1. Introduction
Lipid oxidation has been reported to be responsible for offflavors,
toxic compounds formation and the cause of many
diseases (Shaker, 2006). Lipid oxidation, a mechanism which leads
to rancidity, is very often the decisive factor determining the useful
shelf life of food and other products. This is true even if the fat
content of the product is very low. It has long been recognized that
some essential oils are widely used for antimicrobial activities,
especially in pharmaceutical, sanitary, cosmetic, agricultural, and
food industries (Tepe et al., 2005; Bakkali et al., 2008; Schmidt et al.,
2009).
Oxygen uptake inherent to cell metabolism produces reactive
oxygen species (ROS). The reaction of this species with lipid
molecules originates peroxyl radicals and their interaction with
nucleic acids and proteins conduces to certain alterations and,
therefore, functional modifications (Chaillou and Nazareno,
2006). Antioxidants are compounds that can delay or inhibit
the oxidation of lipid or other molecules by inhibiting the initiation
or propagation of oxidizing chain reactions (Velioglu et al.,
1998).
At present, the most commonly used antioxidants are BHA, BHT,
propyl gallate and tert butylhydroquinone (Özcan and Akgül,1995).
Use of synthetic antioxidants to prevent free radical damage has
been reported to involve toxic side effects (Lim et al., 2011), making
attractive the search for antioxidant and scavenger natural
compounds. Although synthetic antioxidants are commonly added
to foods, there are some toxicity concerns and a trend among
modern consumers toward “all natural ingredients” (Cornwell
et al., 1998; Lim et al., 2011). Therefore, there is a growing
interest on natural and safer antioxidants (Moure et al., 2001; Oktay
et al., 2003; Kamkar et al., 2010). A need for identifying alternative
natural and safe sources of food antioxidants has been created, and
the search for natural antioxidants, especially of plant origin, has
notably increased in recent years (Skerget et al., 2005; Özcan and
Arslan, 2011).
The use of essential oils as functional ingredients in foods,
drinks, toiletries and cosmetics is gaining momentum, both for the
growing interest of consumers in ingredients from natural sources
and also because of increasing concern about potentially harmful
synthetic additives (Reische et al., 1998). The study of essential oils
and their components has been increased due to their relatively
safe status, their wide acceptance by consumers, and their
exploitation for potential multi-purpose functional use (Ormancey
et al., 2001; Sawamura, 2000). Many authors, in fact, have reported
antimicrobial, antifungal, antioxidant and radicalscavenging
properties (Hirasa and Takemasa, 1998; Gianni et al.,
2005; Tuberoso et al., 2007; Bakkali et al., 2008) by spices and
essential oils.
In this study, mint, laurel leaf and myrtle leaf essential oils are
used for investigation the antioxidant effect on some edible oils. For
this aim, the lipid peroxidation, acidity and viscosity changes of
pomegranate kernel, poppy, grape and linseed oils after essential
oils addition and storing in 60 C for 6 weeks, are determined.