A food processor is especially useful for preparing stiff purées that would be too much of a burden for a blender. It is often used for stiff mixtures and purées that were traditionally prepared with a mortar and pestle or by laborious working the mixture through a drum sieve.
It is better not to use a food processor for starchy purées such as those made with potatoes or celeriac, which will quickly become gluey if overworked. In some instances, especially for vegetable and fruit purées and coulis, it is useful to purée the mixture in a food processor before forcing it through a drum sieve.