It seems to be common knowledge that pineapple tenderizes meat. Most sources say that it does so due to proteases (specifically bromelain). However, I've also seen suggestions that acid is an effective tenderizer on its own, and the Wikipedia article on bromelain in the meat tenderizing section says:

Although the quantity of bromelain in a typical serving of pineapple fruit is probably not significant, specific extraction can yield sufficient quantities for domestic and industrial processing.

which is sort of wishy-washy but might mean that there's not actually enough there for tenderizing.

It does seem that pineapple is effective, one way or another. (See for example Will a pineapple marinade reduce a beef roast to paste?)

So what's going on here?

Is the acidity important? Would something equally acidic tenderize just as well? It looks like lemon and lime juice have lower pH than pineapple juice, so how effective are they?

Is the bromelain important? Could you hypothetically neutralize the acidity of pineapple juice and still use it to tenderize, or do you need larger quantities of bromelain extracted for it to be effective?

  • Related (but about cooking, not marinating): cooking.stackexchange.com/q/13424/1672 – Cascabel Jan 27 '16 at 21:49
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    Interesting indeed. I always understood (or rather: assumed) that acidity was the major component in a tenderizer; In a way, it's predigesting the meat. I marinate quite a lot with tamarind, curious to see if there's something else going there. – Willem van Rumpt Jan 28 '16 at 5:55
  • By the way, if anyone wants to do side-by-side comparisons of marinating with fresh pineapple juice/puree, canned/cooked juice/puree, and a plain acid like lemon juice, I'd happily give a bounty for it. – Cascabel Jan 28 '16 at 18:10

Update: After reading a bit on this, (and also fully reading the question) I found that there have been papers written on the effects of acid baths on meat tenderness as well as enzyme treatment: Acid: http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1010&context=animalscidiss Enzyme: http://www.brainromania.ro/uploads/papers/effect-of-marination-with-proteolytic-enzymes-on-quality-of-beef-muscle-2012-409.pdf

It seems that food grade citric acid doesn't affect tenderness that much, where as a solution of Bromalain does, and at a greater effect than that found mixed in with the citric acid of Pineapple. There's no study comparing pineapples to oranges (Eh? See what I did there?) but this seems to say that the citric acid in food may have less of an effect than that of the digestive enzymes in them.

Please see below for previous answer if you'd like to point and laugh at those who skim questions and don't read fully.

So, I think I found the answer: http://science.howstuffworks.com/innovation/edible-innovations/pineapple-enzyme-tenderize-steak.htm

Apparently, acidity aside, the enzymes found in the stem of the Pineapple: Bromelain can divide the proteins found in muscular fiber. I'm going to copy and paste the next part from the article that goes a bit deeper into how Bromelain works (and I'm lazy):

Bromelain works in these capacities due to it's ability to separate amino acids. Amino acids are organic compounds within living cells. Amino acids join by forming peptide bonds, a link that connects one amino acid's amino group with the carboxyl group of another amino acid. When amino acids join through peptide bonds, they form proteins. These proteins can carry out numerous functions in the structure and operation of cells, tissues and organs.

This breaks down the peptide bonds that hold together proteins in collagen, which is what makes meat tough. The enzymes stop around 158 degrees Fahrenheit, so once they start cooking, their work is done. That's why it's important to marinate.

TLDR: Pineapple stems have Bromelain, which aside from a fun nickname breaks down Amino acids and dissolve the peptide bonds in collagen, which causes the firmness in meat.

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    Unfortunately, the question is not what bromelain does to proteins/meat (though you're totally right about that) it's about how strong the effect is from that compared to any effects from acidity when using pineapple juice. – Cascabel Jan 28 '16 at 17:55
  • Ah, right. Well, that teaches me for title skimming. – Beer_en_thu_si_asT Jan 28 '16 at 17:59
  • The article that I brought up doesn't even bring acid into the mix, though. You'd think if it had a comparable affect that it would be covered or at least mentioned? – Beer_en_thu_si_asT Jan 28 '16 at 18:01
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    Hopefully! Sometimes articles like that can end up misrepresenting or oversimplifying, though. I suspect that the bromelain matters at least some, because there's apparently less of an effect with cooked pineapple than with fresh, but I don't actually know how much less, so it's hard to say whether there's still also significant effects from the acid. – Cascabel Jan 28 '16 at 18:07
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    "pieces of meat marinated in a composition consisting of 15 g of pineapple pulp, 200 mL dry red wine, 2 tablespoons honey, 2 tablespoons grated horseradish, 2 teaspoons garlic, 1 tablespoon thyme, 1 tablespoon marjoram, salt and pepper" -- I guess they really wanted to be able to eat the results... and were really confident there's no significant enzymes in wine, honey, horseradish, or garlic?? – Cascabel Jan 28 '16 at 22:38

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