PORK AND PORK QUALITY PIH-128
PURDUE UNIVERSITY. COOPERATIVE EXTENSION SERVICE.
WEST LAFAYETTE, INDIANA
Pork By-Products
Authors
John R. Romans, South Dakota State University
William J. Costello, South Dakota State University
James F. Price, Michigan State University
Richard C. Waldman, Austin, Minnesota
Reviewers
Tom R. Carr, University of Illinois
Frank and Barbara Essner, Chaffee, Missouri
Robert Kauffman, University of Wisconsin
Miriam and John Lewis, Walstonburg, North Carolina
Mr. Tony Javurek, who guided two tours daily at John
Morrell's Sioux Falls packing plant for more than 20 years,
expressed the meat industry philosophy about by-products during
each tour. Tony always said, ``We use all parts of the pig except
the squeal and the curl in its tail.'' This practice took place
during prehistoric times when men and women used animal skins for
clothing and shelter, bones and horns for tools, tendons and
intestines for weapons, tools, and bindings; teeth, claws, feath-
ers, and hair for ornaments; and skins for containers. Modern
society learned well from their ancestors, and, as a result,
today's meat industry utilizes many of the nonmuscle portions of
livestock.
Meat slaughter by-products (offal) include all parts of the
animal that are not a part of the carcass. Cutting and processing
of the carcass result in nonmuscle by-products such as fat, bone,
and other connective tissues. Processed by-products have been a
significant source of income to the meat processing industry. The
United States Department of Agriculture (USDA) Economic Research
Service (ERS) (1990) reported the portion of gross farm value of
swine attributable to edible and inedible pork by-products for
the years 1985 to 1990 ranged from 5.6% to 6.3% and averaged
6.0%. Thus, if hogs are selling for $50 per hundred weight (cwt),
$6.90 of the value of a 230-pound hog represents the worth of the
by-products ($50 x 2.3 cwt x 6% = $6.90). Many different products
and their predominant use are listed throughout the remaining
pages of this fact sheet. However, at times market conditions and
alternate product availability preclude the use which is listed
in which case the item is used in a lower valued product.
The use of by-products is a controversial subject. One seg-
ment of society values the many products made available from by-
products. There is, however, another point of view. There are
concerns about the environment and the related energy costs.
These concerns have made the use of by-products a major economic
and management problem for the meat industry. Today, economics,
modern technology, and the industry's concern for the environment
result in maximum salvage and utilization of all by-product
materials. A hog kill operation with a 1,000-head-per hour capa-
city must be able to process approximately 72,000 pounds of by-
product material per hour. In many communities, the air and water
effluent (flowing out) from meat operations must be as clean, or
cleaner, than the water and air entering the plant.
Edible By-Products
Edible by-products, oftentimes referred to as ``variety
meats,'' are listed alphabetically in Table 1. The yields are
based on a 230-pound hog along with a brief description of the
use of each by-product. Prices for these edible by-products
change, depending on their use and availability. Current prices
are available from the following sources:
The Yellow Sheet, Daily Market and News Service, published five
days weekly by:
The National Provisioner
15 West Huron Street
Chicago, IL 60610
Phone: (312) 944-3380
The Meat Sheet, published five days weekly by:
Meat Research and Reporting Service
643 South Route 83
Elmhurst, IL 60126
Phone: (312) 963-2252
Market News, published weekly and the Blue Sheet published five
days weekly by:
U.S. Department of Agriculture
Agricultural Marketing Service
Livestock & Grain Market News, Room 2623-S
P.O. Box 96456
Washington, D.C. 20090-6456
Your state probably has a livestock and meat market news
publication that is available to residents.
When you have interest in computing the value of these by-
products, you can use the yield factors in Table 1 and the prices
from your most readily available source. The nutritive value of
selected by-products is listed in Table 2.
Table 1. Edible pork by- products yields and uses from a 230- pound
market hog (cont.).
