when buffalo, cow or goat milk—or a combination—is mixed with rennet or an acid and allowed to form into curds which are then heated and stretched until the white cheese reaches its characteristic bouncy consistency. Fresh mozzarella is made from whole milk; the processed version comes in whole milk, part skim milk and skim milk varieties.
Fresh mozzarella is sold in delicatessens, specialty stores and some chain groceries as balls, either in vacuum-sealed packages or liquid form, much like tofu. Processed mozzarella is sold like other commercial cheeses: in balls, slices, shreds or sticks.
Fresh mozzarella has a high moisture content—at least 52 percent—and is soft and creamy. Processed mozzarella has less than 50 percent moisture to make it less perishable.
Because of its mild yet fresh and tangy flavor, fresh mozzarella is often used in salads or sliced and placed atop a tomato slice, then sprinkled with fresh basil and vinegar. Processed mozzarella has a bland flavor, but it melts well, and is mostly used to add creaminess and bulk to dishes which also contain more intensely flavored cheeses, such as lasagna and pizza. It is also eaten plain or fried and breaded as a snack food.
Although fresh mozzarella in the U.S. is made from pasteurized milk, it is still highly perishable and you should eat it no later than the day after you buy it. Processed mozzarella will last about a week in the fridge after you've opened the package.