CHEMICAL PROCESS FOR MEASURING TENDERNESS OF COOKED MEAT

PROCEDE POUR MESURER LA TENDRETE DE LA VIANDE CUITE

English Abstract

CHEMICAL PROCESS
FOR MEASURING TENDERNESS OF COOKED MEAT
ABSTRACT OF THE DISCLOSURE
To predict the tenderness of cooked meat, the concen-
trations of certain trace elements such as copper, cobalt,
iron, zinc, calcium, selenium and silicon and sometimes
cadmium and lead in uncooked meat muscle are measured in
samples taken from the carcass of the animals and samples
from the same muscle are cooked and rated by a sensory taste
panel (STR scores). A formula is obtained by multiple linear
regression of the data using the concentrations of trace
elements as the independent variables and STR as the dependent
variable. To grade a carcass the concentrations of measured
trace elements are entered into the formula and a predicted
STR is calculated. The ratio of the concentration of iron
to zinc provides an especially suitable independent variable
because of its high correlation with tenderness and the ease
of measuring zinc and iron accurately.

Claims

What is claimed is:
1. A process for evaluating the tenderness of meat compris-
ing the steps of measuring the concentration of at least two of
several trace elements in the meat and correlating the concen-
trations of said trace elements as independent variables of a
functional relationship having tenderness as the dependent
variable.
2. A process according to claim 1 in which the step of
measuring the concentration of at least two of several trace
elements comprises the step of measuring the concentration of
iron and zinc in a sample of a carcass.
3. A process according to claim 2 in which the step of
measuring the concentrations of at least two of several trace
elements in the meat includes the step of measuring the con-
centrations of at least two of several trace elements in a
sample of a muscle from a carcass of a beef animal carcass.
4. A process according to claim 2 in which the step of
correlating the concentrations of said trace elements as inde-
pendent variables of a functional relationship having tenderness
as the dependent variable comprises the steps of:
obtaining a plurality of samples of muscle from a plurality
of different carcasses;
28

said step of obtaining a plurality of samples including the
step of obtaining a plurality of samples of the same muscle for
the same species of animal;
obtaining the STR for a portion of each of said samples
from a standard test panel;
measuring the concentrations of said trace elements from
another portion of each of said samples; and
comparing the concentrations of the measured trace elements
for each of said samples as independent variables with the STR
for the same sample as a dependent variable in a regression to
obtain a formula relating STR's as dependent variables with the
concentrations of said measured trace elements.
5. A process according to claim 4 in which a carcass of
the same species of animal is graded by:
taking a sample of the muscle of the carcass;
measuring the concentrations of the trace element in the
sample;
substituting the concentrations of the trace elements into
the formula; and
calculating an STR from the formula.
6. A process according to claim 4 in which said samples
are samples taken from a beef animal carcass.
7. A process according to claim 2 in which the step of
29

measuring the concentrations of at least two of several trace
elements further includes the step of measuring the concentra-
tion of calcium in a portion of the same sample of said carcass.
8. A process according to claim 7 in which the step of
measuring the concentration of at least two of several trace
elements in the meat includes the step of measuring the concen-
tration of at least two of several trace elements in a sample of
a muscle from a carcass of a beef animal carcass.
9. A process according to claim 8 in which the step of
correlating the concentrations of said trace elements as inde-
pendent variables of a functional relationship having tenderness
as the dependent variable includes the step of multiplying the
ratio of the concentrations of iron to zinc by a first constant
and subtracting the product from a second constant, wherein the
first constant is substantially 4.5199 and the second constant
is substantially 6.2386.
10. A process according to claim 7 in which the step of
correlating the concentrations of said trace element as an inde-
pendent variable of a functional relationship having tenderness
as the dependent variable comprises the steps of:
obtaining a plurality of samples of muscle from a plurality
of different carcasses;
said step of obtaining a plurality of samples including the
step of obtaining a plurality of samples of the same muscle for
the same species of animal;

obtaining the STR for a portion of each of said samples
from a standard test panel;
measuring the concentration of said trace element from
another portion of each of said samples;
comparing the concentrations of the measured trace elements
for each of said samples as independent variables with the STR
for the same sample in a multiple regression including all of
said samples to obtain a formula correlating STR's as dependent
variables with the concentration of said measured trace elements;
substituting the concentration of said at least two of
several trace elements in the meat into said formula, whereby
a calculated STR is obtained.
11. A process according to claim 7 in which the step of
measuring the concentrations of at least two of several calci-
fication-influencing trace elements includes the steps of:
mechanically homogenizing a portion of said muscle sample;
exciting said homogenized sample by an X-ray source, whereby
fluoresced photons from the iron and zinc atoms are
quantified as needed to provide an arithmetic ratio of the
abundances of each element in the sample muscle; and
obtaining an arithmetic ratio of the abundance of zinc
and iron in the sampled muscle.
12. A process according to claim 10 in which the step of
measuring the concentrations of at least two of several calci-
fication-influencing trace elements includes the steps of:
31

