BrainStuff Classics: Skim Versus Whole Milk: Which Spoils Faster?

Some food safety charts claim that whole milk goes off more quickly than skim milk, but the scientific evidence is mixed. Learn more about milk science in this classic episode of BrainStuff, based on this article: https://recipes.howstuffworks.com/dairy/does-whole-milk-spoil-faster-than-skim-milk.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of iHeartRadio. Hi brain Stuff.
I'm Lorn vogel Bomb, and this is another classic episode
from the Vault. This one gets into the science behind
the expiration dates on different types of milk, or rather
the lack of science. It turns out it's really more
of a suggestion at best. Hey, brain Stuff, I'm Lauren

(00:26):
vogel Bomb. And we've all had moments of uncertainty and
let's face it, paranoia about the state of the food
sitting in our refrigerators. You might be able to eyeball
some of those suspicious items, check for expiration dates on others,
and with some milk maybe you'll probably take a quick
with and hope for the best. But if you've ever

(00:46):
looked a shelf life chart to figure out how long
your milk might last, you might have noticed that skim
milk is said to last a day or two longer
than whole milk. But is that really true and if so, why?
Before we really get started, I should state that there
is by no means universal agreement on this issue. Some
dairy scientists say skim milk lasts longer because certain fat

(01:10):
loving microbes can't develop as quickly in non fat milk.
Others say that whole milk lasts longer because free fatty
acids might actually be natural preservatives. Still, others say that
maybe there isn't a difference in spoilage at all, it's
just that we notice flavor changes more in one or
the other. There's only been one major controlled study on

(01:30):
these spoilage rates of whole and skim milk, and it
was somewhat inconclusive. Skim milk was found to spoil slightly faster,
but the researchers weren't exactly sure why. Bacteria that are
psychotrophic that is, cold resistant, are what caused spoilage in
the fridge, and in the study, they multiplied at the
same rate in both types of milk. When the milk spoiled.

(01:53):
Both whole and skim contained similar strains of bacteria. There
is a pronounced difference in how whole and skim milk
reacts did when they were injected with the same spoilage microorganisms,
but they affected the milk's taste and smell more than
they did the actual spoilage rate. Whole milk, for the record,
tended to turn sour and skim milk was on the
bitter side, So for the purposes of your average milk consumer,

(02:18):
there's really no hard and fast rule about which kind
will spoil faster. If whole milk does last longer than skim,
the difference is so slight that any given gallon of
skim milk could outlast any given gallon of whole milk.
The spoilage rate depends on so many variables manufacturer production methods,
milk formulation, plant sanitation, storage temperatures, pH level, moisture content,

(02:40):
just to name a few. A small change in just
one of them could give any particular container of milk
a slightly longer shelf life than another. A couple other
factors make things even more ambiguous. For one, it's pretty
much impossible to pinpoint the exact moment of spoilage. Depending
on your sense of smell and taste and your tolerance
for changes and milk flavor, you might turn up your

(03:01):
nose at a gallon of milk that someone else might
readily swig. And there's no federal regulation of milk expiration
dates in the United States. Only twenty states legally standardize
the date that's printed on the bottle, and those standards
very widely. One state might mandate a cell by date
of a certain number of days after pasteurization, whereas milk
jugs in another state would be printed with a use

(03:23):
by date. The upshot don't base your milk purchases on
which type might last longer. If you're concerned about shelf life,
you'd be better off following a few simple steps to
slow down milk spoilage, whether you're a whole or skim drinker. First,
make sure your refrigerator is the correct temperature. It should
be set at forty degrees fahrenheit that's four point four

(03:45):
degrees celsius. Store your milk on an interior shelf instead
of on the door, which fluctuates more in temperature. And
make sure you put your milk back in the fridge
as soon as possible after using it. Leaving it out
on the counter for even a few minutes exposes it
to light and heat, giving bacteria a chance to spring
into action. Today's episode is based on the article does

(04:11):
whole milk spoil faster than skim milk? On how stuffworks
dot com, written by Alison Cooper. Brain Stuff is production
of by Heart Radio in partnership with how Stuffworks dot
com and is produced by Tyler Klaang. For four more
podcasts from my Heart Radio, visit the iHeartRadio app, Apple Podcasts,
or wherever you listen to your favorite shows.