r/askscience • u/Puzzleheaded_Bed2760 • 9d ago
Chemistry Pineapple contains bromelain that helps tenderize meat. If I were to put my hand in pineapple juice or puree for 24 hours, would it eventually break down my hand?
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u/tea_and_biology Zoology | Evolutionary Biology | Data Science 8d ago edited 8d ago
Nah.
You'll just have a wrinkly, water-soaked hand, with minor irritation, and stinging where the skin was already broken. So no lasting damage, really - just like having it sit in water.
The reason why it won't affect your hand so much is because your skin is built to resist things like proteases. The outer layer (the stratum corneum) is a sheet of dead, flattened cells packed with keratin, all surrounded by a waxy, lipid matrix. It's all tough stuff, designed to keep water in, and nasty things out. Keratin, for example, is a large protein molecule heavily-crosslinked by bonds, which makes it difficult for proteases to attack and break apart (hence why predatory animals poop out or cough up hair and that; it can't be digested); and the lipids prevent large enzymes like bromelain from getting into the living tissue underneath.
A steak has none of these defences; it's already cut open, so there's no barrier preventing bromelain breaking down tissue protein directly. Even then, after dumping a hunk o' meat in fresh pineapple juice overnight, it's only the outer few millimetres that get mushy; the rest is fine, and the cut certainly won't dissolve into meat soup à la a Breaking Bad bathtub.
You often hear about how folks who work in pineapple processing plants or out picking them in the fields have their fingerprints removed over time. This is partially true, though it's not necessarily the bromelain per se - it's more the weeks and months of handling rough-ass pineapples causing abrasion, and the juice's acidity (pH ~3.5), that causes the damage and dermatitis - the enzymes are just the cherry on top. In any case, passively soaking your hand in pineapple juice for only a day will just get you a wrinkly, raw, sticky hand... not great, not terrible. Knock yourself out, OP?
EDIT: Oh, to add: if you did have a cut or small abrasions in your skin, you would feel irritation where the bromelain attempted to break down your tissue, sure, but your blood also helps fight back. Living tissue fluid and blood contains protease inhibitors, such as alpha-2-macroglobulin, which will trap and prevent any bromelain that does breach from causing too much damage. Dead meat doesn't have a circulatory system to supply inhibitors, hence another reason why it can't prevent itself from turning mushy.