Addis Ababa University College of Veterinary

Medicine and Agriculture

Lecture Meat Composition

Sisay Woyeso (MSc in Animal Production)

1
 Introduction
• We all know that meat is a very nutritious food which meets
our daily need of various important nutrients like protein, fat,
minerals and vitamins.
• The composition of' muscle is reflected in the composition of
meat.
• The proximate composition in meat includes moisture, protein,
fat, carbohydrate, mineral and vitamin.
• The caloric value of meat mainly depends upon the protein
and fat content of meat.
• Different species meats differ in their caloric value due to the
difference in their chemical composition. Beside this factor
(i.e., species of meat animal), breed. age, sex, plane of
nutrition, exercises etc. also influence the composition of
meat.
 MEAT, FAT AND OTHER EDIBLE CARCASS
PARTS
Sources of meat, fat and animal by-products.
• Meat, fat and other carcass parts used as raw materials
for the manufacture of processed meat products are
mainly derived from the domesticated animal species
cattle, pigs and poultry and to a lesser extend from
buffaloes, sheep and goats.
• In some regions other animal species such as camels,
yaks, horses and game animals are used as meat animals
but play only a minor role in meat processing.
 Histological structure of muscle tissue
• The muscles are surrounded by a connective tissue membrane,
whose ends meet and merge into a tendon attached to the
skeleton (Fig. 1(b)).
• Each muscle includes several muscle fibre bundles which are
visible to the naked eye (Fig. 1(c)), which contain a varying
number (30-80) of muscle fibres or muscle cells (Fig. 1(d) and
Fig. 2) up to a few centimetres long with a diameter of 0.01 to
0.1 mm.
• The size and diameter of muscle fibres depends on age, type
and breed of animals.
• Between the muscle fibre bundles are blood vessels (Fig. 1(e))
as well as connective tissue and fat deposits (Fig. 1(f)).
• Each muscle fibre (muscle cell) is surrounded by a cell
membrane (sarcolemma) (Fig. 2,blue).
• Inside the cell are sarcoplasma (Fig. 2, white) and a large
number of filaments, also called myofibrils (Fig. 1(g) and Fig.
2, red).
• The sarcoplasma is a soft protein structure and contains
amongst others the red muscle pigment myoglobin. Myoglobin
absorbs oxygen carried by the small blood vessels and serves
as an oxygen reserve for contraction of the living muscle.
• In meat the myoglobin provides the red meat colour and plays
a decisive role in the curing reaction (see page 34).
 Changes of pH
• Immediately post-mortem the muscle contains a small
amount of muscle specific carbohydrate, called glycogen1
(about 1%), most of which is broken down to lactic acid
in the muscle meat in the first hours (up to 12 hours) after
slaughtering.
• This biochemical process serves an important function in
establishing acidity (low pH) in the meat.
• In the live animal glycogen is the energy reserve for
the muscles used as fuel for muscle contraction.
• The so-called glycolytic cycle starts immediately after
slaughter in the muscle tissue, in which glycogen, the main
energy supplier to the muscle, is broken down to lactic
acid.
• The build up of lactic acid in the muscle produces an
increase in its acidity, as measured by the pH. The pH
of normal muscle at slaughter is about 7.0 but this will
decrease in meat.
• In a normal animal, the ultimate pH (expressed as
pH24 = 24 hours after slaughter) falls to around pH 5.8-
5.4.
• The degree of reduction of muscle pH after
slaughter has a significant effect on the quality
of the resulting meat
• The typical taste and flavour of meat is only achieved
after sufficient drop in pH down to 5.8 to 5.4.
• From the processing point of view, meat with pH 5.6-
6.0 is better for products where good water binding is
required as meat with higher pH has a higher water
binding capacity.
• The pH is also important for the storage life of meat. The
lower the pH, the less favourable conditions for the
growth of harmful bacteria.
• Meat of animals, which had depleted their glycogen
reserves before slaughtering (after stressful
transport/handling in holding pens) will not have a
sufficient fall in pH and will be highly prone to bacterial
deterioration
 PSE and DFD (see Fig. 3)
• In stress susceptible animals pH may fall very quickly to
pH 5.8 – 5.6 while the carcass is still warm.
