When milk is pasteurized, it's not boiled in the same way as we do at home. Usually, milk is just treated with high heat in a very short period of time (about 15 seconds) enough to kill bacterial spores by letting it pass through thin super hot tubes. The process is often called ultra high temperature (UHT) processing. Most nutrients (calories, calcium) remain the same though there's still some nutritional loss (i.e. vitamins).