Mushrooms are veritable sponges, absorbing as much oil as you put in the pan. But while developing a new method for sautéing mushrooms, we noticed that, once cooked, the mushrooms barely absorbed any oil at all. Here's why (and how).
Anyone who has sautéed mushrooms knows that they're veritable sponges, seeming to absorb as much oil as you put in the pan. But while developing a new method for sautéing these fungi—which calls for steaming them in water before adding any oil to the pan—we noticed that, once cooked, the mushrooms barely absorbed any oil at all. To demonstrate this phenomenon, we carried out the following experiment.
We tossed 100 grams of raw halved, trimmed white mushrooms with ¼ cup of vegetable oil. After 5 minutes, we drained the mushrooms and weighed them again. We repeated this treatment with another 100 grams of mushrooms that we first microwaved until they were just cooked through and then thoroughly dried.
The raw mushrooms absorbed 42 grams of oil (about 3 tablespoons), while the cooked mushrooms picked up just 2 grams of oil (about ½ teaspoon).
The stems and caps of mushrooms are made up of a large network of fibers called hyphae that are 80 to 90 percent water. This tissue also contains numerous air pockets in which oil can collect. Cooking damages the fibers, which release water, and collapses the air pockets, causing the mushroom to shrink. With fewer air pockets to capture oil and less surface area for oil to cling to, our cooked mushrooms picked up just ½ teaspoon of oil, while the raw mushrooms absorbed a whopping 21 times more oil.
Our new method for sautéing takes advantage of a cooked mushroom's inability to absorb much oil. We steam the mushrooms in water until they collapse. Once the pan is dry, we add a mere ½ teaspoon of oil, which coats the mushrooms and helps them brown.