There's a post I saw on reddit that points to the dimple on the side of a milk jug, and makes fun of all the people who don't know what that's for. In the comments are thousands of people giving dozens of different explanations, and all of them are wrong.
It is not there to indicate that the milk has spoiled by popping out due to gasses produced by spoiled milk. If there was enough gas to pop out the dimple, the whole jug would look like a balloon.
It is not there to provide structural integrity, like lateral support to prevent the bottles from crushing. The contents are under pressure, so if there was enough force on the jug from any direction, then the cap would pop off regardless of the shape in the sidewall.
The actual answer is that the dimple is added to ensure that all of the jugs contain the same volume of milk. Plastic jugs are blown into molds, and minor manufacturing variations over time would create jugs that hold different amounts of milk. Larger jugs would hold more than a gallon. They could just fill by volume, but consumers are wary of purchasing a bottle if it appears to be less full than the others. So they add the dimple to make it so that the level of milk is all the way at the top with minimal air between the milk and the cap.
You can verify this yourself by finding different jugs from the same supplier with dimples of different depths, or even no dimple at all. None of those other explanations would explain dimples of different sizes or jugs without dimples.
TLDR everybody is wrong. The milk jug dimples are added to ensure the jug contains the correct volume of milk.
You buy milk in gallon-sized hard plastic containers?
Is that a restaurant thing? How long does a gallon of milk last in your family?
It's a US thing. A gallon of milk will last my family about two weeks, or less if the kids are into baking or breakfast cereal that week. I sometimes put a little milk in my coffee or tea, and I occasionally use some for making sauces or marinades. Very rarely will we throw away milk because it has spoiled, but it has happened. Maybe once a year or so, usually because of a power outage or having to travel unexpectedly.
We also have half-gallon plastic jugs which feature the same dent sometimes. When I was a kid, I remember we even had tiny pint-sized jugs for half and half, but I think that was more of a novelty.
Wait.....the rest of the world doesn't have hard jug gallons? What do they use instead?
Bags
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That.....looks so messy! I know there's no crying over spilled milk, but have you SEEN the price of dairy??? Gotta work a second job just to afford breakfast!
You put em bags into a hard pitcher thing you have at home, and cut the corner. So I guess it's a bit less waste
That guy REALLY should have put an explanation there. Afaik there's one province in Canada that still uses bags. Historically (30 years ago) many countries have used bags. Today most use either tetrapak, smaller bottle style plastic (0.25, 0.5, 1.0 litres) or actual bottles.
Isn't that an Atlantic Canada thing? I know Quebec has them, and I'm pretty sure we weren't the only ones in Canada with bagged milk.
How much does milk cost where you live? Maybe it's just because I live close to the source but milk is around $3 a gallon for me. For another data point eggs are around $2 a dozen, often on sale for $1 (current exchange rates are around 1:1 for dollars to euros for those in euroland)
I miss bag milk. :(
So jealous.
1l cartons
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In Sweden we use 1 to 1,5L cartons.
In Canada, they use gallon sized plastic bags
I've lived in various provinces in Canada. West of Ontario I really only see the waxed-paper cartons or the plastic jugs, stores carry both equally. Eastern Canada carries the plastic bags (and everyone has a plastic container at home they place them in after snipping the bag corner) and often the cartons. Bit weird the custom changes across Canada, and coming from the west I was very confused about the bagged milk when I first moved to Ontario.
Maybe someone else can comment on their experiences. I've never seen bagged milk in a store in the prairies (but I only lived in major cities).
They had milk in 1.3 L bags (sold in packs of 3 for 4 L) in Manitoba about 35 or 40 years ago.
Tbh, I haven't seen bagged milk for quite a while where I live in Canada. It's typically cartons for 2L or less (though sometimes mini plastic jugs too) and plastic jugs as in OP for 4L.
Still very much a thing in Eastern Canada.
Well, a bag holding 3 x 1.3L bags.
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Futuristic technologies such as these
What accursed alien unholy wizardry is this burn my eyes burn my eyes
One liter (0.26 gl) bottles or boxes.
When I grew up here in Sweden, milk came in these containers:
https://en.wikipedia.org/wiki/Tetra_Brik
The design of milk packaging is quite interesting;
https://kommerduihag.se/kommer-du-ihag-hur-mjolkpaket-sag-ut-forr/
15 years or so ago the Brik was changed to this:
https://www.arla.se/artiklar/var-vanligaste-forpackning/
It was apparently done for two reasons:
A smaller version of the tetrahedron style package is still in use for coffee milk.
Square space efficient packaging that you can finish within spoiling time, allowing for fresher products without additives. Easier to pour, packaging easily collapses for easier disposal. Fully printable and recyclable. A superior packaging in every single way.
Bags I think.
I would never drink a milk that lasts two weeks. Real food spoils. This must be some liquid plastic.
Two weeks is an ordinary time for refrigerated pasteurized milk. If you’re used to a shorter timespan, either your milk is unpasteurized, inadequately refrigerated, or you’re at the end of an inefficient distribution chain.
Option number 4. The sanitary standards for packaging milk are very high in North America. This drastically reduces the risk of contamination after pasteurization, which allows our milk to last quite a while. It isn't as sterile as UHT milk, but it tastes more natural.
Well, perhaps used to be. Now the oversight on those kinds of things is gone, and companies can do whatever pleases them. I wouldn't put my trust in their good faith at all.
The proof is sort of in the lifespan of the milk.
I haven’t noticed it going bad sooner yet. It’s possible that other adulterants start showing up, but there are still lawyers that can sue companies if they find them fucking around.
That said we need to kick the fucker who are enabling this shit, out of the government ASAP.
Fresh milk that's been pasteurized and refrigerated should last at least three weeks.