____________________________________________________________________
By-product Wt. (lb.) Uses
____________________________________________________________________
Blood 7.0 According to the United States Department of
Agriculture Food Safety and Inspection Service,
no blood which comes in contact with the surface
of the body of an animal or is otherwise contam-
inated can be used for food purposes. Only blood
from inspected animals may be used for meat food
products. In Europe, blood proteins are utilized
in food to a greater degree than they are in the
USA. Collection systems for blood have been dev-
eloped in Europe which utilize cannula-like fun-
nel devices for blood removal and some draw the
blood directly from the animal's vascular system
into sterilized, vacuumized containers. Blood is
used in many different sausage formulations and
in new cake mixes.
Brains 0.25 Sold in domestic and foreign markets. It is slic-
ed thinly, breaded, and deep fat fried. Alternat-
ely broken into small pieces and mixed with eggs.
Chitterlings Large and/or small intestines. Preferred quality
comes from the middle 2.5 yards of the large int-
estine. Marketed seasonally in the U.S.
Ears 0.60 Generally exported to Latin America but also enj-
oyed in U.S.
Fat 25.0 Amount of backfat depends on the grade of hog.
Lard provides a source of energy and an essential
fatty acid (linoleic) for the human consumer; it
is easily digested, since its melting point is
near body temperature. Lard is useful as a cooking
fat, a shortening, and a flavor ingredient in many
foods. Unrendered fat is used in processed meat,
soups, and snack products.
Feet (front)1.4 each Sold both in domestic and foreign markets.
Heart 0.6 Many are exported. They are normally split and wa-
shed. Some sold fresh to be cooked with moist heat.
Most used in sausage manufacture as indicated on
label.
Intestines (Also see chitterlings)
Sausage casings
Small intestine -20 yards
Large intestine -"Middle" 15-inch cap end (fr-
ont end near small intestine)
Bung afterend - one yard (front
end of bung)
Bung fatend - one yard (rear
end of bung)
Kidneys 0.25 eachSold to Western Europe for human food to be sauteed
and served with a sauce. Many used in U.S. for pet
food.
Liver 3.25 Small U.S. market for pates and braunschweiger.
Excess goes to pet food. Some exported to Western
Europe for human food.
Lungs 1.0 Some people of the world utilize lungs in processed
meats, sausages, and stuffings. Most go to pet food
in the U.S.
Maws 1.5 Used in U.S. and exported to Mexico for soup.
(stomach)
Mechanically Yield of 21-27% from ham and picnic bones. Bones
Seperated Pork are coarse ground,then forced against a sieve to
(MSP) remove soft meat which flows through the holes.
Use is limited and "mechanically separated pork"
must be indicated by label.
Salivary 0.1 Used in Chorizo, a highly spiced, hot, dry Hispanic
glands sausage.
Spleen 0.4 Edible in the export market; mostly used for pet
(melts) food in the U.S.
Skin 10.0 Normally only skin off the back fat, fresh hams,
(whole skin) and bellies is saved for human food, i.e., gelatin
manufacture and pork rinds (snack foods). Gelatin
finds wide use in desserts; in the manufacture of
ice cream; in the making of certain pharmaceutical
preparations and capsules for medicine; in the
coating of pills; in the making of mayonnaise dre-
ssings and emulsion flavors; and in the clarifying
of wine, beer, and vinegar. Pork skin is also used
to manufacture cosmetics.
Snouts 0.65 Used in processed meat products.
Sweetbreads 0.25 Demand for human food is diminished, so most go
(pancreas) into pet food.
Tail 0.25 Sold domestically for an ethnic market or exported
to Latin America.
Testicles 0.40 eachFrom young animals preferred for human food, usua-
lly thinly sliced, breaded and deep-fat fried. Most
go to pet food and to inedible products.
Tongue 0.75 Most exported to Western Europe and Japan. Some dem-
and as fresh product and for canned and processed
meat products.
Uterus 0.75 If saved for human food, exported to Far East to be
used in Orienal dishes.
Weasand 0.13 Sausage manufacture.
(esophagus)
______________________________________________________________________
Table 2. Proximate protein, fat and calorie content of 100 grams
of selected cooked pork variety meats.
