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COOKING OF MEAT | Physics and Chemistry


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Muscle tissue contains approximately 75% of water and 20% of protein consisting of sarcoplasmic, myofibrillar, and connective-tissue proteins. During heating, the thermal denaturation of the meat proteins occurs. According to differential scanning calorimetry measurements, a-actinin denatures at 50 °C; myosin and actomyosin between 54 and 58 °C; sarcoplasmic proteins between 65 and 67 °C; actin between 80 and 83 °C; tropomyosin and troponin at above 80 °C; and titin at 75.6 °C (in beef) or 78.4 °C (in pork). Generally, during heating the globular (sarcoplasmic) proteins expand and fibrous (myofibrillar) proteins contract. The intramuscular collagen fibers shrink in the range of temperature 53–65 °C and gelatinize on further heating (70–80 °C). The structural changes in the meat proteins on heating lead to alterations in the eating quality of meat.
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Physics and Chemistry
K Palka and E W˛esierska, University of Agriculture, Kraków, Poland
r2014 Elsevier Ltd. All rights reserved.
This article is a revision of the previous edition article by K Palka, volume 2,
pp 567570, © 2004, Elsevier Ltd.
Meat is a complex structure composed of muscle bers,
extracellular matrix, lipids, and water. The meat proteins are
the main constituents that form the structure of the meat
product. During heating they undergo signicant structural
changes and therefore the quality of the meat, mainly inu-
enced by the meat structure, also changes signicantly. Among
the sarcoplasmic meat proteins there are globular proteins
and enzymes. A typical example of globular proteins is myo-
globin responsible for meat color. At increased temperatures
the hydrophobic side chains of the compact globular proteins,
in the aqueous environment, undergo expansion and partial
unfolding, followed by association of unfolded proteins.
The large degree of protein association decreases their solu-
bility and precipitates are formed. If, however, the three-
dimensional network is formed, a gel sets. These gels bind the
water and are solid-like in their mechanical behavior. The -
brous proteins (actin, myosin, titin, collagen) have a lot of
hydrogen bonds and show electrostatic interactions that keep
the molecules in register in the large building blocks, which in
turn are broken during heating. The brous proteins contract
on cooking in contrast to the globular proteins, which expand.
Physicochemical processes that occur in the meat tissue during
heating, causing signicant changes in the spatial arrangement
of the meat proteins, affect the nal physicochemical and
sensory properties of the heated meat.
The method of heating is important too. For the same raw
material, to achieve equivalent denaturation of proteins, more
energy is needed during fast (40 °C min
) than during slow
(5 °C min
) heating. Different heating rates dictate the rate of
enzymatic and chemical reactions in the meat. They inuence
the conformation of the meat proteins, enzyme activity,
solubility, and hydration and lead to thermal and hydrolytic
rupture of peptide bonds, thermal degradation, and derivati-
zation of amino acid residues, cross-linking, oxidation, and
formation of sensory-active compounds. Most of those re-
actions can be reected in the meat as either desirable or
detrimental changes in color, avor, juiciness, rheological
properties, and enzyme activity, depending on the various
combinations. These processes are affected by the temperature
and time of heating, pH, oxidizing compounds, antioxidants,
radicals, and other reactive constituents, especially reducing
The susceptibility of the meat proteins to thermal de-
naturation depends on their structure, predominantly on the
number of cross-links, but also on the simultaneous action of
other denaturing agents. Salt bridges, side chain hydrogen
bonds, and a large proportion of residues in α-helical con-
formation increase the thermal stability of proteins. The sta-
bilizing effect is related to heating temperature. On the one
hand, thermal changes cause a decrease of solubility due to
aggregation of the myobrillar proteins, but on the other
hand, they lead to an increase in solubility as a result of the
degradation of tertiary protein structures of intramuscular
collagen. Further effects of heating are gel formation (in most
types of sausages and meat products), hydrolytic changes, al-
teration in the rate of proteolysis, and modication of the
nutritive value.
Chemical Changes in Meat Protein Systems
During heating of meat, conformational changes (heat
denaturation) of the protein systems occur. These changes
take place at a particular temperature, called the denaturation
temperature. The next step in the structural changes during
heating of meat are the proteinprotein interactions resulting
in loss of solubility and aggregation.
Sarcoplasmic Proteins (30% of Total Meat Proteins)
Most of the sarcoplasmic proteins denature between 40 and
67 °C, but their heat aggregation may extend up to 90 °C. The
aggregated sarcoplasmic proteins can form a gel between the
structural meat elements in such a way that they have a role in
the texture of the heated meat. This fraction of proteins also
includes enzymes. Some of them have a tenderizing effect.
During heating of the beef muscles at a temperature below
60 °C for a long time (heating rate of 0.1 °C min
), the col-
lagenases remain active in the meat, and tenderizing effect is
achieved after 6 h, whereas they are inactived at faster heating
at the end temperature of 7080 °C.
