Pork and a marinade are perfect partners. The base flavor of the meat -- mild but not bland, meaty but not beefy -- more or less gets out of the way and lets the marinade do its thing. So you don't have to get aggressive with the spices unless that's your thing. Marinades are made using the same ratio of oil to acid as vinaigrettes -- three to one -- but your acid choices aren't limited to vinegar. Soy, cayenne pepper and Worcestershire sauces all work well with pork's flavor and contain enough acid to work as a marinade.
Mix 3 parts vegetable oil and 1 part acid in a plastic or stainless-steel bowl or container. If the container has a lid, shake it vigorously to mix the marinade base. You can use more than one type of acidic ingredient as long as the total volume equals 1 part.
Add herbs -- such as bay leaf, sage, rosemary, thyme, oregano, basil and parsley -- to the liquid ingredients. Press fresh herbs with the back of a spoon to bruise them for a light flavor. Finely mince them for a stronger flavor.
Add spices, such as allspice, paprika, cumin, turmeric, fennel seeds, cloves, mace and peppercorns. For stronger flavor, toast the spices in a saute pan over low heat until aromatic, then partially crush them with a mortar and pestle before adding them.
Add pungent and aromatic vegetables to the marinade. Choose from crushed garlic, onions, leeks, shallots, ginger and chili peppers.
Season the marinade to taste with kosher salt. Mix the marinade until the oil and acid emulsify and combine.
Place the pork roast in a plastic food container or sealable food-storage bag. Mix the marinade once more and pour it over the pork. Cover the container with its lid or plastic wrap and place it in the refrigerator.
Marinate pork shoulder, blade-in shoulder, boneless shoulder and picnic shoulder for 8 to 12 hours. Marinate rib roasts and loin roasts for 6 to 8 hours. Marinate pork tenderloin for 2 to 4 hours. Turn the roast over in the marinade halfway through marinating.
Take the pork roast out of the refrigerator 45 minutes to 1 hour before you want to cook it. Take the pork out of the marinade and let it sit in a dish lined with paper towels until it reaches room temperature. Discard the marinade.
Substitute cultured buttermilk or full-fat yogurt for oil for more tenderness and to add a slight tanginess to the pork's taste.
If your marinade contains pineapple or papaya juice, marinate the pork no longer than 20 to 30 minutes. Papaya contains papain and pineapples contain bormelain, both enzymes that tenderize protein effectively, but degrade it to mush if left in contact too long.
Do not reuse the marinade for a sauce or for basting the roast as it cooks.