310 Part III: Muscle Foods
Physical Techniques
Near infrared reflectance (NIR) is applied for the
rapid and nondestructive analysis of meat composi-
tion in fat, protein, and water (Byrne et al. 1998,
Rodbotten et al. 2000). This technique has also been
applied to aged meat, giving a good correlation with
texture, and thus constituting a good predictor for
meat tenderness. Video image analysis is very useful
for the measurement of carcass shape, marbling, and
meat color. Conductivity has been in use for several
years to predict meat composition and quality. Ultra-
sounds are based on the measurement of different
parameters such as velocity, attenuation, and back-
scattering intensity and may constitute a valuable
tool for the measurement of meat composition (Got
et al. 1999, Abouelkaram et al. 2000). Texture analy-
sis, as the image processing of the organization of
grey pixels of digitized images, can be used for the
classification of photographic images of meat slices
(Basset et al. 2000). This technique appears to give
good correlation with fat and collagen, which are
especially visible under UV light, and would allow
classification according to three factors: muscle
type, age, and breed (Basset et al. 1999).
Nuclear magnetic resonance has good potential as
a noninvasive technique for better characterization
and understanding of meat features. Thus, magnetic
resonance imaging can give a spatial resolution that
characterizes body composition. This technique is
well correlated to important meat properties such as
pH, cooking yield, and water-holding capacity (Lau-
rent et al. 2000). Magnetic resonance spectroscopy
may be useful to determine the fatty acid composi-
tion of animal fat. This technique may have further
applications; for example, in the possible use of(^23) Na imaging to follow brine diffusion in cured meat
products (Renou et al. 1994).
Biochemical Assay Techniques
Biochemical assay methodologies are based on bio-
chemical compounds that can be used as markers
of meat quality. The mode of operation is essen-
tially schematized in Figure 13.11. Some of the
most promising techniques include assay of proteo-
lytic muscle enzymes and use of peptides as bio-
chemical markers.
The assay of certain proteolytic muscle enzymes
such as calpain I, alanyl aminopeptidase, or dipep-
Figure 13.11.Example of application of biochemical-based methods for evaluation of meat quality. A sample of the
carcass (1)is mixed with buffer (2)for enzyme extraction and homogenization (3). Enzyme extracts are placed in the
wells of a multiwell plate and synthetic substrates, previously dissolved in reaction buffer, are added (4). The
released fluorescence, which is proportional to the enzyme activity, is read by a multiwell plate spectrofluorimeter (5)
and computer recorded (6).