Rendering (animals) - History

History

The development of rendering was primarily responsible for the profitable utilization of meat industry by-products, which in turn allowed the development of a massive industrial-scale meat industry that made food more economical for the consumer. Rendering has been carried out for many centuries, primarily for soap and candle making. The earliest rendering was done in a kettle over an open fire. This type of rendering is still done on farms to make lard (pork fat) for food purposes. With the development of steam boilers, it was possible to jacket the kettle to make a higher grade product and to reduce the danger of fire. A further development came in the nineteenth century with the use of the steam "digester" which was simply a tank used as a pressure cooker in which live steam was injected into the material being rendered. This process is a wet rendering process called "tanking" and was used for both edible and inedible products, although the better grades of edible products were made using the open kettle process. After the material is "tanked", the free fat is run off, the remaining water ("tank water") run into a separate vat, and the solids removed and dried by both pressing and steam-drying in a jacketed vessel. The tank water was either run into a sewer or it was evaporated to make glue or protein concentrate to add to fertilizer. The solids were used to make fertilizer.

Upton Sinclair wrote an expose (1906) on the Chicago meat processing industry which created public outrage. His work helped the passage of the Pure Food and Drug Act of 1907 which paved the way for the creation of the FDA.

The pressure tank made possible the development of the Chicago meat industry in the USA, with its huge concentration in one geographic area, because it allowed the economic disposal of byproducts which would otherwise overwhelm the environment in that area. At first, small companies that sprang up near the packers did the rendering. Later the packers themselves took up the industry once they saw the potential. Gustavus Swift, Nelson Morris, and Lucius Darling were among the early pioneers of the U.S. rendering industry with their personal backing and/or direct participation in the developing rendering industry.

Technological innovations came rapidly as the 20th century advanced. Some of these were in the uses for rendered products and others were in the rendering methods themselves. In the 1920s, a batch dry rendering process was invented, in which the material was cooked in horizontal steam-jacketed cylinders that were similar to the fertilizer dryers of the day. Advantages claimed for the dry process were economy in energy use, a better protein yield, faster processing, and fewer obnoxious odours attending the process. Gradually, over the years, the wet "tanking" process was replaced with the dry process, so that by the end of World War II, most rendering installations used the dry process. In the 1960s, continuous dry processes were introduced, one using a variation of the conventional dry cooker and the other making use of a mincing and evaporation process to dry the material and yield the fat. In the 1980s, high energy costs popularized the various "wet" continuous processes. These processes were more energy efficient and allowed the re-use of process vapours to pre-heat or dry the materials during the process.

After World War II synthetic detergents came on the scene which eventually displaced soaps for both domestic and industrial washing. In the early 1950s over 50% of the inedible fat market disappeared. Diversion in these materials into animal feeds soon replaced the lost soap market and eventually became the single largest use for inedible fats.

The widespread use of "boxed beef" in which the beef was cut up into consumer portions at the packing plant rather than at the retail level in local butcher shops and markets meant that the fat and meat scrap raw materials for renderers stayed at the packing plants and were rendered there by packer renderers, rather than by the "independent" rendering companies.

The rejection of animal fats by diet-conscious consumers led to a surplus of edible fats and their resultant diversion into soapmaking and oleochemicals, displacing inedible fats and contributing to the market volatility of this commodity.