_________________________________________________________________
| Variety Meat Protein Fat Calories |
| (grams) (grams) |
| Brain 12.2 9.5 138 |
| Heart 23.6 5.05 148 |
| Kidney 25.4 4.7 151 |
| Liver 26.0 4.4 165 |
| Lung 16.6 3.1 99 |
| Pancreas (sweetbreads) 28.5 10.8 219 |
| Spleen 28.2 3.2 271 |
| Tongue 24.1 18.6 271 |
|_______________________________________________________________|
From Agriculture Handbook No. 8-10, Composition of Foods, Pork,
1983.
Because variety meats are economical sources of valuable
nutrients, more extensive use of meat animal by-products for
human food has been proposed as one method to reduce world nutri-
tion problems. In addition to enhancing human nutrition, new
developments in meat by-product utilization would increase the
overall efficiency of livestock production. Variety meats are
relatively high in protein; the exception is brain. Liver is the
most nutritious of all meat items. The nutrient density of liver
exceeds that of muscle meats, which are high. An excellent source
of readily digested heme iron, liver also provides B vitamins,
particularly B12, as well as vitamin A to consumers who enjoy its
unique flavor. (Heme is the O2 carrying component of hemoglobin
and myoglobin and is a source of iron more readily absorbed by
the human digestive system than most dietary iron forms.)
Pharmaceutical By-Products
The medical arts have used animal products in the healing
process for centuries. In fact, some animal products have held
``magical'' healing powers for certain societies throughout his-
tory. Similar conditions exist today with minute portions of cer-
tain animal extractives which are used each day and can literally
be the difference between life and death for many humans. The pig
is often used as a model for human research because of the simi-
larity between the two species of several vital systems. Thus,
most of the healing effects described below apply to pigs and
humans.
Internally secreting, ductless endocrine glands are scat-
tered through various parts of the animal body. The substance
secreted by each exercises some specific control over the con-
duct, character, and development of the body. Their functions are
so interrelated that under- or over-secretion of any one of
several of the glands will cause abnormalities. Hormones are some
of the "magical" products which are derived from animal tissues
saved by the meat industry and which are extracted, purified, and
prepared for consumers by the pharmaceutical industry. Enzymes
and other types of chemicals are also derived from animal
slaughter by-products.
Adrenals
The adrenals are also called the suprarenal glands and are
two in number. They are long and narrow and are located on the
medial border of the kidney. They are reddish-brown in color and
somewhat bean-shaped. The cortex (outer portion) produces steroid
secretions essential to life maintenance. The medulla (inner por-
tion) of the gland produces epinephrine which constricts the
blood vessels and increases heart action. Each adrenal gland
weighs approximately 1/2 ounce (14 grams).
Until recently hog adrenal glands were an important source
of many different hormones which physicians used to treat
illnesses or chemical imbalances in the human body. Now, many of
these compounds are made synthetically.
Thyroid
The thyroid gland is dark and triangular shaped, about 2
inches across, may be located some distance from the larynx, has
no isthmus, and somewhat adjoins the esophagus. Its secretion is
an iodine-containing compound termed thyroxin. In the young, a
deficiency of thyroid tissue causes a condition known as ``cre-
tinism,'' resulting in physical deformity and defective mental-
ity, or idiocy. In the adult, it causes a condition known as
``myxedema,'' defined as"severe thyroid deficiency" (hypothy-
roidism), characterized by dry skin and hair and loss of physical
and mental vigor.
Forty fresh hog thyroids are needed to make a pound of thy-
roxin (14 grams to 21 grams per gland).
Parathyroids
Parathyroids consist of four small glands the size of a
grain of wheat. They are located close to the thyroid gland.
Their secretions regulate the calcium content of the blood stream
and maintain the tone of the nervous system. The complete removal
of the parathyroids causes death within a few weeks. To secure 1
pound of parathyroid extract requires the slaughter of approxi-
mately 3,600 animals.
