size is an important physical attribute of foods used in screening solid to separate foreign materials , grading of fruits and vegetables, and evaluating the quality of food materials. In fluid flow, and heat and mass transfer calculations, it is necessary to know the size of the sample. Size of the particulate foods is also critical. For example, particle size of powdered milk must be large enough to prevent agglomeration, but small enough to allow rapid dissolution during reconstitution. particle size was found to be inversely proportional to powder and water holding capacity of whey protein powders.