mechanically homogenizing a portion of said muscle sample;
exciting said homogenized sample by an X-ray source, where-
by fluroesced photons from the iron and zinc atoms are
quantified as needed to provide an arithmetic ratio of the
abundances of each element in the sampled muscle;
obtaining an arithmetic ratio of the abundance of zinc and
iron in the sampled muscle.
13. A process according to claim 1 in which the step of
measuring includes the step of obtaining the ratio of iron
to zinc in the muscle semimembranous of a beef carcass
and the step of correlating includes the step of calculating
a STR from the formula
<IMG>, where
A is substantially 4.5199 and B is substantially 6.2386.
14. A process according to claim 1 in which the step of
measuring includes the step of obtaining by measurement the
ratios of iron to cobalt, silicon to cobalt and iron to zinc in
the muscle semimembranous of a head of cattle and the step of
correlating includes the step of calculating a STR from the
formula
<IMG>
where A is substantially .0543, B is substantially .0503,
and C is substantially 6.6418 and D is 1.1557.
32

15. A process according to claim 1 in which the step of
measuring includes the step of obtaining by measurement the
concentrations of iron, silicon, zinc and calcium in the
muscle semimembranous of a head of cattle and the step of
correlating includes the step of calculating a STR from the
formula:
STR = E x l + A x zinc - B calcium - C x iron - D
x silicon
where A is substantially .0772, B is substantially .1362, C
is substantially .1933, D is substantially .0116 and E is
substantially 13.0741.
16. A process according to claim 1 in which the step of
measuring includes the step of obtaining by measurement the
ratios of iron to calcium, silicon to calcium and iron to
zinc in the muscle semimembranous of a head of cattle and
the step of correlating includes the step of-calculating a
STR from the formula:
<IMG>
where D is substantially 4.1076, A is substantially 5.6932,
B is substantially 1.1783 and C is substantially 2.6509.
33

17. A process according to claim 1 in which the step of
measuring includes the step of obtaining by measurement the
concentrations of calcium, cadmium, lead, cobalt, copper, zinc,
iron and selenium in the muscle semimembranous of a head
of cattle and the step of correlating includes the step of
calculating a STR from the formula
STR = - A x %calcium - B x %cadmium
- C x %lead + D x %cobalt
- E x %copper + F x %zinc
- G x %iron + H x %selenium
+ I
where A is substantially 0.1054 x 104, B is substantially
59.0651 x 104, C is substantially 0.7538 x 104, D is sub-
stantially 4.9301 x 104, E is substantially 3.2299 x 104,
F is substantially 0.1065 x 104, G is substantially
0.0806 x 104, H is substantially 4.0808 x 104 and I is
substantially 9.7360.
34

18. The process according to claim 1 in which the
step of correlating the concentrations of said trace elements
includes the steps of correlating the ratio of the concentrations
of said two trace elements as independent variables of a
functional relationship having tenderness as the dependent
variable.
19. A process according to claim 1 in which the step
of correlating the concentrations of said trace elements as
independent variables of a functional relationship having
tenderness as the dependent variable comprises the steps of:
obtaining a plurality of samples of muscle from a
plurality of different carcasses;
said step of obtaining the plurality of samples
including the step of obtaining a plurality of samples of the
same muscle for the same species of animal;
measuring the tenderness of a portion of each of said
samples using a standard measuring technique for tenderness;
measuring the concentrations of said trace elements
from another portion of said samples; and
comparing concentrations of the measured trace elements
for each of said samples as independent variables with the
measured tenderness for the same sample as a dependent variable
in a regression to obtain a formula relating the measured
tenderness as dependent variables with the concentration of said
measured trace elements.
20. A process according to claim 19 in which the
step of obtaining a measurement of tenderness using a standard
technique for measuring tenderness includes the step of

obtaining the STR for a portion of each of said samples from
a standard test panel.
21. A process according to claim 20 in which a
carcass of the same species of animal is graded by:
taking a sample of the muscle of the carcass;
measuring the concentrations of the trace element
in the sample;
substituting the concentrations of the trace element
into the formula; and
calculating an STR from the formula.
22. A process according to claim 19 in which the step
of obtaining a plurality of samples of the same muscle for
the same species of animal includes the step of obtaining
samples from a beef animal carcass.
36

Description

~67~
SPECIFICATION
This i~vention relates ~o methods of pxedic~ing the
benderne~s of cooked muscles of an animal from data obtained
by chemlcal analysis of representative samples of a repre-
sentative mu~cle from the ~ame animal.
Beef i8 graded in an effort to provide standards by which
the consumer may judge the qual~ty of cooked beef from grading
based on the uncooked meat. One primary characteristic of