• This condition is found most often in pork.
• It can be recognized in the meat as a pale colour, a soft,
almost mushy texture and a very wet surface (pale, soft,
exudative = PSE meat).
• PSE meat has lower binding properties and loses weight
(water) rapidly during cooking resulting in a decrease in
processing yields.
• A reverse phenomenon may arise in animals which have
not been fed for a period before slaughter, or which have
been excessively fatigued during transportation and
lairage.
• In these cases, most of the muscle glycogen has been used
up at point of slaughter and pronounced acidity in the
meat cannot occur.
• The muscle pH24 does not fall below pH 6.0. This
produces dark, firm, dry (DFD) meat.
• Dark meat has a “sticky” texture. Less moisture loss
occurs during curing and cooking as a result of the higher
pH and the greater water-holding capacity but salt
penetration is restricted. Conditions for growth of
microorganisms are therefore improved resulting in a
much shorter “shelf life”.
• DFD conditions occur both in beef and pork.
• PSE and DFD conditions can to a certain extend be
prevented or retarded through humane treatment and
minimization of stress to animals prior to slaughter.
• PSE and DFD meat is not unfit for human consumption,
but not well suited for cooking and frying (PSE loses
excessive moisture and remains dry due to low water
binding capacity while DFD meat remains tough and
tasteless due to the lack of acidity).
• PSE meat can be added to meat products, where water
losses are desirable, such as dry-fermented sausages,
while DFD meat can be used for raw-cooked products
(frankfurter type) where high water binding is required.
 Meat colouring
• The red pigment that provides the characteristic colour of meat is
called myoglobin.
• Similar to the blood pigment haemoglobin it transports oxygen in the
tissues of the live animal.
• Specifically, the myoglobin is the oxygen reserve for the muscle cells
or muscle fibres.
• Oxygen is needed for the biochemical process that causes muscle
contraction in the live animal.
• The greater the myoglobin concentration, the more intense the colour
of the muscle.
• This difference in myoglobin concentration is the reason why there is
often one muscle group lighter or darker than another in the same
carcass.
Myoglobin concentration in
muscles also differs among animal
species.
 Beef has considerably more
myoglobin than pork, veal or lamb,
thus giving beef a more intense
colour (Fig. 4).
The maturity of the animal also
influences pigment intensity, with
older animals having darker
pigmentation
 Water holding capacity
• The water holding capacity (WHC) of meat is one of
the most important factors of meat quality both from
the consumer and processor point of view.
• Muscle proteins are capable of holding many water
molecules to their surface.
• As the muscle tissue develops acidity (decrease of
pH) the water holding capacity decreases (Fig. 5, 429,
430).
Water bound to the muscle
protein affects the eating and
processing quality of the meat.
 To obtain good yields during
further processing including
cooking, the water holding capacity
needs to be at a high level (except
for uncooked fermented and/or
dried products which need to lose
water during processing.
• Water holding capacity varies greatly among
the muscles of the body and among animal
species.
• It was found that beef has the greatest capacity
to retain water, followed by pork, with poultry
having the least.
 Tenderness and flavour
• Meat tenderness plays an important role, where entire pieces
of meat are cooked, fried or barbecued.
• In these cases some types of meat, in particular beef, have to
undergo a certain ripening or ageing period before cooking
and consumption in order to achieve the necessary tenderness
(Fig.6).
• Many meat products are composed of comminuted meat, a
process where even previously tough meat is made palatable.
• The taste of meat is different for different animal species.
However, it may sometimes be difficult to distinguish the
species in certain food preparations.
• For instance, in some dishes pork and veal may taste similar
and have the same chewing properties. Mutton and sometimes
lamb has a characteristic taste and smell, which originates
from the fat.
• Even small quantities of fat, e.g. inter- and intramuscular fat,
may imprint this typical smell and taste on the meat,
particularly of meat from old animals.
• Feed may also influence the taste of meat (e.g. fish meal).
• In addition, the sex of the animal may also give a special taste
and smell to the meat.
• The most striking example is the pronounced urine-like smell
when cooking old boar’s meat.
