its shelf life There are three basic methods used to do this: • Regular pasteurized milk has been heated to 161°F for around 20 seconds This is the standard for most supermarket milks, which have a shelf life of a few weeks • Ultra High Temperature pasteurized milk has been heated much hotter—all the way up to 275°F—for second It is labeled UHT or “Ultra-Pasteurized” and has a shelf life of several months Many organic milk producers use this method of pasteurization, as it allows their milks to sit in supermarket dairy cases for longer (organic milk often doesn’t sell as quickly as regular milk) When packed into specially designed containers, UHT milk can actually keep, unrefrigerated, for months or even years • Low-Temperature pasteurized milk has been held at 145°F for 30 minutes Many small farms pasteurize their milk with this method, as it doesn’t produce the “cooked” flavor that UHT or regular pasteurized milk can have The label generally doesn’t indicate whether the milk is just pasteurized or if it’s been low-temperature pasteurized, so unless you know the producer, chances are it’s the former As far as their cooking qualities go, in most application, all of these types of milk will behave just about the same For making ricotta, however, the higher the temperature the milk has been cooked to, the more breakdown you find in its proteins and sugars For this reason, UHT milk tends to have a slightly sweeter flavor (complex carbohydrates are broken down into simpler, sweeter sugars during the pasteurization process) And UHT milks will not coagulate as well when making ricotta I recommend standard pasteurized milk, Low-Temperature pasteurized milk, or, if you can get it, raw milk ...about the same For making ricotta, however, the higher the temperature the milk has been cooked to, the more breakdown you find in its proteins and sugars... this reason, UHT milk tends to have a slightly sweeter flavor (complex carbohydrates are broken down into simpler, sweeter sugars during the pasteurization process) And UHT milks will not coagulate as well when making ricotta