**2. Corn as healthy food**

Pre-Columbian natives deified this plant due to its relevance in their lives; the sacred book of the Quiche, the Popol Vuh, even tries to explain the origin of man by narrating how corn was

Corn is a monocotyledonous plant cultivated widely around the world and has constituted itself in one very common staple food. Corn and its wild variant, teosinte, belongs to the Poaceae family, of the Maydeas tribe; species of the *Tripsacum* genus are wild variants of corn, also originating in the American continent, but without any direct trade value. This family also includes important agricultural crops, such as wheat, rice, sorghum, barley, and sugar cane. Based on the characteristics of the ear or male inflorescence, the *Zea* genus divides into

In Latin America, corn is a staple food product, and so it is the crop of greatest production, and it is also used as a dietary input for livestock, and for the industrial production of large numbers of products; that is why, from a nutritional, economic, political, and social point of view, it is the most important agricultural product. Generally, the diet of a people develops a collective memory and transcends mere food consumption, expressing socioeconomic rela-

Corn as food has been found in archeological ruins and manuscripts such as the Florentine or the Mendoza Codices, wherein it has been possible to elucidate that corn represented on the main components of the Mesoamerican diet since the Middle Preclassic (1200–400 BC) [4–6]. Archeological remains also show the use and consumption of other plants important during that period; however, ancient settlers developed a preference for corn and it kept growing in

In pre-Hispanic times, the production of flours, pinole, and the ancient equivalent to modern "popcorn" stood out [7]. Currently, corn is widely consumed in of tortillas, arepas, toasts, tamales, snacks, corncobs, and in other various forms. When it comes to tortilla, it is now known that it not ancient as previously thought, but it was already prevalent in Mesoamerican diet by the time the Spaniards arrived at the continent. Today, the tortilla is considered as the basis of Mexican people's diet, directly related to its survival for over 3500 years [8]. The richness of indigenous cuisine based on corn was recorded in the reliable testimonies of conquistadors and chroniclers alike, from Hernán Cortés and Bernal Díaz del Castillo to Bernardino de Sahagún, all of them providing evidence of the high cultural development of ancient Mexicans, as well as of the rich diversity of corn, already noticeable back in those days. The miscegenation resulting from the Spanish Conquest had in gastronomy one of its main manifestations, enriching pre-Hispanic diet with elements from Spanish/Arab cuisine, and the other way around, too. However, the indigenous element dominated in this "food miscegenation," as can be seen in the fact that corn remains a fundamental ingredient and one of the main sources of energy in nowadays Latin American diet. An example of this can be seen in the fact that the average Mexican today obtains 1022 kilocalories and 26.3 g of protein from corn daily, which may represent 50% of an adult's daily intake, based on a diet of 2000

given to mankind by the gods Paxil and Cayalan [2].

30 Corn - Production and Human Health in Changing Climate

tions and revealing acts deeply rooted in cultural symbolism [4, 5].

two sections, luxurians and annuals [3].

kilocalories with 56 g of protein [9].

popularity.

In recent years, cereal consumption has been linked to the reduction of chronic-degenerative diseases such as cancer, obesity, type 2 diabetes, cardiovascular and metabolic problems, and even symptoms associated with neurodegenerative problems. These health benefits have been attributed to the vast variety and high concentration of nutraceutical molecules present in cereals. Strictly speaking, these molecules cannot be considered as nutritional elements in themselves, but as bioactive components that can interact with biological systems from various cellular mechanisms, allowing optimal maintenance of the body's physiological functions, thus preventing the occurrence of diseases [10].

The confusion that usually arises when talking about concepts such as "nutrients," "nutraceuticals," "functional foods," and "nutritional supplements" should be noted. Clarifying these terms becomes relevant if one takes into account that the different qualities of the elements included in these categories can directly impact on their consumption. The term "nutrients" refers to the elements of a diet that can be absorbed by the body and incorporated into different physiological systems, allowing for basic functions to occur. For example, lipids and carbohydrates are known as the source of metabolic energy, as constituents of the cell membrane and as hormonal precursors; in its turn, the integration of proteins into the organism is used as an element of cellular structural reconstitution and integration into enzymatic systems. Also, vitamins and minerals allow for osmotic maintenance to occur, participate in nerve and muscle functioning, and can act as enzymatic cofactors. On the other hand, the term nutraceutical refers to the consumption of substances contained in food, able to promote beneficial effects on health without having direct participation in the basic processes of the different systems. The functional food concept encompasses natural or processed food products that contain biologically active compounds, which may or may not be nutrients. Together, these molecules must have the capacity to promote health benefits, preventing or aiding in the treatment of chronic diseases, in nontoxic quantities that can be included in a daily diet [11]. As an example of the above, the consumption of fish that provide omega fatty acids can be mentioned; also, the consumption of fruits and vegetables rich in minerals, vitamins, and dietary fiber, as well as other foods added with biologically active substances such as antioxidants and probiotics [12].

In recent times, cereals such as corn have been acknowledged as functional foods, as they are an important source of calories, as well as proteins, peptides, carbohydrates, fibers, and antioxidants with a nutraceutical function. The nutritional contribution of corn to the world population is undeniable, partly because of the great versatility of its kernels to produce food. Corn for consumption is mainly processed by three methods: dry milling, wet milling, and alkaline cooking (nixtamalization), and it is through these processes that the raw material for the production of different products is generated. Corn can be consumed in nixtamalized products such as tortillas and chips, in prepared beverages such as chicha morada, atole, tejuino, or pozol, in dishes such as polenta, pozole, or tamales, and all of these are merely a fraction of the many byproducts derived from this cereal. The flexibility with which this plant can be exploited should be emphasized, since its contribution to health keeping and improvement is not limited only to the kernel or its byproducts [13]; other anatomical parts of the plant such as stigmata, cobs, and leaf sheaths have proven to be an important source of nutraceutical molecules, as will be seen later in this chapter.

