We know that, contrary to popular belief, marinades do most of their work on the surface of meat and poultry.
That’s because very few flavor compounds can make it deep into the meat, no matter how long it soaks in the marinade. Tofu is often substituted for meat and poultry in recipes, but it doesn’t behave in exactly the same way. How would it respond to marinating? We set up an experiment to find out.
We marinated blocks of firm tofu in four different marinades—using soy sauce, red wine, yogurt, and lemon and garlic as the various bases—for 15 minutes, 30 minutes, 1 hour, and 2 hours. We then wiped off the excess marinade and baked the tofu in a 300-degree oven until hot throughout. We also baked a control block of tofu that we hadn’t marinated. We trimmed the outer 3 millimeters off each block and had 10 tasters sample the remaining tofus blind, asking them to identify the marinade for each.
Tasters were relatively unsuccessful at matching the sample to the marinade at the 15-minute mark, but their results improved dramatically for the 30-minute set. All 10 tasters correctly identified the sample soaked in the soy-based marinade, and eight of the tasters did the same for tofu from the lemon-garlic marinade, while six were accurate for the red wine and yogurt marinades. Interestingly, the accuracy increased only slightly for the 1- and 2-hour batches.
Unlike meat and poultry, firm (and extra-firm) tofu can be thoroughly seasoned by marinades of all types due to its relatively loose structure. Meat is made up of individual muscle fibers bundled together in tight packages by connective tissue, which translates to a dense, resilient texture. The flavors in most marinades don’t get much farther than skin-deep, with a few exceptions—alliums such as garlic and glutamate-rich foods such as soy sauce, both of which have small, water-soluble molecules. By comparison, firm tofu is made of coagulated curds of soy protein pressed into block form. Marinades are able to seep between curd clumps and migrate toward the center.
That said, some marinades are more effective than others. It was easier for tasters to identify the soy and lemon-garlic marinades because the water-soluble flavor compounds in soy sauce and garlic are better at moving through high-moisture tofu than are the compounds found in red wine or yogurt. Considering that we often cut tofu into bite-size pieces with greater surface area (thus creating more points of entry for marinade), marinating can have a profound impact, seasoning the tofu not only at the surface but also deep inside.