• Meat fit for human consumption but with slightly
untypical smell and flavour, which may not be suitable
for meat dishes, can still be used for certain processed
meat products.
• The typical desirable taste and odor of meat is to a great
extend the result of the formation of lactic acid (resulting
from glycogen breakdown in the muscle tissue) and organic
compounds like aminoacids and di- and tripeptides broken
down from the meat proteins.
• In particular the aged (“matured”) meat obtains its
characteristic taste from the breakdown to such substances.
 Animal fats
• Fatty tissues are a natural occurring part of the meat
carcass. In the live organism, fatty tissues function as
 Energy deposits (store energy)
 Insulation against body temperature losses
 Protective padding in the skin and around organs,
especially kidney and heart.
• Fatty tissue is composed of cells, which like other
tissue cells, have cell membranes, nucleus and cell
matrix, the latter significantly reduced to provide
space for storing fat.
• In the animal body there are subcutaneous fat
deposits (under the skin) and fat deposits
surrounding organs (e.g. kidney, heart) .
• Fat deposits between the muscle fibre bundles of a
muscle are called intramuscular fat and lead in higher
accumulations to marbling.
• Marbling of muscle meat contributes to tenderness
and flavour of meat.
CHEMICAL COMPOSITION OF MEAT
• In general, meat is composed of water, fat, protein,
minerals and a small proportion of carbohydrate.
• The most valuable component from the nutritional and
processing point of view is protein.
• Muscle is the principal component of meat and meat is
the post-mortem aspect of muscle.
• Thus, chemical composition of muscle is reflected in
the proximate composition of meat.
• There is a wide variation in meat composition from
different animals as depicted in table below
 Composition of different species meat
Meat source Protein% Moisture% Fat% Ash%
Beef 21 72 6 1
Chicken 20-23 74-76 2 1
Lamb 18 71.5 9 1.5
Pork 18 77 4 1
Veal 20 75 4 1
• Protein contents and values define the quality of the raw meat
material and its suitability for further processing.
• Protein content is also the criterion for the quality and value of the
finished processed meat products.
• The value of animal foods is essentially associated with their content
of proteins.
• Protein is made up of about 20 aminoacids.
• Approximately 65% of the proteins in the animal body are skeleton
muscle protein,about 30% connective tissue proteins (collagen,
elastin) and the remaining 5% blood proteins and keratin (hairs,
nails).
 Water
• Muscle contains approximately 75 per cent water
(ranges from 65 to 80%) by weight.
• Water is the principal constituent of the extra cellular
fluid and numerous chemical constituents are
dissolved or suspended in it.
• Because of this, it serves as the medium for the
transport of substances between the vascular bed and
muscle fibers.
 Meat Protein

• Generally lean meat contains 16 to 22 per cent

protein.
• Meat proteins are superior to plant protein because
proteins of high biological value are present in meat
in a concentrated form.
• Muscle proteins are broadly divided into following
three categories:
 1. Soluble in water or dilute salt solutions (the
sarcoplasmic proteins)
2. Soluble in concentrated salt solutions
(myofibrillar proteins) Moisture (%)
3. Insoluble in salt solution at low temperature
(proteins of connective tissue and other
fom~ed structures)
• Myoglobin, hae~noglobin and various enzymes
constitute sarcoplasmic protein,
• whereas. ~myofibrillar proteins comprise of actin,
myosin, tropomyosin, troponin, a, p and Y -actinin,
C-proteins, M-proteins etc.
• Major connective tissue proteins are collagen,
elastin and reticulin.
• We have already studied that proteins are made up of
amino acid chain and 20 amino acids are very common.
• Animals can not synthesize amino group which forms
amino acid.
• Therefore, proteins must be provided in the diet of animal
• so that they can synthesize their own amino acids.
• Meat proteins are rich source of essential amino acids viz.,
phenylalanine, valine, tryptophan, threonine, methionine,
leucine, isoleucine and ly sine which are very much
essential for human.
 Meat Fat
• The fat content of meat varies greatly from
species to species (ranges approximately 1.5
to I 3 per cent).
• Fat is found in meat as intracellular deposit or
as marbling or intramuscular in the adipose
tissue depots associated with the loose
connective tissue septa between the bundles.