Myobrillar Proteins (65% of Total Meat Proteins)
Heating of these proteins to a temperature of 65 °C causes a
progressive increase of the surface hydrophobicity, whereas at
higher temperatures it decreases again. This suggests that a part
of the hydrophobic residues participates in proteinprotein
interactions leading to formation of aggregate network. Ac-
cording to differential scanning calorimetry measurements,
α-actinin is the most labile and becomes insoluble at 50 °C;
myosin and actomyosin denature between 54 and 58 °C; actin
between 80 and 83 °C; tropomyosin and troponin at above
80 °C; and titin from pork and beef at 78.4 °C and 75.6 °C,
The heat denaturation of myobrillar proteins in solution
usually results in a gel formation. It is caused by the fact that
especially myosin forms gels at a very low concentration (0.5%
w/w), compared to sarcoplasmic proteins (3% w/w). For
puried myosin, the rmest gels are reached at 45 °C and pH
Encyclopedia of Meat Sciences, Volume 1 doi:10.1016/B978-0-12-384731-7.00128-8404
5.5 or at 60 °C and pH 6. Ionic strength and pH are important
factors determining monomeric or lament structure of the
myosin. At ionic strengths above 0.3 and at neutral pH, the
myosin molecules are dispersed as monomers, forming a
coarse network with large pores. At lower ionic strength the
myosin molecules are assembled in laments, and give a r-
mer gel. On heating, the gel formation of puried myosin
occurs in two steps, in two separate temperature regions. The
rst part of the reaction (aggregation of the globular heads of
myosin) occurs between 30 and 50 °C. The second stage
(above 50 °C), connected with the structural changes in the
helix structure of the myosin tails, leads to a network for-
mation, where hydrophobic groups interact with each other.
For the chicken-derived salt soluble myobrillar proteins (SSP)
heated in 0.6 M NaCl at pH 6, protein unfolding is observed at
3032 °C, proteinprotein association at 3640 °C, and gel-
ation at 4550 °C. A lower degree of aggregation, better water-
holding, and greater softness characterize the breast SSP gels,
whereas a higher degree of aggregation and more hardness
characterize the leg SSP gels.
Connective Tissue Proteins (5% of Total Meat Proteins)
The thermal denaturation of the meat collagen occurs in two
steps. The rst stage of the reaction is its shrinkage observed in
the range of 5365 °C. It involves the breakage of hydrogen
bonds loosing up the brillar structure followed by the con-
traction of the collagen molecule up to one-quarter of its
resting length. The second stage (gelatinization), running at
approximately 7080 °C, is connected with the breaking of
heat-unstable intermolecular bonds. The degree of collagen
shrinkage increases with the quantity of heat-stable (mature)
links. In young animals the epimysium contains primarily
heat-labile cross-links, the perimysium a mixture of heat-labile
and heat-stable, and the endomysium of heat-stable cross-
links. With increasing animal age, the amount of the heat-
stable cross-links in the meat increases. Their higher levels lead
to a development of greater tension in the connective tissue
during heating. The shrinkage temperature of epimysial col-
lagen is usually higher than that of other connective-tissue
membranes in the muscle. The observations made by scanning
electron microscopy (SEM) indicate that after heating of bo-
vine sternomandibularis muscles at the temperature of 60 °C
and 80 °C for 1 h, the epimysium does not show large chan-
ges, whereas the perimysial and endomysial collagen become
granular at 60 °C and start to gelatinize at 80 °C. There are also
differences in solubilization between different types of colla-
gens. The highest thermal stability occurs in collagen of the
endomysium, due to the large contribution of disulde bonds
in type IV collagen. The gelatinization of the intramuscular
collagen depends also on the time of postmortem ageing of
the meat, that probably results from changes in proteoglycans.
In the 12-day-aged bovine semitendinosus (ST) muscles
solubility of collagen is twice as high as in that aged for 5 days.
During heating of the 5 day-aged bovine ST muscles by two
methods in the range of temperatures between 50 and 100 °C,
most of the soluble collagen is found at 70 °C during retorting
and at 80 °C throughout roasting. During roasting of ST, when
the temperature increases up to 90 °C, quantity of soluble
collagen decreases in the meat aged for 5 days remaining at the
same level in the 12 day-aged meat. Therefore, differences in
the thermal collagen solubility of the intramuscular connective
tissue are a consequence of differences in the proportion of
the collagen types, the level of heat-stable cross-linking, and
the level of glucosaminoglycans in the structure, as well as the
time of postmortem ageing and the method of heating.
Heating also causes changes in pH, reducing activity, ion-
binding properties, and enzyme activity. Slight upward change
of pH (approximately 0.3 units) results from exposure of re-
active groups of histidine. Increased reducing activity develops
due to unfolding of the protein chains and exposition of sul-
phydryl groups. Conformational changes in proteins cause
their ability to bind various ions, such as Mg
and Ca
Severe heating of the proteinaceous foods leads to a
development of color and avor compounds due to Maillard
reactions and to thermal degradation of methionine and
cysteine residues as well as other low-molecular weight
The meat fat melts during heating. Solubilization of col-
lageneous connective tissue provides channels through which
melted fat may diffuse, as a component of thermal leak.
