Bioactive substances and product development of cereals-1 www.immy.cn www.immyhitech.com

Bioactive substances and product development of cereals-1

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Mar 16, 2024

Bioactive substances and product development of cereals   www.immy.cn

Whole grains are rich in dietary fiber, vitamins, minerals and other nutrients, and contain phenolic acids, tannins, anthocyanins and phytosterols and other bioactive substances. In view of these nutritional characteristics, there is great potential for basic research and further development of cereals. In order to provide new ideas for the processing and further research of coarse grain crops, the bioactive substances of coarse grains and the nutritional components, product development and health care functions of five representative coarse grain crops were reviewed, and the research conclusions and development suggestions of coarse grains were obtained.

Coarse grains refer to cereals other than wheat, rice, or cereals that are mainly used for animal feed and winemaking. These cereals are mainly produced in the semi-arid tropics of Asia and Africa, where rain-fed farming methods result in low grain yields per unit area (typically less than 1 t/hm2) [1]. Coarse grains mainly include corn, sorghum, oats, barley, millet, barley and amaranth.

They are rich in phytochemicals with antioxidant properties, such as dietary fiber, vitamins, minerals (especially micronutrients such as iron and zinc) [2]. In view of these nutritional properties, cereals are labelled as nutritious foods. Several epidemiological studies have shown that these cereals help fight a variety of chronic diseases such as ischemic stroke, cardiovascular disease, cancer, obesity, and type II diabetes [3-4].

Multigrains have a rough taste and cannot replace our staple grains, but they can be combined with rice and wheat in different proportions to make a variety of nutritious products. Due to their high protein content and balanced amino acid composition (methionine, cystine, and lysine), they are nutritionally comparable to, or even better than, major cereals such as wheat and rice [5]. In recent years, with people's increasing attention to food nutrition and safety, the demand for "diversified, nutritious, healthy, safe and convenient" miscellaneous grains in the international and domestic markets has been increasing, which has made all kinds of miscellaneous grains have good development prospects and can penetrate into the diets of consumers, including consumers in rural and urban, developed and developing countries.

The research and development of the potential uses of these cereals have shown the potential of cereals as formula foods. In addition to being used as food, these grains are also used as feed, syrups, winemaking, biofuels, or biopolymers [6].

1 Bioactive substances in coarse grains

The various components of multigrains are biologically active in addition to providing nutrients.

Among the phenolic compounds include phenolic acids, tannins, coumarins, flavonoids, and alkylresorcinol. Phenols play an important role in the flavor, texture, color, and oxidative stability of plant-based foods [7]. They have special nutritional properties and are usually found in the bran. There are two types of phenolic acids: hydroxycinnamic acid and hydroxybenzoic acid. Hydroxybenzoic acid includes parahydroxybenzoic acid, vanillin, syringic acid, and protocatechuic acid, while hydroxycinnamic acid includes coumaric acid, caffeic acid, ferulic acid, and sapic acid.

Cereals contain a high concentration of tannins, whose main function is to protect the grains from mold contamination to prevent the grains from spoiling, and at the same time, the tannins are also one of the reasons for the bitter taste of the grains. Tannins reduce the digestibility of proteins, carbohydrates and minerals and have gastrointestinal protection, anti-cancer, anti-ulcer and cholesterol-lowering properties. Turngrass is the only millet that contains tannins.

Avenanthramides are amides of cinnamoylanthranilic acid and are found only in oats. It has anti-inflammatory, anti-atherosclerosis, and antioxidant properties[8]. Alkylresorcinols produced by various plants, bacteria, and fungi are bioactive compounds that benefit human health, such as anticancer activity [9-10].

Flavonoids include anthocyanins, flavanols, flavanones, and flavonoid bases. Grains contain a variety of flavonoids, which are usually found in the peel. The 6 common anthocyanins found in cereals are cornflower pigment, mallow pigment, pelargondin, delphinium pigment, petunia pigment, and peony pigment. 3-Deoxyanthocyanins are a unique member of the anthocyanin group that is stable at high pH, which is what makes sorghum a good natural food colorant [11]. The flavonoids in millet are mazein, isomazein, vitexin, isovitexin, saponin and valervin, while vitexin glucoside, glucovite, and vitexin are vitexin glucoside, glucovite, and vitexin in pearl millet. Oats are apigenin, glycosyl vitexin, isovitexin, wheatlavinin and vitexin.

Lignans are a class of phytoestrogens found in barley, oats, rye, and rye. The lignan content in these grains ranged from 8 to 299 μg/100 g [12]. Plant sterols are cholesterol compounds that are mainly found in bran. Most of the phytosterols in grains are in free form, and a few such as fatty acid esters or hydroxycinnamic acid (usually ferulic acid) can be combined with sugars (mainly glucose) to form glycosides. Each 100 g of sorghum contains 46~51 mg of unbound phytosterols [13], and corn, barley and oats contain 70~88 mg/100 g, 55~76 mg/100 g and 35~46 mg/100 g [10], respectively.

Dietary fiber is the edible part of the plant and is not hydrolyzed by enzymes in the digestive tract. Oligosaccharides such as lactulose, fructooligosaccharides, and trans-galacto-oligosaccharides have been reported to be effective in promoting the growth of bifidobacteria and lactobacilli in the human large intestine. Several oligosaccharides found in cereals are galactose derivatives of sucrose, stachyose, and raffinose, as well as fructose-based derivatives of sucrose and fructooligosaccharides [12]. Cereals do not contain vitamin C, vitamin B12, vitamin A, and β-carotene [14]. However, they are a great source of most B vitamins, especially thiamine, riboflavin, and niacin [15]. Cereals also contain a certain amount of vitamin E.

Whole grains contain a variety of anti-nutritional factors that limit their nutrient content, mainly phytic acid and polyphenols [16-17]. It has been reported that phytic acid content is significantly reduced during germination due to phytase activity. The reduction was greatest in the first two days of germination and smaller on days 4 to 6 of germination [18]. Phytase activity can be observed during germination in barley, rye, and oats, which hydrolyze phytic acid into phosphate and inositol phosphate. Similarly, a decreasing trend in polyphenol content was observed between germination and day 6 of these grains [19].

The increase in the protein content of sprouted cereals may be due to a decrease in the number of antinutritional factors (tannins, polyphenols and phytic acid), as well as other macromolecular substances, especially carbohydrates. Blanching significantly reduced polyphenol content (28%) and phytic acid content (38%)

2 R&D of cereal products

2.1 Barley products

Barley is a versatile grain. In food, barley grains are ground to produce barley flour grains, which can be further processed into coarse grains, flakes, and flours. It resembles wheat fruit in appearance, but is slightly lighter in color. Malted barley is rich in maltose, which can be made into maltose syrup, which is commonly used as a sweetener in food. Barley is fermented and used as an ingredient in beer and other alcoholic beverages. In Western countries, whole, flaky or ground barley flour grains are used in breakfast cereals, stews, soups, porridges, breadcrumbs, and baby food [20]. Barley flour can also be added to wheat products such as: bread, cakes, biscuits, noodles, and squeezed snacks.