If a civilization lasted for several hundred years, there's no single answer for that kind of topic. Food is fashion, and is ever changing over time. It's like asking "What did ancient Americans eat between 1600 and 2000?" years in the future, and the answer will vary widely for each century (and regardless of technical progress).
How can you know that to be true as a fact? Do you have a time machine? And new recipes don't need new ingredients to exist. Changing the way you cook things, the temperature, the process, how you mix them, the tools you use, or even random luck can lead to new recipes.
Survivor bias, well known fallacy that Historians are hardly familiar enough with.
Corn syrup, of course.