17
MECHANICAL ME THO03 OF MEA'SURING TENDERNESS OF MEAT
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OREGON STATE COLLEGE
O f a l l of t h e f a c t o r s which constitute q u a l i t y of meat, tenderness
i s without doubt t h e one which i s outstanding in determining whether t h e meat
is s a t i s f a c t o r y o r unsatisfactory when eaten. Tenderness a l s o appears t o be
t h e q u a l i t y f a c t o r which is most d i f f i c u l t t o determine objectively.
In t h i s paper an attempt w i l l be made t o summarize a l l , o r nearly
a l l , of t h e methods which have been reported i n the l i t e r a t u r e with t h e hope
t h a t it w i l l represent t h e present status in solving t h e problem of measuring tenderness. All of the methods which have been used have as t h e i r p r i mary purpose the r e f l e c t i o n of the e q e r i e n c e s of a person chewing a piece
of meat. Chewing a piece of meat involves t h e principles of cutting, shearing, tearing, grinding, and squeezing. Therefore, it may be recognized
immediately t h a t it is no simple matter t o desi@ an instrument which brings
all of these principles t o bear simultaneously, o r I n r e l a t i o n t o one another
as i n chewing. Consequently, most of the inst-nts
proposed are based upon
only one of the principles.
There w i l l be no attempt i n t h i s paper t o evaluate the subJective o r
sensory methods o r t h e h i s t o l o g i c a l and chemical methods used t o measure o r
p r e d i c t tenderness even though i n some instances the r e s u l t s obtained with
instruments have been related t o the results with panels or other means by
the various authors.
Since meat is not a homogeneous material, it should be noted t h a t it
is extremely d i f f i c u l t t o evaluate o r c a l i b r a t e an instrument using samples
of meat. I n instances where a homogeneous material o t h e r than meat has been
used t o study t h e instrument itself, it i s reasonable t o expect t h a t the res u l t s w i l l not be as uniform when meat i s tested. This irmnediately leads one
t o conclude that s e l e c t i o n and number of t h e meat s a q l e s i n experiments involving tenderness is extremely important.
Lehman's Mechanical Devices
Perhaps the earliest report of t h e use of mechanical means f o r determining the tenderness of meat is t h a t of Lehman i n 1907 (1). He used two
devices, one of which determined t h e breaking strength of meat; the other was
a determination of the force required t o shear meat between two c u t t i n g edges.
The Warne r-Brat z l e r Shear
I n 1928, Warner (2) reported briefly t o t h e American Society of Anim a l Production that a shearing device showing promise as a mems of measuring
tenderness of meat was under development. In 1932, Black, Warner, and Wilson
(3) gave a more complete report of t h e use of the instrument i n some extensive
studies of beef from d i f f e r e n t classes and grades of animals. The authors
18
.
described t h i s instrument as consisting "of a steel blade 1/32 of an inch
thick, d r i l l e d with a hole s l i g h t l y l a r g e r than the sample t o be tested.
The hole was made square instead of round t o eliminate the s l i d i n g of t h e
edges across the sauple that would occur if R round hole was used. The
c u t t i n g edge was milled square and then smoothed s l i g h t l y t o e f f e c t a standard, reproducible dullness
."
"A sample of meat was cored out with a keen, steel t o o l 1 1/8 inches
i n s i d e diameter, similar t o a cork borer. The sample was placed in the perf o r a t i o n of t h e steel blade and t h e blade led through a narrow s l i t i n B
wooden miter box. A hand-driven screw pull was used t o gull the blade through
t h e meat, the force required being recorded by a spring-type, self-recording
dynamometer. When t h e instrument i s in operation, t h e load on t h e meat builds
up t o a maxinnun and t h e f r a c t u r e of the sample is sudden and complete."
In cooperation with the U. S. Department of Agriculture, Bratzler
a t Kansas State College i n 1932, in
which he demonstrated the value of what has now become known as the WarnerBratzler Shear as a means of measuring tenderness of meat.
(4) completed a Master of Science thesis
The Warner-Bratcler Shear has been a popular i n s t m n t f o r measuring the shearing of meat. It has been modified by motorizing t o insure a
constant r a t e of p u l i on t h e blade ar@ the blade now commonly used i s triangular i n shape. The d i a l dynammeter f o r measuring force i n pounds and the
use of t h e shearing p r i n c i p l e have remained unchanged.
