Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,
Speaker 1: I'm Lauren vogel Bomb, and we've all had moments of
Speaker 1: uncertainty and, let's face it, paranoia about the state of
Speaker 1: the food sitting in our refrigerators. You might be able
Speaker 1: to eyeball some of the suspicious items, check for expiration
Speaker 1: dates on others, and with some milk maybe you'll probably
Speaker 1: take a quick whiff and hope for the best. But
Speaker 1: if you've ever looked a shelf life chart to figure
Speaker 1: out how long your milk might last, you might have
Speaker 1: noticed that skim milk is said to last a day
Speaker 1: or two longer than whole milk. But is that really
Speaker 1: true and if so, why? Before we really get started,
Speaker 1: I should state that there is by no means universal
Speaker 1: agreement on this issue. Some dairy scientists say skim milk
Speaker 1: lasts longer because certain fat loving microbes can't develop as
Speaker 1: quickly in non fat milk. Others say that whole milk
Speaker 1: lasts longer because free fatty acids might actually be natural preservatives. Still,
Speaker 1: others say that maybe there isn't a difference in spoilage
Speaker 1: at all, it's just that we notice flavor changes more
Speaker 1: in one or the other. There's only been one major
Speaker 1: controlled study on the spoilage rates of whole and skim milk,
Speaker 1: and it was somewhat inconclusive. Skim milk was found to
Speaker 1: spoil slightly faster, but the researchers weren't exactly sure why.
Speaker 1: Bacteria that are psychotrophic, that is, cold resistant, are what
Speaker 1: caused spoilage in the fridge, and in the study, they
Speaker 1: multiplied at the same rate in both types of milk.
Speaker 1: When the milk spoiled, both whole and skim contained similar
Speaker 1: strains of bacteria. There was a pronounced difference and how
Speaker 1: whole and skim milk reacted when they were injected with
Speaker 1: the same spoilage microorganisms, but they affected the milks taste
Speaker 1: and smell more than they did the actual spoilage rate.
Speaker 1: Whole milk, for the record, tended to turn sour and
Speaker 1: skim milk was on the bitter side. So for the
Speaker 1: purposes of your average milk consumer, there's really no hard
Speaker 1: and fast rule about which kind will spoil faster. If
Speaker 1: whole milk does last longer than skim, the difference is
Speaker 1: so slight that any given gallon of skim milk could
Speaker 1: outlast any given gallon of whole milk. The spoilage rate
Speaker 1: depends on so many variables manufacturer production methods, milk formulation,
Speaker 1: plant sanitation, storage temperatures, pH level, moisture content, just to
Speaker 1: name a few. A small change in just one of
Speaker 1: them could give any particular container of milk a slightly
Speaker 1: longer shelf life than another. A couple other factors make
Speaker 1: things even more ambiguous. For one, it's pretty much impossible
Speaker 1: to pinpoint the exact moment of spoilage. Depending on your
Speaker 1: sense of smell and taste and your tolerance for changes
Speaker 1: in milk flavor, you might turn up your nose at
Speaker 1: a gallon of milk that someone else might readily swig.
Speaker 1: And there's no federal regulation of milk expiration dates in
Speaker 1: the United States. Only twenty states legally standardized the date
Speaker 1: that's printed on the bottle, and those standards vary widely.
Speaker 1: One state might mandate a cell by date of a
Speaker 1: certain number of days after pasteurization, whereas milk jugs and
Speaker 1: another state would be printed with a use by date.
Speaker 1: The upshot don't base your milk purchases on which type
Speaker 1: might last longer. If you're concerned about shelf life. You'd
Speaker 1: be better off following a few simple steps to slow
Speaker 1: down milk spoilage, whether you're a whole or skim drinker. First,
Speaker 1: make sure your refrigerator is the correct temperature. It should
Speaker 1: be set at forty degrees fahrenheit that's four point four
Speaker 1: degrees celsius. Store your milk on an interior shelf instead
Speaker 1: of on the door, which fluctuates more in temperature. And
Speaker 1: make sure you put your milk back in the fridge
Speaker 1: as soon as possible after using it. Leaving it out
Speaker 1: on the counter for even a few minutes exposes it
Speaker 1: to light and heat, giving bacteria a chance to spring
Speaker 1: into action. Today's episode was written by Alison Cooper and
Speaker 1: produced by Tyler Clang. Bonus fact for the episode, the
Speaker 1: origin of milks expiration date labels and of expiration date
Speaker 1: labels in general in the United States rests with a
Speaker 1: campaign started by al Capone. To learn more about that,
Speaker 1: check out an episode of my other podcast, Saber. The
Speaker 1: episode is called expiration Dates Best if listened by and
Speaker 1: of course, for more on this and lots of other
Speaker 1: fresh topics, visit our home planet pastuff works dot com.