Rendering (industrial)
Encyclopedia
Rendering is a process that converts waste animal tissue
into stable, value-added materials. Rendering can refer to any processing of animal byproducts into more useful materials, or more narrowly to the rendering of whole animal fatty tissue into purified fats like lard
or tallow
. Rendering can be carried out on an industrial, farm, or kitchen scale
.
The majority of tissue processed comes from slaughterhouse
s, but also includes restaurant grease and butcher shop trimmings, expired meat from grocery stores, the carcasses of euthanized and dead animals from animal shelters, zoos and veterinarians. This material can include the fat
ty tissue, bones, and offal
, as well as entire carcasses of animals condemned at slaughterhouses, and those that have died on farms, in transit, etc. The most common animal sources are beef
, pork
, sheep, and poultry
.
The rendering process simultaneously dries the material and separates the fat from the bone
and protein
. A rendering process yields a fat commodity
(yellow grease
, choice white grease, bleachable fancy tallow
, etc.) and a protein meal (meat & bone meal, poultry byproduct meal, etc.).
Rendering plants often also handle other materials, such as slaughterhouse blood
, feather
s and hair
, but do so using processes distinct from true rendering.
or edible tallow for use in food products. Edible rendering is generally carried out in a continuous process at low temperature (less than the boiling point of water). The process usually consists of finely chopping the edible fat materials (generally fat trimmings from meat cuts), heating them with or without added steam, and then carrying out two or more stages of centrifugal separation
. The first stage separates the liquid water and fat mixture from the solids. The second stage further separates the fat from the water. The solids may be used in food products, pet foods, etc., depending on the original materials. The separated fat may be used in food products, or if in surplus, it may be diverted to soap making operations. Most edible rendering is done by meat packing or processing companies.
One edible product is greaves, which is the unmeltable residue left after animal fat has been rendered.
An alternative process cooks slaughterhouse offal to produce a thick lumpy stew which is then sold to the pet food industry to be used principally as tinned cat
and dog
foods. Such plants are notable for the offensive odour that they can produce and are often located well away from human habitation.
" or "dry-rendered tankage". The cracklings are further ground to make meat and bone meal
.
A variation on a dry process involves finely chopping the material, fluidizing it with hot fat, and then evaporating the mixture in one or more evaporator stages. Some inedible rendering is done using a wet process, which is generally a continuous process similar in some ways to that used for edible materials. The material is heated with added steam and then pressed to remove a water-fat mixture which is then separated into fat, water and fine solids by stages of centrifuging and/or evaporation. The solids from the press are dried and then ground into meat and bone meal. Most independent renderers process only inedible material.
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.
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.
industry to eliminate some difficulties as to the efficient use of the excessive slaughterhouse and restaurant waste, but it also poses some problems in the light of economy and health.
Usually, materials used as raw materials in the rendering process are susceptible to spoilage. However, after rendering, the materials are much more resistant to spoiling. This is due to the application of heat either through cooking in the wet rendering process or the extraction of fluid in the dry rendering process. The fat obtained can be used as low-cost raw material in making grease, animal feed, soap, candles, biodiesel
, and as a feed-stock for the chemical industry. Tallow
, derived from beef waste, is an important raw material in the steel
rolling industry providing the required lubrication when compressing steel sheets. The meat and the bones (which are in a dry, ground state) are converted to what is known as meat and bone meal
. For many years meat and bone meal were fed to cattle. This practice is now prohibited in developed countries because it is believed to be the main route for the spread of bovine spongiform encephalopathy
(mad-cow disease, BSE), which is also fatal to human beings. Meat and bone meal from cattle is, however, fed to non-ruminant
animals and meat and bone meal from non-ruminant animals is fed to cattle in the United States. This may not prove to be a solution to the problem due to the resistant nature of the infectious agent of BSE, a misfolded protein (prion
). Therefore, even if cattle is fed to non-ruminant animals and vice-versa, it will not prevent BSE from occurring. The underlying cause is that the prion survives within the system of the animal that has been fed with meat and bone meal from different animals including cattle. These animals are then eventually rendered and fed to cattle, which also results in the development of the disease.
