**6. Lycopene in tomatoes: Chemical and physical properties affected by food processing**

The importance of lycopene is mainly due to its beneficial properties for human health. Lycopene protects humans from attack by pathogenic agents responsible for a number of chronic diseases, such as cardiovascular disease, different types of cancer (digestive tract, cervix, breast, skin, bladder, and prostate), hypertension, osteoporosis, neurodegenerative diseases, male infertility, and even the transmission of immunodeficiency syndrome from mothers to babies [99].

of the most important antioxidants found in tomato fruits [86, 87]. It is believed that carote‐ noids, found in tomato fruits (which can reach 3.67 mg 100 g-1), may reduce the risk of human diseases, in particular cardiovascular diseases and prostate cancer [88, 89]. Epidemiological studies have shown the existence of an inverse relationship between lycopene intake and prostate cancer risk. Patients with prostate cancer had lower lycopene levels in their blood plasma than control patients [90]. The inverse relationship is also expressed in aggressive prostate cancer cases. Prostate cancer risk was lowered by 83% for the patient group with the highest lycopene plasma levels (0.40 μmol l-1) compared to the lowest concentration (0.18 μmol


There have been several epidemiological studies that have outlined the relationship between lycopene concentrations in the blood plasma and cardio vascular disease risk. One found that men who had coronary disorders had lower lycopene levels in their plasma compared to men without coronary disorders [35]. Alternatively, a study of the relationship between the lycopene level in fatty tissues and heart disease showed that an increased lycopene concen‐

Lycopene consumption efficiency is determined by lycopene (the active principle compound of tomatoes, which acts as an antioxidant) bioavailability. Unfortunately, the mechanism of lycopene uptake remains unclear. It is known that absorption of consumed lycopene reaches only 10% (in some cases can increase up to 30%). Furthermore, lycopene absorption from fresh tomatoes is less than from the processed products (tomato paste or sauce) [7] because the mechanical and thermal treatment of tomatoes enhances lycopene uptake. There are other factors that affect the process of lycopene absorption. It has been found that the addition of oils in tomato dishes enhances carotenoid absorption [95], but the addition of various fibre

It is believed that processed fruits and vegetables are less valuable than fresh, but lycopene is better absorbed from processed tomatoes. Heat-treated tomatoes can have more bioavailable lycopene, and this justifies tomatoes as a functional food [2, 5, 6]. Undoubtedly, the effect will be negligible or absent, if the consumed amount of lycopene is 6-8 mg per day. It has been reported that 25-35 mg of lycopene should be consumed daily, that is, approximately 200 g

Thus, tomatoes, as a source of various antioxidants and vitamins, can increase the human's body resistance to the impact of radiation, reduce cholesterol accumulation, heal some skin

**6. Lycopene in tomatoes: Chemical and physical properties affected by food**

The importance of lycopene is mainly due to its beneficial properties for human health. Lycopene protects humans from attack by pathogenic agents responsible for a number of

more tomato dishes per day can reduce the risk of developing prostate cancer [89, 92].

tration had a protective effect against cardiac dysfunction [93, 94].

diseases, and prevent cardio diseases and prostate cancer [8, 98].

substances can reduce absorption [96].

tomatoes per day [97].

**processing**

l

64 Plants for the Future

The availability of lycopene in food may depend on several factors. First, the carotenoid content of food may be increased by mechanical processing. Food processing may be beneficial because it disrupts food matrices, facilitating the release and solubilisation of carotenoids, resulting in increased carotenoid bioavailability, including lycopene bioavailability [100]. Within the plant, lycopene is part of the matrix in chloroplasts or chromoplasts, and the absorption of lycopene from raw tomatoes is low because it is occurs mostly in the *trans*-isoform and is tightly bound within the matrix [101]. Second, the bioavailability of lycopene is greatly increased by thermal (cooking or by commercial) processing, such as conversion to soups, sauces, and catsup [102]. Nevertheless, increased uptake or higher blood levels of lycopene have been achieved predominantly by the intake of tomatoes or tomato products rather than by the intake of purified lycopene [8, 103]. In synthetic nutritional supplements, lycopene is in the form of an oleoresin embedded in phospholipid complexes and oils. Third, the addition of lipids, such as vegetable oils, increases lycopene absorption [101]. For example, it has been reported that lycopene is more efficiently absorbed when tomato juice is warmed with a supplemental lipid. Moreover, lycopene is lipophilic, and the dissolution of carotenoids in a lipid phase occurs in the stomach and the duodenum. Roldan-Gutiérrez and de Castro [104] reported that, due to the action of bile salts and pancreatic lipases, carotenoids in a lipid phase (droplets) enter the duodenum and form multilamellar lipid vesicles. During intestinal absorption, carotenoids and lycopene incorporate into chylomicrons and interact with other carotenoids [104]. Interactions with other carotenoids are complex and have not been fully studied. For example, β-carotene in the same dish as lycopene causes an increase in the absorption of lycopene [102].