~ ~ 6~
beef which is graded is the tenderness or toughness of the
meat. The tenderness of the meat is related to the texture
of the meat.
The purpose o grading beef is to predict the quality of
the meat that the consumer is about to purchase in a way easily
understood by the consumer. This information is also useful
to producers and researchers. There are several different
grading systems in use for beef but no system has yet been
shown to be sufficiently superior to the others so that it
could eventually become an international standard.
A sensory method utilizing taste-testing of meat is
practiced. This provides a standard against which other
grading methods may be evaluated and compared. This standard
is known as a "standard taste-panel response'l which rates
meat in accordance with scales known as standard taste-panel
responses (STR). Correlation between the results of a given
testing method and the responses of standard taste-panels is
an indication of the usefulness of the given testing method.
In the prior art, there are both visual and mechanical
gradin~ systems for m~at and some work has been done with
proposed chemical methods of grading beef.
A visual process for grading beef is widely used in the
United States. In this process, the quality of the beef is
graded according to the relative abundance of fat dispersion
in the muscle of the beef. This estimate results in a mar-
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~ ~ 67 ~ ~
bling abundance score which is used to convey the quality of
the beef to the consumer.
The visual grading of beef has the disadvantages of being
so~etimes expensive, unreliable ancl of providing results having
a poor corxelation to STR. It may be expensive because trained
observers must perform the grading and it is a relatively slow
system of grading. It is unreliable because it is sub~ective
and ~herefore changeable. One reason that the visual grading
of beef provides results having a poor correlation ~o STR
is that it is based on a visual esti~te of the amount of fat
dispersion in the muscle and the visual observation of the
amount of fat dispersion in the beef muscle is not directly
related to the characteristics that a consumer desires in
beef, the predominant characteristic being tenderness.
There are a number of different mechanical systems for
testing the tenderness of meat. They are generally referred
to as tenderometers. TPnderometers generally measure the
force required for a cutting edge to penetrate the meat or
cut the meat or the breaking resistance of the meat or other
sueh mechanical characteristics. Some tenderometers give
fairly reproducible results but still do not provide a
sufficiently high correlation with the results of a sensory
taste panel.
Studies of meat tenderness from a chemical point of view
have generally been directed to the amount and nature of con-
nective tissue and to the protein-ion relationships in the

~196713~6
muscle. The prior art methods of chemical study of tenderness
have had the disadvantage of not providing useful information
Accordingly, it is an object of the invention t~ provide
a novel method for predicting the tenderness of meat.
It is a still further object o~ the invention to provide
a novel method for predicting the tenderness of beef.
It is a still further object of the invention to provide
a novel method for grading meat which is obJective, economical
and provides results corresponding with STR.
It is a still further object of the invention to provide
a ~ovel chemical method for grading meat.
In accordance with the above and other objects of the
invention, samples of muscle are taken from the carcass of
an animal and the concentrations of certain trace elements in
the samples are measured by appropria~te means such as spec-
~rophotometry or X-ray fluorescence examination. Typical trace
elements which may be measured are copper, cobalt, iron, zinc,
calcium, selenium and silicon, and sometimes cadmium and lead.
The tenderness of cooked meat from the same animal is pre-
dicted by calculating a value corresponding to a STR from anempirical relationship between tenderness and trace elements
concentrations.
To obtain the empirical relationship for a type of meat
such as beef, the concentration of these elements is obtained
in each of a number of representative samples taken from

different carcasses but from the same representative muscle
in each carcass. This concentration may be obtained by
measurement of the wet sample or by drying the sample before
measuring the trace elements. Corresponding samples of the
muscles are cooked and rated by a standard taste panel. A
formula is obtained which expresses the relationship between
the concentrations of the trace elements and the STR from
the taste panel, by using multiple linear regression analysis
of ratios of the elements and STR or of concentrations of
trace elements and STR. Formulas obtained by this process
for beef have been used to predict STR with a 99% correlationO
A particularly useful formula is obtained expressing the
relationship between the ratio of iron to zinc in beef and
the tenderness of the beef. This relationship is particularly
useful because: (1) iron and zinc can be more accurately
measured than many other elements; (2) this relationship has
a sufficiently high correlation wi~h STR; and (3~ the grading
of beef is of exceptional commercial significance.
After the relationship between trace elements and tender-
ness has been determined, carcasses are graded by extracting asample of the selected representative muscle, measuring the
trace element concentrations in the sample and calculating
the predicted tenderness of the meat in the carcass from
the relationship between the trace elements and STR.
This method of grading meat tenderness of beef has the
advantages of being: (1) objective; (2) providing a high

