Rawhide dog chews are dried hypodermic interstitial tissue (second layer of the skin) from cattle raised for meat production. This hypodermic interstitial tissue is quite tough yet flexible, due to collagen fibers that link.
During processing the animal's skin is split into inner and outer layers. The tougher outer layer is used for leather shoes, garments, and upholstery, while the softer inner layer is cut and formed into different shapes for dog chews.
It is important to note that rawhide bones and chews made in USA are the absolute best for your dog. Choosing American Rawhide, Merrick, Dingo, Bone Buddies or Beafeaters brands you give your pet a rawhide chew of premium beefhide from corn-fed American cattle produced under the strictest quality standards. American production processes and sanitation practices are much better and more highly regulated than most other countries producing rawhide bones. In less developed countries a lack of modern roads and refrigeration trucks often requires the use of preservatives to get skins from outer-lying areas to processing plants. In the US fresh beef-hides are refrigerated during shipping to prevent degradation, spoilage, fouling and the need for chemical additives.
The first step in making rawhide chews is transportation of animal's hide to processing plants where it is split, washed with degreasers and detergents, and cleaned. The completely clean rawhide is then sterilized in hydrogen peroxide at the required temperature for the required amount of time. This also has a desired side effect of making the rawhide the yellow-white color you are familiar with.
The wet hides are wrung to remove excess water and slapped on to special cutting tables. With the help of electric knives, rectangular pieces of varying sizes and special shapes are cut from certain portions of the hide. These shapes are forwarded to the tying department where the shapes are rolled and folded to create the various forms (bones, rolls, twists, sticks etc.).
The final shapes are placed on trays and are carried on carts to drying rooms that are temperature controlled to assure drying but not melting. The product is then inspected again and either packaged for sale, or colored in the FDA approved colorings and flavorings, re-dried, and then packaged for sale.