In the absence of the rendering industry, the cost of waste disposal of waste animal material would be very high and would place a significant economic and environmental burden on areas involved in industrial scale slaughtering. This cost may manifest itself through the expensive use of sanitary landfills, incinerators and other similar waste disposal techniques without yielding profit directly out of it leading to the incurrence of opportunity costs. Using substitute products to rendering products may not necessarily prove to be lesser in cost. In spite of the advantages of the rendering process mentioned in this paragraph, it also poses certain economic disadvantages. One is when BSE and its cause has been discovered in the late 20th century. In effect, people were scared off and refrained from eating beef and other kinds of meat. Meat processors, especially beef processors, suffered losses due to a decrease in meat sales and the increase in difficulty in marketing their products, in effect, also causing losses to livestock growers through a decrease in sales. Another is that regular meat inspections discover infected products and animals, which have to be destroyed immediately to prevent further spreading of the disease. The epidemic also affected renderers, as lesser meat processors avail of their services making it difficult for them to allocate their raw materials and that they cannot avail of infected animals and products.
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 oleochemical
s, displacing inedible fats and contributing to the market volatility of this commodity.
The rendering industry is one of the oldest recycling industries, and made possible the development of a large food industry. The industry takes what would otherwise be waste materials and makes useful products such as fuels, soaps, rubber, plastics, etc. At the same time, rendering solves what would otherwise be a major disposal problem. As an example, the USA recycles more than 21 million metric tons annually of highly perishable and noxious organic matter. In 2004, the U.S. industry produced over 8 million metric tons of products, of which 1.6 million metric tons were exported.
into clarified butter
, suet
into tallow
, pork
fat into lard
, and chicken fat into schmaltz
.
Biological tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
into stable, value-added materials. Rendering can refer to any processing of animal byproducts into more useful materials, or more narrowly to the rendering of whole animal fatty tissue into purified fats like lard
Lard
Lard is pig fat in both its rendered and unrendered forms. Lard was commonly used in many cuisines as a cooking fat or shortening, or as a spread similar to butter. Its use in contemporary cuisine has diminished because of health concerns posed by its saturated-fat content and its often negative...
or tallow
Tallow
Tallow is a rendered form of beef or mutton fat, processed from suet. It is solid at room temperature. Unlike suet, tallow can be stored for extended periods without the need for refrigeration to prevent decomposition, provided it is kept in an airtight container to prevent oxidation.In industry,...
. Rendering can be carried out on an industrial, farm, or kitchen scale
Scalability
In electronics scalability is the ability of a system, network, or process, to handle growing amount of work in a graceful manner or its ability to be enlarged to accommodate that growth...
.
The majority of tissue processed comes from slaughterhouse
Slaughterhouse
A slaughterhouse or abattoir is a facility where animals are killed for consumption as food products.Approximately 45-50% of the animal can be turned into edible products...
s, but also includes restaurant grease and butcher shop trimmings, expired meat from grocery stores, the carcasses of euthanized and dead animals from animal shelters, zoos and veterinarians. This material can include the fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
ty tissue, bones, and offal
Offal
Offal , also called, especially in the United States, variety meats or organ meats, refers to the internal organs and entrails of a butchered animal. The word does not refer to a particular list of edible organs, which varies by culture and region, but includes most internal organs other than...
, as well as entire carcasses of animals condemned at slaughterhouses, and those that have died on farms, in transit, etc. The most common animal sources are beef
Beef
Beef is the culinary name for meat from bovines, especially domestic cattle. Beef can be harvested from cows, bulls, heifers or steers. It is one of the principal meats used in the cuisine of the Middle East , Australia, Argentina, Brazil, Europe and the United States, and is also important in...
, pork
Pork
Pork is the culinary name for meat from the domestic pig , which is eaten in many countries. It is one of the most commonly consumed meats worldwide, with evidence of pig husbandry dating back to 5000 BC....
, sheep, and poultry
Poultry
Poultry are domesticated birds kept by humans for the purpose of producing eggs, meat, and/or feathers. These most typically are members of the superorder Galloanserae , especially the order Galliformes and the family Anatidae , commonly known as "waterfowl"...
.
The rendering process simultaneously dries the material and separates the fat from the bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
and protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
. A rendering process yields a fat commodity
Commodity
In economics, a commodity is the generic term for any marketable item produced to satisfy wants or needs. Economic commodities comprise goods and services....
(yellow grease
Yellow grease
Yellow grease is derived from used cooking oil from the fast-food industry. It is used to feed livestock, and to make soap, make-up, clothes, rubber, detergents, and bio-diesel fuel....