~ 6~ 6
correlation with STR; and (3) being suitable as an interna
tional standard because of its high correlation and objectivity.
The above noted and other features of the invention will
be better understood from the following detailed description
w~en c~nsidered with reference to the drawings in which:
Figure 1 is a flow diagram of a process for determining
a formula which~expresses the relationship between trace
element concentrations and the tenderness of meat in accordance
with an e~bodiment of the invention; and
Figure 2 is a flow diagram of a process for grading meat
in accordance with the invention using the formula which
e~presses the relationship determined by the process of Fig. 1.
Broadly, the preferred embodiment of the invention in-
cludes a first process illustrated in. Figure 1 to determine
the mathematical relationship between trace element concen-
trations in a type of animal from samples taken from several
carcasses of that type of animal and thereafter using a
second process illustrated in Figure 2 to grade carcasses of
that type of animal by taking a similar sample from the car-
cass being graded, measuring the trace element concentrationsin the sample and grading the carcass using the formula
expressing the relationship obtained in the first process.
As shown in Figure 1, the relationship between the trace
element concentrations and standard taste responses is de-
termined from a process that includes: (1) the step 10 of

1 ~ 6~
obtaining representative samples of a representative muscle
from a number of different carcasses of the same species of
animal; (2) the step 12 of measuring the concentrations of
certain trace elements in each of the samples; (3~ the step
14 of obtaining STR for the same carcasses for which t~e con-
centrations of the trace elements were obtained; and (4) the
step 16 of determining the formula that expresses the rela-
tionship between trace element concentrations and STR for
the type of meat of the carcass.
In obtaining samples to calculate the relationship between
trace elements and STR, a representative sample of the same
muscle is sampled from several carcasses. For example, the
whole hearts of cattle may be used to calculate the relation-
ship between the STR of cooked beef and the concentrations of
those trace elements in the heart muscle of cattle. In selec-
ting a muscle to be used or establishing the relationship
between trace elements in the meat and the tenderness of the
meat a muacle is selected which is inexpensive and co~veniently
obtained so that the relationship may be inexpensi~ely used to
grade uncooked meat for consumers. Although the concentrations
of the trace elements are not the same in every muscle of a
carcass, any suitable muscle may be used, provided the same
muscle is used for each carcass to be graded or used to
determine the relationship for grading.
Of course, different formulas expressing the relationships

~ ~ ~7 8~ ~
must be determined for each different species of animal to
be graded and for each different muscle to be used as the
grading standard for samples. For example, a for~ula expressing
the relationship between STR and trace elements for beef does
not apply to poultry or pork. Within a giverl species, one
formula is sufficient to express the relationship between
trace eLement c~ncentxations and STR for all breeds. Particular
formulas expressing the relationship between concentrations of
trace elements and STR can, however, be determined for other
types of animals by the same process used to calculate this
relationship for beef. Moreover, it is possible in some in-
stances to grade using a sample from a different muscle than
that used to establish the relationship, provided the muscle
used in grading has concentrations of trace elements that can
be accurately correlated with the concentrations of the trace
elements in the muscle that was taken as the sample to establish
the formula expres3ing the relationship between the trace
elements and the STR. A particularly suitable muscle for
cattle is the muscle Longissimus Dorsi at the twelfth rib
because it is easy to obtain.
Generally, the formula is obtained from wet samples
oi uncooked meat taken from a number of carcasses such as
ten. The concentration is usually expressed in terms of
parts per million of dry matter even though measured from
a wet sample and then corrected for moisture. However,
the meat may be ashed or dried or altered in any manner that

~ 678~6
still permits the measurement of the concentrations of the
trace elements, and a larger or smaller number than ten
carcasses can be used. The larger the number of carcasses
used to establish the relationship, the greater is the
precision of the correlation.
The step 12 of measuring the concentrations of trace
elements in the samples of carcasses is performed using any
o~ several known techniques and combinations of techniques.
The trace elements which are so measured include copper,
cobalt, iron, zinc, calci~m, selenium and silicon, and some-
times cadmium and lead. Cadmium and lead are pollutants
which affect calcification but are not always present or
ordinarily present in very low concentrations, and therefore
ordinarily of relatively minor relevance.
The choice of the measuring technique depends on the
elements that are to be meas~red and the equipment that is
available for the measurements. For example, the samples
may be dissolved in hydrochloric acid and certain trace
elements such as calcium, zinc, iron, lead, cadmium, cobalt
and copper can be measured with absorption spectroscopy.
Other special techniques are used to measure selenium and
silicon because of their low sensitivity to atomic absorption
techniques~
Certain trace elements are measured because it has been
found that there is a relationship between the tenderness of

