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Natural Antioxidants in Poultry Products 193
VetBooks.ir 5.5 SYNERGISTIC EFFECT OF NATURAL ANTIOXIDANTS

Evidence based on pulse radiolysis technique and electron spin resonance
studies supports a redox mechanism, involving reduction of the tocopher-
oxyl radical intermediate by AA to regenerate tocopherol. By this syner-
gistic mechanism, α-tocopherol and AA can mutually reinforce each other
by regenerating the oxidized form of the other. Another mechanism of syner-
gism involves metal inactivating effect of AA. A mixture of α-tocopherol,
AA, or ascorbyl palmitate and phospholipids are also known for their good
synergistic effects leading to inhibition of pigment as well as lipid oxida-
tion. Ascorbate alone enhanced the lipid oxygen radical propagation but
its pro-oxidant effect was reversed when TA was added. Yin et al. (1993)
reported that 10 ppm of vit. E and 500 ppm of vit. C showed the stron-
gest synergism to inhibit pigment and lipid oxidation in meat. Adding rose-
mary to vit. E supplemented meat resulted in lower TBARS than either of
the compound alone suggesting a synergistic effect (McBride et al., 2007).
Mansour et al. (2006) reported synergism of rosemary and marjoram in
minced meat. Combination of oil seed by-products such as rapeseed meal
(0.5 g/100 g meat) or camelina meal (0.7 g/100 g) along with CO extract
2
of rosemary (0.04 g/100 g meat) showed a higher inhibition of lipid oxida-
tion than that of either alone. A very pronounced synergistic effect exists
between rosemary and citric acid. Combinations of oregano and rosemary
essential oils (150 mg/kg each) had a greater effect than those fed individu-
ally or α-tocopheryl acetate (200 mg/kg) on inhibiting lipid oxidation, and
protecting α-tocopheryl acetate concentration in refrigerated meat enriched
with n-PUFAs stored for 15 days. This combination of essential oils also
proved as effective as α-TA in retaining the sensory qualities of breast meat
after 15 days of storage, and was more effective than when these essential
oils were fed individually or at 300 mg/kg. There is a possible synergistic
effect between oregano and rosemary essential oils in preventing lipid oxida-
tion in stored meat enriched with n-3 PUFAs. However, synergistic effects
between various antioxidants need to be exploited in the meat industry.

5.6 MEASUREMENT OF EFFICACY OF AOA

Efficacy of natural antioxidants can be evaluated by various physical and
chemical methods. Physical evaluation of meat color and odor can be
measured by sensory panelists using score card. However, it is always
ensured that the sensory panelists can able to properly recognize the color