UTILIZATION OF SLAUGHTER HOUSE BY-PRODUCTS FOR SUSTAINABLE MEAT INDUSTRY
Dr.S.Prabhakar, Livestock Food processing Expert, Chennai
Meat sector in India plays an important role in providing livelihood to rural people in the country. Animal slaughtering not only provides meat but also valuable by-products to the mankind. By slaughtering and processing of meat animal, only one third is meat while the rest comprise of by-products and waste, which need to be adequately processed and utilized. Traditional markets for edible meat by-products have gradually been disappearing because of concerns about health and economic returns. In response to these problems, meat processors have directed marketing and research efforts toward inedible applications. Efficient utilization of by-products has direct impact on the economy and environmental pollution of the country, the former being an asset and the latter is a responsibility. The yield of animal by-products ranges between 50-60% of the live weight. According to various statistics 107 million livestock and more than 650 million poultry birds were slaughtered annually in India leading to production of 6.3 million tonnes meat. It leaves huge loads of by-products. The load is further increased by dead and fallen animals. The value of unprocessed by-products from buffalo and sheep in India was reported to be quite high. If these by-products are processed then the returns will be almost equal to the value of the meat derived from an animal. Therefore, the potential and scope of by-product utilization is really great which will result in industrial development, employment generation, environmental management and better returns to the farmers. Non-utilization of animal by-products in a proper way may create major aesthetic and catastrophic health problems. Value addition of animal by-products has two benefits. Firstly, the meat industry gets additional revenue by processing them to industrial, household, and cosmetic products; livestock feed additives; pet foods; pharmaceutical and medical supplies etc that otherwise would have been unrealized. Secondly, the costs of disposing of these secondary items are avoided. Utilization of these byproducts as fertilizer contributes a lot in organic farming and could reduce our dependence on synthetic fertilizers. Animal byproducts and wastes are a good source of renewable energy as well its production is economically feasible.
Meat is defined as the flesh of animals used as food . Meat products are defined as those in which fresh meat has been modified by any of several processing methods, including curing, comminution, dehydration, fermentation, or cooking . A by-product is defined as a secondary product obtained during the manufacture of a principal commodity
Nutritive value of meat by-products—————
Edible meat by-products contain many essential nutrients. Some are used as medicines because they contain special nutrients such as amino acids, hormones, minerals, vitamins and fatty acids. Not only blood, but several other meat by-products, have a higher level of moisture than meat. Some examples are lung, kidney, brains, spleen, and tripe. Some organ meat, including liver and kidney, contains a higher level of carbohydrate than other meat materials.
Pork tail has the highest fat content and the lowest moisture content of all meat by-products. The liver, tail, ears and feet of cattle have a protein level which is close to that of lean meat tissue, but a large amount of collagen is found in the ears and feet (Unsal and Aktas 2003). The lowest protein level is found in the brain, chitterlings and fatty tissue. The United States Dept. of Agriculture (2001) requires that mechanically deboned beef and pork contain at least 14% protein and a maximum of 30% fat. The amino acid composition of meat by-products is different from that of lean tissue, because of the large amount of connective tissue. As a result, by-products such as ears, feet, lungs, stomach and tripe contain a larger amount of proline, hydroxyproline and glycine, and a lower level of tryptophan and tyrosine. The vitamin content of organ meats is usually higher than that of lean meat issue. Kidney and liver contain the largest amount of riboflavin (1.697–3.630 mg/100 g), and have 5–10 times more than lean meat. Liver is the best source of niacin, vitamin B12, B6, folacin, ascorbic acid and vitamin A. Kidney is also a good source of vitamin B6, B12, and folacin. A 100 g serving of liver from pork or beef contributes 450%–1,100% of the RDA of vitamin A, 65% of the RDA of vitamin B6, 3,700% of the RDA of vitamin B12 and 37% of the RDA of ascorbic acid. Lamb kidneys,pork, liver, lungs, and spleen are an excellent source of iron, as well as vitamins. The copper content is highest in the livers of beef, lamb and veal. They contribute 90–350% of the RDA of copper (2 mg/day). Livers also contain the highest amount of manganese (0.128–0.344 mg/100 g). However, the highest level of phosphorus (393–558 mg/100 g) and potassium (360–433 mg/100 g) in meat by-products is found in the thymus and sweetbreads (Devatkal et al. 2004b). With the exception of brain, kidney, lungs, spleen and ears, most other by-products contain sodium at or below the levels found in lean tissue. Mechanically deboned meat has the highest calcium content (315–485 mg/100 g).
