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Control of Lipid Oxidation in Muscle Food 359
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9.3.1.4 ESSENTIAL OILS

Due to the doubts arose on the safety of the most common synthetic antioxi-
dants, the efforts of searching for new natural antioxidants usable in foods
have been redoubled. Together with the classical natural antioxidants already
described, other natural substances have been object of study and utilization
for this property in the recent past years.
Essential oils (EOs) are liquid mixtures of volatile compounds obtained
from plants, generally by steam distillation. Several EOs have shown a satis-
factory antioxidant capacity attributed in most cases to the presence in such
mixtures of molecules with antioxidant ability, mainly phenolic compounds
that act as antioxidants due to their high reactivity with the peroxyl radicals.
Phenolic compounds present in EOs are usually assigned to two structural
families according to their hydrocarbon skeleton: (a) terpenoids, formed
by an isoprene unit (hemiterpenoids) or by combination of two (monoter-
penoids), three (sesquiterpenoids), four (diterpenoids) or more isoprene
units, and (b) phenylpropanoids, formed by an aromatic phenyl group and
the three-carbon propene tail of cinnamic acid. Some common phenolic
compounds belonging to these two families (carvacrol or cymophenol, and
thymol, among terpenoids, and eugenol, guaiacol, syringaldehyde, umbel-
liferone, and coniferyl alcohol, among phenylpropanoids) are described as
principal components of several EOs.
EOs from Allium spp. have a chemical composition very different from
most of the other EOs. They are mainly composed of sulfur-containing vola-
tile compounds possessing antioxidant activity (Tsai et al., 2012) that has
been confirmed in different model systems (Banerjee et al., 2003; Iqbal &
Bhanger, 2007).
Being the EOs mixtures of various compounds, the antioxidant prop-
erties of a concrete EO should reflect the antioxidant activity of the most
active or the most abundant antioxidant compounds present in it. However,
it is necessary to take care with this approach, because complex interactions
depending on composition and experimental conditions take place, resulting
in synergistic or antagonistic behaviors among activities that notably affect
the whole antioxidant properties of the EOs (Kulisic et al., 2005).
Besides the botanical source, environmental factors (e.g., soil, climate,
etc.) may affect the actual composition, and therefore the antioxidant activity
of each EO.
In a recent work, Amorati et al. (2013) reviewed the antioxidant activity
of the EOs. For some selected EO, they summarized the data existing in
literature on their main components responsible for the antioxidant activity,