Carotenoids are rich sources of pro-vitamin A. These compounds are usually obtained from pumpkins (Cucurbita maxima, C. pepo, and C. moschata), as well as orange and yellow sweet potatoes. Carotenoids are C40 tetraterpenoids, which stand out for their antioxidant activity. Among them are carotenes (very apolar carbon and hydrogen molecules, like lycopene, β-carotene, α-carotene) and oxygenated derivatives and xanthophylls composed of oxygenated functions (less apolar molecules such as lutein, zeaxanthin, cryptoxanthin). β-Carotene is the most commonly found carotenoid, accounting for 25–30% of the total carotenoid content of plants. It is also the most active carotenoid, with the highest bioconversibility in the human body. β-Carotene is a suppressor of tumorigenesis in the skin, lung, liver, and colon, promoting the cessation of the cell multiplication cycle. Thermal processing can affect the sensory characteristics and the antioxidant compounds, altering the antioxidant potential of foods. Time, temperature, and style of cooking are determinant conditions for the increase or decrease of total antioxidant activity. The biological activity of carotenoids depends on their bioaccessibility and solubilization in the gastrointestinal tract. The purpose of this chapter is to offer information about some raw plant materials containing carotenoids.
- raw plant materials
- yellow bitter and sweet cassava
- sweet yellow and orange potato
Some carotenoids are rich sources of pro-vitamin A and carrots (
Carotenoids are chemically defined as C40 tetraterpenoids (naturally occurring hydrocarbons and their derivatives), obtained by the union of eight isoprenoid (C5) units of five carbon atoms .
The purpose of this chapter is to offer some information about some raw plant materials containing high and lower carotenoid contents.
2. Raw plant materials
Due to their intense and striking colors, carotenoids have always been a subject of interest of scientists. The first report of isolation of these substances is from 1831, from the carrot (
Carotenoids have aliphatic or acyclic structures (open chain) and alicyclic or cyclic structures (closed chain). Cyclic or alicyclic carotenoids can be monocyclic (when there is a ring) or bicyclic (when there is more than one ring) . β-Carotene is the most commonly found of these compounds, accounting for 25–30% of the total carotenoid content of plants  or even more in some of them.
Due to their double-bonded conjugate system, carotenoids exhibit ultraviolet and visible spectral absorption characteristics, and most have maximum absorption at three wavelengths, resulting in a spectrum consisting of three peaks. The greater the number of conjugated double bonds in the carotenoid, the greater the spectrum wavelength .
According to Krinsky et al. , at least seven conjugated double bonds are necessary for a carotenoid to have color, as in the case of ζ-carotene, which gives a yellow color to passion fruit. As the conjugate system is extended, the color also intensifies. Therefore, lycopene with 11 conjugated double bonds gives rise to the red color of tomatoes (
The detection of carotenoids, after separation by liquid chromatography methods, occurs in a characteristic absorption zone between 400 nm and 500 nm wavelength; the detection in cis- or
Carotenoids consist of a wide range of substances, with great structural diversity and varied functions, of which more than 600 have already been identified and had their chemical structures elucidated. They are probably the most occurring pigments in nature, and the many different colors we see are the result of the presence and combination of these different compounds .
The official nomenclature of carotenoids was established in 1974 by the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Biochemistry .
They stand out commercially in the production of rations for breeding sites (fish, crustaceans, and poultry) and are used as food dyes and in aromas. In addition to the food industry, carotenoids play an important role in the pharmaceutical industry due to their nutritional and functional properties, as precursors of vitamin A, antioxidant activity, among others .
They can be divided into two groups: carotenes and xanthophylls. Carotenes are pure hydrocarbons, which have an orange to red coloration. This group includes β-carotene, α-carotene, ζ-carotene, δ-carotene, and lycopene. β-Carotene is the most commonly found of carotenes, accounting for 25–30% of the total carotenoid content of plants and even more in some of them .
It is also the most active carotenoid, with the highest bioconversibility in the human body, covering 15–30% of all serum carotenoids. β-Carotene is described as a suppressor of tumorigenesis in the skin, lung, liver, and colon, promoting the cessation of the cycle of cell multiplication. It also shows a suppression activity superior to that promoted by α-carotene . Lycopene does not have pro-vitamin A activity but is considered as the carotenoid with the highest singlet oxygen sequestration capacity, possibly due to the presence of two unconjugated double bonds, which make it more reactive [12, 13].
Thermal processing can lead to important changes in the sensory characteristics and the content of antioxidant compounds, altering the antioxidant potential of foods. Conditions such as time, temperature, and style of cooking are determinants for the increase or decrease of the total antioxidant activity .