Water-Holding Capacity
The raw meat contains 6975% of water. Heating induces
structural changes, which cause a decrease in water-holding
capacity (WHC) of the meat. As the internal meat temperature
increases, the WHC of meat decreases due to thermal de-
naturation of the meat proteins, especially myosin, which
plays a signicant role in water binding. During heating of
meat, depending on the method, the amount of water de-
creases to 65% at internal temperature of 70 °C and to 60% at
90 °C. The water retention in the heated meat inuences the
quantity of the other basic constituents. The loss of water
during heating of meat results from both evaporation and
exudates. The uid is drained by gravity from the cut surface of
the meat, if the viscosity of the exudate is low enough and the
capillary forces do not retain it. The loss of uid arises pre-
dominantly from the longitudinal channels through the meat
between the ber bundles. In the raw muscle most of the water
(80%) is held within the myobrils. There are only changes in
the water distribution, if the myobrils change in volume. The
bers and ber bundles shrink when their constituents
(myobrils) shrink, giving rise to the two extracellular uid
compartments around bers and ber bundles. The transverse
shrinkage to the ber axis, occuring mainly at 4060 °C,
widens the gap between the bers and endomysium. At 60
70 °C the connective tissue network and the muscle bers
cooperatively shrink longitudinally. This shrinkage causes the
highest increase in water losses during heating. For the sam-
ples of heated meat, the amount of water around ber bundles
increases up to 50 °C, in comparison with the raw meat, which
seems to be in accordance with the transverse shrinkage of
bers and ber bundles. Above 50 °C, these widened gaps
diminish up to 70 °C, probably mainly due to the shrinkage of
the connective tissue. The increase in extracellular space from
70 to 90 °C may be connected with a swelling of the
Cooking of Meat |Physics and Chemistry 405
perimysium and solubilization of the intramuscular collagen,
which occur at this range of temperature.
The extent of the loss of the uid depends on the WHC of
the tissue and the degree of its marbling. The highly marbled
meat shrinks less during heating and remains juicier than the
lower marbled meat. The subcutaneous fat also reduces
moisture losses during dry heating (roasting).
The structural origin of water-holding in the whole meat
and in the highly comminuted products is different. In the
rst, the crucial factor is the shrinkage or swelling of the
myobrils, and in the comminuted meat products, the ability
of the meat proteins to form different types of gels. The
comminution of meat with salt addition leads to solubiliza-
tion of the meat proteins, which exists as a protein gel after
heat treatment. The higher amounts of the soluble myobrillar
proteins create a dense protein network that holds more water.
Effects of Heating on Meat Microstructure
When the meat proteins are exposed to heating, they rst lose
their tertiary structure and undergo several changes in con-
guration. In general, thermal denaturation leads to a loss in
protein solubility. These chemical changes are also associated
with changes in the physical character of the meat tissues.
Elastin, however, is not susceptible to effects of heat. The
transverse shrinkage to the ber axis occurs at 4060 °C, which
widens the gap already present at rigor between the bers and
their surrounding endomysium. There is a controversy re-
garding these observations. Some authors found no changes in
the cross-sectional area on cooking of the neck muscle,
whereas others found that the transverse shrinkage of both
bers and ber bundles of bovine psoas major muscle starts at
approximately 40 °C. There is also a disagreement between the
results presented in the literature with regard to the tempera-
ture, in which the longitudinal shrinkage of the ber starts.
Some observations indicate that bers do not shorten below
60 °C, and the others, that both sarcomere shortening and
ber shortening usually begin at temperatures of 4050 °C.
The divergence in the results may be due to the large biological
diversity within a muscle as well as between different muscles.
At 6070 °C the connective tissue network and the muscle
bers shrink. This is mainly based on the fact that the peri-
mysial collagen shrinks at approximately 64 °C.
In the bovine ST muscles aged for 5 or 12 days and roasted
to internal temperatures in the range of 5090 °C and then
Figure 1 Connective tissue changes on heating. SEM micrographs of perimysium and endomysium from bull ST muscle: after ageing for 5 days
at 4 °C and roasted to 70 °C (a) and to 90 °C (b); after ageing for 12 days at 4 °C and roasted to 70 °C (c) and to 90 °C (d). Reproduced from
Palka, K., 2003. The inuence of post-mortem ageing and roasting on the microstructure, texture and collagen solubility of bovine semitendinosus
muscle. Meat Science 64, 191198.
