Page 101 - Natural Antioxidants, Applications in Foods of Animal Origin

80 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir 2.16 APPLICATIONS OF NATURAL ANTIOXIDANTS/EXTRACTS

IN FOOD PRODUCTS PRESERVATION

Foods of plant origin are stabilized by addition of antioxidants less
frequently than foods of animal origin, perhaps with the exception of
edible and essential oils. In contrast to animal foods, foods of vegetable
origin usually contain natural antioxidants, such as tocopherols, carot-
enoids, or flavonoids in sufficient amounts. The pro-oxidative activity of
iron and other heavy metals is less dangerous in plant materials than that
of heme derivatives in animal products, as plant materials usually also
contain metal-chelating agents. The only important oxidation catalyst in
raw materials and foods of vegetable origin is a group of lipoxygenases
and related enzymes. Synthetic antioxidants prevailed for the stabiliza-
tion of foods of plant origin in earlier applications, but in the last decade
or two, natural antioxidants have been intensively applied, following
consumers’ wishes.
Lipids in foods of vegetable origin are usually more unsaturated than
that of animal origin; therefore, the initiation rate of oxidation reactions is
higher and natural antioxidants, originally present in foods are more rapidly
consumed than in lard or tallow and other animal fats. The stabilization of
products of vegetable origin against autoxidation is thus less efficient than
the stabilization of animal products. Protection factors of natural antioxi-
dants are several times higher in lard than in edible oils.
The initial concentration of natural antioxidants in plant foods is already
near the optimum so that a further addition of antioxidants has only a small
effect, but it is useful for those cases when rapid decomposition of antioxi-
dants is expected. For instance, additional natural antioxidants can be added
to foods heated to high temperature or stored for a long time (Löliger, 1991;
Pokorný &Trojáková, 2001).
Cereal products such as dehulled rice, white flour, or grits, are not usually
stabilized. In whole grain flours, enzymes have to be inactivated to increase
shelf life. After heating, natural antioxidants from brans are sufficient for
lipid stabilization (Table 2.9). Natural antioxidants may be added to break-
fast cereals, the shelf life of which should be long. Rice bran, stabilized
by extrusion, has high natural antioxidant content, and thus it was found
suitable as a component for breakfast cereals with high stability (Saunders,
1989; Pokorný &Trojáková, 2001).