Many organ meats contain more polyunsaturated fatty acids than lean tissue. Brain, chitterlings, heart, kidney, liver and lungs have the lowest level of monounsaturated fatty acids and the highest level of polyunsaturated fatty acids. (Liu 2002). There is three to five times more cholesterol (260–410 mg/100 g) in organ meats than in lean meat, and large quantities of phospholipids. Brain has the highest level of cholesterol (1,352–2,195 mg/100 g) and also has the highest amount of phospholipids compared to other meat by-products. For this reason, the United States Department of Health recommends that limited amounts of these by-products be eaten, because of health concerns. The high cholesterol content of many other organ meats, and the possible accumulation of pesticides, drug residues and toxic heavy metals, is another reason for limited consumption.
Utilization of blood-——–
Animal blood has a high level of protein and heme iron, and is an important edible by-product (Wan et al. 2002). In Europe, animal blood has long been used to make blood sausages, blood pudding, biscuits and bread. In Asia, it is used in blood curd, blood cake and blood pudding (Ghost 2001). It is also used for non-food items such as fertilizer, feedstuffs and binders. According to the Meat Inspection Act of the United States, blood is approved for food use when it has been removed by bleeding an animal that has been inspected and passed for use in meat food products.
Blood is usually sterile in a healthy animal. It has high protein content (17.0), with a reasonably good balance of amino acids. Blood is a significant part of the animal’s body mass (2.4–8.0% of the animal’s live weight). The average percentage of blood that can be recovered from pigs, cattle and lambs are 3.0–4.0, 3.0–4.0 and 3.5–4.0%, respectively. However, the use of blood in meat processing may mean that the final product is dark in color, and not very palatable. Plasma is the portion of blood that is of greatest interest, because of its functional properties and lack of color.
Use of blood plasma in food-———–
Blood is used in food as an emulsifier, a stabilizer, a clarifier, a color additive, and as a nutritional component (Silva and Silvestre 2003). Most blood is used in livestock feed in the form of blood meal. It is used as a protein supplement, a milk substitute, a lysine supplement or a vitamin stabilizer, and is an excellent source of most of the trace minerals. Blood plasma has ability to form a gel, because it contains 60.0% albumin (Silva and Silvestre 2003). Plasma is the best water and fat binder of the blood fraction. Plasma gels appear very similar to cooked egg whites. Plasma forms a gel at a protein concentration of 4.0–5.0%. The strength of the gel increases with increasing concentration. Cooked ham to which were added 1.5 and 3.0% frozen blood plasma, and hot dogs with 2.7% added plasma, were more satisfactory in color than those without it (Autio et al. 1985).
Blood plasma also has an excellent foaming capacity (Del et al. 2008), and can be used to replace egg whites in the baking industry (Ghost 2001). The application of transglutaminase (TGase) from animal blood and organs or microbes to meat products has received a great deal of research. Blood factor XIII is a transglutaminase that occurs as an enzymogen in plasma, placenta and platelets. Transglutaminase was first extracted from bovine blood in 1983, in order to improve the binding ability of fresh meat products at chilling temperature. It showed how myosin was cross-linked by TGase. An important property of the TGase reaction was documented when cross-linking between myosin and proteins (soy, casein and gluten), all commonly used in meat processing Moreover, the restructured meat products can be processed without heating, and their salt and phosphate content reduced, by the addition of TGase from animal blood.
Medicinal and pharmaceutical uses of blood——–
Blood can be separated into several fractions that have therapeutic properties. Liquid plasma is the largest fraction (63.0%). It consists of albumin (3.5%), globulin and fibrinogen (4.0%). In the laboratory, many blood products are used as a nutrient for tissue culture media, as a necessary ingredient in blood agar, and as peptones for microbial use (Kurbanoglu and Kurbanoglu 2004). Glycerophosphates, albumins, globulins, sphingomyelins, and catalase are also used for biological assay. Many blood components such as fibrinogen, fibrinolysin, serotonin, kalikreninsa, immunoglobulins and plasminogen are isolated for chemical or medical uses (Young and Lawrie 2007). Purified bovine albumin is used to help replenish blood or fluid loss in animals. It is used in testing for the Rh factor in human beings, and as a stabilizer for vaccines. It is also used in antibiotic sensitivity tests.
