One of the purposes of creating recipes is to be able to calculate their nutrient profile. If you were doing this manually you would look for the nutrient profile of each ingredient and sum each ingredient’s nutrient contribution. From this you would get an estimate of the recipe’s nutrient profile.
Validating a recipe is a step that ensures, in an automated system, that all ingredients are present in the food database. The nutrient calculation of the recipe can then proceed automatically. Validation will report either that the ingredient does not exist or that the units used to quantify the ingredient are not valid. In either case one must correct the mistake before instructing the program to calculate the recipe values.