Functional Foods

In the daily diet, the consumption of oats, which contain β-glucan polysaccharides, various dietary fiber components, and antioxidant compounds like tocopherol, wields a positive influence on consumer health and decreases the risks of various illnesses and malignancies [104]. In many studies, the valuable fiber components in oats were found to exert both therapeutic and protective activities against cardiovascular diseases, type-2 diabetes mellitus, and various types of cancer, like colon cancer [105–109]. The β-glucans found in oats are reported to have an association with oat’s ability to lower blood cholesterol levels [109]. New data also show that oats positively affect body weight and blood pressure [79].

Barley is known as one of the most ancient cereals to have been produced throughout the world. Archaeological proof demonstrates barley’s presence along Egypt’s Nile River about 17,000 years ago [110, 111]. Production of barley, scientifically known as Hordeum vulgare L., ranks 4th globally after respective maize, rice, and wheat production [112, 113]. Approximately 12% of the grain cultivated in the world is barley [111, 114]. Barley is utilized as one of the necessary raw materials for producing malt and beer, also being widely consumed in the production processes for animal feed [113, 115]. It has been generally used in the feeding of poultry, pigs, and adult ruminants and monogastrics [116, 117]. Of the barley being grown today, approximately 65% is utilized for animal feed, while 33% is used for malt products and 2% is reserved for human consumption [111, 118]. Barley can be farmed on diverse types of soil and in various climates, and it is used by many different cultures and nations [119, 120]. Compared to other types of cereals, it performs better under varied environmental pressures because it is drought-resistant, survives well in winter, and matures early; therefore, it is commonly more economically cultivated compared to other possible crops [111, 121]. The United States, China, India, Russia, and other countries from the former USSR are the major barley-producing countries [122].

Barley grains primarily comprise the husk, the embryo, and the endosperm, consisting of the aleurone and of endosperm cells, which are starchy [123]. The husk is the outer layer of the barley and forms 10%–13% of the grain weight [123, 124]. The embryo is made up of an acrospire, which is a nodal region located in between the shoot and root, as well as a primary root, which is enclosed by a root sheath known as the coleorhiza. Embryos are disconnected from the endosperm during germination by the modified cotyledon (the scutellum) [123, 125]. The endosperm comprises a starchy part and a layer of aleurone around it. The endosperm constitutes the major unit of a barley grain, representing 75% of a grain’s weight [123, 124]. The endosperm’s task is to function like a starchy storage center for nutrients that embryos can utilize in the process of germination [99, 123]. The cells in the aleurone layer include lipids, protein, minerals, and vitamins [123, 124, 126, 127]. Aleurone cells are isodiametric, which is different from the endosperm cells. Apart from the embryo, the sole unit of the grain that contains living cells is the aleurone layer [123, 125].

Barley genotypes are classified as hulled and hull-less. The hull-less variety has better nutritional value compared to the hulled one [120, 128]. Hull-less barley generally has higher amino acid, total protein, and digestible energy contents compared to hulled barley [129–131]. Barley can be described as a perfect source for obtaining β-glucans and complex carbohydrates, two critical constituents of dietary fiber [132]. Barley grain contains 60%–80% carbohydrates, 9%–13% protein contents, 1%–2% fat, and 10%–15% water [132, 133]. The most limiting essential amino acid of cereal species, namely lysine, is found in higher levels in some cultivars [129–131]. Starch is the carbohydrate to be found most plentifully in barley grain, its levels varying between 62% and 77% in terms of the dry grain weight [132, 134]. The dietary fiber content of barley is 14%–25%. Arabinoxylan content is 4%–11%, while the β-glucans, cellulose, and lignin contents are 3%–7% [135–138]. Barley is rich in vitamins, particularly B vitamins, and it also has valuable mineral contents, especially trace minerals [139, 140]. Apart from β-glucans, the compounds in barley such as tocotrienol, phytoestrogens, lignans, polyphenols and phytic acid have been associated with health benefits [140, 141].

Epidemiological studies show that regular barley consumption has the possible ability of lowering the risks of various chronic diseases including colon cancer [111, 142, 143], chronic heart disease [111, 118, 144, 145], gallstones [111, 146, 147], and high blood pressure [111, 148]. There are reports of the role of barley in the maintenance of colon health [111, 149], the induction of stimulation of the immune system [111, 150], and immuno-enhancement [111]. In addition, barley consumption provides a protective effect against toxins, diabetes mellitus, and neurological problems such as Alzheimer disease [111, 151, 152].

Flaxseed comes from Linum usitatissimum L., which is commonly called the flax plant and belongs to the family Linaceae [153–155]. It is also called linseed [156, 157], and it is native to Western Asia and Mediterranean areas [153–155]. Today, however, it is grown in over 50 countries, mainly in areas of the northern hemisphere. Canada produces and exports the largest quantity of flaxseed in the world [153, 158], and India, the United States, China, and Ethiopia are the other major countries that grow flax plant for its seeds [158–161]. In the world, India ranks first in terms of flaxseed cultivation area and third in terms of flaxseed production [158, 160, 161]. The first known evidence of flax cultivation is the use of the flax plant in the manufacture of linen fabric in eastern Turkey in 6000 BC [162, 163]. Flaxseed is used from past to present to obtain linseed oil for industrial purposes such as linoleum, paint, varnish, cosmetics, and ink production [157, 164, 165]. While flax fiber is valuable in producing high-quality linen clothing, milled or ground flaxseed is commonly used as a component of fertilizers and in foodstuffs for animals [162, 163]. Flaxseed is also of value in functional foods because it has several beneficial pharmaceutical and nutritional properties [157, 166].

The seeds of flax plants are oval-shaped and flat; their tips are pointed. They range in color from dark shades to yellow [160, 162]. Seeds are about 3.0–6.4 mm long, 1.8–3.4 mm wide, and 0.5–1.6 mm thick [155, 162]. Embryos account for 55% of hand-cut flaxseed’s overall weight, while the seed coat and endosperm represent 36% of overall weight. Finally, the embryo axis accounts for 4% [160, 162]. Oily flaxseeds are generally larger than fibrous flaxseeds [155, 167]. Flaxseeds possess a chewy, crisp texture and they have a pleasing nutty flavor [155, 168].

The chemical composition of flaxseed depends upon the environmental conditions in which the flax is grown and differs significantly among varieties [169]. The Canadian Grain Commission reported that one variety of Canadian flaxseed had a composition including 41% fat, 20% protein, 28% total dietary fiber, 7.7% moisture, and 3.4% ash [170]. Minor components in flaxseed are vitamins (A, B, D, E) and minerals (cadmium, selenium, etc.), cyanogenic glycosides, trypsin inhibitor, phytic acid, lignans, lina-tine, polyphenols, and cyclolinopeptides (CLs) [162, 170, 171]. Flaxseed includes 8–10 g/kg total polyphenols, about 5 g/kg esterified polyphenols, and 3–5 g/kg etherified polyphenols [172]. It constitutes the richest available resource for obtaining n-3 fatty acid, also known as alpha-linolenic acid. This particular acid accounts for roughly 55% of the total fatty acids that are present in the seeds of this plant [157, 163]. Alpha-linolenic acid may be metabolized by certain types of enzymes in the human intestine to docosahexaenoic acid and eicosapentaenoic acid [157, 173]. It was established that increasing the intake of long-chain polyunsaturated fatty acids in one’s diet, and particularly one’s intake of docosahexaenoic and eicosapentaenoic acids, can reduce disease risks [157, 174].