**3. Carotenoids in tomato and processed products**

## **3.1 Carotenoids in fresh tomato**

Carotenoids are highly abundant in tomatoes [29]. Over 20 carotenoids have been previously characterized in tomato and tomato-based products, this includes lycopene, α-carotene, β-carotene, γ-carotene, ξ-carotene, ζ-carotene, phytoene, phytofluene, cyclolycopene, neurosporene, lutein, violaxanthin, neoxanthin, zeaxanthin, α-cryptoxanthin, and β-cryptoxanthin [26, 27]. The carotenoid content in tomato fruits is unevenly distributed and its composition is highly dependent on the cultivar (genotype), degree of maturation, climatic conditions, environmental factors, and cultural practices [7, 22, 30]. The maximum quantity of total carotenoids and lycopene is found in the outer pericarp, while the locules have a high proportion of carotene compounds [31].

Carotenoids are synthesized in the leaves, flowers, and fruits of tomato plants. Lutein is found in high quantities in the leaves where it functions as a photoreceptor during photosynthesis. The xanthophylls, violaxanthin, and neoxanthin are abundant


#### **Table 2.**

*Mean carotenoid composition of ripe fruits of different types of tomato.*

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

in flowers and are responsible for their characteristic yellow coloration. The ripe fruits of *Lycopersicum esculentum* owe their intense red color to the lycopene, the main carotenoid at this maturity stage [7]. The most widely available carotenoids in ripe tomato fruits are lycopene (≈90%), β-carotene (≈5–10%), and lutein (<1%). Lycopene and β-carotene are mainly responsible for the characteristic color of ripe tomatoes [30]. These carotenoids are important components for the determination of quality characteristics of fresh tomatoes in routine analyses [16, 30]. **Table 2** shows the carotenoid profile of cultivars from different types of tomatoes.

There is a diverse carotenoid profile within tomato cultivars. This is particularly true for traditional varieties constituting a wide source of genetic variation [24]. Tomatoes are abundant sources of lycopene, with average concentrations ranging from 8 to 40 μg/100 g of FW. This represents about 80% of the total dietary intake of this carotenoid [34]. Lycopene is a polyunsaturated compound containing 13 double bonds that can exist in *trans*- and *cis* configurations. In fresh tomatoes, lycopene is principally found in *trans*-conformation [35]. Lycopene is synthesized massively during tomato ripening. Consequently, the highest content of lycopene is observed in ripe tomato fruits [7, 29, 27]. Open field-cultivated tomatoes were reported to have a higher lycopene content (ranging from 5.2 to 23.6mg/100g FW) than greenhousecultivated tomatoes (0.1 to 10.8mg/100gFW) [35].

The β-carotene content in tomatoes is approximately one-tenth of the lycopene content [31]. β-Carotene is equally an essential carotenoid identified in tomatoes, of special interest mainly due to its pro-vitamin A activity [33]. In commercial cherry tomatoes, β-carotene quantity reached 1.26 mg/100 gFW (**Table 2**). The uniqueness of β-carotene is that it is the most powerful precursor to vitamin A (comprised of retinol, retinal, and retinoic acid, which are classified as retinoids). Vitamin A activity can be measured as retinol equivalents (RE) or retinol activity equivalents (RAE). Current assumptions regarding the RAE or RE of the three major provitamin A dietary carotenoids based on their bioavailability from foods, consider β-carotene as a prominent contributor to the vitamin A intake with potential for conversion to retinol, which is twice that of α-carotene and β-cryptoxanthin [36]. The central oxidative cleavage of β-carotene in the intestine catalyzed by β-carotene 15,15′-monooxygenase allows for its conversion to two molecules of vitamin A, compared to one molecule from another provitamin A carotenoids [37]. Lesser amounts of lutein are present in tomatoes, with concentrations up to 338 μg/100 gFW (**Table 2**). Raw tomato purchased from the supermarket was reported to have lutein concentrations up to 32 μg/100 gFW, against a lutein content up to 800 μg/100 gFW reported in a cherry tomato variety [35]. Other carotenoids identified in tomatoes are the colorless hydrocarbon carotenoids (carotenes), phytoene, and phytofluene, precursors of colorful carotenoids such as lycopene and β-carotene [24].

#### **3.2 Carotenoids in processed tomato products**

Although tomatoes are consumed fresh, over 80% of tomato intake is in the form of processed products, such as tomato pulp, ketchup, juice, and sauce [38]. During food processing, the naturally occurring carotenoid composition of products is altered. Reactions induced by heat, acids, light, or oxygen exposure occur as a consequence of the processing steps [39]. Thermal treatment is responsible for an increased level of total carotenoid content and antioxidant capacity by 30% and 15%, respectively. Tomato processing may activate the enzymes ε- and β-carotene cyclase, involved in the synthesis of β- and α-carotene. Consequently, stimulating the


**Table 3.**

*Concentration of carotenoids in processed tomato products.*

production of α- and β-carotene [40]. The concentrations of carotenoids in different tomato products are depicted in **Table 3**.

During tomato processing, an increase in carotenoid content on a fresh weight basis is observed as a result of water loss [41]. This may also be ascribed to the technological treatments of pasteurization and homogenization which can improve the extractability of pigments from the fruit matrix. For canned tomato products, the carotenoid increase can be explained by the use of tomato juice derived from high ripening stage tomatoes with very high lycopene content [42]. Increased content of the major tomato carotenoids, lycopene, and β-carotene was reported after processing at 45°C (drying) and 95°C (thermal treatment of tomato juice) [43]. Similarly, an increase in lycopene content in tomatoes exposed to drying at 42°C was previously demonstrated. This occurs due to the release of lycopene bound from the tissues [44]. A decrease in the lycopene content of dried tomatoes treated at 55–110°C was found [45–47]. On a dry weight basis, there is an increase or decrease of the lycopene content depending on the origin of the tomato variety, while the β-carotene content reduces or remains relatively constant [41]. Nevertheless, in certain instances, processing causes little or no change in the content and activity of naturally occurring bioactive compounds [48].

