Page 293 - Natural Antioxidants, Applications in Foods of Animal Origin

272 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir spectrometrically at 532 nm by the reaction based on the condensation

of two molecules of thiobarbituric acid (TBA) with one of the end prod-
ucts of auto-oxidation, malondialdehyde which results in the red-colored
complex (Dunkley & Jennings, 1951). The other traditional methods
include m-phenylenediamine test, IR value, Anisidine value, Kreis test (for
aldehydes), methods based on the carbonyl content of oxidized fats, and
measurement of oxygen uptake by manometry or polarography (Henick et
al., 1954; Tappel, 1955; Mehlenbacher, 1960). Recent methods of measure-
ment include the use of instruments like electron spin resonance (ESR)
spectrometry, static and dynamic GC/MS, head space GC/MS (electronic
nose), and high performance liquid chromatography (HPLC) (Kim & Morr,
1996; Nielsen et al., 1997; Stapelfeldt et al., 1997; Kristensen & Skibsted,
1999). Certain tests are employed to determine the proneness of the fat to
autoxidize that can be measured by studying the degree of resistance that a
fat bears to autoxidation and it can be seen by iodine value, active oxygen
method, rancimat method, induction period (by measuring manometric
reading for macro work and by using Warburg apparatus for micro studies),
and so forth.
Photoreactions in milk can be measured by monitoring the formation of
1
1 O as a function of light exposure using O fluorescent probe. One of the
2
2
probes, available under the trade name singlet oxygen sensor green (SOSG)
reagent, is highly selective for O , and it does not show any appreciable
1
2
response to hydroxyl radical or superoxide. SOSG is reported (Molecular
Probes, 2004; Airado-Rodríguez, 2011) to emit weak blue fluorescence
peaking at 395 and 416 nm for excitation at 372 and 393 nm. After reaction
with O , it emits a green fluorescence similar to that of fluorescein (excita-
1
2
tion/emission maxima ~504/525 nm) that is measured.

7.6 CHARACTERISTICS, TYPES, AND MECHANISM OF ACTION
OF ANTIOXIDANTS

Antioxidants are the substances that inhibit, retard, or interfere with the
formation of free radicals in fat-rich foods, thus terminating the oxidative
reaction in its initial stage. From a practical standpoint, it means that when
an antioxidant system is properly selected and correctly applied to meet
the needs of a particular food item, will help to maintain the original fresh-
ness, flavor, and odor of the product for a longer period of time than would
otherwise be possible. In the food industry, a substance having the technical
function of delaying the oxidation of nutrients, such as lipids, sugars, and