I'm also wondering where in the files the food reactions are because all I can find are the food item raws.
The item_food.txt RAW file is the only one specifically dealing with food(meals). It is the library of terms that are used in naming prepared meals that your cooks make at the kitchen. The "level" in each entry has to do with what type of meal it is (2 = Easy, 3 = Fine, and 4 = Lavish). If you want to create new names for these meals, you can add them in. They will be randomly picked from all choices based on the food level.
For example, adding:
[ITEM_FOOD:ITEM_FOOD_DUMPLING]
[NAME:dumpling]
[LEVEL:2]
to the item_food RAW will mean that there is now a chance for your dwarven cooks to make dumplings when you select "prepare easy meal" from the kitchen. Mechanically, they will be identical to other easy meals (e.g. biscuits).
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The actual reaction that makes meals is hard-coded in the game. Also, trying to make custom reactions to make meals (the FOOD item) tend to not work. However, if you want to make custom edible foods, and not have them be the random assembly of minced ingredients that dwarven cooking demands, then you can make reactions to make other eat-able items instead and have those items be made out of your new "food".
Some valid eat-able items that you can have your reactions churn out include:
- Cheese
- Fish (will have the prefix "prepared" in front of the material)
- Meat
- Plant
- Plant Growth
- Glob
- Egg
These will be the "item" that the reaction makes. You will still need to assign the material, which would be whatever custom food material it is you want to add.
Remember to have the proper EDIBLE tags on your food material, else your dwarves won't eat it. Also, the type of item you decide to make will determine stockpiling preferences, so keep that in mind as well. I've known a lot of people that have modded in their own custom "meals", like dwarven bread or something like that. The general consensus has been that the "cheese" item tends to work the best in terms of stockpiling your new food with your other edibles with the least hassle in trying to find it.