406 Cooking of Meat |Physics and Chemistry
visualized using SEM, no signicant structural changes are seen
at the internal temperature of 50 °C. However, in the range
between 60 and 90 °C, signicant changes occur both in the
myobrils and in the intramuscular connective tissue, and this
is further affected by the degree of postmortem ageing. The
changes in the connective-tissue structure of perimysium and
endomysium during roasting of the 5-day-aged bull ST mus-
cles to 70 °C are shown in Figure 1(a) and to 90 °CinFigure 1
(b), for the 12 day-aged muscle, the changes are shown in
Figure 1(c) and (d), respectively. The granulation of perimy-
sium and the cracks of endomysium tubes are observed in 5
day-aged meat roasted to an internal temperature of 8090 °C
(Figure 1(b)), however, in 12 day-aged meat after roasting to
6070 °C(
Figure 1(c)). The changes in the myobrillar
structure during roasting of the 5-day-aged bull ST muscles to
70 °C are shown in Figure 2(a) and to 90 °CinFigure 2(b),
whereas for the 12 day-aged muscle in Figure 2(c) and (d).In
the 5 day-aged samples the disintegration of the myobrillar
structure starts at 70 °C(
Figure 2(a)) and is considerable at
90 °C(
Figure 2(b)). In the 12 day-aged meat roasted to 70 °C
(Figure 2(c)), the degree of structural destruction is similar
to that of 5 day-aged meat roasted to 90 °C(Figure 2(b)). At
90 °C complete disintegration of the myobrillar structure of
12 day-aged meat is observed (Figure 2(d)).
As the endpoint temperature increases from 50 to 60 °C,
there is a signicant decrease in the ber diameter. As the
heating temperature is raised, the sarcomere length decreases,
the effects being greater in the aged meat. The larger structural
changes observed during roasting of the more aged meat may
be a consequence of the changes during ageing in both the
cytoskeletal proteins and the intramuscular connective tissue,
leading to a weakening of the transversal and longitudinal in-
tegrity of the muscle bers. In general, the microstructural
changes are considerably less in the meat heated after 5-day
ageing in comparison with the meat heated after 12-day ageing.
There is a high negative correlation (r¼0.97) between
changes in the sarcomere length and the cooking losses during
heating of the bovine ST at the temperature range of 50120 °C
(Figure 3).
Texture and Tenderness of Heated Meat
The rheological properties of meat result from changes in
proteins, with the texture of the meat being affected mainly by
the quantity and cross-linking of collagen; the morphological
structure of the meat tissues; the biochemical state of the
Figure 2 Myobrillar changes on heating. SEM micrographs of myobrils from bull ST muscle: after ageing for 5 days at 4 °C and roasted to
70 °C (a) and to 90 °C (b); after ageing for 12 days at 4 °C and roasted to 70 °C (c) and to 90 °C (d). Reproduced from Palka, K., 2003. The
inuence of post-mortem ageing and roasting on the microstructure, texture and collagen solubility of bovine semitendinosus muscle. Meat
Science 64, 191198.
Cooking of Meat |Physics and Chemistry 407
muscle pre- and postrigor; and the mechanical disintegration
of the muscle structure.
The hardening of the myobrillar structure and the gelat-
inization of the intramuscular collagen depend on the extent
of the postmortem changes (ageing) related to the time-
temperature regime. Generally, hardening of meat is observed
throughout the heating. The rst increase of meat hardness
that occurs after heating in the range of 4065 °C is mainly
due to sarcoplasmic and actomyosin complex protein de-
naturation. A contribution of intramuscular connective tissue
to the changes of toughness is relatively small, although heat-
induced shrinkage of endomysium occurs. This is because
the endomysium is an amorphous, nonbrous sheet. How-
ever, some authors observed an increase in tenderness
of the meat heated up to approximately 50 °C. The reason for
this is probably the fact that the applied stress during mas-
tication is reduced by viscous ow in the uid-lled channels
in between bers and ber bundles. The viscous ow then
becomes lower as the elasticity of the meat increases in that
temperature region. At above 65 °C elasticity acts adversely
and impairs the tenderness, WarnerBrazler (WB) shear
force increases signicantly. The further hardening that occurs
at 6575 °C is connected with the drastic shrinking of the
perimysium and continuation of the myobrillar compo-
nent shrinking. In the range of 7580 °C, there is further
shrinkage and dehydration of the actomyosin component.
The collagen bers begin to granulate, which can result in
crispness of the perimysium. At this time the combining ef-
fects of the myobrillar component and the perimysium are
observed, and the increase in WB shear force becomes lower,
compared with the second phase. At higher temperatures
(8090 °C), the overall inuence of thermal-induced changes
in the intramuscular connective tissue is a tenderizing effect,
whereas the changes in myobrillar proteins result in a
toughening effect.
Meat hardness depends on the ber size and the degree of
sarcomere shortening during heating to 70 °C through tension
caused by collagen bers (mainly endomysium) shortening.
This is also inuenced by many of the differences in the
histological structure and the amount of the collagen bers
type III and type I as well as differences in the collagen cross-
linking. For example, mechanical resistance of the perimysium
at the interface with the endomysium mostly affects hardness
of the heated meat, whereas endomysium shrinkage may re-
sult in a tightening of the structure and squeezing out of
intramuscular water. Prolonged heating of meat (46h) at
relatively low temperatures (5060 °C) improves tenderness
because of enzyme activity up until 60 °C.
