For cleaning foodstuffs in the form of a bulk material, such as cereal grains, rice grains, soybeans, sunflower seeds, coffee beans, and the like, there is provided an optical sorting device (24, 24a, 24a') subsequent to a precleaning system (6), which enables sorting on the basis of color and/or size and/or shape. Each particle of the bulk material is allocated to a particle class determined by parameters and conveyed on a supporting surface transporting the bulk material to a reception area (43, 44, 45) for the respective particle class. To clean the bulk material, impurities and bad particles are sorted out of the product, with the product being partitioned into classes, if required.