My character can eat rocks, now how do i limit it to just rocks?

[KernelCore]

I'm making a DST character mod with the ability to eat rocks and found the following text:

^{-- So you can eat all elementals
    local eater = inst.components.eater
    table.insert(eater.preferseating, FOODTYPE.ELEMENTAL)
    table.insert(eater.caneat, FOODTYPE.ELEMENTAL)
    eater.inst:AddTag(FOODTYPE.ELEMENTAL.."_eater")}

    ^{local _TestFood = eater.TestFood
    eater.TestFood = function(self, food, testvalues)
        -- So you can only eat rocks, out of all stuff of the elementals group
        if food and food.components.edible and food.components.edible.foodtype == FOODTYPE.ELEMENTAL then
            return food.prefab == "rocks"
        end
        return _TestFood(self, food, testvalues)
    end}

    ^{-- So you benefit for eating rocks
    eater.oneatfn = function(inst, food)
        if food and food.prefab == "rocks" then
            -- rocks give 1 hunger back by default, 1 + 9 = 10
            inst.components.hunger:DoDelta(9)
        end
    end}

It works well and I figured out how to manipulate it for other values. The problem I have right now is how my character can eat other elementals. How can I limit this to just rocks?

I've included the main lua file and the entire mod folder in 2 separate uploads.

goatroo.lua

goatroo 2.zip