Fibers: Healthy Component in Whole Wheat and Rye Flours

*María Laura Gómez Castro, Claudia Cecilia Larregain, Ethel Noemi Coscarello and Roberto Jorge Aguerre*

## **Abstract**

The demand for foods made with whole grain ingredients that improve health continues to grow. The health benefits of whole grain cereal are well recognized and are attributed to the presence of dietary fiber and phytochemicals. Consumption of whole grain cereals has been associated with protection against cardiovascular disease and type 2 diabetes. The wheat and rye whole grain flours have a total fiber content that gives a healthy contribution for the daily feeding of the population. After applying a malting process, the composition of fibers is modified by increasing the fraction of soluble fibers. These fibers are prebiotic and improve flour functionality. In this chapter, we will study the properties of whole malted flour of wheat and rye and how it benefits health.

**Keywords:** functional flour, fibers in cereal, malting process, prebiotic, arabinoxylans

### **1. Introduction**

Food and Agriculture Organization (FAO) of the United Nations and World Health Organization (WHO) expert's meeting in human nutrition agreed that carbohydrate intake should be at least 55 parts in 100 of total calories [1]. Caloric intake should be mainly complex carbohydrate available with low glycemic index. This recommendation emphasizes the consumption of foods that meet these properties. The term "fiber" means carbohydrate polymers, which are neither digested nor absorbed in the human small intestine. The properties of dietary fiber, as the retention capacity of water and oil, have beneficial results on food products by improving their organoleptic characteristics and their physiological effects on the human organism. The quality of the fibers varies according to the type of cereals and according to the processes that are carried out to obtain their flour. In previous works carried out in our laboratory and in other research centers, on rye malt, this procedure generates an increase of soluble fibers, maintaining total fiber content.

The flour made form rye has greater fiber content than the flour wheat. The properties of dietary fiber have beneficial physiological effects on the human organism. Some components of soluble fiber are called prebiotics, defined as food ingredients that positively affect the host.

Prebiotics are defined as nondigestible substances. The dietary fiber maintains biological activity within the human organism by selective stimulation of growth of beneficial microorganisms either naturally present or therapeutically introduced to intestine. The intestinal microflora ferments prebiotics. Prebiotics saccharide belonging to the inulin group, GlcpFruf [α-d-fructopyranosyl-(β-dfructofuranosyl) n-1-d-fructofuranose], Frup-Fruf [β-d-fructopyranosyl-(β-dfructofuranosyl) n-1-d-fructofuranose] where n = 10–60; fructooligosaccharides, FOS (apart from oligofructose with n = 2–9 and, eventually, d-glucose, d-xylose, d-galactose and mannose residues) and non-digestible sugars, NDO. The oligofructose is present in wheat, onion, garlic, endive, leeks, asparagus, and others. In breast milk, the levels of oligosaccharides are relatively high, from 3 to 6 g/L; bifidobacterium selectively digests FOS and NDO and stimulates the development of colonies. Babies fed by the formula, that is, that refers to prebiotics, promote the development of probiotic bacteria, which inhibit the growth of pathogenic bacteria, the bacterial digestion of nutrients, especially proteins, and the decrease of their allergenicity. Probiotic bacteria synthesize cytoprotective short-chain acids, B and K vitamins, and polyamines and degrade the fiber by improving the action of the colon and by increasing the volume of feces [2].

Arabinoxylans (AX) (sometimes called pentosans) are the main non-cellulosic polysaccharides that are abundant in cereals. In the wheat and rye, they differ in their solubility in water, being some soluble and some others insoluble. Watersoluble and water-insoluble fractions are separated through stirring and from a centrifugation. These compounds have healthy benefits. The health benefits are prebiotic effect together with their ability antioxidant. This properties makes these are prevention agents of the colon cancer disease. At the metabolic level, the AX control glycemic and cholesterol levels are also immune regulator agents. During the later years, the research and interest of the AX have gathered considerable attention.

Arabinoxylans are composed of a chain, β(1–4) of xylose units, with variable branches of arabinose in (1–2) or (1–3) [3]. The solubility is modified according to the degree of substitution. The smaller the number of lateral branches, the greater the insolubility of the AX and the possibility of generating insoluble complexes [4]. The AX form viscous solutions with pseudoplastic behavior, and in the presence of certain oxidizing agents, the gels are much stronger and stable. This involves the action of ferulic acid in the formation of cross-links between the AX chains [5]. The texture of the bread increases during the cooking due to the crosslinking of the AX, whose natural levels in the wheat flour determine the quality of the bread, in the functional and nutritious properties [6].
