An interesting sidebar in our “Is Your Milk Spoiling Faster?” discussion is why does most organic milk stay fresher longer? It’s not because the cows are free of bovine-growth-hormone and the commune-members sing them lullabies every night.
Rather, much of organic milk is “ultra-pasteurized.” This means the pasteurization process occurs at a higher temperature than just regular pasteurization. More bacteria get killed, and so it stays fresh for longer. Not all organic milk is ultra-pasteurized, and some regular milk is, so be sure to look for milk that says “ultra-pasteurized.” An exciting entry on the different kinds of pasteurization can be found here.
However, pasteurization removes both good and bad bacteria, as well as proteins and flavor. So, unless you’re gonna install a cow in your kitchen, or join the raw-milk underground, there’s going to be a tradeoff. Personally, I only use milk as a conduit for cereal so it doesn’t really matter what it tastes like, it just needs to not go bad within two days of purchase.
(With thanks to commenter VA_White!)