The Cutting G a g e of Tressler, Birdseye, and E?urray
In 1932, Treseler, Birdseye, and NUrrcU, (5) described an instrument
which they had constructed t o determine t h e pressure needed t o cut o r puncture
pieces of meat. The instiwnent consisted simply of a Schrader tire-pressure
gage having a blunt penetrating instrument inserted i n it, The puncturing o r
c u t t i n g snd of t h e instrument was described as being made of metal rod 2$
inches long and 5/16 inch in diameCer. !Fhe end was symmetrically tapered t o
a cone about 3/8 inch in height and with an angle of 13 degrees, The point
was rounded t o have a rgdiya of about 0.08 inches
.
I n using the c u t t i n g gage, as it was called, a sample of meat 3
inches square and 1 inch t h i c k was clamped a t its periphery, A s the cutting
instrument was pressed through t h e meat, it was free t o perforate completely
without obstruction. E i g h t readings were taken on each sample. The pressure
gage was calibrated 80 that the readings could be converted t o pounds.
In the second paper by Tressler and Murray ( 6 ) , t h i s c u t t i n g gage
had been modified t o be motor driven. Also, it was concluded t h a t t h i s i n strument was not as s a t i s f a c t o r y as the penetrometer described below.
The Penetrometer of Tressler, Birdseye, and h r r q
In the same paper ( 5 ) i n which t h e c u t t i n g gage (see above) was described, a penetroneter was also described. The l a t t e r was an instrument then
in use in t h e New York Testing Laboratory f o r testing bituminous materials.
When first used t o t e s t meat, a penetrating needle 1 3/8 inches long and 0.15
19.
inches i n diameter was used.
0.07 inches.
The needle had a rounded point with a radius
The meat sample was held i n a l-inch deep container which was 1.5
inches i n diameter and was covered with a p l a t e having a 3/8 inch hole i n
the center. In the second paper ( 6 ) regarding t h i s instrument, a modified
sample container was described, It was a metal rectangular box with a telescoping t o p portion equipped with wing nuts on the side t o tighten it firmly
over the meat sample, The top had eight 3/8 inch holes through which t h e
needle of the penetrometer was inserted.
In operating t h i s penetrometer, the needle point was brought t o rest
i n the v e r t i c a l position on the top of t h e meat. A 255 gram weight was then
placed over the needle and held f o r exactly f i f t e e n seconds a t which time a
reading of t h e distance of penetration i n millimeters was recorded. The distance of penetration was recorded on a d i a l geared t o t h e movement of the
needle.
The Child-Satoriue Shear
I n 1938, Satorius and Child (7) reported some tenderness measurements using an instrument which recorded t h e number of pounds force on a gage
as shearing bars were pulled across a d u l l blade with a t r i a n g u l a r opening
through which the sample of meat was placed.
-
The Volodkevich Tenderness Instrument
Also i n 1938, Volodkevich (8), working a t t h e I n s t i t u t e of Refrigeration, University of Karloruhe, Germany, described an instrument i n which two
metal wedges o r a r t i f i c i a l t e e t h w e r e used. The meat sample was placed between
t h e two wedges, one of which was stationary, the other being movable by mechanicalmeans. The movement of the wedge was recorded on a revolving drum,
thereby giving a continuous recording of the exertion of pressure on the meat
sample. The slope o r character of the curve and t h e area under t h e curve on
t h e graph were used t o i n t e r p r e t t h e tenderness c h a r a c t e r i s t i c s of t h e sample.
Improvements i n t h i s instrument were reported by Krumbholz and
Volodkevich i n 1943 (9)
The Winkler Instrument
This instrument, reported by Winkler i n 1939 (lo), was similar i n
many respects t o t h e Volodkevich instrument and measured t h e force a s work
expressed i n u n i t thickness of sample. It also recorded curves which r e r mitted analysis of t h e character of t h e sarnple by t h e i r shape o r slope. The
area under t h e curve w a s used i n determining t h e work involved.
Motorized Ch r i et e l Texturemeter
In 1955, Miyada and Tappel (11) described the use of a Christel Texturemeter modified by attachment of an e l e c t r i c motor and reduction gears. The
t o t a l work and maximum shear force required t o press shearing prongs through
c y l i n d r i c a l samples of meat were recorded a t two-second i n t e r v a l s and work
20
.
diagrams were obtained by p l o t t i n g the recorded data i n pounds of force as a
function of distance measurements. Maximum shear readings were obtained by
knowing the c r e s t of the force-distance diagram. The area under the curve
represented t h e t o t a l work involved. Studies with beeswax as a homogeneous
sample indicated that t h i s method has considerable promise.
