In your case, I'd make a many-to-many table. One recipe can have many ingredients, and one ingredient can appear in many recipies.
If we have a recipie table:
CODE
RECIPIE
RecepieID,RecepieName
1,"Chocolate Mousse"
2,"Chocolate Cookies"
3,"Lemon Cake"
And a reference table of ingredients:
CODE
INGREDIENT
IngredientID,IngredientName
1,"Chocolate Chips"
2,"Lemons"
3,"Sugar"
4,"Fish oil"
We might have this RecepieIngredients table. (Or, we might not; I don't cook, so what the heck do I know?)
CODE
RECEPIEINGREDIENTS
RecepieID,IngredientID
1,1
1,3
2,1
2,3
3,2
3,3
In RECEPIE, the RecepieID is the primary key. Similarly, in the INGREDIENT table, the IngredientID is the PK.
In RECEPIEINGREDIENTS, the primary key has two columns: (RecepieID, IngredientID). The RecepieID there is a foreign key back to the RECEPIE table, and the IngredientID is a foreign key back to the INGREDIENT table.
I hope that helps, and that you can understand the examples--representing database tables in a forum is pretty cumbersome.