The deal with shelf-stable milk and the perils of ultra-high temperature pasteurization.

While dumping one of those tiny, individual serving tubs of half-and-half into my coffee the other day, a co-worker turned to me and said “what’s the deal with milk that doesn’t need to be refrigerated?” Good question.

But first let’s delve into the psychological underpinnings that made him pinch his face and sneer at my creamer — uncontrollable lactophobia. My wife suffers from it, which is why I’m often confronted with two open cartons of milk in our fridge.

“Honey, what’s up?” I enquire, knowing the answer.

“I think that one is bad,” she replies, pointing to a carton with a sell-by date weeks away. I go through the motions of opening the carton and smelling the potentially offensive stuff, but I know the result. It’s not bad. It never is.

Why this weekly ritual? “How can they sell milk a month or two before the expiration?” counters my dairy-paranoid wife. “It isn’t possible. I don’t trust it.”

Dairies can and, more often than ever, do sell milk with sell-by dates that seem impossibly far away, thanks to ultra-pasteurization. It’s also how certain types of milk can sit unrefrigerated on the grocery store shelves, or in tiny plastic canisters in a bowl at the local diner, for upward of six months.

Regular pasteurization is still the norm for mass market product from regional dairies, the most common form of milk you’ll find in the refrigerator section at the store. Essentially, the dairy heats milk to 161 degrees for about 15-20 seconds to kill any potential pathogens in the liquid. Works great, and gives you a state-mandated refrigerated shelf-life of about 12 days to three weeks.

Ultra-high temperature (UHT) pasteurization jacks the milk to 250 degrees or more for a fraction of second before a rapid cooling process that keeps the milk from cooking. That kills all the same stuff as regular pasteurization, along with destroying spores that decay milk over time. That extends regular shelf-time to about two months. Add in aseptic packaging that’s been treated with pathogen killers and you can plop a gallon of milk next to the Cap’n Crunch for a long, long time. Or, in my case, leave a hoarded box of Land O’ Lakes creamer tubs sitting under your desk.

We like killing pathogens, you think, so let’s subject all milk to UHT! Not so fast. Those high temperatures kill more than bad germs. A bunch of chemical reactions occur that change the flavor of the milk and occasionally impart off flavors. It also reduces folate content by about 85 percent and can reduce vitamins B12, C and thiamine. One Australian study even found that as early as a month after pasteurization, UHT milk began to gelatinize and thicken, or even stale. Still won’t kill you, but that doesn’t mean it’s a pleasant accompaniment to a couple warm Toll House cookies.

Still, UHT is seeing extended popularity, especially in organic milk production. Ironic? A little. The problem is that modern organic dairy farming is a big business, since traditional grocery store chains and places like Whole Foods demand a large, consistent supply of product before they’ll sign a contract with your company. That means centralized facilities near organic cattle sites, which means longer travel times compared to traditional dairies with regional production. Which means UHT.

Which also brings up the now-classic divide between organic and local foods: is fresh and local better than organic and shipped? Would you rather have hormones and better tasting milk, or no hormones and milk that uses a heck of a lot of fossil fuels to get to you, maybe months after leaving the cow?

Tough choice. Especially if no one remembers to pick up a carton of organic cream for the office fridge.

Don't want to waste? Check back tomorrow for tips on what to do with "soured" milk.

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