The Food Grinder as a Tenderometer
In the same paper t h a t t h e Motorized C h r i s t e l Texturemeter was reported, Miyada and Tappel (11)gave r e s u l t s of studies i n which a food grinder
was used t o measure tenderness. By wiring the motor of the grinder i n series
with an A. C . anmreter and recording the ampere readings a t five-second i n t e r vals, it was possible t o p l o t power consumption i n watts as a function of
time t o represent t h e t o t a l energy expended i n grinding t h e sample. Theoretically, it WEG stated, increased toughness of meat would produce a corresponding increase i n current consumption by the grinder.
This method was also t e s t e d with
s i z e s and shapes. Pieces of freeze-driecl
samples approximately 1 x 1 x 3/8 inchee,
the studies reported. Work diagrams were
of cooked beef.
+
tax and with meat samples of various
bice s femoris of beef were cut i n t o
re ydrated, and pressure cooked in
obtained by grinding 150 t o 1 7 0 grams
Recording Strain-Gage Denture Tenderometer
Since a l l mechanical means f o r measuring tenderness of food are designed t o simulate at l e a s t some of the components of chewing i n the human
mouth, it is not surprising t h a t an attempt should be made t o u t i l i z e complete
a r t i f i c i a l human dentures i n an apparatus. Although Volodkevich (8) had used
p a r t i a l dentures i n h i s instrument, it was not u n t i l 1 9 5 5 that Proctor, Davison,
Malecki, and Welch (12) reported construction of an apparatus which simulated
t h e frequency of chewing cycles and t h e coordination of grinding and crushing
motions of chewing and included means f o r measuring and recording these motions.
Briefly, t h e instrument consists of p l a s t i c dentures fastened t o an
a r t i c u l a t o r with simulated cheeks, l i p s , and tongue made from r e s i l i e n t
p l a s t i c material t o keep t h e food between t h e teeth. The upper movable dent u r e s are actuated by a motorized s p e c i a l transmission device t o give both
v e r t i c a l and lateral movements toward the firmly fixed lower denture. Strain
gages of an e l e c t r i c a l resistance type w i r e d t o 8, preamplifier and o s c i l l o scope were used t o record t h e s t r a i n s resulting from t h e chewing action. The
mechanism is so constructed t h a t the frequency of chewing was 45 cycles per
minute.
Tenderness of the food being measured was represented by t h e maximum
deflection i n millimeters from a zero l i n e which can then be converted t o
force (pounds). I n t e s t i n g t h e instrument with a tension apring and a l s o
with a piece of firm sponge rubber, the range of e r r o r a t 99.7410 probability
l e v e l was about 276 w i t h t h e spring and 2.3$ with t h e rubber. Tests with
c e r t a i n fruits, vegetables, and bread indicated the a d a p t a b i l i t y of t h e instrument. Relationships of readings obtained w i t h t h e Christtal Texturemeter
and w i t h the Strain-Gage denture Tenderometer showed that when f i r s t b i t e
measurements were made with the latter, t h e relationship between t h e two
21
instruments i s non-lineay. Apparently there is a f’undamental difference in
the q u a l i t a t i v e i n t e r p r e t a t i o n by the two instruments.
In a subsequent publication, Proctor, Ikvison, and Brody (13) reported a l t e r a t i o n s i n the Strain-Gage Denture Tenderometer whereby forcepenetration diagrams could be obtained. Characteristic diagrams f o r numerous
foods including r a w and broiled steak and sausages were reported,
It appears t o the author that t h e Strain-Gage Denture Tenderometer
o f f e r s an excellent opportunity f o r studying the chewing mechanism of the
hiurnan and the r e s u l t s so far have i l l u s t r a t e d t h e complexity of t h e mechanics
of chewing and t h e v a r i a b i l i t y o f c h a r a c t e r i s t i c s f r o m one food t o another.
It probably also selves t o i l l u s t r a t e that any instrument designed t o perform
only one function such as cutting, shearing, compression, o r penetration does
not give the complete picture of what i s experienced when a food i s chewed.
The Kramer Shear-Press
In 1951, Kramer, Aamlid, Guyer, and Rodger6 (14) described a new instrument f o r measuring tenderness of f r u i t s and vegetables. This instrument,
the rugged construction of which distinguishes it from most other instruments,
uses hydraulic pressure t o force a s e r i e s of metal plungers (plates) downward
through product held in a metal box. Originally t h e pressure required t o
plunge through the material i n the box was determined by measuring the pressure
of the hydraulic f l u i d . Nore recently 8 Dillon mechanical pressure gage* has
replaced the hydraulic pressure gage t o give a wider range of pressure recordings. I n e i t h e r arrangement, the Shear-Press measures the maximum pressure
required t o force the plunger through t h e material.