~ 67 ~V ~
meat and th concentrations of these trace elements in the
meat. A closer correlation is obtained when more than two
of t~e elements are used and a relationship is determined
either with the trace elements as separate terms of an
equation, ratios ~o each other, groups of ratios, factors or
groups of factors.
Trace elements are elements that are found in small
percentages within the musrle. Some of them provide closer
correlations than others. One ratio of ~race elements which
provides an unexpectedly good correlation and which is especial-
ly suitable for measurements because of the large quantities
found in the muscle is the ratio of iron to zinc. Both iron
; and zine are found in quantities such as a hundred parts per
million of dry matter whereas other trace elements for which
a correlation has been found are on the order of ten parts per
mlllion. Consequently, the ratio of iron to zinc is especially
suitable for use in establishing standards for the grading of
meat.
An especially suitable measurement for iron and zinc can
be made by homogenizing the uncooked tissue by any mechanical
means including the use of a sonic device. In this measuring
.technique, thP homogenate is pressed against a*Mylar film and
the air bubbles are encouraged to escape from the*Mylar film's
~urface by vibration thus insuring a good surace for the
* Trade Mark of DuPont de Nemours E . I . & Co .
10 -

~ ~ 6~
testing procedure. The sample, thus prepared, is excited
by Bremsstrahlung or other radiation from an X-ray tube and
the fluorescence photons of the iron and zinc atoms are cap-
~ured and recognized, quantified and r~ported using ED~X
equipment or the equivalent thereof. EDAX equipment is manu-
factured by EDAX International Incorporated, Prairie View,
Illinois. This~measures the concentrations of iron--and-zinc
which may be used directly to determine the formula expressing
the relationship between the STR and the concentrations of
these elements. After-the formula ha~ been determined these
measures may be used to grade carcasses by calcula~ing an
STR representing tenderness from the determined relationship
of the individual concentrations of :iron and zinc or their
ra~ios with the STR.
The step 14 of cooking a portion of samples from each
animal and obtaining STR for the sample is performed using
known and standardized methods and conditions. The STR are
ratings provided by standardized taste panels. A scale is
used and this scale may be arbitrarily selected.
Standard taste panels are groups of trained personnel who
taste samples of cooked meat under standard conditions and rate
~he cooked meat. The procedure provides a known standard
against which tenderness measuring techniques can be compared.
The panel rates the particular quality of meat being ~ested
on a given hedonistic scale. For example, a goodness scale
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~ ~ ~7 ~ ~
of one to five may be used with one being selected for the
lowest-rating and five for the highest ra~ing. The STR pro-
vides the closest possible measurement standards to those of
an ordinary consumer.
The step 16 of determining the formula which expresses
the relat-ionship between the trace element concentrations and
STR employs known mathematical techniques. An especially
suitable technique is step-wise multiple linear regression
analysis which may be performed in accordance with standard
computer programs or may be done by hand. In performing such
an analysis, the concentrations of trace elements, ratios of
- trace elements or multiple factors of trace elements are used
as the independent variables and the STR as the dependent
variables. Any range of hedonistic values may be selected
and corresponding different equations with different
coefficlents are obtained. A hedonistic standard having a
range of from one to five has been conveniently related to
the ratio of the concentrations of iron to zinc to obtain
particularly useful formulae.
O~ course, the same muscles or groups of muscles should
be used in all of the samples to obtain a meaningful correla-
~ion but muscles having similar concentrations of trace
elements may be substituted for each other and muscles for
which the concentrations of trace elements are related in a
known way may be substituted for each other and the differences
in concentration accounted for mathematically so that the
-12-

~67~16
correlation may be obtained from a mixed group o muscles
or from a similar muscle such as the heart whereas amples
are actually taken in the carcasses that are being rated
after the rela~ionship between the trace elements and STR
has been determined.
It is not known why suitable equations are obtained using
standard multiple linear regression analysis procedures in
which a set of STR values are the dependent variables and each
set of trace element concentration values are independent
variables or in which the set of STR values is the dependent
variable and the varous possible ratios or factors of the
elemental concentrations are the independent variables. How-
ever, it is believed that this relationship occurs because
the trace elements indicate the extent of calcification of
the m~scle tissue which has occurred during the life of the
animal as its age increases and as its diet has included these
elements. The elements studied are known to affect calcifi-
cation of biological tissues.
This relationship between tissue calcification and tough-
ness is assumed because the toughness of meat i3 increased
with age and ~ith certain diets as a result of chemical changes
t~king place in the connective tissue of the ~uscle. The
chemical change i8 indicated in the increased calcification of
t~e connective tissue with time. A possible reason for the
relationship between calcification and the toughness of meat is
-13-

