443Chapter 25
Physical Sensors for Quality Control
during Processing
Marta Castro - Gir á ldez , Pedro Jos é Fito , Fidel Toldr á , and Pedro Fito
Introduction
The meat industry constitutes one of the main
sectors in the developed countries due to its
important protein contribution to the human
diet. The meat market has markedly changed
during the past several years, and the trend is
toward elaborate high - quality meat products.
For this reason, the industry must obtain meat
quality information during the production
process, in order to maintain quality stan-
dards. Over the past few years, certain physi-
cal sensors have been developed in order to
provide reliable meat quality information.
These sensors can be used in the process line
to obtain objective information in a fast and
nondestructive way. The most important are
mainly based on electromagnetic energy,
ultrasounds, and resonance techniques. These
sensors can directly provide important infor-
mation about meat composition and struc-
ture; sometimes, the information provided by
the sensor does not allow discrimination of
low - quality pieces, and it has to be imple-
mented with additional information on the
product.
This chapter presents an overview of
the main electromagnetic physical methods
for controlling meat products throughout
the production process. Moreover, a brief
summary of the most important marketed
sensors is presented.
Methods Based on
Electromagnetic Energy
There exist different kinds of sensors based
on the interaction of food with electromag-
netic waves, particularly: sensors using
visible radiation, ultraviolet or infrared,
microwaves, radiowaves, x - rays, or very
high frequency waves (Nuclear Magnetic
Resonance). Some applications have been
available in the market for several years,
particularly for laboratory use.
There exist also in - line applications for
foods: detection of foreign components
through the application of x - rays or control
of food composition by using Near Infrared
(Holm 2003 ). Concretely, microwave spec-
troscopy is currently used for the determina-
tion of moisture content in some cereals and
fruits (Kraszewski 1991, 1996 ; Kraszewski
and Nelson 1992, 1993a, b, 1994 ; Kraszewski
et al. 1998 ; Nelson and Bartley 2000 ),
density determination (Kress - Rogers and
Kent 1987 ; Kraszewski and Nelson 1992 ),
or, for example, fruit ripening (Nelson et al.
1993, 1994, 1995, 2006, 2007 ). There also
exist in - line applications for the meat
sector — for example, the evaluation of meat
tenderness by using x - ray absorptiometry
(Kr ö ger et al. 2006 ). Some of these applica-
tions will be described throughout this
chapter.