DEAR DR. BLONZ: Please explain a bit about marinades, and how the enzymes they contain work. Is it true that they are heat-activated and need temperatures around 170 to work? If that is the case, how could they possibly work in the refrigerator, or even at room temperature? -- D.S., Sun City, Arizona
DEAR D.S.: Marinades are used to infuse or enhance flavors and/or affect the texture of food. Depending on their makeup, they can also help slow spoilage. When used with meats, they can reduce the risk of carcinogenic compounds forming during high-heat grilling and getting deposited on the food. This takes place when a fatty food is cooked directly over hot coals; carcinogenic substances can form when the drippings hit the hot coal surface, and can then get carried back to the food in the resulting smoke. (It's a good reason not to inhale the smoke from your grill, and to arrange fatty foods so that they are not directly over the coals.) Marinades that are acidic and contain herbs such as rosemary, garlic, thyme, oregano and basil tend to be the most effective in lowering carcinogenic formation.
Marinades are usually acidic, using a citrus, wine or vinegar base, but these days any flavorful substance into which a food is immersed might be referred to as a marinade. It is the acidic nature of a marinade that can help break down muscle tissues or plant fibers to help with the penetration of flavors. All of this is an effect of the pH, or acidity. Heat does not activate or inactivate the process, but it can proceed more rapidly at warmer temperatures, or if the food is cut or pierced to increase the available surface area.
Marinading is usually done at refrigerator temperatures in non-aluminum containers. Avoid overdoing it, as you could end up with mushy results. Another bit of advice: Don't use any leftover marinade that has touched your uncooked meat, poultry or seafood as a sauce later. The only exception would be if it were brought to a boil first, to lower the risk of food poisoning. If you want to use your marinade as a finishing sauce, set a portion aside ahead of time.
The topic becomes a bit more complex if the marinade contains tenderizing enzymes. Enzymes are substances that change other substances without themselves being changed. Our body relies on enzymes to digest many of the foods we eat, but enzymes can also be used in food preparation to help tenderize meats.
Often coming from fruits such as papaya or pineapple, such enzymes will slowly break down muscle fibers at cooler temperatures, but their action speeds up as the temperature rises. This is not an "activation" so much as the fact that different enzymes have different ideal circumstances under which they work. Our own bodily enzymes tend to work best around 98.6 degrees F, which makes perfect sense. The enzymes from fruits, such as papain (from papaya) or bromelain (from pineapple) have their peak activity level at 120-140 degrees F. Plant enzymes can be inactivated by high heat, which is the reason that fruits or vegetables, prior to being put away for storage, are often blanched (dipped briefly in boiling water) to inactivate their breakdown enzymes.
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