The biological activity of carotenoids depends on their bioaccessibility and solubilization in the gastrointestinal tract. Due to their lipophilic nature, these compounds do not disperse well in the aqueous medium of the gastrointestinal tract. Therefore, it is important to analyze how food matrix and processing affect their bioaccessibility. Rodriguez-Roque et al.  formulated beverages with mixtures of fruit juices and water, milk, and soy applying three treatments: high intensity pulse electric fields, high pressure processing, and thermal treatment, to evaluate bioaccessibility of carotenoids and on lipophilic antioxidant activity. Bioaccessibility of carotenoids was reduced after all treatments, except for
2.2. Orange flesh sweet potato (
Sweet potato (
It is a herbaceous crop with extensive growth in tropical and subtropical regions of the world, being important in many developing countries. Archeological, linguistic, and historical evidences establish that sweet potatoes originated in the region of Central and South America. The ability of this crop to adapt to a wide variety of climatic conditions allowed for its development in tropical and temperate regions of Africa, Asia, and the Americas. Compared to other crops, sweet potatoes are able to grow at an accelerated rate under various environmental conditions and are highly adaptable under marginal growing conditions. It has a short production cycle, high nutritional value, and sensory versatility in terms of color, flavor, and texture .
In Brazil, sweet potato presents low average productivity due to the occurrence of pests and diseases, inadequate production technology, and the absence of selected cultivars. However, improved productivity can be easily achieved through the use of seedlings from disease-free matrices obtained from tissue culture laboratories .
Its forms of consumption are the same as those of other sweet potato cultivars, as well as having similar production techniques. Its planting can be carried out at any time of the year, provided that the minimum local temperature in the period is equal to or above 15°C .
In the form of flour,
Many authors evaluated the β-carotene content in orange sweet potato cultivars and found variable contents: Hangenimana et al.—79.84 μg g−1 , Takahata et al.—187.00 μg g-1 , Lako et al.—150.0 μg g−1 , Kidmose et al.—108.0 μg g−1 , Teow et al.—226.00 μg g−1 , Wu et al.—84.00 μg g−1 , and Failla et al.—281.00 μg g-1 .
The average found for the centesimal composition in orange flesh sweet potato was moisture—83.91 g 100 g−1, ash—0.52 g 100 g−1; protein—0.69 g 100 g−1; lipids—0.10 g 100 g−1; carbohydrates—13.42 g 100 g−1, respectively, with a caloric value of 57.34 kcal 100 g−1 .
The orange sweet potato pulps have the potential to be used as food-based supplements to reduce vitamin A deficiency since β-carotene is one of the carotenoids with pro-vitamin A activity for human diet, exerting important functions in human physiology, acting as antioxidants, as protective pigments of the human retina, and as precursors of retinoids that influence gene expression .
Orange-fleshed sweet potato (OFSP) is a carotenoid-rich vegetable. Thermal treatment to process sweet potatoes can decrease the contents of these compounds in foods, reducing their bioactive properties. Raman spectroscopy can be employed as a fast tool in food analysis, especially to detect low concentrations of carotenoids and to monitor their degradation profile along time. Sebben et al.  evaluated two drying methods, hot air and microwave in a rotating drum, coupled to quantitative Raman spectroscopy. A 50% decrease in the carotenoid contents were found for both types of drying methods. The results were reproducible. The best linear correlations were R2 = 0.90 for hot air and 0.88 for microwave dried samples, respectively.
Vitamin A deficiency (VAD) is a public health problem in some regions of Brazil. Enhancement of the use of orange-fleshed sweet potatoes as a pro-vitamin A source can be a strategy for prevention of this deficiency. Berni et al.  compared the pro-vitamin A contents, vitamin A equivalencies and β-carotene (βC) bioaccessibilities of two varieties (
Islam  analyzed total carotenoids and
Sweet potatoes have been the aim of research over the years due to their functional and nutritional properties. Carbohydrates, proteins, lipids, carotenoids, anthocyanins, phenolic acid conjugates, and minerals constitute versatile nutrients in different parts (tubers, leaves, stems, and stalks) of sweet potato. The unique composition of sweet potato provides various beneficial effects such as antioxidant, hepatoprotection, anti-inflammatory, anticancer, antidiabetic, antimicrobial, anti-obesity, and antiaging activities. Factors which affect the nutritional composition and bio-function of sweet potatoes include the varieties, parts of the plants, extraction time and solvents, post-harvest storage and processing. Differences between the
Sweet potato (
Yellow sweet potato is mostly produced in small scale by farmers. It is a source of energy and carotenoids in the human diet; however, it is a highly perishable crop. To increase its industrial use, yellow sweet potato flour was produced for use in bakery products. Nogueira et al.  evaluated the technological quality and the carotenoid content in sweet breads produced by replacing wheat flour with 0, 3, 6, and 9% yellow sweet potato flour. The increase in yellow sweet potato flour concentrations in bread resulted in a decrease of specific volume and firmness and an increase in water activity, moisture, orange coloring, and carotenoids. Storage led to the most significant changes after the 5th day, with a reduction in intensity of the orange color. The β-carotene content varied from 0.16 to 0.47 μg g−1 in breads with yellow sweet potato flour. The results suggest that the use of yellow sweet potato in breads can be beneficial for consumers’ health and for the agricultural business as well.
