methods for their objective color specification is very important for
the food industry.
1.4 Color
Measurement
The color of the food can be evaluated visually or instrumentally.
The visual analysis of the color consists in the evaluation of its
characteristics by means of the sense of sight/vision. Information
concerning the training and selection of the panelists, sample presentation, illumination requirements, observation geometry, etc.
for the visual assessments can be found in classical reference texts
[24, 25]. The visual color assessment can also be carried out by
comparing the color of a test sample with those of standards present
in color scales or atlases (DIN system, Munsell system, OSA-UCS
system, and Ostwald system, among others). The main advantages
of the visual evaluation of color is that is a cheap and simple
methodology which does not usually require sophisticated instrumentation, although the color specification achieved is
subjective [4].
Among the main advantages of the instrumental evaluation of
color in relation to visual methods is that the inevitable subjective
component of the latter can be eliminated. Other advantages
include rapidity, minimal or no manipulation of the samples, the
possibility of automation, versatility, the possibility of the acquisition of a large volume of information (colorimetric parameters,
spectroscopic data), among others [4]. In these types of analysis,
the color is expressed by means of the color coordinates. Certain
characteristics related to the light, the object and the observer must
be adjusted beforehand to ensure a correct measurement of the
color (see Note 1). There are two main types of instruments that
measure the color of an object: those that directly measure the
tristimulus values, called colorimeters, and those that measure the
radiometric or photometric magnitude that characterizes the
source or object from which the tristimulus values are calculated
(spectrophotometer and spectroradiometer) [26].
1.4.1 Colorimeters
Colorimeters directly measure the color of primary radiation sources
(which emit light) and secondary radiation sources (which reflect or
transmit external light), obtaining the tristimulus values X, Y,
Z optically, not mathematically. The colorimeter reproduces the
response of only a standard observer and a preestablished standard
illuminant, so the values obtained may differ from one instrument
to the other [27].
1.4.2
Spectrophotometers
Spectrophotometers measure the spectral distribution of transmittance or reflectance of an object from which the color can be
calculated under different theoretical conditions. In the spectrophotometer the transmittance measure is the ratio between the
amount of transmitted light that reaches the detector once it has
passed through the sample and the amount of light incident on
108
Paula Mapelli-Brahm et al.
the food industry.
1.4 Color
Measurement
The color of the food can be evaluated visually or instrumentally.
The visual analysis of the color consists in the evaluation of its
characteristics by means of the sense of sight/vision. Information
concerning the training and selection of the panelists, sample presentation, illumination requirements, observation geometry, etc.
for the visual assessments can be found in classical reference texts
[24, 25]. The visual color assessment can also be carried out by
comparing the color of a test sample with those of standards present
in color scales or atlases (DIN system, Munsell system, OSA-UCS
system, and Ostwald system, among others). The main advantages
of the visual evaluation of color is that is a cheap and simple
methodology which does not usually require sophisticated instrumentation, although the color specification achieved is
subjective [4].
Among the main advantages of the instrumental evaluation of
color in relation to visual methods is that the inevitable subjective
component of the latter can be eliminated. Other advantages
include rapidity, minimal or no manipulation of the samples, the
possibility of automation, versatility, the possibility of the acquisition of a large volume of information (colorimetric parameters,
spectroscopic data), among others [4]. In these types of analysis,
the color is expressed by means of the color coordinates. Certain
characteristics related to the light, the object and the observer must
be adjusted beforehand to ensure a correct measurement of the
color (see Note 1). There are two main types of instruments that
measure the color of an object: those that directly measure the
tristimulus values, called colorimeters, and those that measure the
radiometric or photometric magnitude that characterizes the
source or object from which the tristimulus values are calculated
(spectrophotometer and spectroradiometer) [26].
1.4.1 Colorimeters
Colorimeters directly measure the color of primary radiation sources
(which emit light) and secondary radiation sources (which reflect or
transmit external light), obtaining the tristimulus values X, Y,
Z optically, not mathematically. The colorimeter reproduces the
response of only a standard observer and a preestablished standard
illuminant, so the values obtained may differ from one instrument
to the other [27].
1.4.2
Spectrophotometers
Spectrophotometers measure the spectral distribution of transmittance or reflectance of an object from which the color can be
calculated under different theoretical conditions. In the spectrophotometer the transmittance measure is the ratio between the
amount of transmitted light that reaches the detector once it has
passed through the sample and the amount of light incident on
108
Paula Mapelli-Brahm et al.