Nervous System
Hog brains are a potential source of cholesterol, the raw
material from which vitamin D3, the ``sunshine'' vitamin neces-
sary in building bones and teeth, is made. Cholesterol also comes
from the spinal cord.
The hypothalamus, a small inner basal portion of the brain,
produces relatively small molecules that cause the release of
various hormones from the pituitary gland.
Pituitary
Located at the base of the brain and well protected in a
separate bone cavity, the pituitary gland is about the size of a
pea and is grayish yellow in color. It is made up of an anterior
and a posterior lobe which have distinct functions. The anterior
lobe is known to produce (1) the growth-promoting hormone (GH),
(2) the thyroid-stimulating hormone (TSH), (3) the luteinizing
hormone (LH), (4) prolactin, (5) the follicle-stimulating hormone
(FSH), and (6) the adrenal-cortex-stimulating hormone (ACTH). The
posterior lobe excretes hormones that (1) control blood pressure
and pulse rate, (2) regulate the contractile organs of the body,
and (3) govern energy metabolism. Pituitary glands in hogs pro-
duce a great number of hormones used to control human growth and
metabolism problems and to regulate activity of the body's other
endocrine glands.
Pineal
The pineal gland is about one third the size of the pitui-
tary, reddish in color, and located in a brain cavity behind and
just above the pituitary. Its secretion regulates early
growth-hastening or retarding puberty and maturity. The hog's
pineal gland secretes the hormone melatonin, which is used in
treatment of personality and mental disorders. It also affects
the color of the skin and the formation of freckles.
Stomach
Linings of the hog's stomach contain proteins and enzymes
used in many commercially produced digestive aids and antacids.
Intestines
Heparin is classified as one of the "essential" pharmaceuti-
cals and is obtained almost exclusively from the inner lining
(mucosa) of the hog's small intestine and from the lungs. It is a
natural anticoagulant used to thin the blood and dissolve,
prevent, or retard clotting during surgery, especially during
organ transplants. Heparin is also used as a gangrene preventa-
tive in cases of frostbite and as a burn treatment.
Enterogastrone, a hormone taken from the hog duodenum
(beginning of the small intestine), is used to regulate gastric
secretions in the stomach. It is also used experimentally to
speed the emptying time of the stomach. Secretin hormone, also
from the duodenum, stimulates pancreas glands to produce pan-
creatic juices. It is injected in humans to test for disease of
the pancreas.
Liver and Spleen
Bile is synthesized in the cells of the liver and passes
through the hepatic and cystic ducts to the gall bladder, where
it is stored. Cholic acid has been purified from bile. It is an
intermediate in the formation of chenodeoxycholic acid and urso-
deoxycholic acid which are also derived from bile to be used in
the treatment or prevention of gallstones. Catalase is an enzyme
from the liver that is used in dairy processing, mainly cheese
making. Splenic fluid affects capillary permeability and blood
clotting time and speeds up recovery from inflammatory conditions
(redness and swelling).
Testes and Ovaries
Hyaluronidase, an enzyme that attacks the complex glycopro-
tein, hyaluronic acid, found in joints and other connective tis-
sues, is derived from testes. Hyaluronidase is used as a spread-
ing factor to aid drug dispersion in connective and other tis-
sues. Hog ovaries are a source of progesterone and estrogens used
to treat various reproduction problems in humans. Sow ovaries are
the major source of relaxin, a hormone often used during child-
birth. It requires the slaughter of 145 female hogs to produce 1
pound of fresh ovaries from which corpus luteum and ovarian
extracts are prepared.
Lungs
Lungs may be used as a source of heparin, but intestinal
mucosal heparin extractions are more easily purified. Lung tissue
is a source of a pancreatitis treatment product called aprotinin.
Heart
Hog heart valves from young pigs to full-sized market hogs
are specially preserved and treated and surgically implanted in
humans to replace heart valves that have been weakened or injured
by rheumatic fever or through birth defects.
