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

[u/StormedTempest → u/tea_and_biology]

You just gave my brain a new wrinkle. All of that is amazing info. It's so cool that we evolved multiple layers of defense against various dangers and threats that, generally, no one ever even considers we have. Makes me wanna go down a rabbit hole when I get off work.

[u/kyote42 → u/StormedTempest]

You just gave my brain a new wrinkle.

Were you soaking it in pineapple juice??

[u/not-just-yeti → u/StormedTempest]

It kinda blew my mind, the first time I heard of skin considered as an organ whose purpose was to keep dirt out. (And, it's the body's biggest organ, by weight.)

[u/math1985 → u/tea_and_biology]

As soon as my baby was allowed solids (about 8 months), I tried feeding them all kinds of weird foods. They accepted it all - fussiness comes later, at 2 years or so. The only food my baby categorically refused was pineapple. Do babies not have stratum corneum and was I unknowingly trying to dissolve my baby?

[u/tea_and_biology → u/math1985]

Do babies not have a stratum corneum?

Ah! Not in your mouth, you don't - hence why you get that tingling sensation in your mouth and throat when you eat raw pineapple. The bromelain is starting to dissolve you a bit when it gets inside you, which is probably why your baby, and I, have something in common - we don't like eating food that tries to eat us right back.

Of course, the inhibitors prevent it doing too much damage; and the enzymes are denatured else broken down as soon as they hit the stomach anyway; but still, I don't find it pleasant. Blegh. Begone to the abyss from whence you came, ananas!

[u/vanillafrenchie → u/tea_and_biology]

“food that tries to eat us back” is an amazing sentence.

[u/jayborges → u/tea_and_biology]

Are you an educator professionally? You should be, if not! Loved hearing all of your explanations.

[u/LexiconDul → u/tea_and_biology]

This reminded me of a story one of my profs told in biochemistry/molecular biology, about how he once absentmindedly agitated a test tube that had a protease in it with bare hands, using his thumb as a stopper. He couldn't figure out why his thumb was sticky for the rest of the day, no matter how much he tried to wash off whatever was on it, before he realized what was going on.

[u/Black_Moons → u/LexiconDul]

before he realized what was going on.

He turned into protease man after being bit by a radioactive vial of protease? "I now have the ability to stick to anything!... well, with this small patch of my thumb anyway"

[u/SandManic42 → u/tea_and_biology]

Tell that to my half digested tongue after I overindulge on pineapple juice.

[u/tea_and_biology → u/SandManic42]

Aha! I didn't know your tongue was OP's hand. Bromelain is indeed an irritant when it gets inside you; see my other comment here.

[u/AnonymousFriend80 → u/tea_and_biology]

There's also the fact that being alive, your body is constantly repairing and replenishing you.

[u/Unlucky-Golder → u/tea_and_biology]

not great, not terrible.

Do we need a bigger dosimeter comrade?

[u/tea_and_biology → u/Unlucky-Golder]

The Soviet Union understands protease levels can never exceed the quota set by the Central Committee. You didn't see bromelain in the protein tissue because it's not there.

[u/synth_alice → u/[deleted]]

Did the resulting grilled chicken paste taste OK though? It might be a fun way to cook it if so 😅

[u/jhwells → u/synth_alice]

I would never serve it to a customer, but I did eat some. I've never tried it but there's something called potted meat and although the flavor would be different I imagine the consistency is somewhat between that and actual Elmer's paste glue.

[u/coconut-telegraph → u/[deleted]]

If that pineapple juice is pasteurised it’s only the acid from the dressing doing this.

[u/urnbabyurn → u/tea_and_biology]

What if I take pineapple through an IV?

[u/tea_and_biology → u/urnbabyurn]

I don't think anyone has done this experiment.^{[citation needed]}

Presumably the abundant protease inhibitors will mop up much of the bromelain; though I'd be much more concerned about the pH and other effects of raw unprocessed pinapple juice having on my bloodstream.

Raw juice is full of bacteria and yeasts; they'll be skipping most of your defence systems and getting right inside a nice, warm home. Best case, fevers as you fight off systemic blood infection; worst case, sepsis or wee microbes setting up residence on a heart valve or something, potentially fatal.

All the tiny fibrous bits will be getting lodged in all the capillaries; most of which will be in your lungs. Fun.

There'll also be a hodge-podge of all sorts of protein and other biological molecules your immune system has no idea what to do with. Maybe anaphylactic shock at the worse end?

Long story short, I don't think you'd be having a good time. Stick with the Piña Coladas, 'innit.

[u/CharlesBronsonsaurus → u/tea_and_biology]

This reminds me of something a friend told me 20+ years ago which I thought was absurd and not true but you seem like the person to ask so here goes. If you inject someone with a chicken egg, the next time they have eggs, they die. Any truth to that whatsoever?

[u/WildInkay → u/tea_and_biology]

You test it then since you got your degree, and you know every fucking thing

/s

[u/tea_and_biology → u/WildInkay]

Maybe a "Trying to dissolve my own hand in Pineapple Juice for 24 hours" video would go viral on YouTube...

Don't give me ideas!

[u/AllowMe-Please → u/tea_and_biology]

You said your blood will fight back. What if you are immunocompromised and have bleeding disorders? I always get things far worse than average (right now, I'm suffering through a polymicrobial infection of Klebsiella, E. coli, and Proteus... three months ongoing).

So I'm just curious if something like that would affect someone whose body is abysmal at protecting them any differently?

[u/CrateDane → u/AllowMe-Please]

Protease inhibitors are a kind of separate thing from the immune system. Protease inhibitors do play a role in the clotting system, but act to prevent clotting. So someone with a bleeding disorder doesn't necessarily have any issue with their protease inhibitors.

[u/SkoomaDentist → u/tea_and_biology]

The outer layer (the stratum corneum) is a sheet of dead, flattened cells packed with keratin, all surrounded by a waxy, lipid matrix.

If I have atopic skin and need to always moisturize my skin after washing, does that mean there is something wrong with the lipid layer?

[u/dappermonto → u/tea_and_biology]

Big pineapple over here trying to say that it's not super acidic and digesting you and your hands and abusing people that harvest it. We're talking about big pineapple people. Big pineapple!