Two excellent references on the topics of edible and inedible meat by-products are Pearson and Dutson (27,28). Although values may vary considerably due to such factors as international trade and changing consumer patterns of preferences, by-products account for about 10% of the value of products from the slaughter of domestic animals (29).

Edible meat by-products that are consumed directly or used in processed products are parts such as tongues, livers, hearts, tails, and brains. Other materials that are classified as by-products are meat trimmings from the carcass, head, neck, and viscera. These materials include cheek meat, weasand meat, giblet meat, head meat, salivary glands, and diaphragm meat. A list of these byproducts, their potential uses and world production figures are given by Goldstrand (29). More recent export values of meat and meat by-products are shown in Table 4.

Mechanically separated meat is a continuously changing edible meat by-product. Engineering developments and regulatory requirements greatly affect the production methods, quality, and utilization of these products. There are no up-to-date comprehensive reviews of these products, because much of the methodology of processing and engineering is proprietary. The USDA FSIS regulates the composition and labeling of meat produced by advanced meat/ bone separation machinery and recovery systems (30). The development of meat/bone separators have advanced such that bones no longer need to be ground or crushed by the separating machine. Rather, the bones emerge from the process in a manner consistent with hand-deboning operations that use knives. The modern systems produce distinct whole pieces of skeletal muscle tissue with a well-defined particulate size consistent with ground meat. There is no powdered bone or bone marrow in the product. Systems for producing these products use compression, heavy-duty sieve cylinders, warming, and centrifugationto separate meat from bone and fat. These materials are widely used in comminuted meat products, with separated beef being used in ground beef patties and mechanically separated poultry being widely used in sausage products. The mechanically separated tissue is usually sold at a lower price than hand-deboned tissue. As it is often finely comminuted, it is especially prone to oxidation and must be kept frozen or refrigerated for a minimum time before being incorporated into processed products.

Edible tallow and lard are still produced in abundance as by-products of the slaughter, fabrication, and retail cutting and processing of cattle and hogs. The 1986 production of these two materials was 2.4 billion pounds in the United States alone (31).

Inedible by-products are produced in abundance by the meat industry. The market forces that cause changes in the demand for inedible by-products are the supply of live-

Table 4. U.S. Export Values for Selected Animal Products for Calendar Year 1997

Product Export values ($ million)

Animal fats 531

Hides and skins 1618

Red meats, fresh, chilled, frozen 4090

Red meats, prepared or preserved 401

Pet foods, dog and cat food 735

Poultry meat 2423

Source: USDA Foreign Agricultural Service Statistics.

stock, feed supplies, substitute products, product safety and health concerns, trade barriers, and politics (32). The raw materials processed into inedible by-products are hides, skins, pelts, hair, feathers, hooves, horns, feet, heads, bones, toenails, blood organs, glands, intestines, and fatty tissues. By recycling these inedible products, not only are very useful materials created for human use and animal feeds, but the material from a meatpacking plant that is classified as waste is greatly reduced. Two major recent developments that affect by-product values were the outbreak of bovine spongiform encephalopathy (BSE) and the growth of the biotechnology industry for synthesizing substitutes for natural gland extracts. The BSE outbreak in the United Kingdom resulted in the prohibition of feeding ruminant meat and bone meal to other ruminants and may eliminate the feeding of much meat and bone meal to meat animals (33).

Pet food literature is limited, and much of the work is proprietary. As shown in Table 4, pet food is a large volume and value export from the United States. According to a 1998 survey by the American Pet Products Association, 59% of U.S. households own a pet and Americans spent more than $21 billion on their pets in 1997 (34). A complete discussion of the use of meat products in pet foods is presented by Corbin (35).

Homemade Pet Food Secrets

Homemade Pet Food Secrets

It is a well known fact that homemade food is always a healthier option for pets when compared to the market packed food. The increasing hazards to the health of the pets have made pet owners stick to containment of commercial pet food. The basic fundamentals of health for human beings are applicable for pets also.

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