Why does orange juice need to be refrigerated but oranges don’t?

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A breakfast musing

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Oranges have a protective layer of the peel on them. That won’t make them last forever of course and refrigerating will probably help extend that timeline, but having the peel on there as a barrier is helpful.

Oranges have a peel. Which acts as a protective barrier to keep out harmful bacteria.

Orange juice doesnt have that so it will quickly get bacteria in it that will start to multiply and make the juice go bad. Keeping it refrigerated slows down that process.

It’s essentially the same principle behind be able to leave unopened jars of mayo out but needed to refrigerate an open jar

**TL;DR:** ***Air greeblies.***

Think about how an orange grows.

It starts off as a tiny lower bit of a flower. The petals then fall off and the orange tree starts pumping water and starch and other nourishing stuff into it. So it grows, and forms a peel, with little bits of starchy water (and seeds too, if not seedless) safely stored in it and completely away from air. All the time this pumping and growing takes place, the inside of the orange is sealed from the outside air, so no microbes or bacteria or yeast or other floaty or fly-delivered greeblies like that can get in there.

Then, it ripens and the starches convert to sweet sugars, still protected from all those air greeblies. And greeblies LOVE sugar. And if they get into sugar water, they multiply and spoil it. Especially if it’s warm.

You pick your orange and juice it in a factory. Suddenly, even if you try not to, maybe that super-sugary-water is exposed to air! Now there’s no peel to protect that wonderful sugary water from the greeblies, so maybe greeblies got in!

So, in case the juicing process causes exposure to greeblies, they ask you to refrigerate it, because greeblies don’t grow as fast in cold sugary water and so it won’t spoil so quickly. That’s even more important when you break the seal on it by pouring your first glassful in your greeblie-infested home.

Whole oranges? If they have greeblies inside, you’ll know by the soft brown or moldy spots. But oranges don’t get those quickly – they’ve evolved not to. So they kind of visually tell you they’re still safe because nobody broke their peel seal.

Same reason you would not last long if all you juice was squeeze out. Tomato I believe?

If I slice open my skin deep into my flesh (muscle) and leave it, it WILL get infected since now my protective layer (skin) is gone and bacteria can penetrate. Same as the orange peel. Protective layer. However, if I put my open wound into a refrigerated environment, I still mostly likely will get infection, it just would take longer since the cold inhibit/slow the growth of most bacteria. This is why once you peel skin off the orange, refrigerate it so it will last longer before going bad

The other reasons are correct, but I imagine it’s also because nobody wants to drink warm orange juice and and are fine with or prefer eating room temperature oranges.

Similarly, how come milk will go bad on the counter overnight but a cake with frosting made of cream will be ok for a few days?

Basically the same reason human blood need refrigeration when you take it out of the body. Decay.

The air is full of airborne microbes and spores of decomposers such as yeast and mold. Unless the orange juice was made in a lab-grade clean room guaranteed to be free of any and all spores, dust, and microbes, it almost certainly got contaminated with microbes that will begin to ferment the juice unless it is kept at temperatures inhospitable to microbial reproduction.

Oranges have a peel, but more importantly, the juice of an orange is stored in rice grain sized baggies called cells. When you juice an orange, you’re breaking up all the little baggies, and this lets the air get into the juice. Air makes juice go bad.