Pancreas
The pancreas is commonly known as the pork sweetbread, but
it should not be confused with the commercial veal sweetbreads
(thymus gland). The pancreas has both internal and external
secretions, the latter passing into the small intestine to effect
the digestion of starch, protein, and fat. The internal secretion
(insulin) regulates sugar metabolism. Failure of the pancreas to
regulate sugar metabolism results in the affliction known as dia-
betes mellitus.
Diabetes was a killer disease before it was discovered that
animal insulin could be used in humans. Insulin, first isolated
by Drs. Banting and Best, is secured from specialized groups of
cells in the pancreas known as the islets of Langerhans. Insulin
is used extensively in treating diabetes.
The pancreas glands from approximately 60,000 hogs produce 1
pound of pure insulin, enough to treat 750 to 1,000 diabetics for
one year. A year's production of 85 million market hogs could be
the source of 1,400 pounds of insulin. The chemical structure of
hog insulin most nearly resembles that of humans. This is signi-
ficant because approximately 5% of all diabetics are allergic to
insulin from other animals and can tolerate only insulin from
hogs.
A product referred to as humulin is in production and
replacing animal sources of insulin. Although priced higher, dia-
betics are increasingly using humulin. All newly diagnosed
patients are put on the new product and many animal insulin users
are being converted. This new product is a result of biotechnol-
ogy and is replacing porcine insulin as biotechnological methods
of synthesis become more efficient and cheaper.
Glucagon is a pancreatic hormone given to raise the blood
sugar level and to treat insulin overdoses in diabetics, or when
a low blood sugar episode is caused by alcoholism. It has a spe-
cialized use in the treatment of some psychiatric disorders. Kal-
likrein is a proteolytic enzyme from the pancreas which is also
called kininogenase. It catalyzes a hydrolysis that forms kalli-
din. Kallidin dilates vascular smooth muscle tissue and thus
reduces blood pressure. Chymotrypsin is an enzyme used to cleanse
wounds and to remove dead tissue where ulcers and infections
occur.
LPH (lipotropic hormone) is used as a digestive aid and is
important in the digestion and absorption of fats and oils. Pan-
creatin is a mixture of pancreatic enzymes used to treat faulty
digestion in humans. Because of its high-fat digestive capabil-
ity, pancreatin is also used in the treatment of cystic fibrosis,
a disease afflicting approximately 4 million people in this coun-
try.
Trypsin is a digestive aid that helps break down food by
aiding in the hydrolysis of protein in the upper part of the
small intestine. Trypsin and the enzyme chymotrypsin are
prescribed to remove dead and diseased tissue from wounds and to
speed healing after surgery or injury. Other extracts made from
the pancreas, such as pancreatin, are used as a remedy for intes-
tinal disorders.
Skin
Gelatin from hog skin collagen is used for coating pills and
making capsules. Gelatin is taken orally to improve fingernail
strength. See later discussion of pork skins as burn bandages. A
porcine collagen product has been developed to stimulate clotting
during surgery. The product is applied directly on the surface of
the bleeding tissue.
Blood
Blood albumin from meat animals is used in human blood Rh
factor typing. Blood fibrin extract from hog blood is used to
make amino acids that are part of parenteral (infused as
intravenous) solutions for nourishing certain types of surgical
patients. Fetal pig plasma is important in the manufacture of
vaccines and tissue culture media. Fetal blood contains no anti-
bodies and is unlikely to stimulate immune reactions.
Thrombin, a blood protein, helps create significant blood
coagulation. It is valuable in the treatment of wounds, particu-
larly in cases in which the injury is in an inaccessible part of
the body, such as the brain, bones, or gastrointestinal tract (as
in the case of peptic ulcers). Thrombin is also used in skin
grafting to help keep the graft in place and to "cement" gaps
where tissues have been surgically removed.
Plasmin, a hog blood enzyme which has the unique ability to
digest fibrin in blood clots, is used to treat patients who have
suffered heart attacks. This proteolytic enzyme is combined with
deoxyribonuclease from the pancreas to aid in the removal of dead
tissue that results from certain vaginal infections. It is a
valuable cleansing agent for infected wounds or clotted blood and
can speed up the healing of skin damaged by ulcers or burns. Hog
blood is also used in cancer research, microbiological media, and
cell cultures.