Utilization of hides and skins————–
Animal hides have been used for shelters, clothing and as containers by human beings since prehistoric times. The hides represent a remarkable portion of the weight of the live animal, from 4% to as much as 11% (e.g. cattle: 5.1–8.5%, average: 7.0%; sheep: 11.0–11.7%; swine: 3.0–8.0%). Hides and skins are generally one of the most valuable by-products from animals. Examples of finished products from the hides of cattle and pigs, and from sheep pelts, are leather shoes and bags, rawhide, athletic equipment, reformed sausage casing and cosmetic products, sausage skins, edible gelatine and glue (Benjakul et al. 2009).
Stacking of hides and skins———-
After the hide is removed from the animal, it should be cured quickly to avoid decomposition by bacteria and enzymes. There are four basic treatments. One is air-drying, the second is curing with salt, and the third and fourth are curing by mixer and raceway respectively. Salt curing is often used for the raw hides. The quality of cured hides and skins is usually based on their moisture and salt content. The moisture level of hides should be in the range 40–48%, if they are to remain in good condition during storage or shipping.
Gelatin from hides and skins———–
Gelatin is produced by the controlled hydrolysis of a water-insoluble collagen derived from protein. It is made from fresh raw materials (hides or bone) that are in an edible condition. Both hides and bones contain large quantities of collagen. The processing of gelatin from hide consists of three major steps. The first step is the elimination of non-collagenous material from the raw material. This is followed by controlled hydrolysis of collagen to gelatin. The final step is recovery and drying of the final product.
Uses of gelatin in the food and pharmaceutical industries————-
Gelatin extracted from animal skins and hides can be used for food (Choa et al. 2005). The raw material can also be rendered into lard. In the United States, Latin America, Europe and some Asian countries, pork skin is immersed, boiled, dried and then fried to make a snack food (pork rinds) and in U.K they are called “pork scratching”. Collagen from hides and skins also has a role as an emulsifier in meat products because it can bind large quantities of fat. This makes it a useful additive or filler for meat products. Collagen can also be extracted from cattle hides to make the collagen sausage used in the meat industry.
Gelatin is added to a wide range of foods, as well as forming a major ingredient in jellies and aspic (Jamilah and Harvinder 2002). Its main use is the production of jellied desserts, because of its “melt in the mouth” properties, but is also added to a range of meat products, in particular to meat pies. Gelatin is also widely used as a stabilizer for ice cream and other frozen desserts. High-bloom gelatin is added as a protective colloid to ice cream, yoghurt and cream pies. The gelatin is thought to inhibit the formation of ice crystals and the recrystallization of lactose during storage.
Approximately 6.5% of the total production of gelatin is used in the pharmaceutical industry (Hidaka and Liu 2003). Most of it is used to make the outer covering of capsules. Gelatin can also be used as a binding and compounding agent in the manufacture of medicated tablets and pastilles. It is used as an important ingredient in protective ointment, such as zinc gelatin for the treatment of ulcerated varicose veins. Gelatin can be made into a sterile sponge by whipping it into foam, treating it with formaldehyde and drying it.(Estaca et al. 2009). Such sponges are used in surgery, and also to implant a drug or antibiotic directly into a specific area. Because gelatin is a protein, it is used as a plasma expander for blood in cases of very severe shock and injury. Gelatin is an excellent emulsifier and stabilizing agent for many emulsions and foams. It is used in cosmetic products, and in printing for silk screen printing, photogravure printing etc. (Arvanitoyannis 2002).
