**2. Carotenoids: definition, classification, and food sources**

Carotenoids represent a large family of non-water-soluble pigments that range from yellow to red and are predominantly found in fruits and vegetables [9, 10]. Generally, carotenoids are a class of isoprenoid molecules that are commonly referred to as pigments due to their characteristic yellow to red color. This physical property is due to a polyene chain containing 3–13 conjugated double bonds that act as a chromophore. All photosynthetic organisms (such as plants and algae) and some non-photosynthetic bacteria and fungi synthesize carotenoids that are tetraterpenes (terpenes consisting of eight isoprene units, C40H64) derived from phytoene, a 40-carbon isoprenoid [11, 12]. Some carotenoids called higher carotenoids are made up of a 45- or 50-carbon skeleton, while those having carbon skeletons with fewer than 40 carbons are called apocarotenoids [13]. Carotenoids can be synthesized de novo by flora and microbes, and do not occur naturally in mammals with minor exceptions [14]. Therefore, carotenoids found in animal tissues are either directly obtained from their diets or partially modified during metabolic reactions [15, 16]. Carotenoids are essential compounds in all photosynthetic species, such as algae, cyanobacteria, and plants, and are involved in basic physiological processes, such as photoprotection and photosynthesis. They serve numerous important functions, such as light-harvesting, photoprotection during photosynthesis, and photooxidative damage prevention, and also accumulate in non-photosynthetic organs of plants, such as fruits, pericarps, seeds, roots, and flowers. They provide color to flowers and fruits which is useful in pollination and seed dispersal through pollination vector attraction. They also serve as precursors for the biosynthesis of the phytohormone, abscisic acid (ABA) in non-photosynthetic organs [12, 13, 16].

*Potential of Carotenoids from Fresh Tomatoes and Their Availability in Processed Tomato-Based… DOI: http://dx.doi.org/10.5772/intechopen.103933*
