Page 210 - Natural Antioxidants, Applications in Foods of Animal Origin

Natural Antioxidants in Poultry Products 189
VetBooks.ir Further studies are needed to identify the specific compounds in hydrolysate

that are responsible for the overall antioxidative capability.

5.3.2.2 CARNOSINE

Carnosine is a naturally occurring skeletal muscle dipeptide, which consists
of alanine and histidine. Its function in muscle is not completely understood,
but it is thought to act as both a buffering agent and as an antioxidant. The
antioxidant mechanism has been postulated to be a combination of its ability
to act as a chelator, free radical scavenger, and hydrogen donor. Carnosine
is water soluble, thus permitting the inactivation of lipid oxidation cata-
lysts such as heme pigments, iron, lipoxygenase and singlet oxygen, and
free radicals in the aqueous phase of muscle. The color protecting effects of
carnosine were greater than BHT, α-tocopherol, or sodium tripolyphosphate.
Some researchers also investigated the interactions between carnosine and
the different redox states of myoglobin and concluded that it does not stabi-
lize oxymyoglobin or significantly catalyze the reduction of met-myoglobin
formation. Djenane et al. (2004) concluded that the combination of carno-
sine (50 mM) with AA (500 ppm) provided the best antioxidant protection
for meat during refrigerated storage. Surface application of carnosine or AA
combination or alone resulted in an effective delay of oxidative deterioration
of meat.

5.3.2.3 CHITOSAN

Chitosan, a linear polymer of 2-amino-2-deoxy-β-D-glucan, is a deacetylated
form of chitin, a naturally occurring cationic biopolymer. It occurs as a shell
component of crustaceans (crab and shrimp), as the skeletal substance of
invertebrates, and as the cell wall constituent of fungi and insects. Chitosan
possesses a positive ionic charge which gives its ability to bind with nega-
tively charge fat, lipid, protein, metal ions, and macromolecules. Chitosan is
GRAS by the US FDA. Chitosan retards lipid oxidation by eliminating the
pro-oxidant activity of ferrous ions. The AOA of chitosan could also be due
to its chelating ability with free iron released from myoglobin degradation.
Soultos et al. (2008) indicated that chitosan concentration of 1% in pork
sausages show 80% decrease in MDA level after 14 days while that retard
lipid oxidation upto 70% in meat products after three day storage at 4 °C.