You must balance time and effectiveness when you tenderize beef without sacrificing one for the other. You have several tenderizing options that all do the same thing -- break down tough muscle fibers and collagen -- but only a few do it quickly. The chemical, or enzymatic and quick-curing, method and the mechanical, or cubing and tearing, method are the two quickest and most-effective.
Certain naturally occurring enzymes, known as cysteine proteases, accelerate collagen breakdown between muscle fibers, basically eating away the stuff that makes meat tough. You usually see collagen in the form of tendons, ligaments and other gristly bits, but it also holds individual muscle fibers together and gives muscles, like a chuck roast, their shape. You find tenderizing enzymes in everyday ingredients, such as bromelain from pineapple, papain from pineapple and actinidin from kiwi. Enzymatic tenderizing, although quick and effective, is a two-edged sword. If you use too much, or let the meat marinate too long, the meat turns to mush, unless you're using actinidin, which works a bit differently than papain and bromelain. To tenderize meat quickly with actinidin, add a tablespoon or two of pureed kiwi fuit to a marinade and let the beef marinate 15 to 30 minutes before cooking.
Protein molecules twisted into coils and held in place by hydrogen bonds comprise a basic muscle fiber. However, the structure of muscle fibers in tough meat differs slightly from those in naturally tender cuts. Tough meat comes from muscles in highly exercised areas, such as the leg or shoulder, which have protein molecules coiled more tightly than those in other lesser-used muscles, such as the tenderloins that runs along the spine. Tenderizing loosens, or denatures, protein coils. Denaturing occurs naturally over time, as with dry-aged beef, or with sodium, as with salt-cured or brined meat. Salt-curing requires a lot of salt and time -- as long as six months for large cuts-- but protein starts to denature within 30 minutes to one hour on steaks. To tenderize with salt, simply sprinkle 1 teaspoon or so of kosher salt on both sides of the steak one hour before cooking it. Then rinse off the salt and pat it dry before cooking -- no need to salt a second time.
Tenderizing doesn't get much simpler than cubing. No enzymes, no denaturing, just the physical breakdown of muscle and connective tissue. When you cube meat, or puncture it with numerous small blades, you slice through tough tissue, which makes it easier to chew. You often can't see the signs of cubing when done in moderation. In fact, most steakhouses cube inexpensive cuts with handheld, spring-loaded blade tenderizers that insert 48 steel blades about 3/4 inch through the steak. You can buy blade tenderizers for home use and tenderize beef in about one minute. Lay the meat flat on a cutting board and "stamp" the meat with the tenderizer about four times on each side in various, equally spaced locations, like when you stamp paper with a rubber stamp.
Like cubing, pounding meat with the textured, or "toothy," side of a meat mallet tears apart tough muscle fibers and rips apart connective tissue, but in a more-obvious way. To tenderize with a mallet, place the beef on a cutting board and cover it with plastic film. Smack the meat with the textured side of the mallet, using glancing strikes. Strike the meat uniformly several times on both sides until a sharp knife slices through the edge easily.