• Meat fats are generally simple triglyceride in
Composition of Meat nature, but beef and mutton have
mixed triglycerides.
• Caloric value of fat depends on fatty acid composition.
• Meat mainly contains saturated and mono unsaturated
fatty acids.
• Commonly occurring saturated fatty acids of meat are
palmitic acid and stearic acid.
• Oleic, linoleic and linolenic acids are major
unsaturated fatty acids in meat.
Compositionof amino acids of different
meats
 4 Carbohydrates in Meat
• Though carbohydrate is a minor component of animal
tissues in terms of overall composition, but it plays a very
important role in conversion of muscle to meat.
• Main carbohydrate of meat is glycogen which is a polymer
of glucose.
• It is found particularly in the muscle and organ meat like
liver.
• In well fed animals, liver contains 50 mg glycogen per
gram of liver tissue.
• Generally 10-20mg of glycogen is present in 1 gram of
muscle
• In fasting stage of animal before slaughter, liver
glycogen is converted into glucose to maintain blood
glucose concentration at a constant level.
• In anaerobic condition, muscle glycogen is used to
produce energy for contraction and then broken down
to lactic acid.
• The post-mortem changes and onset and completion
of rigormortis greatly depend on glycogen reserve of
the muscle.
• Other carbohydrates present in meat are
mucopolysaccharides associated with the connective
tissues, glucose and intermediates of glycolytic
metabolism like lactic acid, acetoacetic acid.
 Minerals in Meat
• Numerous minerals of physiological significance are
present in meat.
• Meat contains sodium, potassium, magnesium,
chlorine, phosphorus, iron, calcium, sulphur etc.
• It is a very good source of iron because 100 grams of
cooked meat supplies 35 per cent of daily iron
recommendation.
• 100 grams of liver supplies almost 100 percent of
iron recommendation for an adult human
• Iron is present as haernoglobin, Composition of Meat
myoglobin and certain other enzymes in animal
tissues.
• Calcium is mainly present in bone and teeth of the
animal, but its concentration in muscle and other
edible tissues is not sufficient to meet the
recommended daily allowance.
Mineral content of raw meat (mgI100 gram
meat)
Mineral Lamb Pork Beef

Sodium 75 70 65
Potassium 295 385 355
Magnesium 15 18 18
Iron 1.2 2.3 2.8
Calcium 10 9 11
Phosphorus 147 145 171
 6 Vitamins in Meat
• Generally lean meat is an excellent source of B-
complex group of vitamins but is a poor source of fat
soluble vitamins like A, D, E and K and water soluble
vitamin C.
• Meat fats provide these fat saluble vitamins to some
extent. Certain organ meats contain vitamin C in
minor quantities.
• All of the B-complex vitamins are present in meat
and in a concentrated fortn in liver.
• Contents of Bcomplex group vary among different
species meats.
• Pork is superior to beef, veal, lamb or poultry meat
in terms of containing Bcomplex vitamins
• Thiamin content of pork is 8- 10 times higher than other
meats but its vitamin B,, content is less than other.
• Liver of any animal is a - good source of vitamin B, i.e.,
thiamin.
• During cooking, some of these water soluble vitamins
are lost.
• Generally, 100 grams of cooked meat supply 25-60 per
cent of recommended (RDA) B-complex vitamins.
Vitamin Content of Various Raw Meats (per
100 gram)
Vitamin Beef Pork Mutton
A(I.U) Trace Trace Trace
B1 Thiamin(mg) 0.07 1.0 0.15
B2 riboflavin(mg) 0.20 0.2 0.25
Nicotinic Acid(mg) 5 5 5
Pantothenic Acid(mg) 0.4 0.6 0.5
Biotin(mg) 3 4 3
Folic Acid(mg) 10 3 3
B6(mg) 0.3 0.5 0.4
B12 (mg) 2 2 2
C or Ascorbic acid 0 0 0
(mg)
D(I.U) Trace Trace Trace
Other Minor Components of Meat
• Besides the above mentioned components of meat,
there are also some non-protein nitrogenous
substances like nucleotides, and peptides etc.