Inedibile Pork By-Products
Fats
Meat slaughter and processing plants that have rendering
facilities must have two separate rendering units. The two units
must be separated physically to prevent any intertransfer of raw
material, product, or contamination from the inedible-rendering
area to the edible-rendering area. In pork operations, all soft
tissue, some bones, sweepings, scrapings, and skimmings that are
not classified as edible or do not have other uses are cooked and
processed into inedible fat and meal by rendering. Dead hogs or
condemned pork products are processed by inedible rendering
facilities.
Rendered pork fat is known as grease. A major domestic use
of grease is animal feeds. These fats are usually stabilized with
an approved antioxidant to prevent rancidity development which
would make the feed unpalatable. Fat is the richest food nutrient
in terms of energy and as such has been used successfully in cat-
tle, poultry, swine, and pet feeds. In addition to the energy
value, fats reduce the dust, improve the color and texture,
enhance the palatability, increase pelleting efficiency, and
reduce machinery wear in the production of animal feeds.
During 1987, the pet food industry produced approximately 9
billion pounds of dog and cat food at a 1987 retail value of $5.7
billion. Comparable figures were $350 million in 1958 and $1.6
billion in the mid-1970s. Animal fats are used as energy sources,
and meat meal is used extensively in some products for protein
and mineral sources as well as for palatability enhancement. The
pet and animal food industry utilizes some fresh by-products
(uncooked) for canned and fresh frozen pet and specialty animal
foods (zoo foods, mink food, racing and guard dog food, and fox
food).
Fatty Acids
Fatty acids are obtained from animal fats through a process
referred to as splitting and are used in ever increasing quanti-
ties in the manufacture of scores of products. The list of uses
for fatty acids and other derivatives of natural pork fats by the
chemical industry is extensive: biocides-substances destructive
to many different organisms, cellulose processing, cosmetics,
dyestuffs, explosives, fabric conditioners, foodstuffs, lacquers
leather and paper goods, linoleum, lubricants, metal soaps, min-
ing, mineral oil additives, plastics, road making rubbers, soaps,
synthetic resins, tobacco, textiles, varnishes, and washing and
cleaning agents.
Oils
Lard oil, made from ``A'' white grease, is used for making a
high-grade lubricant which is used on delicate running machine
parts. The oil from "B" white grease is sometimes called "extra
neat's-foot oil" and is used in giving viscosity to mineral oils.
The oils made from the brown grease are used in compounding cut-
ting oils, heavy lubricating oils, special leather oils,
illuminating oils, and are combined with paraffin in candle mak-
ing.
Soap
Lard oil is also used for the manufacture of soap. Prior to
the 1960s, the greatest utilization of grease had been in soap
making. During the mid-twentieth century, soap production
declined significantly, due primarily to the increased use of
phosphate-based detergent powders and liquids. Domestic use of
animal fats in soap has also been diluted by use of plant lipid
sources. This development of detergents and other cleaning agents
and replacement by vegetable fats posed serious threats to the
market for the major products of the rendering industry. New
markets were researched and developed in the feed industry, in
the export market, and in application of fatty acids to indus-
trial uses. The loss of a portion of the soap market stimulated
the renderers to expand markets and diversify the products of the
industry.
Modern soap making occurs in continuous processing systems
which utilize fatty acids stripped from raw fats. Soap making
originated and remained a batch process involving more time and
less technology until the middle of this century.
Soap is biodegradable and therefore has an advantage over
the phosphate-based detergents that replaced soap for many uses
some years ago. Phosphates tend to accumulate in the water supply
and are responsible for the stimulation of algae growth and oxy-
gen depletion in lakes and streams. Fat-based cleaning products
with detergent-like traits, effective in hard and cold water,
have been developed and are in use in various parts of the world.
Environmental concerns and fat utilization research have rein-
stated fat-based materials in the cleansing market.
