Perhaps you've had this experience:
You have a recipe that relies heavily on chicken or beef broth for flavor. In order to "parvise" the recipe (or make it vegetarian), you replace the meat broth with immitation chicken or beef broth from a mix. The recipe works beautifully, but you're not happy about your reliance on phony meat, so one day you nobly prepare a homemade vegetable stock and use that instead. To your surprise, the flavor is one-dimensional and unappealing. You were better off with the mix.
A Boston Globe article that I read recently got me thinking about this phenomenon in a new light. The article is about the fifth and least familiar taste, umami. The word umami, which roughly translates as "delicious" in Japanese, was first used to describe a specific taste by the Japanese chemist Kikunae Ikeda, who isolated monosodium glutamate, or MSG. Contrary to popular belief, there is no evidence that MSG is unhealthy unless you're allergic to it; unfortunately, however, many people are.
Scientists attribute umami to certain amino acids and nucleotides including, but not restricted to, glutamate. It seems that the flavor develops in meat as it cooks and the proteins are broken down into amino acids. (Braising meat is the best way to bring out the umami.) Vegetables develop umami as they ripen. Fermentation brings out the umami in wine, beer, and Asian foods like miso and fish sauce.
Clear vegetable broth isn't nearly as umami-rich as chicken broth or soup mix with MSG, presumably because you need a higher concentration of specific vegetables in order to get deep umami flavor. A rich mushroom, squash, or tomato broth is fine, but only if you're making mushroom, squash, or tomato soup.
The authors of The Fifth Taste: Cooking With Umami claim that you don't need MSG to make umami-rich food, and they seem to have plenty of vegetarian recipes to offer. Still, it seems to me that takes a bit more to pack umami into a vegetarian dish than a fleischig one. Here are a few tricks that I've found bring out the flavor I now know as umami in parve soups:
1. Make soups hearty, not thin and clear.
2. Use crushed tomatoes or tomato puree if the flavor is compatible with the type of soup you're making.
3. Add chunks of sweet potato or winter squash to vegetable, split pea, and lentil soups.
4. Add a splash of dry wine (preferably red, if you're using tomatoes).
5. Let soup simmer for a good 3-5 hours, if not longer.
As for parve hot and sour soup, vegetarian grape leaves, and matsa farfel kugel, I'm sticking with the MSG.
(Cross-posted to Kosherblog.)