September 8, 2007

Pseudo Food Science

Posted by Eric at 2:52 pm | Category: Food, Links, Science

I enjoy cooking; I think in general, a lot of people who like chemistry and biology also really like cooking. Maybe it’s because they like working with their hands.

Anyway, I saw this post, where they suggest heavily salting a steak before grilling in order to make it taste better. Sounds like a good idea; maybe I’ll try it next time.

Then they have a really weird argument about why the salting works. They claim that salt first sucks some water out of the steak (ok, no argument there). Then, the salt supposedly dissolves a bit and moves back into the steak (which they mistakenly call “osmosis”; really, the first step is osmosis). Ok, not beyond the stretch of imagination; I’m not an expert in surface and fluid chemistry. This higher ionic concentration in the steak then denatures (they say “relaxes”) the proteins in the steak, and “relaxed” proteins are more tender and juicy. (Of course, denaturing proteins is not really the same as relaxing them, for the same reason that stretching a Slinky toy out straight doesn’t relax the toy.)

Sorry, not buying it. Denaturing proteins doesn’t make things tender and juicy; in fact, it tends to do the opposite. Consider egg white; it’s pretty much pure protein. It’s goopy. Cooking it makes the proteins denatured, which unravels them from their mostly globular state, making little networks out of them. Hence, uncooked egg white = liquid, cooked egg white = solid. Cooking proteins and denaturing them tends to make them form more fibers and solidify meat. Hence, a well-done steak is stiffer and harder than a rare steak, because more of the protein is denatured.

So what makes steak nice and juicy? Well, the concept might seem gross, but it’s your saliva. More saliva = more juicy. Salty things are juicier because they make you salivate more. Ever try eating an unsalted saltine cracker without water? Compare that to a salted saltine cracker. The latter is much easier to get down without getting thirsty. So your saliva is probably the biggest component of the “juicy” or “dry” taste.

The salting of the meat doesn’t make it juicy because it denatures the protein (or make it “relaxed”). It makes the meat taste better because the meat becomes saltier, and salty tastes good. It’s the same reason chargrilling steak tends to make it taste juicier, because for a lot of people, chargrilled things make them salivate more. And rare meat has more fat (and I presume more salty blood and fluids) left in the steak, which tends to make people salivate, too.

This knowledge becomes instantly useful in a school cafeteria. Every once in a while, my school would serve “pepper steak”, which was usually dry as a bone, and it felt like I was eating leather. I always salted both sides of the steak liberally, and though it’s no substitute for a properly seasoned and grilled steak, it did make the meat substantially more palatable.

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7 Responses to “Pseudo Food Science”

  1. Mike Says:
    September 17th, 2007 at 4:05 am

    Seems you missed the part where it makes the steak tender. We tried this method tonight on steaks cut from frozen then thawed bottom round. Made the steak tastier and more tender than normal.

    Do you have an explanation on why the salt would tenderize the steak?

  2. Eric Says:
    September 17th, 2007 at 7:43 am

    I’m figuring the largest affect on the senses is due to the salivation, which will both make the steak seem juicier and more tender. Salting the outside of the steak will most likely have a minimal effect on the actual physical properties of the bulk meat, simply because a layer of salt on the outside for an hour and a half just won’t have much of an effect on the liquid distribution in the dead meat.

  3. Mike Says:
    September 17th, 2007 at 1:29 pm

    The salt made the steak easier to cut and chew. At least this is how it seemed, will have to try it again and see if I get the same result.

  4. Michael Says:
    September 21st, 2007 at 11:03 pm

    I’ll stick my neck out and suggest:

    Salt may help denature some proteins. Perhaps not to the same degree as cooking or acid will. I imagine more so that it interrupts ionic bonds within and between proteins, causing them to disassociate. This may break up longer or more complex networks of proteins into smaller units thus making it more tender. Mushing it up so to say.

    Collagen is most likely the main protein of interest here, as after death, and following rigor mortis, the internal cellular protein network breaks down. I believe that this is why meat is hung as it allows the meat to relax again and soften up.

    I found an article in the journal of Biochem. I just read the abstract but it talks about how KCl salt reduces the thermal stability of collagens. One cannot extrapolate then that NaCl will do the same, however one can hypothesise. Other articles merit the effects to the Cl- anion and other anions.

    http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1177473

    Regarding juiciness:

    I imagine the salt will extract water from the cells into the extracellular matrix. Thus liberating more fluid which can be detected when chewing. Combine this with increased salivation etc and the answer could be thus so. Salt also competes for water with proteins and this may also liberate more water from extracellular proteins further increasing the liberation of juice when chewing.

    Thoughts?

  5. Eric Says:
    September 22nd, 2007 at 11:09 am

    It’s possible that the salt does denature the proteins, but I’m skeptical that the denaturing process leads to tenderness in the meat. Note that the paper you found says that KCl reduces the thermal stability of individual, soluble collagen molecules, not cross-linked fibrils, which is the predominant form of collagen that our teeth and knives encounter. In fact, they see an opposite effect, that salt increases the aggregation and stability of fibrils. So in that regard, salt doesn’t seem to affect the protein stability itself.

    I can see that the salt might disrupt a few bonds between integrins and ECM, but does enough salt dissolve with a dry rub (as opposed to brining)? I’m not sure it would; in addition, proteins (especially structural proteins) do tend to be robust to small perturbations in salinity. Full denaturation and disruption of complexes generally requires detergents, since protein interaction surfaces tend to be hydrophobic.

    As for fluid flow, there probably is a little bit, but if there’s really a nontrivial amount, then water will probably seep out of the steak due to the osmotic pressure of the salt rub, resulting in dry meat (since the water would evaporate upon cooking).

  6. rodrigo Says:
    November 9th, 2007 at 5:31 pm

    You are incorrect. Cooking initially denatures proteins, but they coagulate and regroup- that happens after 140 degrees in meat, and that’s where meat starts to get tough. Go study!

  7. Eric Says:
    November 10th, 2007 at 2:36 am

    Well thank you for that awfully condescending remark.

    In any case, perhaps I’m wrong about the denaturation of proteins. I’m just a chemist and a molecular biologist, so I don’t have much experience with macromolecules at high temperatures.

    But l don’t still don’t buy the salting argument. I doubt salt diffusion works that well in a dry rub; just consider that the diffusion constant of salt ions in water is on the order of 10^-5 cm^2/sec, which means that in two hours, the salt diffuses roughly a couple millimeters into the meat, assuming that meat is as fluid as water…which it isn’t. I’m sorry, but steak tends to be a little thicker than a few millimeters and a little bit more solid than water. Hence, no way that the salt is having effects on proteins a centimeter down. No, salt can, at most, have an effect on the top two millimeters or so of meat. And that part gets grilled anyway, which is a much stronger effect than any salt concentration change will be.

    How about you go study for a bit and come back with some numbers to justify your position?

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