~ 6~Q6
discussed on page 291 of Bloom, William and Fawcett, Don W.:
A Textbosk of Histology 9th Edition, W. B. Saunders Company,
Philadelphia 1968. Therefore it is believed that the amount
of the trace elements affects the toughness of the meat.
These elements include iron, calcium, cobalt, copper,
selenium, si~icon and zinc, and sometimes cad~ium and lead.
It was known that these elements are found in meat. It is
believed that the ratio of iron to zinc is paxticularly well
correlated to tenderness because zinc increases the amount of
marbling which inhibits calcification, and ~he iron decreases
marbling by promoting its o~idation thereby allowing calcifica-
tion to increase.
Zinc i8 a constituent of insulin and aids in the con-
version of blood glucose to glycogen and therefore to the
syntheses of adipose tissue from blood glucose. Consequently
the amount of marbling increases with the amount of zinc. The
ratio of iron to fat free muscle is nearly constant. Accord-
ingly ~he iron to zinc ratio is an inverted fraction closely
related to the marbling to meat ratio.
A-~milar measuring technique is applicable to meats in
general since toughness in meats is related to calcification
of connective tissue in all meats. Consequently, this
technique should yield suitable relationships for swine or
poultry.
It is a surprising result that such high correlations
are obtainable between trace element concentrations and
-14-

~ 67 8~ 6
tenderness. It is synergistic that the ratio of the two
elements, iron and zinc, which are easiest to measur~ with
accuracy should be suitable and provide a sufficiently high
correlation.
The calculations may be made according to any standard
step-wise multiple linear regression analysis technique such
as that described in Ezekiel M. METHODS OF CO~RELATION ANALYSIS,
Second Edition, John Wylie and Sons, 1941 and computer programs
are available for performing these calculations.
Particular formulas have been obtained using sevQral of the
elements ~or beef and these formulas have been derived from the
tead rness results of a standard test panel. A high correlation
has been obtained between the trace element concentrations and
tenderness (STR) and a lesser correlation between measurements
with a tenderometer and tenderness (STR). This indicates that
the chemical tests in aceordance with ~his invention provide
better predictability to the standard test panel than the
mechanical texture test used for this comparison.
After a relationship has been determined between two or
more of the trace element concentrations of ratio~ thereof and
the STR, it is possible to grade meat from carcasses using
Ramples taken from the meat in accordance with the process
illustrated by the flow diagram in Figure 2.
In this process, an uncooked sample is taken of a muscle
of each carcass to be graded which muscle is preferably the
same muscle used in determining the formula which expresses the
relationship between the trace element concentra~ions and the
STR as shown at step 18 in Figure 2. After obtaining suitable
-15-

samples, the step of measuring trace element concentrations in
the sample shown by the block 20 in Figure 2 is performed. The
same trace element concentrations which are the independent
variables in the formula to be used are determined and Pntered
into the formula. This concentration or ratio of concentrations
or product of concentrations is entered into the formula and a
calculation made of the STR in accordance with step 22 in the
flow diagram of Figure 2.
EXAMPLES
The following non-limitative examples illustrate the in-
vention.
GENERAL CONDITIONS
The samples used for the examples were taken from the same
muscle in ten carcasses. More specifically the samples were
fi~e gram shavings from the muscle semimembranosus of cattle.
For each of the examples, a sensory test panel which in-
cluded nlne panelists simultaneously judged the tenderness and
juicyness of cooked beef muscle. The judgements were made on
five-point continuous hedonic scale from excellent with a
rating o five down to poor with a rating of one. The mean
tenderness score for each sample was the mean of all values
reported by the panel for that sample expressed as a decimal
value of units, tenths and hundredths. The specific conditions
of this entire procedure have been reported in the thesis for
degree o Master of Science of Mr. Leslie Vavak, the University
o Nebraska, Department of Food Technology, Lincoln, Nebraska,
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1975. This book is in the Univer ity of Nebraska Library.
An evaluation of samples taken from the same muscles was
obtained from a rotating knife tenderometer. The instrument
used was that manufactured by Feed Service Company and described
in Anderson, P.C., Rapp, J.L.C. and Costello, D.F., 1972,
ROTATING DULL KNIFE TENDEROMETER, Food Technol. 26 (1:25-30).
Seven of the nine elements of interest were analyzed by atomic
absorption spectrophotometry. These are: calcium, cadmium,
cobalt, copper, iron, lead and zinc. A dry ashing technique
was applied for the distribution of organic matter. The mois-
ture content of the samples were each determined prior to the
measurement of the residual alements.
Data was obtained indicating a correlation between the
trace elements and the tenderness of the meat as determined by
standard test panel responses by a tenderometer. This data is
shown in Table I.
In preparing the samples for measuring any of the trace el-
ements calcium, zincJ iron, lead, cadmium, cobalt and copper, the
samples were dissolved in 50% HCl while heating to a medium heat.
F~r the calcium and zinc de~erminations with absorption
spectrophotmetry, two grams of the dry sample were diluted to
100 milliliters volume. Then they were further diluted with
40 milliliters sample solution being added to a 10 milliliter
lanthanum (5% solution) into a 100 milliliter ~olume. The
final dilutions were two grams dissolved in 100 milliliters
which was then diluted with 40 milliliters of the solution
being put in 100 milliliters of five percent lanthanum which is

