Page 323 - Natural Antioxidants, Applications in Foods of Animal Origin

302 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir DF and natural antioxidants, such as polyphenol compounds (Saura-Calixto,

1998).
The definition of DF according to the American Association of Cereals
Chemists Expert Committee (De Vries, 2003) includes “cell wall polysac-
charides, lignin and associated substances resistant to hydrolysis by the
digestive enzymes of humans.” In this definition, “associated compounds”
are included for the first time in an official definition of DF. Polyphenols
linked with DFs could be one of the associated compounds. Later the concept
of the antioxidant activity of insoluble material was introduced (Serpen et
al., 2007) as it is able to exert a marked antioxidant activity also by a solid–
liquid interaction. The insoluble materials, particularly ADFs survive in the
gastrointestinal tract for a long time and quench the soluble radicals that are
continuously formed in the intestinal tract (Babbs, 1990).
The most abundant phenolic compounds in cereals belong to the chem-
ical class of hydroxycinnamic acids (HCA). Ferulic acid (FA) is the main,
followed by diferulic acids and by sinapic acid, p-coumaric acid, and caffeic
acid; benzoic acid derivatives have also been described (Vitaglione et al.,
2008). About 95% of grain polyphenols are linked to cell wall polysac-
charides through covalent ester bonds. FA is bound to the arabinoxylans
via the acid group acetylating the primary hydroxyl at the C position of
5
α-arabinofuranosyl residues (Hatfield et al., 1999). In case of fruits and
vegetable, phenolic compounds could also be linked to pectin and to other
polysaccharide structures (Ishii, 1997; Jiménez-Escrig et al., 2001a; Saura-
Calixto & Díaz-Rubio, 2007).
The antioxidant capacity of DF linked polyphenols has been largely
underestimated because of their low water and organic solvent solubility.
In order to get actual value, it is necessary to perform multiple step extrac-
tion and an appropriate chemical hydrolysis to release phenolics and to
permit them to exert antioxidant activity in the in vitro assays. In the view
of constituents present in the ADF, it can be used on one hand as a dietary
supplement to improve gastrointestinal health and to prevent cardiovascular
diseases (Pérez-Jiménez et al., 2008), and on the other as an ingredient in
meat products to improve technological qualities and prevent lipid oxidation
(Sánchez-Alonso et al., 2007).

8.3 POLYPHENOLS AND DIETARY FIBER QUALITY

The antioxidant moiety associated with DF fundamentally determines its
structure and consequently physical properties. The presence of FA linked to