Animal fats rendering processes

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). 

Along with the reduced consunq>tion of meat products, the production of rendered animal fats has also declined. Beef tallow consumption has increased greatly since 1950 due to its distinctive flavor and stability as a frying medium. In 1985, 460,000 metric tons of beef tallow were used in the U.S. for baking and frying, but this figure was reduced to 289,000 metric tons in 1990 and is probably less this year. The decreased production of beef tallow has made it unprofitable for renderers to continue Ae processing procedures required to produce edible tallow (i). 

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. 

As animal fats are a potential feedstock for biodiesel production, Cummins et al. (142) assessed the danger of a human contracting CJD as a result of the use of tallow as a fuel in diesel engines. They concluded that the risk was several orders of magnitude less than the rate of spontaneous appearance of CJD. Thus, scientific analysis indicates that processed (i.e., rendered) animal fat is not an agent of transmission of BSE. Nonetheless, especially in the United Kingdom, the public remains skeptical. This has in some cases led to less use of animal fats in feed applications. Especially in the United Kingdom, the BSE epidemic has reduced the amount of domestically available tallow (because of condemnation) and increased the use of other lipids in place of animal fats. 

Edible animal fat in the United States can be rendered only in food grade plants under inspection of the U.S. Department of Agriculture (USDA) (1). The majority of tallows and greases used domestically in animal feeds and pet foods are feed grade. The National Renderer s Association (NRA) describes rendering as a process that... 

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 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). 

The rendering industry processes or recycles animal and poultry byproducts such as animal fat, bone, hide, offal, feathers, hoofs, horns, hair, and blood. For example. 

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. 

The fats and oils produced from the rendering process provide a concentrated source of energy for use in animal feeds. Addition of fat in feeds also reduces dustiness of the feed and makes it more palatable. Fats and oils also provide important... 

Rendering is accomplished via a variety of equipment and processes. It is a process of both physical and chemical transformation, using trimmings from the production and processing of food animals for meat. AU of the rendering processes involve the application of heat, the extraction of moisture, and the separation of fat when it is part of the raw material. 

At this point, the raw material goes into either a batch or continuous cooking system. Within the cooking system, the heating and grinding action breaks down the fat cells in the animal tissue to release the fat. The rendering process consists essentially of two steps. First, the raw material is heated or cooked to evaporate the moisture. The second step is the removal of fat. 

The rendering process converts raw animal or fish tissue into various protein, fat, and mineral products, all of which are transformed into rich granular-type powders and fats with specific nutritional and chemical components. The animal byproduct raw material has approximately 60%-f of water and yields about 20% protein and 20% fat. These protein, fat, and mineral fractions are then available for a variety of uses. The annual volume in the United States approximates 4.2 million metric tons of animal protein and 4.2 million tons of rendered fat. 

The animal feed industry is a major user of rendered animal fats, recycled restaurant grease, and cooking oils. Fats are the highest caloric dense feedstuff and foodstuff. In addition, fats and certain of their component fatty acids are essential and indispensable for body functions in addition to their caloric function. The U.S. rendering industry processes about 5.3 million metric tons (MMT) of the following fats on an annual basis ... 

In general, crude fish oils and animal fats cannot be used directly to produce oleo-chemical compounds they must first be refined or further processed. Free fatty acids are usually thought of as impurities in commercially available rendered fats. Consequently, manufacturers of purer grades of tallow will refine tallow and other fats by adding a caustic material compound such as sodium hydroxide to form soaps of fatty acids, which are washed out with water. 

Animal fats are produced batch-wise with the use of manual techniques or at industrial scale using batch, semi-continuous or continuous processes called rendering. Rendering involves the splitting of the fat bearing raw material into... 

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