Have the purity of potables play some rule in the food we make. But instead of affecting amount of biles make them affect food category restoration. At 100% they would restore 2x more (or 2x more often) food category.
To make it more consistent have each potable restore some food category, even if only by a small amount (for example 50% chance to restore by 5%). So carrots, parsley, raddishes etc.
For example carrots would restore potatoes, raddishes would restore pumpkins, parsley would restore berries, oakworth would restore shellfish and so on.