Animal fats from rendering

Waste animal fat from rendering can no longer be added in the feed-food chain. These animal fats can now be used in diesel engines to produce green electricity after refining. The fuel for these engines can only contain maximum 2% FFA, a low ash content, and the P-content must be lower than 10 ppm. 

BHA and BHT, which are both fat soluble, are effective ia protecting animal fat from oxidation, and are often added duting the rendering process. Propyl gallate is also effective, but it has limited fat solubiUty, and turns bluish black ia the presence of iron. It is typically used as a synergist ia combination with BHA or BHT. TBHQ is most effective against oxidation ia polyunsaturated vegetable oils (qv), and is often used ia soybean oil (19). 

Approximately 4.1 million MT of inedible animal fats are rendered in the United States annually (Table 1). The major sources, in order of decreasing tonnage, are beef packing, pork packing, spent restaurant fats, and broiler and turkey processing. Only about 5% of the total supply of inedible fat is recovered from dead stock (1). 

Animal fats are rendered tissne fats that can be obtained from a variety of animals. Examples of edible animal fats are butter, lard (pig fat), tallow, ghee, and fish oil. They are obtained from fats in the milk, meat, and under the skin of the animal. Typical fatty acid composition of some animal fats and oils are summarized in Table 5.5. 

Fa.ts nd Oils. Eats and oils from rendering animal and fish offal and vegetable oilseeds provide nutritional by-products used as a source of energy, unsaturated fatty acids, and palatabiHty enhancement. Eats influence the texture in finished pet foods. The use and price of the various melting point fats is deterrnined by the type and appearance of the desired finished food appearance. 

Such feedstocks include non-refined virgin oils, used cooking oils that commonly have an FFA level of >6% and tallow (6%), yellow grease obtained from rendered animal fat (up to 15% in FFAs) and brown grease obtained mainly from traps installed in commercial, municipal or industrial sewage facilities (>15%). The production of... 

Tallow is waxy body fat rendered from animal tissue, usually that of beef or sheep. It is isolated by heating, and allowed to solidify. Tallow has been used in leather preparation, as a lubricant, in food preparation, and in making candles and soap. It is used as food for domestic animals, mostly for poultry. Tallow candles bum quickly and have a low melting point. They were generally less expensive than wax candles, and easier to make. Suet is another name for animal fat, usually applied to that from sheep. 

Rendering. The rendering process is applied on a large scale to the production of animal fats, such as tallow, lard, bone fat, and whale oil. The fatty tissues are chopped into small pieces and are boiled in steam digesters. The fat is gradually liberated from the cells and floats to the surface of the water, where it is collected by skimming. A similar method is used in the extraction of palm oil from fresh palm fruits. 

Lipids are biological materials that are insoluble in water but soluble in nonpolar organic solvents. Here the term will be used interchangeably with acylglycerol, the primary component of animal lipids. These are classihed as either fats or oils. The former are predominantly solid at room temperature (24°C), and the latter are liquid. The depot lipids of animals are generally fats. The major animal fats (also termed meat fats) of contemporary commerce are produced from pigs Sus scrofa), in which case they are termed lard and rendered pork fat, from the fat of cattle Bos taurus) or sheep Ovis aries) and termed tallow, or from poultry (primarily chickens. Callus gallus) and termed poultry fat. Tallow... 

Animal fat, and within this category, poultry fat, which is fat obtained from poultry tissues via commercial rendering or extracting. It consists primarily of acylglycerols and contains no additions of free fatty acids or other materials. The total fatty acid content exceeds 90%, with unsaponfiables and insoluble impurities making up no more than 2.5% and 1%, respectively. The presence of any added antioxidants must be stated. 

The hrst fat and oil products used by humans were probably rendered from wild animal carcasses. Then, as animals were domesticated, their body fat became an important food source and was used for other things such as lubricants, illuminates, and soap. Lard or hog fat became the preferred animal fat for edible purposes, whereas the other animal fats were used for nonedible applications. The more... 

Animal fat (AAFCO number 33.1) is obtained from the tissues of mammals and/or poultry in the commercial processes of rendering or extracting. It consists predominantly of triacylglyerol esters of fatty acids and contains no additions of free fatty acids or other materials obtained from fats. It must contain, and be guaranteed for, not less than 90% total fatty acids, not more than 2.5% unsaponifi-able matter, and not more than 1% insoluble impurities. Maximum free fatty acids and moisture must also be guaranteed. If the product bears a name descriptive of its kind or origin (e.g., beef, pork, or poultry), it must correspond thereto. If an antioxidant is used, the common name or names must be indicated, followed by the words used as a preservative. Includes IFN 4-00-409 (animal poultry fat). 

Fatty animal tissues, free from muscle and bone, usually contain 70-90% fat, the balance being water and connective tissue. Connective tissue is high in protein, hence the dried solids from rendering (tankage, cracklings, stick, etc.), like the solid residue from oilseeds, is marketed as a protein concentrate for animal feeds. 

Norris described modifications of continuous wet rendering operations in the previous edition of this book (43). He described several methods, current at that time, that involved disintegration to separate fat from animal tissue, followed by centrifuging to remove sludge from the liquid phase, followed by clarification of the finished fat (44-47). He also described a different operation that involved hammer milling bony material in a stream of cold water from which the fat was subsequently recovered (48, 49). 

The low temperature in solvent extraction of oilseeds should produce a better oil than oil from the high-temperamre environment of screw-pressing. Solvent, however, extracts some nontriglycerides that are not pressed out by screw-pressing, so screw-press oil is generally of better quality than solvent-extracted oil. Although some animal fats are solvent extracted, most renderers full-press in screw-presses. Solvent extraction of oilseeds, on the other hand, is widely practiced. The section below is based primarily on research conducted with oilseeds. Some of it, however, would also apply to extraction of animal fats. 

Rendering is a global industry with markets throughout the world. Table 1 outlines the global import and export of meat meal by continent for the period 1992-2002. The data is taken from the FAO database and is only available through 2002 (2). As the United States dominates the North and Central American region, U.S. data has been shown separately from the rest of North and Central America. Table 2 shows similar data for rendered animal fats over the same period of time (2). 

Animal Fat is obtained from the tissues of mammals or poultry in the commercial processes of rendering or extraction. It consists predominantly of glycerol esters of fatty acids and contains no additions of free fatty acids or other materials obtained from fats. It must contain, and be guaranteed for, not less than 90% total fatty acids, not more than 2.5% unsaponifiable matter, and not more than 1% insoluble impurities. 

Grease is animal fat with a titer below 40°C. Choice white grease is derived primarily from the rendering of pork offal whereas yellow grease is derived from restaurant grease (4). 

The major use of rendered fats is in the production of tallow soaps and in the area of fat hydrolysis, sphtting triglycerides into fatty acids, and byproduct glycerine. As the soap-making industry grew and became more refined, the quality standards and specifications for animal fat became more precise to meet the soap industry s need. The specihcations and terminology, from the soap industry, form the basis for the quality standards and characteristics used today. 

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