Page 325 - Natural Antioxidants, Applications in Foods of Animal Origin

304 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir microstructure that lead, directly or indirectly, to lower levels of antioxidants

or their bioaccessibility.
In a study on evolution of antioxidant compounds from lime residue
during drying Kuljarachanan et al. (2009) found that blanching decreased
both the antioxidant contents and activities of the residues due to thermal
degradation and loss with the blanched water. During drying initially
nomilin and limolin increased followed by sharp decrease due to thermal
degradation. In this case the product temperature was found to be a major
factor controlling the changes of limonoids. The amounts of vitamin C and
phenolic compounds decreased as the product temperature increased and the
moisture content decreased during drying.
Effect of air-drying temperature on physicochemical properties of
DF and antioxidant capacity of orange (Citrus aurantium v. Canoneta)
by-products (peel and pulp) was investigated (Garau et al., 2007). It was
observed that dehydration promoted important modifications affecting
both the physicochemical properties of DF and the antioxidant capacity
of orange by-products. The major modifications on the DF components
were observed when either extended drying periods, or elevated drying
temperatures were applied. Dehydration at around 50–60 °C appar-
ently promoted the minor disruption of cell wall polymers, in particular
of pectic substances. However, significant decreases in water retention
capacity, fat adsorption capacity, and solubility values were detected for
both by-products with increased drying temperature. The by-products
studied here were quite resistant to the different heat treatments applied
within the range of 40–70 °C. It was suggested that in order to preserve
the fiber quality and/or the antioxidant capacity, air drying temperature
should be controlled.

8.5 SOURCES OF ANTIOXIDANT DIETARY FIBER

Almost all the plant materials contain ample amount of DF. These mate-
rials are also enriched with various secondary metabolites acting as defense
systems which are either present in free form or associated with DF. The
plant materials as a source of ADF can be numerous; however, in the present
chapter only those sources are mentioned which have been investigated as a
source of antioxidant and DF. These sources are categorized here into four
groups (Fig. 8.1).