In a recent refinement of t h i s Shear-Press, called t h e Lee-Kramer
Shear-Press, a s e n s i t i v e d i a l mechanical pressure indicator which r e g i s t e r s
through a proving ring i s placed between the hydraulically operated piston
and the plunger p l a t e s , thus providing a more d i r e c t measure of force against
t h e product being t e s t e d .
A still later modification by Decker (15) u t i l i z e s a transducer in
conjunction w i t h the Dillon mechanical pressure gage, which, when connected
through an amplifier t o a recording device, r e s u l t s i n a corrtinuous chart recording of pressure as the plunger p l a t e s traverse through t h e product. The
recorder provides a pressure-time curve which can then be u t i l i z e d t o measure
t h e t o t a l work required t o penetrate the product,
A recent publication by Shannon, Muion, and Stadelman (16) presented
r e s u l t s with poultry meat t o show that there was a high correlation between
Kramer Shear-Press values (maximum pounds of force per gram of sample, using
one whole side of cooked b r e a s t ) and panel evaluation by chewing (number of
chews necessary p r i o r t o swallowing a 1 cm. cube of chicken). The samples of
chicken t e s t e d i n t h e Shear-Press were of such s i z e t h a t t e n blades were
forced through them.
*W.
C . Dillon, Inc., Van Nuys, California.
22
To t h e author's knowledge, the Shear-Press has not been reported t o
be used t o measure tenderness of meat, but i n our laboratories, we have had
some success in using it w i t h both cooked chicken and cooked beef. Samples
were prepared by c u t t i n g cylinders one inch i n diameter with a cork borer.
inch thick d i e and sheared off
The cylinders were then placed i n a p l a s t i c
inch t h i c k and one inch
with a sharp blade, thus making each sample exactly
i n diameter. The samples were placed i n the bottom of the t e s t c e l l box and
the Shear-Press operated so that plunger p l a t e s pushed through the sample.
The maximum force i n pounds per square inch was recorded f o r each sample.
t
Although we have made some e f f o r t s t o determine t h e precision of t h e
instrument, we have not been successful in obtaining adequate data t o compare
r e s u l t s with other tenderness measuring devices. One would expect, however,
t h a t t h e Shear-Press would have mechanical advantages over the Warner-Bratzler
Shear and most other instruments.
We have made an e f f o r t to adapt the desim of the c u t t i n g blade of
t h e Warner-Bratzler Shear t o the K r a m e r Shear-Press. However, t h i s ha8 not
been perfected.
Discussion
O f a l l of the instruments f o r measuring tenderness reviewed here,
the Warmer-Bratzler Shear has been by far the most widely used i n estimating
tenderness of meat. It has become w h a t might be termed standard laboratory
equipment where tenderness of meat i s t o be measured objectively. Whether o r
not it can be e a s i l y replaced by another instrument would be simply conjecture.
There i s l i t t l e doubt that t h e I*Jarner-Bmtzler Shear can be improved
upon mechanically t o reduce experimental error. A t least one study, by
Hurwicz and Tischer (171, has been conducted recently t o show that the variat i o n observed i n the experimental r e s u l t s can be ascribed primarily t o the
apparatus. These authors determined the maximum shear force, t h e t o t a l time
necessary f o r f a i l u r e i n shear, and the slope of the shear force versus time
curve f o r parawax and beeswax and various combinations of these two homogeneous materials. They came t o t h e conclusion that the slope of t h e shear
force versus time curve displayed the smallest coefficient of v a r i a t i o n
(4.795 v8. 7.41$ f o r maximum shear force).
The Kramer Shear-Press, with a l l of its modifications shows promise
as an instrument f o r measuring tenderness of meat and warrants further carel p u l study.
Conclusions
1. Of a l l of the several instruments which have been suggested f o r
use i n determining the tenderness of meat, the Warner-Bratzler Shear appears
t o have been the instrument of choice.
There is a great need f o r studies of instruments themselves t o
help solve the problem of objective determination of tenderness.
2.
3,
h r t h e r intensive study of the mechanics of chewing is needed.
23.
meat.
4. It is highly desirable t o have extensive rheological studies of
1.
Lehman, K. B. Studies of the causes f o r the toughness of meat.
Arch. Hyg. 63, 134 (1907).
2.
Warner, K. F. Progress report of the mechanical t e s t f o r tenderness of
meat. Proc. Am. SOC. Animal Production, 1928, p, 114.
3.
