special milk?

according to the label, a starbucks coffee(r) frappuccino(r) coffee drink is "a lowfat creamy blend of starbucks(r) coffee and milk." my question is why doesn't the milk sour in a week? i mean, the bottle in front of me has a "best taste by" date of february 6, 2006. surely milk would sour before then. i'm vexed.