Meat Meals
The dry, defatted, high-protein material which results from
rendering varies, depending on the raw materials used and the
processing technique employed. Protein products of rendering may
be utilized in a number of ways but are marketed most extensively
as animal feeds. It is necessary that the nutrient content and
availability of feed ingredients be standardized, because animal
nutritionists have detailed knowledge of specific nutrient
requirements and are using computers to balance diets for
specific amino acids and micronutrients. Animal protein sources
used in livestock diets have not been well-standardized in the
past. However, the U.S. rendering industry is installing render-
ing systems that result in less heat damage to nutrients and
improved quality control of raw materials and handling. This is
an effort to standardize rendered protein products. In addition
to reducing variation in nutrient content and availability, the
improved methods reduce potential microbial contamination of
valuable feed ingredients.
Most nonfat products (of rendering) may be utilized as
organic fertilizers. Some adhesives utilize animal proteins,
especially blood meal or dried blood, as base materials. Bone
meal is marketed to the manufacturers of china, instrument keys,
steel alloys, glass, water-filtering agents, and enamels.
The major nonfat products of rendering are described below
as feedstuffs, since that is the principle use of the materials
listed. The International Feed Number (IFN), which is an identif-
ication system for feed ingredients, is indicated for each pro-
duct.
Tankage, Digester Tankage, and Wet-rendered Tankage: IFN
5-00-386
The meat animal soft-tissue by-products and dead animal tis-
sues have been rendered using direct steam-pressure (wet-
rendering) systems. Dried blood is often added. The crude protein
level is high (55% to 60%), but availability of and amounts of
certain essential amino acids are low. Tankage is a good source
of calcium and phosphorus.
Tankage, with Bone: IFN 5-00-387
The product has increased calcium and phosphorus levels (4.4
% or more), with a corresponding decreased protein level. It is
similar to tankage but with a greater amount of bone.
Meat Scrap(s), and Meat Meal: IFN 5-00-385
The raw materials are similar to tankage but are rendered in
steam-jacketed tanks (dry rendering). The lower processing tem-
peratures result in improved protein quality. Dried blood is not
added to meat meal, as is often true for tankage. When phosphorus
exceeds 4.4%, the product must be identified as meat and bone
meal.
Meat and Bone Scrap or Meal: IFN 5-00-388
The addition of bone to meat scrap increases calcium and
phosphorus content and reduces protein; therefore, its value as a
feed ingredient is reduced in some cases.
Blood Meal: IFN 5-00-381 spray, 5-00-380 meal, 5-26-006
flash
Dried blood is high in protein (80%), especially the amino
acid lysine but unpalatable as a feed ingredient and has reduced
digestibility. Flash dried (atomized into hot vacuum chamber)
blood is a better quality feed source. Plasma is the watery part
of blood left when red cells are removed. When spray dried, a
process that does not destroy the fluid's protein and amino
acids, it may be used as a protein supplement in pig starter
diets. Blood products are used as adhesive bases and bonding
agents.
Bone Meal, Steamed Bone Meal, and Special Bone Meal: IFN
6-00-400
Bones are ground and rendered to remove the fat and mois-
ture, and the largely mineral remainder is reground. The composi-
tion may vary due to differences in raw materials or processing
techniques and contains 7% to 15% protein.
Pigskins
Most U.S. pork processors have used or are presently using a
scalding and dehairing technique which leaves the skin attached
to pork carcasses until they are processed into wholesale or
retail cuts. With such a system, the only fresh skin available of
any consequence is that resulting from the fatback and the hams.
This skin is largely used in gelatin production. However, more
packers are removing the whole skin rather than dehairing, which
results in pork skin usable for leather.
Pigskin is used as leather for gloves, wallets, handbags,
brief cases, toiletry cases, tobacco pouches, book bindings, and
leggings. The pigskin leather is tough and produces scuff-
resistant footwear. The hog bristle (hair) is unique in that it
grows through the skin from the follicle in the subcutaneous fat
layer. The holes, or pores, through which the hairs pass, result
in a naturally "air-conditioned" type of leather.