, choice white grease, bleachable fancy tallow
Tallow
Tallow is a rendered form of beef or mutton fat, processed from suet. It is solid at room temperature. Unlike suet, tallow can be stored for extended periods without the need for refrigeration to prevent decomposition, provided it is kept in an airtight container to prevent oxidation.In industry,...
, etc.) and a protein meal (meat & bone meal, poultry byproduct meal, etc.).
Rendering plants often also handle other materials, such as slaughterhouse blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
, feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
s and hair
Hair
Hair is a filamentous biomaterial, that grows from follicles found in the dermis. Found exclusively in mammals, hair is one of the defining characteristics of the mammalian class....
, but do so using processes distinct from true rendering.
Process variations
The rendering process varies from plant to plant in many ways.- Whether the end products are to be used as human food is based on the type of raw material and the processing methods.
- Whether the end products are to be used as animal or pet food.
- The material may be processed wet or dry. In wet processing, either boiling water or steam is added to the material, causing fat to rise to the surface; in dry processing, fat is released by dehydrating the raw material.
- The temperature range used, whether high or low.
- Processing may be either in discrete batches or in a continuous process.
- The processing plant may be operated by an independent company that collects the material on the open market, or by the packing plant that produced the material.
Rendering processes for edible products
Edible rendering processes are basically meat processing operations and produce lardLard
Lard is pig fat in both its rendered and unrendered forms. Lard was commonly used in many cuisines as a cooking fat or shortening, or as a spread similar to butter. Its use in contemporary cuisine has diminished because of health concerns posed by its saturated-fat content and its often negative...
or edible tallow for use in food products. Edible rendering is generally carried out in a continuous process at low temperature (less than the boiling point of water). The process usually consists of finely chopping the edible fat materials (generally fat trimmings from meat cuts), heating them with or without added steam, and then carrying out two or more stages of centrifugal separation
Centrifugation
Centrifugation is a process that involves the use of the centrifugal force for the sedimentation of mixtures with a centrifuge, used in industry and in laboratory settings. More-dense components of the mixture migrate away from the axis of the centrifuge, while less-dense components of the mixture...
. The first stage separates the liquid water and fat mixture from the solids. The second stage further separates the fat from the water. The solids may be used in food products, pet foods, etc., depending on the original materials. The separated fat may be used in food products, or if in surplus, it may be diverted to soap making operations. Most edible rendering is done by meat packing or processing companies.
One edible product is greaves, which is the unmeltable residue left after animal fat has been rendered.
An alternative process cooks slaughterhouse offal to produce a thick lumpy stew which is then sold to the pet food industry to be used principally as tinned cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
and dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
foods. Such plants are notable for the offensive odour that they can produce and are often located well away from human habitation.
Rendering processes for inedible products
Materials that for aesthetic or sanitary reasons are not suitable for human food are the feedstocks for inedible rendering processes. Much of the inedible raw material is rendered using the "dry" method. This may be a batch or a continuous process in which the material is heated in a steam-jacketed vessel to drive off the moisture and simultaneously release the fat from the fat cells. The material is first ground, then heated to release the fat and drive off the moisture, percolated to drain off the free fat, and then more fat is pressed out of the solids, which at this stage are called "cracklingsCracklings
Cracklings or crackling is a crisp, deep fried food that may be made from various animals. Pork rind cracklings are popular in the American south. The skin of all kinds of poultry are used to make cracklings, including duck, chicken, goose and game birds...
" or "dry-rendered tankage". The cracklings are further ground to make meat and bone meal
Bone meal
Bone meal is a mixture of crushed and coarsely ground bones that is used as an organic fertilizer for plants and formerly in animal feed. As a slow-release fertilizer, bone meal is primarily used as a source of phosphorus....
.
A variation on a dry process involves finely chopping the material, fluidizing it with hot fat, and then evaporating the mixture in one or more evaporator stages. Some inedible rendering is done using a wet process, which is generally a continuous process similar in some ways to that used for edible materials. The material is heated with added steam and then pressed to remove a water-fat mixture which is then separated into fat, water and fine solids by stages of centrifuging and/or evaporation. The solids from the press are dried and then ground into meat and bone meal. Most independent renderers process only inedible material.