Drip loss ranging from 20% to 40% of the original weight
and shrinkage also has an effect on rheological properties.
Meat with a high pH has lower cooking losses and is more
tender after heating.
For the bovine ST and psoas major muscles at the same stage
of ageing, boiled (100 °C), roasted (170 °C), or fried (160 °C)
to the end temperature of 75 °C, WB shear force values are the
highest for boiled, middle for roasted, and the lowest for fried
muscles indicating that the method of heating is also important.
The sensory-evaluated toughness of the whole bovine
biceps femoris muscle decreases drastically in the range of
temperature from 55 to 60 °C, thereafter increases again up to
80 °C. For the comminuted meat products from the same
muscle, the hardness increases over the whole temperature range
and is signicantly lower than the toughness of the whole meat
at heating temperatures below 60 °C. It means that the spatial
arrangement of the bers is most important for the textural
properties of the meat and the comminuted meat products.
50 60 70 80 90 100 121
Sarcomere length (µm)
Cooking losses (%)
Temperature (°C)
Cooking losses Sarcomere length
Figure 3 Effect of heating temperature on cooking losses () and sarcomere length (–––) of beef ST muscle samples retorted after 5 days
ageing at 4 °C. Reproduced from Palka, K., Daun, H., 1999. Changes in texture, cooking losses, and myobrillar structure of bovine M.
semitendinosus during heating. Meat Science 51, 237243.
408 Cooking of Meat |Physics and Chemistry
See also:Chemical and Physical Characteristics of Meat:
Chemical Composition; Palatability. Connective Tissue: Structure,
Function, and Inuence on Meat Quality. Conversion of Muscle
to Meat: Glycolysis. Cooking of Meat: Cooking of Meat; Flavor
Development; Heat Processing Methods; Maillard Reaction and
Browning; Warmed-Over Flavor
Further Reading
Bailey, A.J., Light, N.D., 1989. Connective Tissue in Meat and Meat Products.
London: Elsevier.
Kołczak, T., Krzysztoforski, K., Palka, K., 2008. Effect of post-mortem ageing,
method of heating and reheating on collagen solubility, shear force and texture
parameters of bovine muscles. Polish Journal of Food and Nutrition Sciences 58
(1), 2732.
Kołczak, T., Pospiech, E., Palka, K., Ł˛acki, J., 2003. Changes of myobrillar and
centrifugal drip proteins and shear force of psoas major and minor and
semitendinosus muscles from calves, heifers and cows during post-mortem
ageing. Meat Science 64, 6975.
Laakkonen, E., 1973. Factors affecting tenderness during heating of meat. Advances
in Food Research 20, 257323.
Lawrie, R.A., 1998. Meat Science. Oxford: Pergamon Press.
Li, C.B., Zhou, G.H., Xu, X.L., 2010. Dynamical changes of beef intramuscular
connective tissue and muscle ber during heating and their effects on beef shear
force. Food Bioprocess Technology 3, 521527.
Nishimura, T., Hattori, A., Takahashi, K., 1996. Arrangement and identication of
proteoglycans in basement membrane and intramuscular connective tissue of
bovine semitendinosus muscle. Acta Anatomica 155, 257265.
Offer, G., Knight, P., 1988. The structural basis of water-holding in meat. In: Lawrie,
R. (Ed.) Developments in Meat Science, vol. 4. London: Elsevier, pp. 63243.
Offer, G., Knight, P., Jeacocke, R., et al., 1989. The structural basis of the water-
holding, appearance and toughness of meat and meat products. Food
Microstructure 8, 151170.
Palka, K., Daun, H., 1999. Changes in texture, cooking losses, and myobrillar
structure of bovine M. semitendinosus during heating. Meat Science 51,
Palka, K., 2003. The inuence of post-mortem ageing and roasting on the
microstructure, texture and collagen solubility of bovine semitendinosus muscle.
Meat Science 64, 191198.
Pospiech, E., Greaser, M.L., Mikołajczak, B., Chiang, W., Krzywdzinska, M., 2002.
Thermal properties of titin from porcine and bovine muscles. Meat Science 62
(2), 187192.
Purslow, P.P., 2002. The structure and functional signicance of variations in the
connective tissue within muscle. Comparative Biochemistry and Physiology Part
A 133, 947966.
Sikorski, Z.E., 2007. Proteins. In: Sikorski, Z.E. (Ed.), Chemical and Functional
Properties of Food Components. New York: CRC Press, pp. 155160.
Tornberg, E., 2005. Effects of heat on meat proteins Implications on structure and
quality of meat products. Meat Science 70, 493508.
Cooking of Meat |Physics and Chemistry 409
... Furthermore, the selection of the cooking method and final end-point temperature should be appropriate according to the muscle type and specific physical changes the muscle undergoes during heating. Cooking methods such as grilling, roasting, and frying lead to the solubilization of collagenous connective tissue, which results in the formation of channels through which moisture and melted fat can be lost (due to dripping) (Palka & Wesierska, 2014;Warriss, 2000) (refer to Section 3.2). Since the cooking method can introduce tenderness variation in meat products, many researchers have attempted to determine the cooking methods which are both precise and repeatable (McKenna et al., 2004). ...
