I have a family favorite flank steak marinade that uses vegetable oil. Can I substitute olive oil (health reasons) and get the same taste and marinade? I am worried that when the meat is marinaded over night in the refrigerator that the olive oil will harden. Thank you for your assistance.--Sandy
The reason for using fat of any sort in a marinade is because many flavor compounds dissolve in fat, but very little or not at all in water. The oil carries those flavor compounds onto the surface of the meat.
Very little oil is actually needed to accomplish this. Only enough to lightly coat the meat. For a typical marinade, a few tablespoons of oil per cup of other liquids should be enough. The exception, of course, being pastes that are made of herbs puréed in an oil base, like pesto.
Contrary to popular belief, the oil does not help to tenderize the meat. Marinades only penetrate the outer 1/8" (3 mm) or so and therefore can not affect the interior. Since the meat is made up largely of muscle fibers which are saturated with water, it is almost impossible for the oil in particular to penetrate even that far.
So, to answer your question, olive oil will be perfectly fine, as it doesn't have to stay liquid to do its job. In fact, I use olive oil for marinades all of the time.
In order to be sure that the oil soluble flavor compounds are carried to the meat, finely chop any fresh herbs that you use, and mince or press garlic. Combine the herbs, spices and other flavoring ingredients like garlic with the oil before adding the other liquids. Also, I am a fan of putting the meat and marinade into a resealable plastic bag, since this allows you to redistribute the marinade by "massaging" the meat through the bag. This helps distribute the oil, and therefore the flavors, over the surface of the meat.