Collagen casing products were developed in Germany in the 1920s, but only gained popularity in the United States in the 1960s. The processing does not convert the collagen into a soluble product, as in the case of gelatin. Instead, it results in a product which retains a relatively high degree of the native collagen fiber, and is strong enough to be used as a casing for sausages and other products. The extracted collagen is mixed with water and converted into a dough, which is extruded by either a wet or a dry process. The tube of extruded collagen is then passed through a concentrated salt solution and a chamber of ammonia to precipitate the collagen. The swollen gel contracts to produce a film of reasonable strength. It can be improved by the addition of glycerin, to make it more flexible. The tube is then dried to 10.0–15.0% water content.
Medicinal and pharmaceutical uses of hides and skins————
A product made from extracted collagen can stimulate blood clotting during surgery. Pork skin is similar to human skin, and can be converted into a dressing for burns or skin-ulcers. Pork skin used as a dressing needs to be cut into strips or into a patch, shaved of hair, split to a thickness of 0.2–0.5 mm, cleansed, sanitized and packaged. It can be used for skin grafting. When used for skin grafting, it is removed from the carcass within 24 h of the death of the pig.
Utilization of bone————
Eleven percent of pork carcasses, 15% of beef carcasses and 16% of lamb carcasses are bone. These values are higher if they include the meat clinging to the bone. The marrow inside some of the bones can also be used as food. The marrow may be 4.0–6.0% of the carcass weight (West and Shaw 1975). For centuries, bones have been used to make soup and gelatine. In recent years, the meat industry has been trying to get more meat from bones, and new techniques have been used for this purpose. The beef, pork or lamb produced by mechanical deboning produces tissue that is called “mechanically separated”, “mechanically deboned” or “mechanically removed”. Such meat is now approved for use in meat products (mixed or used alone) in many countries (Field 1981). In 1978, mechanically separated red meat was approved for use as red meat in the United States.
Normally, if a high percentage of mechanically separated red meat is incorporated into products, the flavor and quality are reduced. The color becomes darker, and the meat is softer with higher water content. For this reason, the level of mechanically separated meat is usually limited. It should be noted that mechanically recovered meat has a bad consumer perception in some countries connected with health concerns with Bovine Spongiform Encephalopathy (BSE) contamination (Arvanitoyannis and Ladas 2008). A level of 5.0–20.0% in hamburger and ground beef, and 10.0–40.0% in sausages, has been suggested by the meat industry.
Many countries already have regulations covering products which contain mechanically separated red meat. In the United States, mechanically separated meat cannot be used for hamburgers, baby food, ground beef or meat pies. A level of 20% is the maximum in sausage emulsion. In Denmark, if mechanically separated red meat is used at levels of more than 2% it has to be declared on the label. In Australia, if mechanically deboned beef or mutton is present in exported products, the quantity must be shown on the label, plus the maximum level of calcium, the moisture content and the minimum protein level.
Meat and bone meal (MBM) was widely recommended and used in animal nutrition as a protein source in place of proteinaceous feeds because of its content of available essential amino acids, minerals and vitamin B12. MBM and related rendered protein commodities have potential for use in applications other than animal feed, including use as a fuel or a phosphorus fertilizer
Utilization of glands and organs————-
Glands and organs as food
Animal organs and glands offer a wide variety of flavors and textures, and often have a high nutritional value. They are highly prized as food in many parts of the world, particularly Southeast Asia. Those used as human foods include the brain, heart, kidneys, liver, lungs and spleen. They also include the tongue, the bovine pancreas and udder, the stomach and uterus of pigs, the rumen, reticulum, omasum and absomasum of sheep and cattle, and the testes and thymus of sheep and pigs .
The brain, nervous system and spinal cord are usually prepared direct for the table rather than processed for industrial use. They are blanched to firm the tissue before cooking, because of the soft texture. The membranes are peeled from the brain before cooking. Heart meat is generally regarded as relatively touch, reflecting the nature of the cardiac muscle. Heart is used as a table meat. Whole hearts can be roasted or braised. Sliced heart meat is grilled or braised. Heart meat is often also used as an ingredient in processed meats. Kidneys are generally removed from the fatty capsule which holds the kidney in place. The ureter and blood vessels need to be trimmed before the kidneys are prepared for cooking. Kidneys may be cooked whole or in slices, and are generally broiled, grilled, or braised. Liver is the most widely used edible organ. It is used in many processed meats, such as liver sausage and liver paste (Devatkal et al. 2004a). Livers from lambs, veal calves and young cattle are preferred for the table in the United States and Europe, because they have a lighter flavor and texture. Consumers in Southeast Asia, However, generally prefer livers from pigs. Livers are braised or broiled. Pig, calf and lamb lungs are mainly used to make stuffing and some types of sausages and processed meats (Darine et al. 2010).