... During the heating of meat, conformational and structural changes in the protein systems occur. These changes occur at the denaturation temperature and involve the transformation of a well-defined folded protein structure into an unfolded state (Palka & Wesierska, 2014). The chemical changes in the meat protein system are due to the molecular interactions that occur when thermal treatments are applied (Gómez et al., 2020). ...
... The gel formation of myosin occurs in two steps. At approximately 30-50 • C, the globular heads of myosin aggregate which leads to gel formation, and above 50 • C, the helix structure of myosin tails changes, which leads to further gel formation (Palka & Wesierska, 2014;Sharp & Offer, 1992). Generally, myosin forms the firmest gels at around 60 • C; however, the temperature may differ based on the pH u of the meat (Palka & Wesierska, 2014;Sharp & Offer, 1992). ...
Although many efforts have been made to improve and control the eating quality of meat, there is still high variability in palatability, which may ultimately result in customer dissatisfaction. Beef meat is especially intricate to study since consumers have specific preferences for degrees of doneness. The degrees of doneness in beef is known to affect its physicochemical properties and have a subsequent effect on palatability. Nevertheless, an in‐depth investigation into the exact changes that occur with increasing internal end‐point temperatures of meat is yet to be explored. With researchers implementing various cooking methods and cooking conditions (i.e., sample preparation and internal end‐point temperatures), the results of studies are often impossible to compare. This review provides an overview of the various benefits and drawbacks of the cooking methods commonly used at home, in commercial enterprises, and research on meat. Furthermore, the physicochemical changes in meat with increasing degrees of doneness are discussed in detail with considerations of the subsequent changes in the sensory properties of meat.
... Meat protein is usually denatured by heat in a temperature range of 50-85 • C [25]. Thermal denaturation of protein can also induce structural changes leading to an increase in protein surface hydrophobicity [26,27], a loss of protein solubility, and an increase in protein-protein aggregation [28]. According to BCA assay (Figure 2a), the data showed that at the intestinal phase, protein concentration of CB digested using M1 was significantly lower than that of CB digested using M2 (p < 0.05). ...
... in protein surface hydrophobicity [26,27], a loss of protein solubility, and an increase in protein-protein aggregation [28]. According to BCA assay (Figure 2a), the data showed that at the intestinal phase, protein concentration of CB digested using M1 was significantly lower than that of CB digested using M2 (p < 0.05). ...
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Chicken meat from spent laying hens (SHs) has been considered as nutritive as the meat of commercial broilers (CBs) based on chemical composition. High insoluble collagen in SH meat might reduce protein digestibility and bio-accessibility compared to CB meat. This study aimed at comparing the in vitro protein digestibility of CB and SH cooked breast meat. In the first part, CB samples were digested using two static in vitro digestion methods and collected at different digestion points for determining the degree of hydrolysis (DH). The method providing a greater DH value was chosen for comparing protein digestibility between CB and SH samples. The activities of used enzymes during in vitro digestion were evaluated based on bicinchoninic acid assay 2,4,6-trinitrobenzenesulfonic acid colorimetric method, gas chromatography-mass spectrometry, and sodium dodecyl sulfate-polyacrylamide electrophoresis. Particle size distribution of solid content collected from hydrolysate was also determined. The results showed that after digestion, CB showed 1–3 mg/mL protein concentration lower, while 7–13% DH and 50–96 µmoL/g protein-free NH2 groups higher when compared to those of SH. Based on sodium dodecyl sulfate-polyacrylamide electrophoresis, CB samples exhibited greater intensity of band at MW < 15 kDa than that of SH. Regarding particle size in terms of volume weighted mean (D[4,3]), at the end of the oral phase, the end of the gastric phase, and the beginning of the intestinal phase, D[4,3] of the SH samples were 133.17 ± 2.16, 46.52 ± 2.20, and 112.96 ± 3.63 µm, respectively, which were greater than those of CB (53.28 ± 1.23, 35.59 ± 1.19, and 51.68 ± 1.25 µm). However, at the end of the intestinal phase, D[4,3] of SH and CB, which were 17.19 ± 1.69 and 17.52 ± 2.46 µm, respectively, did not significantly differ from each other. The findings suggested a greater in vitro protein digestibility of cooked CB breast meats than that of SH ones.
... moisture content, can also be explained by the lower fat content. This is due to the fact that in the cooking loss, in addition to water loss due to protein denaturation [47], the fat loss is also measured [48]. ...
