Page 37 - Natural Antioxidants, Applications in Foods of Animal Origin

16 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir and cooked beef, both during cooking and subsequent storage. Chaijan

(2011) reported that salting caused an increase in lipid oxidation in tilapia
muscle. The effect of sodium chloride on fat oxidation depends on the level
of free moisture in the system (Pearson et al., 1977). According to Love and
Pearson (1971), the oxidative effect of sodium chloride may be attributed to
the action of the reactive chloride ion on lipids, or to a modification of the
heme proteins catalyzing lipid oxidation.

1.4.6 MUSCLE pH

Several studies have shown that lipid oxidation in muscle foods increases
with a decrease in pH (Chen & Waimaleongora, 1981; Ogden et al., 1995;
Tichivangana & Morrissey, 1985). Acid injection and marination have been
used as a practice to improve the water-holding capacity and tenderness of
muscle foods (Ke et al., 2009). In general, the lower the pH values, the
stronger the prooxidant effect. Rapid formation of the oxidized forms of
heme proteins (methemoglobin and metmyoglobin) might contribute to the
rapid oxidation of muscle at acidic pH values (Chaijan et al., 2007). An
increase in iron solubility with decreasing pH could also increase oxida-
tion rates. Vareltzis and Hutin (2007) observed that exposing hemoglobin
and microsomes to low pH affected lipid oxidation rates. When isolated
membranes alone were exposed to low pH, they were less susceptible to
hemoglobin-promoted lipid oxidation. Exposure of cod hemoglobin to pH
3 decreased its prooxidant activity compared to untreated cod hemoglobin
(Vareltzis & Hultin, 2007). However, if cod hemoglobin and isolated cod
microsomes were exposed to low pH together, oxidation was promoted
(Vareltzis & Hultin, 2007).
Hemoglobin-mediated lipid oxidation can be accelerated by reduction in
pH and could be due to enhanced autoxidation of hemoglobin at reduced pH.
Hemoglobin from different fish is known to promote lipid oxidation in fish
muscle differently (Maqsood et al., 2012). Maqsood and Benjakul (2011a)
monitored the lipid oxidation of washed Asian seabass mince added with
hemoglobin from various fish at different pH (6, 6.5, and 7) during 10 days
of iced storage. Hemoglobins accelerated lipid oxidation more effectively
at pH 6, compared with pH 6.5 and 7 as indicated by the higher PV and
TBARS.