Chemistry Reference
In-Depth Information
14.1 Overview
The interest in antioxidants in the field of food chemistry decades ago had, as a
target, retardation or prevention of lipid oxidation. The examined compounds,
which were mostly synthetic, were added to food or tested in the laboratory at
levels corresponding to good manufacturing practices (i.e., ~0.02% of the fat or
oil content of the food matrix). Later on, the introduction of the biological
oxidative stress concept and increased evidence of the contribution of dietary
antioxidants, such as polyphenolic compounds, vitamins C and E, and
carotenoids, to support the body's defense mechanism against in vivo oxidants
(reactive oxygen and nitrogen species) renewed the interest and concern in
antioxidants. This resulted in a large number of published works in the field of
food chemistry, as well as in the life sciences. Some studies showing the pos-
sible mutagenic activity of synthetic food antioxidants, together with the
increasing demand of consumers for natural ingredients, have also raised interest
in natural antioxidants. All these urged the need to develop suitable
methodologies for the study of individual constituents and/or extracts from
innumerable dietary or novel sources. To this day, various methods for the
assessment of antioxidant activity have been reported in the literature. The
characteristics of the most frequently employed methods have been critically
presented in peer review articles over the years. The various methodologies
employed so far are broadly classified into those evaluating changes in a lipid
substrate and those measuring free radical scavenging activity, either directly or
using a suitable probe. Focus on radical scavenging activity has been given, as
this is considered to be the main mechanism of action of phenolic compounds
(AH), which are the most widely distributed natural antioxidants and constitute
the major part of those consumed on a daily basis.
The large amount of effort invested in developing tests and in executing
studies on natural antioxidants resulted in a great diversity of methods, as well as
the accumulation of a tremendous amount of data which have created much
confusion in the field. The data presented are often conflicting or difficult to
compare, since the protocols applied differed significantly between methods
despite the fact that the same chemical reagents were used. Almost a decade ago,
the complexity of antioxidant activity was highlighted, the multitude of factors
affecting the behavior of antioxidants in a system, as well as the different
mechanisms of action reported for antioxidants were extensively discussed. The
impact of Professor Edwin Frankel's contributions to this evolution is unques-
tionable. Since then, investigators have refined methodology and introduced
more than one tests in their experimental part. Still, the main concern is the
critical need for standardized protocols. This is emphasized in all reviews on
antioxidant methodology since 2000, thus, motivating related scientific societies
to be engaged with the issue. Owing to the interest in antioxidants beyond the
application as food additives, the American Chemical Society (ACS) organized
the first International Congress on Antioxidant Methods in Orlando in 2004, in
which 140 scientists from 18 countries participated. The discussions had as an
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