2.3. Pumpkins (
A great number of pumpkin varieties, each of which contains a different amount of carotenoids, are cultivated worldwide . In several Brazilian regions,
Carotenoids have antioxidant activity, but few are converted in retinol (an active form of vitamin A) by the human body. Among more than 600 carotenoids which have pro-vitamin A activity, the most known are α- and β-carotene, and these are susceptible to degradation (isomerization and oxidation during the cooking process).
There are various studies about carotenoids from pumpkins, mainly β-carotene, and the large diversity of landraces and cultivars, among them the
Priori et al.  evaluated the genetic variability for the synthesis of bioactive compounds, total phenolic compounds, carotenoids, antioxidant activity, and minerals of 10 accesses of pumpkin (
2.4. Yellow sweet cassava (
The manioc plant (
In Brazil, there are about 1200 varieties, classified as bitter or sweet according to its hydrocyanic acid content. Originated from South America, manioc (
Cassava is easily adapted to different types of soil and climate, usually grown on a small scale with little or no technology adoption, basically using family workers. In the case of Brazil, it is widespread throughout the region bounded by the geographic tropics. The world production has increased over the last decades, due to factors such as genetic improvement, use of technology in planting, and expansion of cultivated areas. However, the expansion of the areas remains centralized in the countries that have a tradition in the planting of this culture [3, 40].
The economies of African countries, the largest producer continent, and Latin America are based on the exploitation of the primary sector. Therefore, countries seek to increase production of crops that are strategic for maintaining the economy and serving the domestic market, raising production more than in other continents (Africa) or maintaining production (Latin America) in the last decades. On the other hand, Thailand, located on the second largest cassava (Asian) producer continent, is the largest cassava root exporting country.
The African continent, the world’s largest producer of cassava roots, does not have countries that excel in the export trade of the product, prevailing the service in the domestic market, indicating that the crop is produced mainly by small producers, in precarious production systems, with little or no application of modern management and fertilization technology. Brazilian production stood out among the 80 cassava producing countries, reaching around 13% of world production , demonstrating that there is still room for growth of Brazilian production if modernization of plantation using technology and improvement is implemented. Ten states produced about 80% of the Brazilian production, with Pará and Bahia accounting for 36% of this total and Paraná, Rio Grande do Sul and Maranhão, 26%. The other five: Amazonas, Minas Gerais, Ceará, São Paulo and Mato Grosso do Sul contributed 18% of this production . Overall, 62% of the national production comes from the North and Northeast regions. Brazil has encouraged the production and commercialization of agricultural products inside the country, through government financing programs such as the National Family Agriculture Program (PRONAF). This program is based on support for rural development, on the strengthening of family agriculture and its organizations, for example, cooperatives, as a segment that generates jobs, incomes, and increases the nutritional quality of these populations .
In the last 10 years, efforts were made to identify new varieties of able yellow cassava to improve the nutritional quality for the populations with malnutrition problems, situated in the tropics, particularly in the Brazilian northeast, where the cassava constitutes one of the main cultivations and almost the only source of nutrients. The cassava culture of yellow coloration can be an excellent source of carotenoids, precursors of vitamin A such as α and β-carotene.
The total and α and β-carotene in raw varieties of bitter and sweet yellow cassava as well as in cooked ones were evaluated by Oliveira et al. . A total of 28 varieties were analyzed: 12 in bitter, 11 in sweet yellow cassava, and 5 other varieties of bitter yellow cassava. The variability among the varieties of bitter yellow cassava revealed higher total carotenoids content compared to sweet yellow ones. However, the proportion of β-carotene in relation to the total carotenoids content was larger in the varieties of sweet yellow cassava. The bitter yellow cassava roots presented a variation in the total carotenoid content from 1.97 to 16.33 μg g−1 and β-carotene from 1.37 to 7.66 μg g−1, respectively. The isomers 13, 9-Z and all-
The evaluation of β and α-carotene and total carotenoids content in cultivars, accesses, biofortified, and landraces of sweet potatoes, pumpkins, and yellow sweet and bitter cassava is very important to obtain plant raw materials with high contents of carotenoids that can be used for cultivation and minimize hunger in the low-income populations of all ages around the world [46, 47].
The authors wish to thank the Carlos Chagas Filho, Embrapa – Food Technology, BioFORT Network and Harvest
Conflict of interest
There is no interest conflicts.