*2.1. Wheat*

Wheat (Triticum aestivum, Triticum durum) is a cereal of ancient culture, whose area of origin is located between the Mediterranean Sea, the Black Sea, and the Caspian Sea, and is currently cultivated all over the world [20]. Wheat has a protein content of 13–14%, higher than that of the other main cereals and staple foods; therefore, it is the main plant source of protein in human nutrition worldwide. A total of 100 g of wheat provides 327 calories; wheat is also an important source of dietary fiber, niacin, several B vitamins, and other dietary minerals. Furthermore, 75–80% of total wheat protein is made up of gluten [21].

#### 2.1.1. Starch and Protein

Starch, on average, is approximately 80% of the dry weight of the endosperm and consists of a mixture of two polymers, amylose and amylopectin, in a ratio of about 1:3. The protein content of wheat has wider variations than the starch content [22]. An analysis from the World Wheat Collection, after comparing 212,600 germplasm lines, showed a wide variability of the protein content, with a range from 7 to 22% of protein on dry weight [23]. Similarly, the result of the comparison analysis between 150 lines of wheat grown under the same agronomic conditions, as part of the HEALTHGRAIN program, highlighted a variation in the protein content of wheat from 12.9 to 19.9% with regard to wholemeal flours and from 10.3 to 19.0% for white flours [24] More than half of the total protein content of the wheat grain, as already stated above, is made up of gluten, in a measure directly proportional to the total protein content [25].

#### 2.1.2. Wheat Fibers and Cell Wall Polysaccharides

According to the 2009 Codex definition [26], dietary fiber (DF) is a " ... carbohydrate polymer with a degree of polymerization (DP) not lower than 3, which are neither digested nor absorbed in the small intestine . . . "

The European Commission under Commission Directive 2008/100/EC [27], subsequently established under Regulation (EU) No. 1169/2011 of The European Parliament and of The Council [28], further defines DF. In this definition, all carbohydrates with a degree of polymerization (DP) ≥3 can be included in dietary fiber; of these, the most common in cereals are fructo-oligosaccharides.

Whole wheat is among the main sources of DF and mainly comprises non-starch polysaccharides (NSPs), which are derived from the cell walls. Most of the fibers are removed during grinding, as refined flour has an extremely low amount of fiber. The amount of fiber in whole wheat varies from 12 to 15% of the dry weight, mainly concentrated in the bran. The most common fiber of wheat bran, equal to about 70%, is arabinoxylan (Figure 2); this is composed of hemicellulose, and β-glucan (20%) as well as a small amount of cellulose (2%) and glucomannan (7%) [29]. Bran obtained from grinding includes a set of compounds that comprise up to 45–50% of cell wall material [30]. The pericarp is the main component and is composed of about 30% of cellulose, about 60% of arabinoxylan, and about 12% of lignin [31].

**Figure 2.** Arabinoxylan (drawn by ACD/ChemSketch).

#### 2.1.3. Antioxidant Components and B Vitamins in Wheat

The grain of wheat contains numerous antioxidants, mainly concentrated in the bran and germ, parts absent in refined white wheat flour. The main antioxidants in the wheat grain are terpenoids (including vitamin E) and phenolic acids [21]. In the wheat grain, phenolic acids are mostly derivatives of hydroxycinnamic acid. In particular, these are dehydrodimers and dehydrotrimers of ferulic acid and synapic and p-coumaric acids [32]. In the outer layer of the bran, we find most of the phenolic acids, mostly bound through ester bonds, to the structural components of the cell wall. The highest shares of antioxidants are found in the outermost layer of the endosperm (i.e., the aleurone). Therefore, the antioxidant properties (i.e., the presence of relevant quantities of phenolic compounds) are directly correlated to the aleurone content of the wheat grain [33]. Among the polyphenols of wheat and other cereals, ferulic acid is the predominant. Other classes of antioxidants contained in wheat bran are flavonoids, carotenoids (mainly lutein), and lignans [34,35].

Wheat is an important source of the so-called "methyl donors", important cofactors in the methylation process, necessary for the synthesis of dopamine and serotonin as well as for the biosynthesis of melatonin and coenzyme Q10. The main component is betaine glycine, therefore, in smaller quantities, it is choline (precursor of betaine) and trigonellin (a structural analogue of betaine and choline). Concerning B group vitamins, wheat is a good source of thiamin (B1), riboflavin (B2), niacin (B3), pyridoxine (B6), and folate (B9) [21].

#### 2.1.4. Health Effects

The health effects of wheat are due to the high content of numerous nutrients and fibers as well as proteins and minerals. Wheat, if consumed as whole wheat, is recommended in several daily portions in the nutrition of both children and adults in quantities equal to about one third of the total diet. For example, whole wheat is a common component found in breakfast cereals and is associated with a reduced risk for various pathologies. Thanks also to the high intake of insoluble fiber, whole wheat in the diet contributes to reducing the risk of coronary heart disease [CHD], stroke, cancer, and type 2 diabetes mellitus as well as helping to reduce mortality due to all causes [36,37].
