Fridge vs. no fridge, part 1: Milk

You can tell a lot about somebody based on what they do with their milk when they get home from the supermarket.

It may seem like a strange detail, but in different countries, unopened milk either does or does not need to be kept cold. So if you know whether a person zips home from the store and puts that jug, carton or bag in the refrigerator, you might be able to guess where they live.

But why? People in the U.S. might balk at milk left on the counter for days, while Europeans and some South Americans might wonder why Americans keep theirs chilly. The answer? A mix between how the milk is pasteurized (heated at a high temperature to kill pathogens) and packaged.

In many countries, milk is kept in aseptic packaging, meaning that it is sterile. Milk in this packaging can last for months at room temperature, only requiring refrigeration upon being opened.

“Dairy products that have been heat-sterilized and wrapped in sterile packaging do not require refrigeration, as the sterilization prevents the milk from spoiling,” NY Nutrition Group founder Lisa Moskovitz told Fitness Magazine.

There are several advantages to this way of packaging. Costs can be saved if milk doesn’t need to be kept cold during transportation to the store. The shelf life is longer, too. It works well in residential kitchens that don’t have the large refrigerators common in the U.S. For these reasons, some manufacturers do indeed sell unrefrigerated milk in U.S. stores, but it hasn’t taken off in a country that seems to prefer fresher milk.

Pasteurization also plays a role. Most of the milk in the U.S. is pasteurized by being heated to around 160°F for a short time. Milk processed in this way lasts for about a week and requires refrigeration. Milk that goes into aseptic packaging, however, is heated to much hotter temperatures — around 275°F — for an even shorter time. This process is called ultra-high temperature pasteurization (UHT). Milk treated this way can last for up to six months before being opened.

In part 2 of this blog post, we look at why eggs get the refrigerator treatment in some countries, but not others.

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