174 Chapter 8
observed by other researchers is usually a
surface phenomenon. Shear force values are
measured in a way to avoid the surface hard-
ening. Sensory panels, however, evaluate all
of the cooked meat, including the surface.
This may explain the differences seen
between shear force measurements and
sensory evaluation.
Cooking temperatures are important to the
tenderness of meat from older animals. The
increased cross - linking of collagen due to
age reduces tenderness. Beilken et al. (1986)
reported peak shear force values were not
infl uenced by animal age until heating tem-
peratures reached 50 ° C. Peak shear force
values of veal decreased above 50 ° C, and at
55 ° C, animal age differences became signifi -
cant. Peak shear force values decreased
above 55 ° C and 60 ° C for intermediate and
oldest age groups. At temperatures above
65 ° C, peak shear force values increased up
to 80 ° C before decreasing. The initial force
values increased steadily, with heating tem-
peratures up to 70 – 80 ° C before declining.
Final internal temperature also impacts
the juiciness of meat products. Fjelkner -
Modig (1986) reported pork fried to an inter-
nal temperature of 60 ° C was much more
juicy than that fried to 80 ° C. Boles et al.
(1991) also reported improved sensory scores
for pork chops cooked to 71 ° C compared
with chops cooked to 77 ° C. This difference
in juiciness could be related to the increased
cook yields seen with lower fi nal internal
temperatures (Boles et al. 1991 ).Color Development
Cooking has an important function in stabi-
lizing cured meat pigment formed by the
action of nitric oxide with myoglobin
(V ö sgen 1992 ). Without cooking of the
product, the color is more red than pink and
is less stable than it is after cooking. This is
one of the important functions of cooking for
cured meat production. End - point tempera-an increase in shear force upon cooking
occurred between ambient temperature and
60 °. Laakkonen et al. (1970) , however,
reported a major decrease in shear values
between 50 and 60 ° C, and Leander et al.
(1980) observed an increase in shear force as
the internal temperature increased from 63 ° C
to 73 ° C. Hearne et al. (1978) reported a small
decrease in shear values when the internal
temperature was between 40 ° C and 50 ° C,
with a greater decrease in shear value taking
place between 50 ° C and 60 ° C, and no differ-
ence seen between 60 ° C and 70 ° C. Alterations
in the collagen and meat microstructure
could explain some of the differences in the
observations reported.
Davey and Neiderer (1977) suggested
that heat tenderizes meat in three distinct
stages. The fi rst stage, up to 65 ° C, was from
increased proteolytic breakdown of myofi -
brillar elements; the second stage, between
70 ° C and 100 ° C, was through the destruction
or solubilization of collagen with little loss
of myofi brillar strength; and the third stage,
beyond 100 ° C, was from a combination of
collagen and myofi bril breakdown. These
researchers concluded that cooking in the
range of 70 ° to 100 ° C halved shear force
values and were as effective as aging in
increasing tenderness.
Sensory evaluation of meat cooked to dif-
ferent internal temperatures has been
reported. Some of the information does not
agree with what has been reported for shear
force values. Ritchey and Hostetler (1965)
reported no difference in ease to fragment a
sample when steaks were cooked to an inter-
nal temperature between 61 ° C and 80 ° C, and
scores for amount of connective tissue and
softness of connective tissue increased as the
internal temperature increased. Boles et al.
(1991) however reported reduced initial and
sustained tenderness when pork chops were
cooked to 77 ° C compared with 71 ° C.
Fjelkner - Modig (1986) also reported reduced
tenderness when chops were cooked to
higher internal temperatures. The hardening