Once contact with a certifying agency is made, the detective work begins. The manufacturer must supply a complete, detailed list of every ingredient in the product, including preservatives, release agents, stabilizers or other inert ingredients. In addition, every step in the manufacturing process, every cleansing agent used on the equipment and all other products produced on the same premises require close investigating and supervision. The certifying agency must track down each ingredient to its ultimate source. If, for instance, the ingredient is meat or a meat by-product, the item cannot be kosher unless the meat source itself is strictly kosher.
Any oil used in the manufacture of foodstuffs has to be traced back to the oil processor.
Many vegetable oils are produced in machinery that is also used to process animal fats and oils. In such a case, of course, the oil is not recommended. Some ingredients with innocuous sounding names need special attention. Therefore, the supervising agency must conduct a complete and intense investigation into the origin of all the ingredients. The process by which ingredients are produced must also be carefully checked.