Each food will have atributes that can be seen by examining the item. Or once the item is consumed, you can view the effects by looking at your character sheet (CTRL C) and looking at the modifiers .
Most food buffs are pretty much useless, unless they are made my a chef, an then there are only a few foods that I think are worth paying for...
Angarian Fishak Supprise for example buffs your Mind for between 400-600 points for 500 or so seconds. You can also buy the ice cream that buffs your willpower and focus. (fishak sells out in a matter of minuets once it hits the vendors BTW)
The crap you /forage is only really worth feeding to pets when they moan at you