why does milk stay good inside the body warm but curdles when not refrigerated outside of the cow?
In: Biology
Same reason warm meat stays good in the body, but needs refrigeration.
Living creatures have amazing levels of defense against bacteria, but when it dies (or a substance is removed from the living thing) those defenses die too.
It’s exposed to the same immune system as the body’s. So the reason it doesn’t go bad is the same reason why the whole animal doesn’t go bad.
Because it doesn’t get the time to spoil as your body is actively removing nutrients very rapidly. Milk is a great example:
If you can digest milk sugar, lactose, then everything goes fine. Your body extracts the sugars and digests them. Any bacteria that digest the milk must survive and replicate on what’s left behind, so their growth is severely slowed and the milk dries out/gets digested by friendly bacteria and becomes poop.
If you can’t digest milk sugar, then the milk essentially is spoiling in your gut. The bacteria rapidly consume the sugar and mass replicate. Your body reacts to this and you get diarrhea.
Immune system.
Same reason your flesh dosent rot but dead meat outside the fridge does like u/j[amcdonald120](https://www.reddit.com/user/jamcdonald120/) explained. Milk in mammary glands is fiercely guarded from germs by your bodies defense so you dont get sick from the milk and dont transmit diesease to offspring.
Even Pasteurized milk has around 20,000 colony forming units of bacteria per ml. Warm milk curdles because the bacteria reproduce much faster at warmer temps. An acidic waste product, lactic acid, is produced by the bacteria. When enough lactic acid accumulates it shifts the pH of the milk to acidic. The pH shift denatures (snarls or breaks) the milk protein which changes from water soluble to insoluble and it drops out of the liquid. Boom, curdled milk.
Milk spoils when unrefrigerated because bacteria consume the nutrients in it and replicate. When you drink milk, your body is the one breaking down and consuming the nutrients. The bacteria in your gut assist in this process, but the nutrients end up in your bloodstream and poop instead of being used to grow the bacterial colony. It doesn’t stay “milk” for long after you consume it, it becomes half-digested stomach contents and eventually poop as a result of being digested.
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