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
Soap
In chemistry, soap is a salt of a fatty acid.IUPAC. "" Compendium of Chemical Terminology, 2nd ed. . Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford . XML on-line corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN...
and candle
Candle
A candle is a solid block or cylinder of wax with an embedded wick, which is lit to provide light, and sometimes heat.Today, most candles are made from paraffin. Candles can also be made from beeswax, soy, other plant waxes, and tallow...
making. The earliest rendering was done in a kettle
Kettle
A kettle, sometimes called a tea kettle or teakettle, is a small kitchen appliance used for boiling water. Kettles can be heated either by placing on a stove, or by their own electric heating element.- Stovetop kettles :...
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
Sanitary sewer
A sanitary sewer is a separate underground carriage system specifically for transporting sewage from houses and commercial buildings to treatment or disposal. Sanitary sewers serving industrial areas also carry industrial wastewater...
or it was evaporated to make glue
Glue
This is a list of various types of glue. Historically, the term "glue" only referred to protein colloids prepared from animal flesh. The meaning has been extended to refer to any fluid adhesive....
or protein concentrate to add to fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
. The solids were used to make fertilizer.
The pressure tank made possible the development of the Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
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
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, 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.
Advantages and disadvantages of rendering
Rendering has been introduced to the food processingFood processing
Food processing is the set of methods and techniques used to transform raw ingredients into food or to transform food into other forms for consumption by humans or animals either in the home or by the food processing industry...
industry to eliminate some difficulties as to the efficient use of the excessive slaughterhouse and restaurant waste, but it also poses some problems in the light of economy and health.
Usually, materials used as raw materials in the rendering process are susceptible to spoilage. However, after rendering, the materials are much more resistant to spoiling. This is due to the application of heat either through cooking in the wet rendering process or the extraction of fluid in the dry rendering process. The fat obtained can be used as low-cost raw material in making grease, animal feed, soap, candles, biodiesel
Biodiesel
Biodiesel refers to a vegetable oil- or animal fat-based diesel fuel consisting of long-chain alkyl esters. Biodiesel is typically made by chemically reacting lipids with an alcohol....
, and as a feed-stock for the chemical industry. Tallow
Tallow
Tallow is a rendered form of beef or mutton fat, processed from suet. It is solid at room temperature. Unlike suet, tallow can be stored for extended periods without the need for refrigeration to prevent decomposition, provided it is kept in an airtight container to prevent oxidation.In industry,...
, derived from beef waste, is an important raw material in the steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
rolling industry providing the required lubrication when compressing steel sheets. The meat and the bones (which are in a dry, ground state) are converted to what is known as meat and bone meal
Meat and bone meal
Meat and bone meal is a product of the rendering industry. It is typically about 48 - 52% protein, 33-...
. For many years meat and bone meal were fed to cattle. This practice is now prohibited in developed countries because it is believed to be the main route for the spread of bovine spongiform encephalopathy
Bovine spongiform encephalopathy
Bovine spongiform encephalopathy , commonly known as mad-cow disease, is a fatal neurodegenerative disease in cattle that causes a spongy degeneration in the brain and spinal cord. BSE has a long incubation period, about 30 months to 8 years, usually affecting adult cattle at a peak age onset of...
(mad-cow disease, BSE), which is also fatal to human beings. Meat and bone meal from cattle is, however, fed to non-ruminant
Ruminant
A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...
animals and meat and bone meal from non-ruminant animals is fed to cattle in the United States. This may not prove to be a solution to the problem due to the resistant nature of the infectious agent of BSE, a misfolded protein (prion
Prion
A prion is an infectious agent composed of protein in a misfolded form. This is in contrast to all other known infectious agents which must contain nucleic acids . The word prion, coined in 1982 by Stanley B. Prusiner, is a portmanteau derived from the words protein and infection...
). Therefore, even if cattle is fed to non-ruminant animals and vice-versa, it will not prevent BSE from occurring. The underlying cause is that the prion survives within the system of the animal that has been fed with meat and bone meal from different animals including cattle. These animals are then eventually rendered and fed to cattle, which also results in the development of the disease.
In the absence of the rendering industry, the cost of waste disposal of waste animal material would be very high and would place a significant economic and environmental burden on areas involved in industrial scale slaughtering. This cost may manifest itself through the expensive use of sanitary landfills, incinerators and other similar waste disposal techniques without yielding profit directly out of it leading to the incurrence of opportunity costs. Using substitute products to rendering products may not necessarily prove to be lesser in cost. In spite of the advantages of the rendering process mentioned in this paragraph, it also poses certain economic disadvantages. One is when BSE and its cause has been discovered in the late 20th century. In effect, people were scared off and refrained from eating beef and other kinds of meat. Meat processors, especially beef processors, suffered losses due to a decrease in meat sales and the increase in difficulty in marketing their products, in effect, also causing losses to livestock growers through a decrease in sales. Another is that regular meat inspections discover infected products and animals, which have to be destroyed immediately to prevent further spreading of the disease. The epidemic also affected renderers, as lesser meat processors avail of their services making it difficult for them to allocate their raw materials and that they cannot avail of infected animals and products.
