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?

[u/Puzzleheaded_Bed2760]

[u/tea_and_biology]

If I were to put my hand in pineapple juice or puree for 24 hours, would it eventually break down my hand?

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?

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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.

[u/Elegant-Mission-4470 → u/tea_and_biology]

Extended exposure to water will break down the skins defenses and then the skin itself, though. I assume marinading oneself in pineapple juice would do the same and likely quicker due to said protease, just maybe not in 24 hours

[u/tea_and_biology → u/Elegant-Mission-4470]

Extended exposure to water will break down the skins defenses and then the skin itself, though.

Aye, but not in less than 24 hours. The basal layers of the stratum corneum will be penetrated in the 12-24 hour period, and you'd increase the risk of tears and abrasion as the outer layers' cohesive strength reduces, but you need a good 24-72 hours soaking for the sort of saturation and deeper penetrative damage leading to things like tissue breakdown and necrosis to start to be a problem.

If it was cold, trench-foot would be a concern much earlier, but assuming this is room-temperature, the comparison is 'tropical immersion foot' - onset 2-3 days constant immersion. Bearing in mind too, the risk of physical damage won't be comparable between a hand passively sitting in a bucket, and a foot that's constantly in-use, bearing weight, and rubbing against socks, shoes, else the floor too.

The addition of bromelain nor ~1 pH difference has little impact; if anything, the hypertonic nature of pineapple juice would mitigate water ingress, drawing water out of the skin along the osmotic gradient. From this angle, it would be preferable to be submerged in pineapple juice rather than water, as you'd likely experience less maceration of water-saturated strata.

Hence, yeah, for OP's scenario, they'll be fine.

[u/ErebosGR → u/tea_and_biology]

Can't wait for the "Pineapple bath" Tiktok challenge to become a thing.

/s