lL~1671~
TABLE I
1 2 3 4
STR 4.23 3.71 4.26 4.02
Ro~atiIlg
Knife .52 .64 .80 .48
Tend3x~ter
Cobalt %.000042 .000044 .000041 .000044
Copper %.000079 .000081 .000079 .000070
Iron % .0025 .0021 .0026 .0023
Zînc % .0038 .0056 .0053 .0040
Calcium %.0054 .0065 .0054 .0054
Silicon %.0047 .0043 .0040 .0054
.
6 7 8
. _ _ , ,
STR 3.23 3.07 3.62 1.71
Rota~g
Knife .57 .29 .62 .22
Te~3~er
Cobalt %.000045 .000041 .000044 .000046
Copper %.000099 .000077 .000097 .000084
Iron % .0031 .0025 .0027 .0032
Zinc % .0049 .0033 .0045 .0039
Galcium %.0053 .0048 .0051 .0055
Silicon %.Q045 .0050 .OQ50 .0047
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78~
TABLE I (Cont ' d)
9 10
STR 2. 23 1 . 34
Rotat~g
Kni:Ee . 22 . 28
TOEld~net~
Cobalt % . 000043 . 000045
Copper % . 000073 . 000088
Iron % . 0035 . 0031
Zinc % . 0037 . 0031
Calcium % . 0049 . 0053
Silicon % . 0043 . 0047 . .. .. .. ..
..
- 19 -

6~D6
equal to 125 milliliters per liter gram tdry) of onP percent
lanthanum solution. In other words, the dilution factor is
approximately 125.
For the iron measurment, two grams of dry sample were
diluted ~o 100 milliliters volume. This provides a dilution
factor of approximately 50. For the lead, cadmium, cobalt and
copper, ten grams of dry sample were diluted to 50 milliliters
of volume or five grams dry sample were diluted to 25 milli-
liters of volume.
Seleni~ was measured by other methods. The method se-
lected was the method described by Cummings, L.M., Martin, J.L.
and Maag, D.D., 1965, AN IMPROVED METHOD FOR DETERMINATIOI~ OF
SELENIUM IN BIOLOGICAL MATERIAL, Analyt. Chem 37:430.
To determine the amount of silicon, approximately three to
four grams of wet muscle tissue were dried and ashed and re-
duced to solution. One method for accomplishing this is de-
scribed in Rainwater, F.H. and Thatcher, L.~., 1960, METHODS
FOR COLLEC~ION AND ANALYSIS O~ WATER SAMPLES: Geological Survey
Water Supply Paper, 1454, Washington, U.S. Government Printing
~ffice, 259.
An iron to zinc ratio is obtainable by a superior method.
~his method is to homogenize the sample and press it against
a*Mylar film. The air bubbles are removed from the surface by
vibxating the surface. The ~ample, thus prepared, is excited
by Bremsstrahlung or other radiation from an X-ray tube and the
fluorescence of the iron and zinc atoms measured by EDAX equip-
* Trade Mark of DuPont de Memours E.I. & Co.
.~
-20-

~ ~ ~7
ment or the like.
This technique is fast, subject to automation and pro-
vides accurate results. X-ray fluorescence examination re-
quires less than one minute per sample. When the ratio of iron
to zinc is used as the independent variable, this ratio should
be measured with an error of less than plus or minus two per-
cent although five percent is tolerable.
Iron, selenium and cobalt concentrations yield statisti-
cally significant correlations (r=20.5-0.8) with sensory panel
tenderness responses and lead yields a statistically signifi-
cant correlation (r = -0.66). Zinc does not yield significant
correlations by itself. All correlations are relatively low to
be used as an accurate standard for grading meat.
However, when a step-wise multiple regression analysis is
performed, correlation coefficients are obtained which are suf-
ficiently close to be used to predict the responses of a
sensory taste panel and to be used for grading meat. These
results show a close correlation when the percentage of the
element is based on dry weight of the tissue rather than on the
20 ~et weight, with both the responses of the sensory taste panel
and a tenderometer. A suitable regression to be used is
described in Cochran, Cox EXPERIMENTAL DESIG~S, John Wylie
and Sonsj Inc., New York, 1968, Second.

