If you're like me, you've noticed that organic milk tends to have a longer shelf life and tastes better so I tend to spend the extra money because aside from our 1 year-old, the family drinks milk erratically and I prefer the taste. But are these properties of the organic nature of the milk? It turns out that there is a simple explanation for both that is quite interesting and may (or may not) change your mind on spending extra on organic milk.
First is the question of longer shelf life. This is actually a result of logistics. There are fewer farms providing organic milk so it often has to travel further and undergoes a high temperature pasteurization process that kills all bacteria:
The process that gives the milk a longer shelf life is called ultrahigh temperature (UHT) processing or treatment, in which milk is heated to 280 degrees Fahrenheit (138 degrees Celsius) for two to four seconds, killing any bacteria in it.
Compare that to pasteurization, the standard preservation process. There are two types of pasteurization: "low temperature, long time," in which milk is heated to 145 degrees F (63 degrees C) for at least 30 minutes*, or the more common "high temperature, short time," in which milk is heated to roughly 160 degrees F (71 degrees C) for at least 15 seconds.
The different temperatures hint at why UHT-treated milk lasts longer: Pasteurization doesn’t kill all bacteria in the milk, just enough so that you don't get a disease with your milk mustache. UHT, on the other hand, kills everything.
Interestingly, UHT treated milk no longer needs refrigeration (prior to opening). Your grocer keeps it refrigerated as a matter of consumer expectation (how silly we Americans are).
The answer to the second question actually arises from the answer to the first. The process of UHT actually changes the chemical nature of the milk by breaking down some proteins and cooking some of the sugars. Organic milk tastes different not because it's organic, but because of the pasteurization process which happens to change some of the molecular structure of the milk:
UHT sweetens the flavor of milk by burning some of its sugars (caramelization)....UHT also destroys some of the milk’s vitamin content—not a significant amount—and affects some proteins
So there you have it; organic milk does indeed taste different from non-organic milk, but it's not a placebo effect and it's not because it's organic. If you're a European in the US and you find our milk tastes funny, try the organic milk.
I may take up this article on giving non-organic UHT milk a try.