Scalded skins can be pulled using skinning equipment, but
the leather becomes 10% thinner and has less tensile strength
than does the leather from unscalded skins. The heat damage
incurred during scalding makes many skins unsuitable for use as
leather. Scalding is more labor efficient when done during the
slaughter phase; additional labor is required to remove the skins
at later stages of processing.
Specially selected and treated hog skins, because of their
similarity to human skin, are used in the treatment of humans
suffering from massive burns and injuries that have removed large
areas of skin. It is also used in the healing of persistent skin
ulcers. Hog skins are cut into strips or patches, shaved to
remove the hair, split to 0.008 inches to 0.020 inches in thick-
ness, and then cleansed, sanitized, and packaged. The skins are
applied directly to the injured areas to decrease pain, inhibit
infection, and prevent loss of body fluids.
Glue and Gelatin Stocks
The three main types of glue are hide glue, bone glue, and
blood albumin glue. The latter is water resistant and is used
widely in the manufacture of plywood.
The oldest and widest use for glue is in the furniture and
veneer industry. Glue has so many varied uses that it has been
said that glue holds the world together. It is used in sizing
paper; in the manufacture of wool, silk, and other fabrics; in
sizing straw hats; in sizing walls that are to be painted; in
sizing barrels or casks that are to contain liquids; on the heads
of matches to make an air-tight cap over the phosphorus; in the
manufacture of sand and emery paper to hold the abrasive on the
paper; in the manufacture of dolls, toys, and ornaments; in the
making of picture frames, mirror frames, rosettes, billiard
balls, composition cork, imitation hard rubber, printing rolls,
mother-of-pearl, gummed tape, paper boxes, calcimine, automobile
bodies, caskets, leather goods, and bookbinding; and many other
products.
The two types of gelatin according to their source are hide
gelatin and bone gelatin. Both types of gelatin are used in the
making of ``facial'' court plaster, in photography, in electro-
plating, as a bacteria culture medium, and for various other
uses.
Blood
Whole blood contains around 21% protein. If the blood is
allowed to coagulate, the gelled portion contains fibrin and cel-
lular proteins, whereas the blood albumin remains in the fluid
serum. The fibrin portion is sold as dried blood in tankage or
fertilizer. The serum is clarified and dried and sold as blood
albumin. Blood albumin is used in certain malt extracts and in
fixing pigment colors in cloth and in finishing leather, clarify-
ing liquors, and manufacturing glue. Blood is also used in the
manufacture of buttons and imitation tortoise shell articles.
Hair
Hog bristles for making brushes were formerly imported from
China but are now produced in the United States in increasing
amounts. It requires considerable hand labor to collect the
proper length bristles. It is found over the shoulder and back of
the hog. The fine hair of most of our domestic hogs is not suit-
able for brush making; it is processed and curled for upholster-
ing purposes.
Sources
National Live Stock and Meat Board, 444 North Michigan Avenue,
Chicago, IL, 60611.
National Pork Producers Council, P. O. Box 10383, Des Moines, IA,
50306.
Pearson, A. M., and T. R. Dutson. 1989. Edible Meat By-Products.
In: Advances in Meat Research. Vol. 5. Elsevier Science Publish-
ers, Ltd., New York, NY.
Romans, J. R., K. W. Jones, W. J. Costello, C. W. Carlson and P.
T. Ziegler. 1985. The Meat We Eat. (12th Ed.). The Interstate
Printers and Publishers, Danville, IL.
USDA. 1990. Livestock and Poultry Situation and Outlook Report.
LPS-43, Economic Research Service,
NEW 12/90 (7M)
______________________________________________
Cooperative Extension Work in Agriculture and Home Economics,
State of Indiana, Purdue University and U.S. Department of Agri-
culture Cooperating. H.A. Wadsworth, Director, West Lafayette,
IN. Issued in furtherance of the Acts of May 8 and June 30, 1914.
It is the policy of the Cooperative Extension Service of Purdue
University that all persons shall have equal opportunity and
access to our programs and facilities.
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