Page 197 - Natural Antioxidants, Applications in Foods of Animal Origin

176 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir supplemented, as well (Galobart et al., 1999). Studies have shown no clear

negative impact of omega-3 enrichment on other quality criteria of eggs,
including their functional properties.

5.3.1.2 ALOE VERA

Aloe is a genus containing about four hundred species of flowering succu-
lent plants belonging to Lileaceae family (Mohammad, 2003). True aloe
vera plant is called Aloe barbadensis Miller (Shahzad et al., 2009). The
mucilaginous jelly from the parenchyma cells of the peeled, spineless leaves
of the plant is referred as aloe vera gel. The gel is a watery-thin, viscous,
colorless liquid which contains 99% water and 1–0.5% solid matter at pH
4.5 (Shahzad et al., 2009). The gel exhibits antioxidant, antibacterial, anti-
fungal, as well as antiviral activity as it contains aloin, aloe-emodin, barb-
loin, emodin, anthraquinone glycosides, glycoprotein, gamma-lanoline acid,
prostaglandins, and mucopolysaccharides (Shafi et al., 2000; Singh et al.,
2010). Ethanolic extract of fresh aloe vera juice possessed stronger radical
scavenging activity than that of aloe vera powder, and the antioxidative
effect of aloe vera extracts was correlated to its development stage (Zhang
et al., 2001).

5.3.1.3 ASCORBIC ACID

AA is a chelating agent that binds metal ions; it also scavenges free radicals
and acts as a reducing agent. At high levels (> 1000 mg/kg), AA inhibits
oxidation; however, at low levels (< 100 mg/kg) it can catalyze oxidation
and warmed over flavor (WOF) development (Ahn & Nam, 2004). In the
presence of AA, iron stimulates oxidation in muscle membranes, presum-
ably through the involvement of hydroxyl radicals. Sepe et al. (2005) found
that sodium ascorbate and sodium erythorbate more effectively maintained
red color and maintained myoglobin in the reduced state in cooked ground
meat patties than AA and ascorbyl palmitate. The solubility of ascorbate
affects its ability to prevent discoloration (Mancini et al., 2006). The lack of
effectiveness of the hydrophobic antioxidant may be a result of localization
of components responsible for bone discoloration within the aqueous phase.
AA and phosphates appear to work synergistically to inhibit lipid oxidation.
AA and tocopherol reduction of lipid oxidation in meat can be enhanced by
adding sesamol, especially as storage time increases (Ismail et al., 2008).