As every home cook, I've gone through the stage when I marinated every piece of protein that crossed my kitchen threshold (chicken, beef, pork, lamb, shrimp, fish, etc). If it had parents, it needed to soak in something. Ah -- those good old college days full of so much enthusiasm and so little knowledge about how to cook. A few years later, I learned that a marinade has as much impact on the tenderness and flavor of your meat as the government has on the state of the economy. Sure they can hurt. But can they help? Nope.
Yes, I became a culinary and political libertarian. My only goal in cooking proteins was to choose them wisely and not screw them up. Salt, pepper, and heat became my only ingredients. "But what about complexity of flavor?" might you ask. Surprisingly, as all the rubs and marinates got dropped, flavor got more complex because I discovered the ultimate power of the Maillard reaction, or in layman terms "browning." Browning is your friend. When proteins brown, hundreds of different flavor compounds are created. That's where dropping the marinades and rubs actually helps. In order to maximize browning, the proteins need to be absolutely dry (otherwise they steam rather than brown). They also need to make great contact with the hot cooking surface. All the liquids in the marinades make your proteins wet, and the chunky ingredients, like garlic, prevent good contact with the cooking surface (it's the garlic that ends up browning and often burning rather than the protein itself). I tried wiping the marinades off before cooking the protein. That helped a lot in the browning department, but seemed like an awful lot of fuss all for nothing. Leaving the protein completely alone and not marinating at all seemed to work just as well and was a lot easier. Salt and pepper right before cooking, and into the hot skillet it goes. I wrote about the searing technique before, using scallops as an example, but the same applies to all proteins.
I am still a strong believer in this minimalist approach. That's what I teach in my classes. If you want to be a great cook, you need to know how to take a protein, salt, pepper, and heat and turn them into a spectacular meal. If you think that Worcestershire sauce, soy sauce, mustard or some other secret ingredient will come to your rescue, keep on dreaming. It all boils down to your ability to judge how much salt to use and how to test for doneness.
This sounds somewhat austere and implies that all your beef dishes should taste the same, all your lamb dishes should taste the same, etc. Far from it. That's where the sauces and garnishes come in. Is red wine lovely with beef? Of course! But instead of soaking a steak in it before cooking, why not make a red wine reduction sauce to put on the steak when it's done? Is lamb just begging for garlic? How about topping it with garlic herb butter after it's done? This way you get the best of both worlds -- the garlic flavor is fresh and intense and the meat is perfectly brown and complex tasting.
Salting in advance does work
Of course, as soon as you come up with any sort of strict rules, like "proteins should never be pre-treated," you start discovering exceptions. So, never say never. There is one ingredient that does do wonders when left on a protein for a long period of time before cooking -- salt. Judy Rodger's from the Zuni Cafe opened my eyes to the beauty of pre-salting. Unlike most ingredients commonly found in marinates, salt is the one that penetrates very deeply even into large pieces of meat given long enough time (like 24-48 hours). Acid on another hand only penetrates about 1/4 inch of meat usually resulting in an outer layer that's mushy and dry rather than tender and juicy. So, what does the deep salt penetration give you?
More evenly seasoned protein
This is true for all of them from chicken to shrimp. Salt intensifies the flavor of a protein. The move evenly we can distribute it, the better each bite is going to be.
Slightly better browning
This benefit is tiny, but it is a nice side effect. When proteins are salted, their surface gets wet. People often worry about the protein losing juiciness, which is not the right problem to worry about. The real problem is reduced browning due to increased surface moisture. That's why I always salt immediately before starting to cook a protein rather than 10-15 minutes in advance. But a day in advance is even better. This way you can dry it thoroughly before cooking and don't need to put any more salt on it, keeping the outside as dry as possible. What about the moisture loss due to salting? Some people think it's such a big problem that they salt their proteins AFTER cooking. That's just silly. The amount of liquid drawn out by salt is tiny compared to how much protein loses due to the heat of cooking. Some moisture lose is unavoidable, but it's much better controlled by not overcooking than by avoiding salt.
Increased tenderness and juiciness
It's very easy to get over confident here and assume that if a protein is pre-salted for a day or two, it will be tender and juicy. I am still a firm believer that most of tenderness and juiciness is controlled through getting doneness just right. Below 120F, the moisture is still trapped within the cell walls, and you can't easily access it by chewing. 120F-140F, the proteins coagulate, forcing liquid out of the muscle cells, which then collects within the protein sheath. That's when your protein is the juiciest but still tender. After 140F, it's all downhill from there. The proteins get tougher and the liquid gets squeezed out. That's where salting in advance can really help. It gives you an additional 20 degrees or so before the protein gets seriously tough and squeezes all the moisture out of itself.
So for all practical purposes, salting a day or two ahead gives you the most benefit with poultry and pork since they are usually cooked to higher than 140F. I haven't noticed a big improvement in tenderness or juiciness of my beef and lamb when I salt far in advance because I cook them to 130F (internal temp after resting). I do cook most fish to as high as 135F (internal temp after resting), but it's such a tender protein that toughness is usually not an issue and as long as you don't go over 140F, it will still be juicy. This is not to say that salting in advance can ever hurt. It's always beneficial particularly when it comes to outer layers that reach higher temperature than the center. But for chicken and pork, it's a tremendous difference that is worth planning in advance.
Other in advance ingredients
After further reading, I found that there are other ingredients that can be helpful when put on a protein way in advance. Lactic acid helps with tenderizing the outer layers of chicken without turning them mushy the way wine or vinegar does. This explains the tradition of many cuisines to soak chicken in yogurt or buttermilk before cooking. Sodium glutamates can penetrate to the center of even very large pieces of protein given enough time (just like salt does). The most glutamate rich product is MSG (health risks of which, by the way, have been blown completely out of proportion), but there are plenty of others that are less controversial: miso paste, tomato paste, soy sauce, etc.
The important thing is to figure out what does an ingredient do for you before dumping it on an unsuspecting protein. It's also good to know the trade offs. Sure, the soy sauce will make salmon more flavorful, but will it make it stick to the grill? The brine might make your chicken really juicy, but will it prevent its skin from getting crisp? Salt is the only ingredient I know of that always helps and never hurts when put on any protein before cooking and allowed time to penetrate. The other ones are a bit tricky.
This is just some food for thought. As all advice on my blog it mostly applies to Western European cooking where proteins are cooked in large pieces and meats are either cooked to medium-rare or braised. There are many cuisines where proteins are cut very small and cooked all the way through. Different cooking principles apply there.
In cooking, just like in everything else in life, rules are only there to be broken. But basic principles like "less is more" can often be helpful.