models.rb

# "Lookup" Tables modeled on USDA data

class Food
  has_many :nutrients
  has_many :weights
end

class Nutrient 
  belongs_to :food
  has_one :nutrient_definition
end

class NutrientDefinition
  belongs_to :food
end

class Weight
  belongs_to :food
end

# -----------------------------

class Recipe
  has_many :ingredients
end

class Ingredient
  belongs_to :recipe
  has_many :ingredient_profiles
  has_many :nutrients, :through => :ingredient_profiles
end

# "cache" tables, so profiles don't have to be re-created for each display

class IngredientProfile
  belongs_to :ingredient
  belongs_to :nutrient
end

# for aggregated nutrient values
class RecipeProfile
  belongs_to :recipe
end

Ingredients should get flagged after creation depending on whether they have been found in the lookup tables:

Red flag: ingredient not found in foods table

Yellow flag: ingredient found, but not with the measurement indicated (e.g. 1 "clove" of flour)

Green flag: ingredient found and nutritionally analyzed

If ingredient gets green flag, entries will be made into the ingredient_profiles table with the nutrient_id (e.g. Kcal, Protein, Carbs) and the amount of that nutrient for the measurement of the ingredient.