The relationships between the chemical structure of carotenoids and the features of their UV–visible absorption spectra have
been long-known and have been treated in great detail in the
bibliography [5]. The translation of this information into color
parameters is more recent though [6, 7]. The carotenoids absorb
mainly violet and bluish light (ca. 400–500 nm), so they typically
exhibit yellow, orange, or reddish tones (Fig. 2) [3]. In particular, it
is considered that at least 7 c.d.b. are necessary for a carotenoid to
exhibit color [6, 7]. Thus, phytoene and phytofluene, with 3 and
5 c.d.b. respectively, are colorless carotenoids. In addition to the
chemical structure of carotenoids, its colors may depend on other
factors such as concentration, aggregation of molecules or interaction with other molecules [3].
1.3 Importance of
Color in Foods
The color of food is one of the first sensory characteristics that we
perceive and one of the most important attributes for the consumer. The visual perception of color is a factor of great importance
because it can have an impact on the emotions of the consumers
and therefore can be a decisive factor in the food purchasing decisions, being, in many cases, even more important than the perception of taste and smell [8]. In fact, it is well known that consumers
can relate color to other sensory characteristics, like sweetness and
flavor [9]. As an example, in olive oil, whose color is mainly due to
carotenoids and chlorophylls, green color is associated with bitter
and spicy tastes while yellow with fruity flavors [10]. The importance of colour in foods owing their color mainly to carotenoids like
citrus and olive oils as well as visual and instrumental color measurement methodologies is reviewed elsewhere [11, 12]. Therefore,
one of the major interests of the food industry for carotenoids lies
in the use of them as colorings in food and feed. Both carotenoids
(like β-apo-8
0 -carotenal, canthaxanthin, lutein, lycopene, or
β-carotene,) and carotenoid containing products (paprika, annatto,
diverse extracts) are approved for this purpose by diverse regulatory
bodies [3, 13]. Among the foods carotenoid can be used as colorant additives are sauces, dairy, soft drinks, fruit juices, butter, margarines, and confectionery, among others [14].
Carotenoids are also used in feed additives to confer appealing
colours to foods of animal origin like egg yolk or fish flesh. Both,
carotenoids obtained by chemical synthesis (such as astaxanthin or
canthaxanthin, among others) or products containing these carotenoids (such as petals of Tagetes erecta as source of lutein, red
pepper as source of capsanthin or microbial or crustacean sources
of astaxanthin) have been used [15–22]. The livestock industry is
also making important efforts to increase the consumption of
carotenoids in livestock to obtain meat with more attractive colors
for the consumer [23]. Given the unarguable significance of the
color of foods for the consumers, the use of affordable and reliable
Applications of Visible Spectroscopy and Color Measurements in the. . .
107
been long-known and have been treated in great detail in the
bibliography [5]. The translation of this information into color
parameters is more recent though [6, 7]. The carotenoids absorb
mainly violet and bluish light (ca. 400–500 nm), so they typically
exhibit yellow, orange, or reddish tones (Fig. 2) [3]. In particular, it
is considered that at least 7 c.d.b. are necessary for a carotenoid to
exhibit color [6, 7]. Thus, phytoene and phytofluene, with 3 and
5 c.d.b. respectively, are colorless carotenoids. In addition to the
chemical structure of carotenoids, its colors may depend on other
factors such as concentration, aggregation of molecules or interaction with other molecules [3].
1.3 Importance of
Color in Foods
The color of food is one of the first sensory characteristics that we
perceive and one of the most important attributes for the consumer. The visual perception of color is a factor of great importance
because it can have an impact on the emotions of the consumers
and therefore can be a decisive factor in the food purchasing decisions, being, in many cases, even more important than the perception of taste and smell [8]. In fact, it is well known that consumers
can relate color to other sensory characteristics, like sweetness and
flavor [9]. As an example, in olive oil, whose color is mainly due to
carotenoids and chlorophylls, green color is associated with bitter
and spicy tastes while yellow with fruity flavors [10]. The importance of colour in foods owing their color mainly to carotenoids like
citrus and olive oils as well as visual and instrumental color measurement methodologies is reviewed elsewhere [11, 12]. Therefore,
one of the major interests of the food industry for carotenoids lies
in the use of them as colorings in food and feed. Both carotenoids
(like β-apo-8
0 -carotenal, canthaxanthin, lutein, lycopene, or
β-carotene,) and carotenoid containing products (paprika, annatto,
diverse extracts) are approved for this purpose by diverse regulatory
bodies [3, 13]. Among the foods carotenoid can be used as colorant additives are sauces, dairy, soft drinks, fruit juices, butter, margarines, and confectionery, among others [14].
Carotenoids are also used in feed additives to confer appealing
colours to foods of animal origin like egg yolk or fish flesh. Both,
carotenoids obtained by chemical synthesis (such as astaxanthin or
canthaxanthin, among others) or products containing these carotenoids (such as petals of Tagetes erecta as source of lutein, red
pepper as source of capsanthin or microbial or crustacean sources
of astaxanthin) have been used [15–22]. The livestock industry is
also making important efforts to increase the consumption of
carotenoids in livestock to obtain meat with more attractive colors
for the consumer [23]. Given the unarguable significance of the
color of foods for the consumers, the use of affordable and reliable
Applications of Visible Spectroscopy and Color Measurements in the. . .
107