Once ingested, corn proteins are hydrolyzed by the activity of gastrointestinal enzymes such as pepsin, trypsin, and chymotrypsin. In vitro, this process can be carried out by the addition of enzymes, or by acidification or fermentation. Nonetheless, in vitro hydrolysis processes have shown some drawbacks, for example, when using acids, controlling the process can be complicated and some amino acids can be lost; also, protein hydrolysis turns out to be inefficient under the process of fermentation. As of late, enzymatic digestion has been chosen for in vitro isolation of bioactive peptides, which has proven to be a more efficient process. From two-amino acid peptides to 30-amino acid polypeptides can be isolated by means of these processes. Hydrophobic amino acids can be counted among peptides with bioactive capacity, structured with a positive charge and a proline in their C-terminal end [19]. On the other hand, dipeptides and tripeptides have greater resistance to the degradation of stomach, pancreatic, and intestinal proteases and peptidases, and larger peptides (six amino acids and

The Maize Contribution in the Human Health http://dx.doi.org/10.5772/intechopen.78700 33

Studies have shown that bioactive peptides can have beneficial effects on health, mainly as antihypertensive, anticholesterolemic, antioxidant, anti-inflammatory, anticarcinogenic, antimicrobial, and others, due to their immunomodulatory properties. Likewise, it has been reported that they can help decrease the effects associated with high alcohol consumption. A large number of bioactive peptides have been obtained by means of the hydrolysis of zeins proteins, for example, the tripeptide lysine-proline-proline, and from the γ-zein protein, the valine-histidine-leucineproline-proline-proline polypeptide, whereas the tripeptide proline-arginine-proline, which has also shown a biological functional activity, has been isolated from the α-zeins protein, as well as MBP-1 peptides from the corn kernel. Successful efforts have been made to isolate other peptides from corn gluten meal, such as Cys-Ser-Gln-Ala-Pro-Leu-Ala or Tyr-Pro-Lys-Leu-Ala-Pro-Asn-Glu. Overall, it has been observed that a large number of peptides can be isolated from the different components of corn, although their possible biological activity is still undergoing further research, as it is still necessary to carry out studies that help find the mechanisms from

As for the total fiber contained in corn, resistant starch is a type of non-digestible fiber, as it is highly resistant to the activity of digestive enzymes. The presence of resistant starch seems to be directly related to the percentage of amylose content. In normal corn, the presence of 34% of amylose is related to 0.8% of resistant starch, while high-amylose corn starch, the recorded presence of 83% amylose results in 39% resistant starch [21, 22]. However, resistant starch can be metabolized by the microbiota of the large intestine through fermentation and this in turn results in small chains of fatty acids [23]. Both the starch and the resistant starch contained in corn kernels have grown in relevance due to their possible function as regulators of body weight, thus a possible natural alternative for the treatment of obesity. On the other hand, these elements have also been linked to liver protection and the prevention of type 2

In turn, phenolic compounds are a group of molecules whose chemical structure is made up of several hydroxyl groups linked to an aromatic group. When two or more rings are conjugated, a polyphenolic structure is generated; depending on the number of aromatic rings and the structural elements that bind them together, thousands of polyphenols have been identified. The polyphenols synthesized in corn can be classified into three groups according to their

larger) have a higher biological activity outside the intestine [20].

which these peptides can exert their biological activity.

diabetes [24, 25].

Corn kernels consist mainly of fiber, ranging from 61 to 86%, depending on the variety of the plant. Approximately 99% of the fiber is found in the endosperm and consists of starch (approximately 73% of the total weight), and the rest of resistant starch. The kernel also contains non-starch polysaccharides such as cellulose, hemicellulose, and, to a lesser extent, lignin (approximately 10% of the total weight), located mainly in the brand. Protein follows; depending on the variety of corn, it can range from 6 to 12%, calculated on the dry basis, while lipids represent around 3–6%. Out of these, between 81 and 85% is stored in the germ. Other phytochemical elements can also be found in pigmented and yellow varieties, in the form of secondary metabolites, phenolic compounds, and carotenoids for the most part. A very wide range of phenolic content exists among corn varieties, which has been assessed by the quantification of total polyphenols under the Folin–Ciocalteu reagent method, reporting amounts of 1756 mg of gallic acid equivalent/100 g of sample for a variety of purple corn with Andean genotype [14] and 266 mg gallic acid equivalent/100 g of sample for varieties of purple corn with Mexican genotype [15]. When it comes to Mexican white corn, amounts of 260 mg of gallic acid equivalent/100 g of sample have been reported; likewise, it is likely that corn types with a high profile of carotenoids contain a higher concentration of phenolic compounds, reporting 320 mg of gallic acid equivalent/100 g of sample [15]. It should be noted that yellow corn varieties have reported the highest carotenoid content, with an average dry base concentration of 13 μg of β-carotene equivalent/100 g of sample [16], although red varieties also synthesize carotenoids.

These elements act as nutraceuticals depending on their bioavailability, molecular structure, physicochemical characteristics, and their physiological effects, as well as on the properties acquired or lost after the different food byproducts have been processed.
