Tonight I marinated some portobellos in 1 part balsamic, 1 part soy sauce, and 2 parts olive oil (with some garlic & herbs thrown in). I added no salt b/c of the soy sauce. I marinated them for two hours, and although they came out OK, they were still under seasoned for my palate. Wondering if I should have upped the soy sauce component or just marinated longer? I worried that the acid in the balsamic might start to break down the mushrooms if I left them longer. Any thoughts?