Black, W. H., ifarner, K. F., and blilson, C . V. Beef production and q u a l i t y
as affected by grade of' steer and feeding grain supplement on
grass. U. S. Dept. Agr, Tech. Wllletin 217 (1931).
4. Bratzler, L;yman J. Physical research in meat ( f i n a l report) U.S.D.A.
and Kansas S t a t e Bperiment Station (1933),
M, S. Thesis, Kansas State, 1932, "Measuring the tenderness of
meat by m a n s of a mechanical shear."
5.
Tressler, D. K., Birdseye, C. and Ehrray, W, T. Tenderness of meat.
I. Determination of r e l a t i v e tenderness o f c h i l l e d and quickfrozen beef. Ind. Eng. Chem. 24, 242 (1932).
6.
Tressler, D. K., and Murray, I?. T, Tenderness of meat. 11. Determina t i o n of period of aging Grade A beef required t o produce a tender
quick-frozen product. Ind. Ebg. Chem. 24, 890 (1932).
7.
Child, A. M.,
8.
Volodkevich, N. N. Apparatus f o r measurements of chewing resistance or
tenderness of foodstuffs. Food Research 3, 221 (1938).
and Satorius, M. J. ESfect of coagulation on press f l u i d ,
shear force, muscle-cell diameter, and composition of beef muscle.
Food Research 2, 619 (1938).
9. Krumbholz, G.,
10. Winkler, C . A.
and Volodkevich, N. N.
Gafienbauwiss 17, 543 (1943).
Tenderness of mat. I. A recording apparatus f o r its
estimation and r e l a t i o n between pH and tenderness. Can, J.
Research 17, p. 8-14 (1939).
and Tappel, A. I,. Meat tenderization. I. Two mechanical
devices f o r measuring texture. Food Technol, Vol. 10, No. 3,
March, 1956, p. 142.
11. Miyada, D. S.,
12. Proctor, B, E., Davison, Sol, Malecki, G. J., and Welch, May.
A recording Strain-gage denture tenderollleter f o r foods. I. Instrument evaluation and i n i t i a l tests. Food Technol. 9, 471 (1955)
13. Proctor, B, E., Dsvison, Sol, Brody, A. L.
.
A recording Strain-gage dent u r e tenderometer f o r foods. 11. Studies on t h e masticatory force
and motion, and the force-penetration relationship. Food Technol.
7, 327 (1956).
24.
14. Kramer, A., Aamlid, K., Guyer, R. B., and Rodgem, H. P,, Jr. Mew
shear-press predicts quality of canned l i m a beans. Food Eng. 23,
112 (1951)
.
15.
Decker, R. W, An instrument f o r measuring the rheoloaical properties
of a g r i c u l t u r a l commodities. Presented before American Society
of Agricultural Ebgineers, Chicago, I l l i n o i s (1956)
.
16.
Shannon, W. G., Marion, W. W., and S t a d e ' t , W. J. Effect of tempera t u r e and tim of scalding on the tenderness of breast meat of
chicken. Food Technol. 11, 284 (1957).
17.
3urwicz, E., and Tischer, R. G. Variation i n determinations of sheer
force by means of t h e "Bratzler-Varner Shear". Food Technol. 8,
391 (1954).
DR. HENRICKSON: Thank you, Harold, f o r those very important
and i n t e r e s t i r g remarks. I wonder, are you planning t o carry on the study
of evaluating these various instnunents?
DR. SCHUIEZ: Yes, as a matter of fact, we have a number of
measurements which I might have reported, but t h e y are so preliminary
I preferred not t o do i t . W
e rather favor the meat grinder type, but
we want to compsre t h e r e s u l t s there with t h i results with t h e Kmmer
shear and also with the Warner-Bratzler and the organoleptic. In each
instance we have comparisons with t h e organoleptic measurements.
DR. KENRICKSOM: Before we move i n t o t h e next t o p i c I should
like t o know if Bruce Morgan is here. I overlooked him. Be was very
much on the committee that planned t h i s program and he made a number of
suggestions.
I am sure that you will haxe some questions as we move on
through t h e program. I ahould like t o ask you t o jot them down so t h a t
during the discussion period, which will be led by D r . Hiner, we can
bring them up.
Now w e have heard about the mechanical means of measuring
tenderness. We have asked Dr. Deatherage if he would take the chemical
approach. W
e have overburdened him just a l i t t l e by asking him t o appear
t h i s morning and then t h i s afternoon, but 1 feel confident that he will
have some good information f o r us. Dr. Deatherage on "Basic Chemical
Considerations
."