Moreover, during exposure to thermoenergy, oxygen, and light, lycopene can undergo isomerisation and degradation. Isomerisation converts all-*trans*-isomers to *cis*-isomers and results in a reduction of the biological properties of lycopene [99]. Red tomatoes normally contain 94%-96% all-*trans*-lycopene. All-*trans*-lycopene is thermodynamically the most stable form. Some authors have reported that the formation of *cis*-isomers of lycopene may increase biological activity. *Cis*-isomers are more soluble in bile acid micelles and may be preferentially incorporated into chylomicrons compared with *trans*-isomers [105]. *Cis*-isomers of lycopene have distinct physical characteristics and chemical behaviours from all-*trans*-isomers, includ‐ ing decreased colour intensity, greater polarity, lesser tendency to crystallise, and greater solubility in oil and hydrocarbon solvents. However, these physical characteristics have a direct impact on the sensory qualities and consumer health benefits of food. The determination of the degree of lycopene isomerisation during processing and storage would provide a measurement of the potential health benefits of tomato-based foods [99].

An overview of the observed results of Haymann and colleagues [106] during the isomerisation processes of lycopene is given in Fig. 16. The study demonstrated that various *cis*-isomers (predominantly *5-cis*- and *9-cis*-lycopene) were formed during energy-rich irradiation, whereas at the same time degradation of all-*trans*-, *15-cis*-, *13-cis*-, and *7-cis*-lycopene occurred [108]. A theoretical study on the *cis−trans* isomerisation of lycopene revealed that *5-cis*- and *9 cis*-lycopene are more stable than other isomers since their rotational barrier to reisomerise the all*-trans* configuration is higher (Δ*E*<sup>r</sup> ‡ = 35.2 kcal/mol and 23.1 kcal/mol, respectively) than that of all other isomers (Δ*E*<sup>r</sup> ‡ = 16.8 to 19.9 kcal/mol) [106]. Furthermore, the stability of *5-cis*lycopene and *9-cis*-lycopene is also induced by their much lower relative energy compared to other isomers. Those effects lead to the accumulation of the *5-cis*- and *9-cis*-isomers during irradiation with halogen lamp. In contrast, low rotational barrier (Δ*E*<sup>r</sup> ‡ = 22.1 kcal/mol) and one of the highest potential energies of all mono*-cis*-isomers results in a dominant degradation of *7-cis*-lycopene during energy-rich irradiation [106, 107]. All-*trans*-lycopene underwent degradation, while the concentration of *cis*-isomers, mainly *13-cis* and *9-cis*, increased. The investigation showed that the *5*-*cis*-isomer changed distinctively during lycopene storage compared to the other lycopene isomers [106].

**Figure 16.** Thermal and photoinduced isomerization leads to degradation and formation of lycopene isomers in lyco‐ pene extract [106].

After intestinal absorption, carotenoids are carried to the blood stream by chylomicrons via the lymphatics. Concerning transport in the plasma, carotenoids are transported by lipopro‐ teins, and transport depends on the carotenoid structure. Therefore, lycopene is found in the aqueous interface at the lipoprotein surface. For this reason, lycopene is transported in lowdensity lipoproteins, and oxygenated carotenoids are transported in both low-density and high-density lipoproteins [104].

It is important to develop more attractive ready-to-eat products to contribute to the increased consumption of fruit and vegetable products and their health benefits for consumers. Food processing should be adapted to enhance the bioavailability of nutrients [108]. Additional information needs to be collected on the thermal behaviour of lycopene before we can have definitive answers regarding its physical state and stability during processing and cooking. Little is known about the stability of lycopene in supplemental form [109].
