Tuesday, August 28, 2012
I found a few mentions of this online, but I wanted to make a large, explicit post for any of those interested: Trader Joe's milk sucks for milk steaming. Do not try to make lattes or cappuccinos out of this. You will not get microfoam. You will get vaguely good-looking foam that disintegrates after nothing more than a single tap on the carafe.
I've encountered this before in other milks as well, but never with the consistency of Trader Joe's. I have never gotten a gallon of milk that worked. Other brands, be they Garelick, Hood, or Rhody Fresh, have had the odd bad jug, but by and large, they're fine.
I read one theory that is associated with the age of the milk. I know the basics of milk steaming chemistry, and had never heard of age having a significant effect on milk steaming performance. This also didn't line up with my experiences of Rhody Fresh, which as the name says, is fresh. Namely, I have had more bottles of Rhody Fresh than any other brand that simply would not steam.
I think it has to do with the pasteurization process. Trader Joe's milk, as with most supermarket milks, is pasteurized. That means that the milk is raised to a temperature of about 150 degrees Fahrenheit for about thirty seconds. The temperature isn't high enough to cause breaks in the proteins and lactose, meaning that after it cools down, it should steam up just fine.
What I suspect happens sometimes is the milk doesn't cool down as they expect, the temperature gets too high, or they heat the milk for too long, thus causing the proteins to break, thus making smoothly steamed milk impossible. I don't know why Trader Joe's is more affected by this than other brands. Moreover, I don't even know if it's just my Trader Joe's locations. I'd imagine that different farms provide milk to different stores.
So if you buy a lot of milk at Trader Joe's, and you've found that your ability to steam has fallen off a cliff, it's not in your head. It's actually the milk. Just go buy something else.