Marinades make for interesting food science

Q. I hope you can help. I am a high school culinary-arts instructor and have been doing research on marinades only to come up with more questions than answers. In particular, I read an article that said that the enzymes in a marinade are heat-activated and didn't start working until 170 degrees. I've searched everywhere, including the encyclopedia, and could not confirm this. I do know that enzymes are denatured at boiling but did not know that they were activated at higher temperatures. I thought that just from sheer sitting in the marinade, the tenderizing would take place, whether in the refrigerator or at room temperature.

Also, this reference to marinades starting to activate at 170 degrees did not make sense when considering ceviche, which is not cooked. I wrote the author, and she referred me to the encyclopedia, but I could not find a specific reference. I would truly appreciate any help you can offer.

F.L., via e-mail

A. I agree that the information is a bit confusing. I could find no support for a 170-degree activation. I think your information may have had a typo.

To begin with, marinades are used to infuse or enhance flavors and/or affect the texture of food. Depending on the make-up, they can also help slow spoilage.

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. The acidic nature of a marinade can break down muscle tissues or plant fibers to help with the penetration of flavors. All this is an effect of the pH (acidity).

Heat does not activate or inactivate, but the process proceeds more rapidly at warmer temperatures or if the food is cut to increase the surface area. Much depends on the food involved and what is desired. Facilitating the activity of a marinade doesn't make sense if it ruins the food.

Marinating is usually done at refrigerator temperatures in nonaluminum containers. Avoid overdoing it, as you could end up with mushy results, and don't use any marinade that has been with your meat, poultry or seafood as a sauce unless it has been boiled first to lower the risk of food poisoning. (One option is to set aside a portion of the marinade for this purpose.)

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. It is not an activation as 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. However, enzymes from fruits, such as papaya or pineapple have their peak activity level at 120 degrees to 140 degrees. These enzymes can be inactivated by high heat, which is the reason that fruit or vegetables, prior to being put away for storage, are often blanched (dipped briefly in boiling water) to inactivate breakdown enzymes.