Food can help define cultures, continued....
Once you associate different foods with specific cultures, you have another tool in your GMing palette. If your PCs walk into an area, they can be assaulted by familiar smells that might give them a clue about what they are dealing with. Once you establish, for instance, that kobolds like to soak their meat in a bitter, horseradish-based solution the party that enters the cave system and begins to feel their eyes watering may pick up the hint that there are kobolds about. Similarly, walking into a tavern and smelling a strong mix of mint and rosemary might indicate that the innkeep is, say, an elf.
The way food is prepared and served can also say a lot about a culture. Does everything get slapped together into some sort of mush or is it prepared artistically? It is easy to associate the former with primitive cultures and the latter with civilization, but breaking expectations can sometimes lead to interesting results. Perhaps a warrior-culture makes elaborate displays of their enemies corpses - they might emphasize artistry in food preparation as a reflection of that (or, if they eat their enemies, they might be the same thing). Food can be intricately tied into religion, such that the act of sitting down and eating a meal is in itself a religious ritual.
Also consider eating utensils. An organized, warlike culture (say, hobgoblins) might eat with a single dagger - and perhaps it is one that they carry with them at all times and use in battle. A more bestial culture (orcs?) might use false talons that fit over their fingers to represent some sort of a connection to a totem creature. Others might use their hands. A more refined culture might use an elaborate set of utensils - or a single, elegant one.
Preparation methods can also say quite a bit. Stews and soups are generally considered simple, hearty fare. Elaborate preparation methods (consider the turducken) can imply wealth and decadence.
If you are dealing with non-human cultures, you may wish to consider using ingredients that are not, strictly speaking, food. Dwarves might add clay to many of their foods. Elves may be able to digest some plants that humans cannot. Goblins might grind up bones and add the resulting powder to breads.
Next: using food as a motivator.