## **4. Bioavailability of tomato carotenoids**

Only 25 carotenoids are present in the human bloodstream, out of approximately 40 carotenoids present in foods normally included in the human diet and most of these carotenoids found in human blood are present just in fresh tomato and related products [43]. This is due to the selective intake of carotenoids in the gastrointestinal tract and the food matrix surrounding them [16, 43]. Carotenoids present in the human serum tend to be associated with specific body tissues. For example, lycopene is concentrated in the prostate, β-carotene is concentrated in the corpus luteum, and lutein and zeaxanthin are concentrated in the neural retina and brain neocortex. These carotenoids can retard the development of disease at these locations based on reducing inflammatory and oxidative stress [49]. For carotenoid intake, the food matrix made up of fiber or protein must first be broken down by mastication, gastric acid, pancreatic enzymes, and bile acids to ensure the release of these nutrients [16]. Carotenoid release from the tomato matrix and its subsequent incorporation in the oil and micellar phase are crucial steps in rendering these compounds bioavailable during digestion [20]. There is a great variation in the bioaccessibility and bioavailability

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

of different dietary carotenoids between the type of food consumed (whether it is chopped or pureed, raw or cooked, and whether or not fat is consumed simultaneously), and for a given carotenoid in different foods [36, 50]. Bioaccessibility is defined as the fraction of carotenoid released during digestion from the food matrix to mixed micelles and thus, made accessible for absorption in the gut following digestion [51], whereas bioavailability of carotenoids is the amount of these micronutrients that are absorbed by the intestinal absorptive cell, transported in the bloodstream and/or deposited in target tissues where it can exert its biological function [52].

#### **4.1 Processing effects on tomato carotenoid bioavailability**

The bioavailability of carotenoids is higher from processed foods than their raw or less processed counterparts [52]. In general, the relative bioavailability of carotenoids has been estimated to vary from less than 10% in raw, uncooked vegetables to 50% in oils or commercial preparations [50]. Processing techniques such as grinding, marinating, fermentation, freezing, and moderate heating improve the release and absorption of carotenoids. This is explained by the release of these nutrients from the food matrix as a result of the disruption of plant tissues and the transfer of carotenoids to the lipid carrier. It is believed that since carotenoids in plant tissues occur in the form of complexes with proteins, mild thermal processes allow them to break down these connections and destroy cellulose structures in plant cells, thus contributing to an increase in the absorption of these compounds [53]. The bioavailability of β-carotene is improved as a result of gentle heating or enzymatic disruption of the vegetable cell wall structure during processing [48]. Lycopene bioavailability is higher in thermally processed tomato products, such as paste, puree, ketchup, juice, soup, and sauce, than in fresh tomatoes [33, 35, 54]. This fact could be attributed to the lower availability of lycopene from the raw tomatoes where it is probably bound in the surrounding food matrix [55]. The incorporation of oil in tomato sauce has been reported to enhance the accessibility and extractability of carotenoid compounds in tomatoes. A constant quantity of fat and other ingredients significantly increases the bioavailable lycopene in tomato paste compared to fresh tomatoes [40]. Previous research demonstrated that a combination of homogenization and heat treatment improves the bioavailability of carotenoids from fruits and vegetables. Studies on the effect of heat treatment and homogenization on the carotenoid bioavailability of industrially heat-treated peeled and canned tomatoes have shown that blood plasma lycopene responses increased with increasing degree of homogenization and additional heat treatment, while homogenization enhanced the plasma response of β-carotene only if the tomatoes were not subjected to additional heat treatment [56]. Moreover, high-pressure homogenization has a greater impact on the bioavailability of carotenoids compared to homogenization under normal pressure, since it disrupts extra cell membranes [42].

#### **4.2 Effect of isomerization on bioavailability**

The physical state of carotenoids has been proven to significantly impact their bioaccessibility and bioavailability and consequently their health-promoting properties [39]. Carotenoids exist in a variety of geometric isomers and predominantly occur in their all-trans conformation in fresh tomatoes. For instance, trans-lycopene accounts for approximately 95% of the lycopene present in raw tomatoes [48]. Food processing may induce the formation of cis isomers possessing different biological properties. Trans-to-cis isomerization can also be initiated during storage [55]. Trans-isomers are thermodynamically more stable, whereas cis are more polar, more soluble in oil and hydrocarbon solvents, and are less prone to crystallization than their all-trans counterparts [38, 55]. More than 50% of the carotenoids identified in the human body are in the cis configuration, suggesting that this is the most bioavailable form [40]. Several reports have demonstrated that the cis isomers of lycopene are more bioavailable and play a more important biological function than all-trans lycopene properties [57, 58] because of being more soluble and easily absorbed from the intestinal lumen than the trans-lycopene [59]. Therefore, lycopene from processed tomato products is generally more bioavailable than the one from the unprocessed counterparts. Nevertheless, inadequate processing and storage conditions can cause isomerization during the byproducts' formation, diminishing the absorption of carotenoids and making the product less desirable to the consumer [20]. On the other hand, cellular studies reported that cis isomers of β-carotene are not easily absorbed by intestinal enterocytes. High quantities of cis isomers of ß-carotene are not detected in the bloodstream, suggesting preferential absorption of the all-trans isomer of nutrients possessing provitamin A activity [52].