Economic impacts
Other major factors which impacted the industry in the 20th century were the popularization of chemical fertilizers, the development of synthetic detergents, the widespread adoption of "boxed beef" in the USA, and the change in consumer eating habits to reject animal fats. In the early 20th century the low cost of synthesis of artificial nitrogen fertilizers undermined the economic use of animal waste to enrich soils. This resulted in the loss of a substantial market for meat by-product solids. But this lost market was replaced by the realisation that these products made good feed for animals. After World War II synthetic detergents came on the scene which eventually displaced soaps for both domestic and industrial washing uses. Thus, 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 oleochemical
Oleochemical
Oleochemicals are chemicals derived from plant and animal fats. They are analogous to petrochemicals derived from petroleum.The formation of basic oleochemical substances like fatty acids, fatty acid methyl esters , fatty alcohols, fatty amines and glycerols are by various chemical and enzymatic...
s, displacing inedible fats and contributing to the market volatility of this commodity.
The rendering industry is one of the oldest recycling industries, and made possible the development of a large food industry. The industry takes what would otherwise be waste materials and makes useful products such as fuels, soaps, rubber, plastics, etc. At the same time, rendering solves what would otherwise be a major disposal problem. As an example, the USA recycles more than 21 million metric tons annually of highly perishable and noxious organic matter. In 2004, the U.S. industry produced over 8 million metric tons of products, of which 1.6 million metric tons were exported.
Kitchen rendering
Rendering of fats is also carried out on a kitchen scale by chefs and home cooks. In the kitchen, rendering is used to transform butterButter
Butter is a dairy product made by churning fresh or fermented cream or milk. It is generally used as a spread and a condiment, as well as in cooking applications, such as baking, sauce making, and pan frying...
into clarified butter
Clarified butter
Clarified butter is milk fat rendered from butter to separate the milk solids and water from the butterfat. Typically, it is produced by melting butter and allowing the different components to separate by density...
, suet
Suet
Suet is raw beef or mutton fat, especially the hard fat found around the loins and kidneys.Suet has a melting point of between 45° and 50°C and congelation between 37° and 40°C....
into tallow
Tallow
Tallow is a rendered form of beef or mutton fat, processed from suet. It is solid at room temperature. Unlike suet, tallow can be stored for extended periods without the need for refrigeration to prevent decomposition, provided it is kept in an airtight container to prevent oxidation.In industry,...
, pork
Pork
Pork is the culinary name for meat from the domestic pig , which is eaten in many countries. It is one of the most commonly consumed meats worldwide, with evidence of pig husbandry dating back to 5000 BC....
fat into lard
Lard
Lard is pig fat in both its rendered and unrendered forms. Lard was commonly used in many cuisines as a cooking fat or shortening, or as a spread similar to butter. Its use in contemporary cuisine has diminished because of health concerns posed by its saturated-fat content and its often negative...
, and chicken fat into schmaltz
Schmaltz
Schmaltz or schmalz is rendered chicken, goose, or pork fat used for frying or as a spread on bread, especially in German and Ashkenazi Jewish cuisine. Also is very common in Ukrainian cuisine Schmaltz or schmalz is rendered chicken, goose, or pork fat used for frying or as a spread on bread,...
.
Further reading
- Meeker DL (ed). (2006). Essential Rendering: All About The Animal By-Products Industry. Arlington, VA: National Renderers Association. p 95–110. ISBN 0-9654660-3-5 (Warning: large document).
- Link above broken - NRA link here to National Renderers Association [nationalrenderers.org/assets/essential_rendering_book.pdf Essential Rendering Overview (16 Page Document) ]
Industry organizations
- Australian Renderers' Association Inc.
- National Renderer’s Association (US)
- Fats and Proteins Research Foundation (US)
- Animal Protein Producers Industry (US)
- United Kingdom Renderers' Association (UK)
Kitchen rendering
- "Rendering Lard 2.0" by Melissa Schneider, An Obsession With Food (blog), January 12, 2006.