• Nucleotides like adenosine monophosphate (AMP),
adenosine diphosphate (ADP), adenosine
triphosphate (ATP), nicotinamide adenine
dinucleotide (NAD) play an important role in
conversion of muscle to meat.
• They are also important in the development of meat
flavour as they act as flavour enhancers.
• Peptides like carnosine and anserine are
present in all species but anserine is present
especially in some birds and balenine in pig
muscle.
• These contribute to buffering capacity of meat and
flavour of meat.
• Creatine and creatinin also play important role in
post-mortem changes of meat.
 FACTORS AFFECTING COMPOSITION OF
MEAT
• Meat obtained from all type of meat animals of all
age groups and both sexes are not same from the view
point of chemical composition.
• Following factors influence the composition of meat:
Species Training and Exeruise
Breed Plane of Nutrition
Sex
Age
Anatomical Location of Muscles
 Species
• Species of meat animal affects the composition of meat
greatly.
• It is also evident from the composition of different species
meat.
• For example, total nitrogen content (fat-free) i.e., nitrogen
factor for pork has ranged from 3.45 to 3.6,
• for mutton it is 3.50 and for beef it ranges from 3.4 to
3.65.
• Again, pig muscles have more linoleic acid than cattle or
sheep whereas sheep muscles have relatively higher
content of stearic acid.
 Breed
• Breed exerts important intrinsic influence on
biochemical composition of muscle as we1 l as meat.
• For example, intramuscular fat percentage is greater
in case of beef cattle (i.e., cattle reared for meat
purpose) than that of dairy cattle (i.e., cattle reared for
milk purpose).
• Duroc pig has higher content of saturated and
monounsaturated fatty acids and lower
polyunsaturated fatty acids in intramuscular fat than
British Landrace pig.
 Sex
• Chemical composition of meat also varies with
the sex of the meat animal.
• Generally, intranscular fat content of male
animal is less than female and that of castrated
animal is more than the sexually entire
animals.
 Age
• The composition of meat varies with the
advancement of age of the meat animal irrespective
of species, breed and sex.
• There is a trend of general increase in most
parameters other than water with the increasing age.
• With increasing age, there is great increase in
intramuscular fat and in myoglobin content, lesser
increase in total and sarcoplasrnic nitrogen and the
decrease in moisture.
• Connective tissue content of muscle varies greatly
with the age of the animal.
• In young, salt soluble collagen concentration is
higher than the adult one because the degree of
intra and intermolecular cross-linking between
the polypeptide chains in collagen increases
with increasing animal age.
 Anatomical Location of Muscles
• Anatomical location of muscles is the most complex
intrinsic factor affecting the composition of meat.
• Certain chemical parameters of beef muscles from
different anatomical locations are given in the
following Table.
 Chemical parameters of various beef
muscles
Muscle Moisture (%) Intramuscular Total Nitrogen Hydroxy
fat(%) (% fat free) procline(ng/g
Longissimus 76.51 0.56 3.54 520
dorsi(lumbar)
Psoas 77.34 1.46 3.3 350
Triceps(lateral 77.23 0.73 3.45 1000
head)
 Training and Exeruise
• Composition of meat also dependa on training and
exercise of the animals to some extent.
• The muscles which are used more during exercise and
training, are darker in colour due to more myoglobin
codtent.
• Systematic training over a period of time results in
increased stores of muscle glycogen and ultimately
leads to lower ultimate pH (post-mortem).
 Plane of Nutrition
• Level of nutrition affects the composition of meat as it
has a general effect on the growth of the meat animals.
• Fat of the animals which are maintained on a high
plane of nutrition, is synthesized from carbohydrates
and this fat has lower iodine number.
• In poorly fed and emaciated animals, linoleic acid is
more and palmitic acid is less.
• If pigs are fed with high level of unsaturated fat, then
there will be deposition of unsaturated intramuscular
fat in their body
• In sheep, high plane of nutrition increases the
content of intramuscular fat and decreases
moisture percentage.
• Undernutrition leads to marked increase in the
water content of muscles, increase in the
percentage of intramuscular collagen and
decrease in salt-soluble and acid-soluble
components.