Do you ever wonder why milk tastes different in Korea? It has to do with the pasteurization method. North America uses the HTST method (high temperature, short time), while Korea has, for the most part, used the UHT method (ultra high temperature).
HTST kills spoilage microorganisms, and consists of heating the milk to 74°C for 10-20 seconds. With correct cooling, and chilled distribution, it has a shelf life of 1-2 weeks.
UHT kills microorganisms AND spores in milk, giving it a shelf life of 6-9 months (until opened) without refrigeration or preservatives. UHT consists of heating the milk to 138° C for 2-3 seconds.