78~
EXAMPLE 1
The concentrations of calcium, iron, silicon and zinc
were measured as described above and STR were obtained from
; samples of the s~me muscles. Coefficients were obtained
from a computer run of multiple step regression with STR
values being one to five and the independent variables being
the ratios of iron to calcium9 iron to zinc and silicon to
calcium. Form~la A was obtained. All percentages were
measured from dry samp~es and corrected to wet samples. The
STR calculated in this example corresponds to the measured
STR as shown in Table II.
EXAMPLE 2
The concentrations of iron, silicon, zinc and calcium
were measured and the STR are obtained as described above.
The coefficients were obtained from a multiple step-wise
regression on a computer program with the concentrations of
iron, silicon, zinc and calcium as the independent variables
and the STR responses as the dependent variable. Formula B
was obtained. The calculated STR correspond to the measured
STR as shown in Table III.
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~6'7~
FGRMULA A
STR = 4.1076 x 1 - 5.6932 lron
-~ 1.1783 ilnium + 2-6509 calcium
TABLE II
Calculated
Animal Number Actual STR STR
1 4.23 3.22
2 3.71 4.11
3 4.26 3.85
4 4.0~ 3.9g
3.23 3.45
6 3.07 3.17
7 3.62 3.91
1 71 2.39
9 2 23 1.89
1.34 1.45
FORMULA B
STR 3 ~ .0772 ~inc - .1362 calcium - .1933 x iron%
--.0116 x silicon% + 13.0741 x 1
TABLE III
Calculated
. Animal Number Ac~ual STR STR
1 4.23 0.3269E 01
2 3.71 0.3981E 01
3 4.26 0.4315E 01
4 4.02 0.3728E 01
3.23 0.3117E 01
6 3.07 0.3665E 01
7 3.62 0.3796E 01
8 1.71 0.1856~ 01
9 2.23 0.1985E 01
1.34 0.1704E 01
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78~6
EXAMPLE 3
The concentrations of iron, cobalt, silicon and zinc were
measured as described above and the STR were obtained. The same
multiple step-wise computer program was used with the ratios
of iron to cobalt, silicon to cobalt and iron to zinc as
the independent variables and the STR as the dependent vari-
ables. The coPfficients are shown in FormNla C and the measured
and calculated STR are shown in Table IV.
EXAMPLE 4
The concentrations of iron and zinc were measured as
described above and the STR were obtai.ned. The same multiple
step-wise computer program was used with the ratios of iron to
zinc as the independent variables and the STR as the dependent
variables. The coefficients are showm in Formula D and the
measured and calculated STR are shown in Table V.
EXAMPLE 5
The concentrations o calcium, cadmium, lead, cobalt,
copper, zinc, iron and selenium were measured and described
above and the STR were obtained. The same multiple step-wise
-24-

~oG~ D6
FORMULA C
STR = .0543 x irobn%~/ + .0503 x cO~alOt~n/70- 6.6418 x ir~non
- 1.1557 x 1
TABLE IV
Animal Number Actual STR STR
1 4.23 3.35
2 3.71 3.87
3 4.25 3.95
4 4.02 4.05
3.23 3.42
6 3.~7 3.27
7 3.62 3.92
8 1.71 2.32
9 2.23 2.03
1.34 1.20
FORMULA D
STR - ~4.5199 x iin% + 6.2.386 x 1
TA8LE V
Animal IlumberActual S~R STR
1 4.23 3.26
2 3.71 4.54
3 4.26 4.02
4.02 3.63
3.23 3.38
3.07 2.81
7 3.62 3.52
8 1.71 2.53
g 2.23 1.96
1.34 1.71
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~L~6~7~6
FORMULA E
SrR = - 0.1054 x ~/ccalcium x 104 - 59.0651 x ~/&admium x 104
- O. 7538 x ~lead x 104 + 4.9301 x ~/~balt x 104
- 3.2299 x ~/~copp~r x 104 + 0.1065 x ~/æinc x 104
- O. 0806 x ~/Oiran }c 104 + 4.0808 x ~/Osel~rL~un x 104
9. 7360 x 1
TABLE VI
Animal Number ~ctual STR Calculated
4.23 4.21
2 3.71 3.75
3 4.26 4.17
4 4. 02 3 . g8
3.23 3.33
6 3.07 3.1g
7 3.62 3.53
8 1.71 1.75
9 2.23 2.22
1.34 1.24
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1 ~ 67 ~ 6
computer program was used with the concentrations of calcium,
cadmium, lead, cobalt, copper, zinc, iron and seleniu~ as the
independent variables and the STR as the dependent variables.
The coefficients are shown in Formula E and the measured and
calculated STR are shown in Table VI.
... As can be understood from the above description, the
method of this i~vention-has the advantages of being: (1)
objective since it is based on measurements rather than visual
: observation; (~) providing a high correlation with STR; and
; (3) being suitable as an international standard because of its
high correlation and objectiveness. Moreover, when the ratio ~'
of iron to zinc is used as the independent variable, grading
may be done quickly and inexpensively.
Although specific examples have been described with
particularity, many modifications of the examples are possible
in the light of the above teachings. It is therefore to be
understood that, within the scope of the apended claims the
invention may be practiced other than as specifically described.
-27-