Animal intestines are used as food after being boiled in some countries. Animal intestines are also used in pet food or for meat meal, tallow or fertilizer. However, the most important use of the intestines is as sausage casings (Bhaskar et al. 2007). Animal intestines, when removed from the carcass, are highly contaminated with microbes and very fragile. They must be cleaned immediately after the slaughter of the animal. To make them into sausage casing, they are removed from the abdomen. The ruffle fat is separated from the intestines, and the faeces stripped out. Sometimes they are fermented, though this is not often done today. The inner mucosa membrane is separated from the casing, all strings and blood are removed, and the intestines are finally soaked salted and packaged.
Medicinal and pharmaceutical uses of glands and organs——————–
Animal glands and organs are traditionally used as medicine in many countries, including China, India and Japan. The endocrine glands secrete hormones (i.e. enzymes that regulate the body’s metabolism). These include the liver, lungs, pituitary, thyroid, pancreas, stomach, parathyroid, adrenal, kidney, corpus luteum, ovary and follicle. The glands are collected only from healthy animals. Locating the glands needs some experience. They are often small and encased in other tissue.
Different animals have different glands that are important. The function of glands also depends on the species, sex and age of the animal. The best method of preserving most glands to stop tissue breakdown from bacterial growth is by rapid freezing. Before freezing, the glands need be cleaned, and the surrounding fat and connective tissue trimmed off. The glands are then placed onto waxed paper and kept at −18 °C or less. When the glands arrive at the pharmaceutical plant they are inspected, then chopped and mixed with different solutions for extraction, or placed in a vacuum drier. If the dried gland contains too much fat, solutions such as gasoline, light petroleum, ethylene or acetone are used to remove the fat. After drying and defatting, the glands or extracts are milled into a powder and made into capsules, or used in a liquid form. They are tested for safety and potency before they are sold.
Brains, nervous systems and spinal cords are a source of cholesterol which is the raw material for the synthesis of vitamin D3. Cholesterol is also used as an emulsifier in cosmetics (Ejike and Emmanuel 2009). Other materials can be isolated from the hypothalamus of the brain for the same purpose. The hormone melatonin, extracted from the pineal gland, is being evaluated for the treatment of schizophrenia, insomnia and other problems, including mental retardation.
Bile consists of acids, pigments, proteins, cholesterol etc., and can be obtained from the gall bladder. It is used for the treatment of indigestion, constipation and bile tract disorders. It is also used to increase the secretory activity of the liver. Bile from cattle or pigs can be purchased as a dry extract or in liquid form. Some ingredients of bile, such as prednisone and cortisone, can be extracted separately, and used as medicines. Gallstones are reported to have aphrodisiac properties, and can be sold at a high price. They are usually used as ornaments to make necklaces and pendants.
The liver is the largest gland in animals. The liver of mature cattle usually weighs about 5 kg, while that of a pig weighs approximately 1.4 kg. Liver extract is produced by mixing raw ground liver with slightly acidified hot water. The stock is concentrated into a paste in a vacuum at a low temperature, and is used as a raw material by the pharmaceutical industry. Liver extract can be obtained from pigs and cattle, and has been used for a long time as a source of vitamin B12, and as a nutritional supplement used to treat various types of anaemia. (Colmenero and Cassens 1987; Devatkal et al. 2004a, b). Heparin can be extracted from the liver, as well as the lungs and the lining of the small intestines. It is used as an anticoagulant to prolong the clotting time of blood. It is also used to thin the blood, to prevent blood clotting during surgery and in organ transplants.
Progesterone and oestrogen can be extracted from pig ovaries. It may be used to treat reproductive problems in women. Relaxin is a hormone taken from the ovaries of pregnant sows, and is often used during childbirth.
