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Speaker 1: Welcome to brain Stuff, a production of iHeartRadio. Hi brain Stuff.

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Speaker 1: I'm Lorn vogel Bomb, and this is another classic episode

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Speaker 1: from the Vault. This one gets into the science behind

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Speaker 1: the expiration dates on different types of milk, or rather

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Speaker 1: the lack of science. It turns out it's really more

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Speaker 1: of a suggestion at best. Hey, brain Stuff, I'm Lauren

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Speaker 1: vogel Bomb. And we've all had moments of uncertainty and

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Speaker 1: let's face it, paranoia about the state of the food

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Speaker 1: sitting in our refrigerators. You might be able to eyeball

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Speaker 1: some of those suspicious items, check for expiration dates on others,

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Speaker 1: and with some milk maybe you'll probably take a quick

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Speaker 1: with and hope for the best. But if you've ever

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Speaker 1: looked a shelf life chart to figure out how long

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Speaker 1: your milk might last, you might have noticed that skim

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Speaker 1: milk is said to last a day or two longer

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Speaker 1: than whole milk. But is that really true and if so, why?

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Speaker 1: Before we really get started, I should state that there

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Speaker 1: is by no means universal agreement on this issue. Some

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Speaker 1: dairy scientists say skim milk lasts longer because certain fat

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Speaker 1: loving microbes can't develop as quickly in non fat milk.

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Speaker 1: Others say that whole milk lasts longer because free fatty

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Speaker 1: acids might actually be natural preservatives. Still, others say that

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Speaker 1: maybe there isn't a difference in spoilage at all, it's

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Speaker 1: just that we notice flavor changes more in one or

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Speaker 1: the other. There's only been one major controlled study on

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Speaker 1: these spoilage rates of whole and skim milk, and it

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Speaker 1: was somewhat inconclusive. Skim milk was found to spoil slightly faster,

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Speaker 1: but the researchers weren't exactly sure why. Bacteria that are

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Speaker 1: psychotrophic that is, cold resistant, are what caused spoilage in

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Speaker 1: the fridge, and in the study, they multiplied at the

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Speaker 1: same rate in both types of milk. When the milk spoiled.

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Speaker 1: Both whole and skim contained similar strains of bacteria. There

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Speaker 1: is a pronounced difference in how whole and skim milk

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Speaker 1: reacts did when they were injected with the same spoilage microorganisms,

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Speaker 1: but they affected the milk's taste and smell more than

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Speaker 1: they did the actual spoilage rate. Whole milk, for the record,

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Speaker 1: tended to turn sour and skim milk was on the

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Speaker 1: bitter side, So for the purposes of your average milk consumer,

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Speaker 1: there's really no hard and fast rule about which kind

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Speaker 1: will spoil faster. If whole milk does last longer than skim,

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Speaker 1: the difference is so slight that any given gallon of

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Speaker 1: skim milk could outlast any given gallon of whole milk.

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Speaker 1: The spoilage rate depends on so many variables manufacturer production methods,

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Speaker 1: milk formulation, plant sanitation, storage temperatures, pH level, moisture content,

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Speaker 1: just to name a few. A small change in just

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Speaker 1: one of them could give any particular container of milk

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Speaker 1: a slightly longer shelf life than another. A couple other

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Speaker 1: factors make things even more ambiguous. For one, it's pretty

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Speaker 1: much impossible to pinpoint the exact moment of spoilage. Depending

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Speaker 1: on your sense of smell and taste and your tolerance

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Speaker 1: for changes and milk flavor, you might turn up your

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Speaker 1: nose at a gallon of milk that someone else might

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Speaker 1: readily swig. And there's no federal regulation of milk expiration

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Speaker 1: dates in the United States. Only twenty states legally standardize

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Speaker 1: the date that's printed on the bottle, and those standards

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Speaker 1: very widely. One state might mandate a cell by date

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Speaker 1: of a certain number of days after pasteurization, whereas milk

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Speaker 1: jugs in another state would be printed with a use

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Speaker 1: by date. The upshot don't base your milk purchases on

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Speaker 1: which type might last longer. If you're concerned about shelf life,

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Speaker 1: you'd be better off following a few simple steps to

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Speaker 1: slow down milk spoilage, whether you're a whole or skim drinker. First,

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Speaker 1: make sure your refrigerator is the correct temperature. It should

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Speaker 1: be set at forty degrees fahrenheit that's four point four

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Speaker 1: degrees celsius. Store your milk on an interior shelf instead

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Speaker 1: of on the door, which fluctuates more in temperature. And

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Speaker 1: make sure you put your milk back in the fridge

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Speaker 1: as soon as possible after using it. Leaving it out

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Speaker 1: on the counter for even a few minutes exposes it

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Speaker 1: to light and heat, giving bacteria a chance to spring

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Speaker 1: into action. Today's episode is based on the article does

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Speaker 1: whole milk spoil faster than skim milk? On how stuffworks

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Speaker 1: dot com, written by Alison Cooper. Brain Stuff is production

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Speaker 1: of by Heart Radio in partnership with how Stuffworks dot

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Speaker 1: com and is produced by Tyler Klaang. For four more

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Speaker 1: podcasts from my Heart Radio, visit the iHeartRadio app, Apple Podcasts,

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Speaker 1: or wherever you listen to your favorite shows.