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Larger processing equipment to produce minced meat could affect its structure due to intensive processing and a high energy intake in the meat mass. To assess if this would result in alterations in the minced meat quality, finely chopped meat (FCM) was added in different concentrations (15, 30, 45, 60, 75, 90, and 100%) to minced meat and quality parameters were analyzed. FCM was used to simulate different intensity of an unintended destruction of meat cells due to various processes. The amount of non-intact cells (ANIC) was determined histologically and furthermore, soluble protein content, water holding capacity, mechanical and sensory texture, and scanning electron and confocal laser scanning microscopy was applied to analyze the meat structure and quality. ANIC indicated that even adding 15% FCM was statistically (p < 0.05) distinguishable from 100% minced meat and 30% FCM had already 50 Vol.-% ANIC. In contrast, the addition of 15% or 30% FCM did not result in significant differences in drip loss of raw and cooked meat as well as mechanical and sensory texture analysis. This study showed that intensive processing might be detectable via ANIC, but that the minced meat quality was not affected.
A major driver for consumer acceptability of meat is cooked texture, which encompasses descriptors such as tenderness, hardness, chewiness, and graininess. Cooked meat texture is determined by connective tissue, myofibrillar proteins, and related components, the contributions of which vary according to concentration, quaternary structure, and strength of intermolecular bonds. Sensory panel is the gold standard for determination of cooked meat texture, but is time-consuming, expensive, and samples of interest are destroyed in the process. Cooked meat texture therefore has been characterized by numerous mechanical technologies, the most popular of which is Warner-Bratzler shear force, although it also destroys the sample of interest. Cooked meat texture has most recently been described using visible and near-infrared light spectroscopy, which has shown substantial promise as a noninvasive, in-line predictive tool, and rapid evaporative ionization mass spectrometry (REIMS). Development of technology that effectively, accurately, and reproducibly predicts cooked meat texture from the raw product will rely upon understanding how meat components affect meat texture.
This study aims to build a model for predicting the hardness of meat products by considering their protein fractions and protein structural changes during production. Protein solubility is considered an indicator of protein structural changes. The obtained model results show that structural changes of sarcoplasmic and myofibrillar proteins occur during production. The gelling capacity is formed by the effect of the three protein fractions, namely myofibrillar, sarcoplasmic and stromal. The obtained model allows the prediction of the hardness of meat products based on their protein fraction contents with error below 5%, thus reaching a significant adjustment between real process data and the simulated model.
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Globular and fibrous proteins are compared with regard to structural behaviour on heating, where the former expands and the latter contracts. The meat protein composition and structure is briefly described. The behaviour of the different meat proteins on heating is discussed. Most of the sarcoplasmic proteins aggregate between 40 and 60 °C, but for some of them the coagulation can extend up to 90°C. For myofibrillar proteins in solution unfolding starts at 30-32°C, followed by protein-protein association at 36-40°C and subsequent gelation at 45-50°C (conc.>0.5% by weight). At temperatures between 53 and 63°C the collagen denaturation occurs, followed by collagen fibre shrinkage. If the collagen fibres are not stabilised by heat-resistant intermolecular bonds, it dissolves and forms gelatine on further heating. The structural changes on cooking in whole meat and comminuted meat products, and the alterations in water-holding and texture of the meat product that it leads to, are then discussed.
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Changes in myofibrillar protein content and centrifugal drip proteins of psoas major and minor (PM) and semitendinosus (ST) muscles of calves, heifers and cows taken from carcasses on the 1st, 6th and 12th day of post-mortem cold storage were estimated. Washed myofibrils and centrifugal drip from muscles were analysed using SDS-PAGE 10 and 12% polyacrylamide gels. No significant changes were observed in content of contractile proteins, α-actinin and regulatory proteins (except for TN-T). There were no significant differences between muscles from investigated groups and between muscles aged in chilled conditions. The levels of titin T1 during ageing varied slightly. The 30 kDa-fraction appearance was fastest in calf, slower in heifer and slowest in cow muscles. More pronounced differences in the level of protein degradation with regards to muscle type, age of animals and time of storage were found in the centrifugal drip of meat. In the drip, the level of high molecular weight proteins was higher in muscles from young animals and in the muscles stored longer. The opposite was observed in case of 26-28 kDa proteins. Their amount in muscle drip decreased with increased storage time. The rate of proteolysis and release of cytoskeletal proteins during cold storage of muscles were related to change in shear values of roasted meat. The highest rate of protein degradation was observed in PM calf muscle and the lowest rate in ST cow muscle. The fastest tenderization process was registered in calves muscles and the slowest tenderization in cows.
Chemical and Functional Properties of Food Proteins presents the current state of knowledge on the content of proteins in food structures, the chemical, functional, and nutritive properties of food proteins, the chemical and biochemical modification of proteins in foods during storage and processing, and the mutagenicity and carcinogenicity of nitrogenous compounds. It emphasizes the structure-function relationship as well as the effects of practical conditions applied in food processing on the biochemical and chemical reactions in food proteins and food product quality. The first ten chapters discuss structure-function relationships, methods of analysis of nitrogenous compounds, chemical and enzymatic modifications, nutritive roles, and mutagenicity and carcinogenicity of food proteins. The following six chapters describe the proteins of meat and fish, milk, eggs, cereals, legumes, oilseeds and single cell organisms, and present detailed information on the effects of conditions applied in storage and processing on the reactions in proteins and their impact on quality attributes of food products.
