On Marinading

Not all cuts of meat are created equal. Some are flavorful, some are bland. Some melt in your mouth like butter, some are tough and chewy enough to almost not be worth eating. Fortunately, most meat-based problems can be solved through ample application of a marinade. A good marinade will do three things: tenderize the meat, keep it moist, and impart flavor. Flavor is the easy part - toss ingredients into a bag, and the liquid will more or less taste like a lovely mess of those ingredients... assuming that the meat is moist and properly tenderized. So how does one construct a good marinade? 

Without marinade, I guarantee you this would be awful.

kongsky / freedigitalphotos.net

I'll start with maintaining moisture, since that one's less complicated. In common parlance, the word "moist" refers to something containing an appreciable amount of water. Unfortunately, meat doesn't quite work that way. Meat can be poached or boiled - completely soaked in water - and it can still come out dry. What we think of as moisture in meat is actually fat. The health conscious among us attempt to avoid fat, but a bit of fattiness is essential for meat that tastes good and feels succulent. Thankfully, regular ol' meat fat isn't the only thing that can give our mouths the impression of moisture! Most lipids (for cooking purposes, fats and oils) are able to accomplish this. Olive oil is a great way to go. Canola oil and vegetable oil are also moderately healthy, but differ in taste. One of the reason that a lot of meat-based recipes call for butter is because it, as a fatty substance, is able to keep the meat feeling moist. Unfortunately, excessive butter use is pretty much a highway to heart disease.

I'd like to note that moisturizing is probably the least important part of a marinade. Oils provide you with a buffer; if you overcook the meat, having a fatty marinade will give you a bit of forgiveness. If you cook the meat properly, a oily/fatty marinade isn't necessary.

Tenderizing, to me, is potentially the most important part of a marinade. This is the reason you marinade skirt steak; by default, skirt steak is a flavorful but tough piece of meat. Marinading it makes it soft and buttery. Skirt steak, along with most other tough cuts of meat, has a lot of connective tissue in it. Connective tissue (including cartilage, also called gristle) is primarily made from a rubber/plastic-like protein called collagen. When a marinade tenderizes a meat, its primary goal is to destroy/denature collagen molecules. This eliminates the toughness from the meat. There are three primary ways to accomplish this.

Acids attack the collagen strands with thousands of tiny warriors, whittling it into a weakened state. There are plenty of acids that will do, but vinegars and acidic juices are probably the best examples. The other primary means of attack is based on enzymes - naturally existing proteins in certain ingredients that will selectively denature and destroy collagen. Pineapple and papaya are two fruits containing such enzymes. The third way of destroying collagen is through use of a salt solution, or brine. Lots of salt will treat collagen in much the same way that acidic solutions will. It binds to a ton of different areas on the collagen molecule, effectively denaturing it. It can be very effective to marinade poultry, for example, in a brine with nothing else added. 

Those of you who read the recipe for my first full meal on this blog will notice something missing - alcohol. I had intuitively thought that alcohol would help a marinade to penetrate meat. Ethanol, after all, is toxic to cells in no small part because of its ability to pierce through their membranes and penetrate them. Unfortunately, my logic was misplaced. The ethanol will generally start do denature meat, but not quite as much as you would like it to. Rather than fully break down the collagen, it makes it take on a more rubbery conformation. If you have too much alcohol in a marinade you start to prematurely cook the exterior, which actually hinders the meat's ability to absorb flavor. If you want to put wine, beer, or liquor into a marinade, you should first heat it on a stove so that all the alcohol evaporates away. Then, you can get the flavor and/or acidity without the negative side-effects. The chicken recipe I linked to came out pretty good, in my opinion - perhaps this is because I didn't really use a ton of rum in it. Next time I'll boil the alcohol in the rum away and use more acid.

But I digress. The most important parts of a marinade are salt, acid, and (if you're feeling adventurous) enzymes. These are responsible for tenderizing your meat, and that tenderness helps flavors to penetrate and add the lovely flavors you may be looking for. A bit of fat or oil will help to keep the meat moist and may preserve some of the original flavor. It's important to keep in mind that marinades take time to do their work. Collagen denaturation isn't instantaneous, and it can take a while for the marinade to penetrate deep into the meat. Devoting time to a long marinade (preferably overnight in the fridge) is especially important with tougher cuts of beef, lamb, and pork.

As somewhat of a side note, most lipids won't mix nicely with most acids. If you want to have a more homogeneous marinade, you should use an emulsifier to help the the oil-based and water-based fluid mix together. Honey and mustard are pretty commonly used emulsifiers. Egg yolk can also create a nice emulsion, but its flavor may not be as nice for marinading.

One last thing. A couple of days ago, I used yogurt as a marinade for chicken. Yogurt makes a fantastic base for marinading for two reasons. Coming from dairy, it by default contains lots of lovely animal fats and proteins to impart moisture. Secondly, the bacteria that are responsible for the direct creation of yogurt create lactic acid from sugars much as yeast create alcohol. This lactic acid helps to tenderize meat.