It shall be unlawful for all persons collecting milk or cream on routes to do any sampling, testing, or grading en route. All sampling, testing, and grading must be done in a licensed milk or cream station or a dairy manufacturing plant. No pouring from one can to another shall be done except in a licensed milk or cream station or a dairy manufacturing plant. Only containers specifically manufactured for the handling of milk or cream shall be used. No milk or cream to be used in the manufacture of food products shall be delivered in an unwholesome condition to a carrier.