Research in recent years has revealed a fascinating world at the microscopic and molecular levels of muscle. This chapter is an attempt to bring together some of the findings and compare them with the results obtained from empirical studies in which meat has been cooked by different methods. To describe the total behavior of meat during cooking, it is necessary to review numerous detailed studies on various parameters of meat itself, as well as its response to heat. Several different biochemical reactions occur during the cooking process. Apparently, a well-cooked roast represents a well-balanced harmony of these reactions. In all biochemical reactions, both time and temperature are important. This is particularly true during meat cookery. Many factors influence the characteristics of cooked meat: Physiological maturity, fat content, enzymes, pH, postmortem age and contraction state, moisture-binding ability, behavior of proteins during heating, rate of temperature rise, and heating method. The tenderness of meat is influenced by the contraction state of the raw muscle. Thus, muscles that have not been able to shorten during storage after slaughter are tenderer than those that have contracted. If it were possible to develop a cooking method that would shrink the muscles as little as possible, the cooked meat could be tenderer. Usually tenderness is evaluated on cooked meat samples. However, cooking methods have varied in the reports found in the literature. As this chapter shows, it may be difficult to compare the results from different studies, unless a standard cooking method is developed. It seems necessary to give exact information of the cooking procedure before one is able to evaluate and compare the results. Possibly “the ideal temperature range” for a standard cooking procedure would be rather narrow.
Changes of meat shear force and its characteristics during cooking have been extensively studied, but great variability existed due to the cooking method among different studies. This study was designed to focus on the dynamic changes of beef intramuscular connective tissue (IMCT) and muscle fiber during water-bath heating and their effects on beef shear force. At 4 d postmortem, beef semitendinosus muscles were divided into 11 steaks and then cooked respectively to an internal temperature of 40, 50, 55, 60, 65, 70, 75, 80, 85, and 90°C (the remainder was not cooked as control). Collagen content and its solubility, transition temperature of perimysia and endomysia, fiber diameter, and Warner–Bratzler shear force values (WBSF) were determined. The results showed that fiber diameter decreased gradually during cooking, concomitant with the increases in filtering residue and WBSF. The maximum transition temperature (T max) of endomysial components was lower than that of perimysial components (50.2 vs. 65.2°C). Muscle fiber and IMCT (especially perimysia) shrank during cooking, resulting in the increase of WBSF when the internal temperature was lower than 75°C, but further cooking led to the disintegration of perimysial structure, lowing up the increase of WBSF between 75 and 90°C. For beef semitendinosus muscle, the internal temperature of 65°C is a critical cooking point where meat gets tougher.
Vacuum-packed slices of bovine semitendinosus (ST) muscle were retorted to internal temperatures of 50, 60, 70, 80, 90, 100, and 121°C. Changes in texture of the meat were evaluated by measurements of Texture Profile Analysis (TPA) parameters. Changes in microstructure were evaluated using a Scanning Electron Microscope (SEM) and measuring fibre diameter and sarcomere length. Cooking losses were also estimated. During heating the TPA parameters changed independently of each other. They reached a maxima at different endpoint temperatures of the meat and then decreased. A decrease in fibre diameter was observed in samples heated to 60 and 121°C. Sarcomere length decreased continuously in the range 50-121°C. Cooking losses increased with increased heating temperature. Relationships between changes in sarcomere length and cooking losses and between springiness and fibre diameter were found.
Bovine semitendinosus (ST) muscles aged for 5 and 12 days at 4 °C were roasted at 170 °C to internal temperatures of 50, 60, 70, 80 and 90 °C. Microstructural changes in meat were evaluated using a scanning electron microscope (SEM). Texture profile analysis (TPA) and measurements of the shear force values of samples were conducted using a texture analyser. The cooking losses and quantity of total and soluble collagen were also estimated. The structure of intramuscular connective tissue and myofibrillar structure of meat after 5 days of ageing was very regular. In 12-day-aged samples fibrous and myofibrillar structures were less distinct, damages of endomysium tubes appeared and fibres of perimysium were swelled. Ageing of ST muscle for 12 days caused a two-fold increase in the quantity of soluble collagen and a two-fold decrease in the value of TPA parameters-hardness and chewiness, as compared to 5-day-aged samples. The decrease in fibre diameter and sarcomere length during roasting started at 60 °C in 5-day-aged meat and at 50 °C in 12-day-aged samples. The shear force values measured after roasting were lower for 12-day-aged meat than for 5-day-aged samples. The quantity of soluble collagen in roasted meat increased at an internal temperature of 80 °C. At a higher temperature of meat this variable depended on the degree of meat ageing. The cooking losses during roasting of meat were about 3% lower for 12-day-aged than for 5-day-aged samples. In the examined range of internal temperature of meat the cooking losses and the sarcomere length were negatively correlated.