The pancreas provides insulin, which regulates sugar metabolism and is used in the treatment of diabetes. Glucagon extracted from the cells of the pancreas is used to increase blood sugar, and to treat insulin overdoses or low blood sugar caused by alcoholism. Chymotrypsin and trypsin are used to improve healing after surgery or injury.
The intestines of sheep and calves are used for the manufacture of catgut, to make internal surgical sutures. The lining of the small intestines of pigs and cattle can be collected while the intestines are being processed into casings. It is either preserved in a raw state, or processed into a dry powder for shipment to heparin manufacturers.
Utilization of edible tallow and lard————–
Animal fats are an important by-product of the meat packing industry. The major edible animal fats are lard and tallow. Lard is the fat rendered from the clean tissues of healthy pigs. Tallow is hard fat rendered from the fatty tissues of cattle or sheep. Lard and edible tallow are obtained by dry or wet rendering. In the wet rendering process, the fatty tissues are heated in the presence of water, generally at a low temperature. The quality of the lard or tallow from this process is better than that of products from dry rendering. Low-quality lard, and almost all of the inedible tallow and greases, are produced by dry rendering. Rendered lard can be used as an edible fat without any further processing. However, because of consumer demand, lard and tallow are now often bleached and given a deodorizing treatment before being used in food.
Traditionally, tallow and lard were used for deep frying (Weiss 1983). However, this use is declining in the fast-food industry, due to consumer health concerns. An alternative liquid tallow product has been developed for the preparation of French fries and other fast foods, since less fat is absorbed. Tallow and lard are also used for margarine and shortening (Ghotra et al. 2002). Some edible lards are used in sausages or emulsified products (Chrysam 1985).
Utilisation of Slaughter House Waste Material for the Preparation of Animal Feed———
India ranks topmost in the world in livestock holding and has the potential to utilize slaughterhouse by products to partly meet the growing requirement of animal feeds. The total availability of offal/bones in the country generated from large slaughterhouses is estimated to be more than 21-lakh tonnes/annum. Besides other uses, it can also be used for the preparation of animal feeds. The total requirement of animal feed has been estimated at 37 million tonnes. This includes 24 million tonnes of cattle feed (which as per the directive of the Department of Animal Husbandry, Govt. of India cannot have slaughter house waste material). Slaughterhouse waste material has the potential to partly replace 13 million tonnes of animal feed material. Slaughterhouse wastes can be used as inputs to feeds for the poultry, fi8sh and pets like dogs and cats. Presently in India, live stock feed production is more of cereal based and less of animal by-product based. This results in livestock, especially poultry, pig and fish competing with humans for grains and cereals which can easily be replaced with slaughterhouse waste. Slaughterhouse waste is first converted into intermediate products like Meat Bone Meal (MBM), Di0calciumphosphate (DCP) & bicalphos (BCP) which are essentially feed supplements. They are then mixed with various crop ingredients to make a complete feed for animals. Meat Bone Meal is a protein is a protein and phosphorous supplements for animal feed manufacturers. It is used upto 5% of total feed. DCP and BCP are essentially phosphorous supplements for animal feed manufacturers and are used to the extent of 1% of total feed. Currently total production of MBM in India is around 55200 tonnes/annum and total estimated demand is 77500 tonnes/annum. So the gap between production and supply of MBM is around 22300 tonnes/annum. Leading manufacturers of MBM in India are Standard Agro Vet (P) Ltd., Allanasons Ltd., Hind Agro Ltd., Al Kabeer, Hyderabad.
Animal by-products and fats are excellent feed ingredients for poultry. As with any ingredient, quality control standards must be established and professional relationships maintained with suppliers. When high quality materials are available, there is almost no limit to how they can be successfully employed in poultry feeds. At the present time, in many countries the major impediment to such incorporation does not involve the quality of animal by-products, but public misconceptions regarding the wholesomeness of these materials.
There are many applications of meat by-products like feed ingredients for livestock, poultry and aquaculture as well as for pet foods, energy valorisation through biodiesel production, new substances as alternative to plastics and protein hydrolysates to be used for technological purposes or as a source of bioactive peptides with relevant physiological effects. Research efforts are going ahead to produce new substances with new applications or improving those existing processes. So, the innovation is continuously addressed towards adding value and finding new applications to meat by products.
Reference-On request.
