Page 92 - Natural Antioxidants, Applications in Foods of Animal Origin

Natural Antioxidants: Occurrence and Their Role in Food Preservation 71
VetBooks.ir of food or beverage and only low concentration of it is required to achieve

the desired pH level. Phytic acid has the potential to prevent color degra-
dation in food or beverage including anthocyanin. Phytic acid is the most
potent natural iron chelator and has strong bacteriostatic and antioxidant
action (Graf et al., 1987; Graf & Eaton, 1990). Phytic acid is found to have
similar iron-chelating properties as desferrioxamine, a drug commonly used
to kill germs, tumor cells, or to remove undesirable minerals from the body
(Hawkins et al., 1993). The chelating stability constants of magnesium ion
and calcium ion of phytic acid are compared favorably with that of EDTA.
In fruits and vegetables, phytic acid helps to prevent oxidative browning
by inhibiting polyphenol oxidase. Phytic acid may be used as a safe preser-
vative and antioxidant in food products (Graf et al., 1987). Prevention of
browning of cut lotus root by phytic acid was investigated by immersing cut
lotus root in 0.5% phytic acid, 1.0% phytic acid, and distilled water with no
additives (control) then removed after 1 h. The cut lotus root with phytic acid
showed significant prevention of browning. The chelate action of phytic acid
compared to synthetic chelating agent, sodium metaphosphate was studied.
Sodium metaphosphate, an effective metal ion chelator has the greatest
salt forming activity among phosphates, particularly with calcium salts.
Iron chelate ability of phytic acid was superior to sodium metaphosphate
at pH 5.0. Phytic acid sequesters metal ions promoted oxidation, discol-
oration, and loss of flavor. Iron may cause discoloration in wine or fruit
juice. Hence, phytic acid can be added to chelate polyvalent iron cations to
prevent or treat these problems and make a wine more stable and commer-
cially acceptable. Phytic acid is a natural antioxidant. Phytic acid forms a
chelate with iron, thereby preventing the radical formation and oxidative
damage. It blocks the formation of hydroxyl radicals and suppresses lipid
peroxidation. In fruits and vegetables, phytic acid helps to prevent oxidative
browning by inhibiting polyphenol oxidase. Phytic acid may be used as a
safe preservative and antioxidant in food products (Graf et al., 1987). Graf
et al. (1987) reported the effects of added phytate upon iron-mediated OH
production and arachidonic acid peroxidation. Substantial amount of OH is
produced by a superoxide-generating system in the presence of iron alone.
Even greater amounts of OH are evolved if adenosine diphosphate (ADP)
is added to chelate the iron. Generation of this oxyradical, however, is
completely blocked by the addition of micromolar amounts of phytic acid. It
is important to note that the inhibition of OH generation is found over a wide
range of phytate:iron ratios from 1:4 to 20:1 (Graf et al., 1984). The effect is
due to occupation of all iron coordination sites by phytate; all iron-phytate
chelates prepared were completely soluble. Similarly, phytate prevents the