What is the formal definition of "savory" when used in cooking? I hear a lot about things coming in either sweet or savory forms — e.g. crepes — but in context it doesn't seem that savory is the term for all things that are not sweet. Does it have to do with preparation methods? Ingredients? Taste of the final product?
I have been assuming that "sweet" means something like "sugary," as it does in common usage; please correct me if that's not the case here.
In cooking, "Savory" does generally refer to a flavor profile that is anything other than sweet.
"Sweet" doesn't have to necessarily be sugary sweet...basil, tarragon, fennel, carrots, beets, etc. have sweet flavors that are not excessively sugary sweet.
The term "neutral" is typically used for things like crepes and choux paste (eclair paste) because when made in their traditional style they are neither savory nor sweet and can work with either flavor profile.
There isn't a formal definition, but you have the correct basic idea. Sweet means something you would think of as sugary enough to qualify as dessert, or at least like a breakfast muffin - any case where sweetness is the most dominant of the basic tastes (sweet / salty / sour / umami / bitter). Savory is everything else.
There are plenty of cases where this line can be quite aggressively straddled to the point where which category a dish fits in would be debatable. This is especially true in the sort of hypermodern 30 course Alinea / El Bulli type menus, where there are often specific courses that act as a transition from the savory to the sweet world.
Savory, called Umami in Japanese, implies the presence of Glutamates, the carboxylate anions and salts of the amino acid glutamic acid. The identification Glutamate receptors on the tongue only took place in the past decade, although the ability of the tongue to detect glutamates has long been know. In the early Twentieth Century, a Japanese scientist isolated monosodium glutamate (MSG) while researching the savoriness of seaweed broth.
In short, just as saltiness signifies sodium ions, savory signifies glutamates.
Sweet and savory are not opposite flavours or tastes. They can and do coexist to some degree in most food ingredients, example the tomato. Beef is savoury but contains some sugars. The only tastes that are opposites are sour (acidic) and bitter (alkaline), these cannot co-exist for long as they react together to form new flavours. So its not the absence of sugar but what the dominant taste is. The ancient romans put honey with virtually all meats and fishes. Weather the dish turned out as a sweet or savory depended on how much honey they added.
