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Fig. 12.24 Hydroxyl amines mode of action.
trimethyl-6-quinolone, have antioxidant activity (de Koning, 2002). Kumar et
al., however, found evidence for the formation of a substance that could trap
alkyl radicals, and postulated that this was the nitroxyl radical (Kumar et al.,
2007). Such thinking is very reminiscent of the cyclic mechanism postulated to
explain the carbon-centered radical trapping behavior of HALS.
While hydroxyl amines are also efficient carbon-centered radical scavengers
in polymer systems, they differ from HALS both in their lack of steric
hinderance and in their mechanism of action. Nitrones are thought to be the
intermediates responsible for the stabilization observed as shown in Fig. 12.24
Schwarzenbach et al. (2001). The authors are not aware of any naturally
occurring compounds in foods that are acting in this manner, but it is interesting
to note that the polyamine, spermine, present in all eukaryotic cells has been
postulated to serve as a free radical scavenger protecting DNA from free radical
attack. A primary N-hydroxylated compound was suggested as an intermediate
(Ha et al., 1998).
12.7 Conclusion
Synthetic and natural antioxidant additives play a significant role in the modern
food industry. While the progress in controlling unwanted oxidation in foods has
been enormous, significant advances in our capabilities will be required to meet
the challenges of the future. For those consumers who reject the use of synthetic
antioxidants in foods, many effective natural alternatives are available. It is our
belief that even better natural antioxidant formulations are possible and will
come about by combining the highly effective natural phenolics now available
with natural, synergistic chelators, secondary antioxidants, carbon-centered
radical scavengers and quenchers. The polymer industry shows us what kinds of
chemistries will be needed. Truly effective control of oxidation in foods will rely
on complex mixtures of antioxidant components capable of attacking the lipid
oxidation pathway at multiple points. Such mixtures will also need to be tailored
with respect to their physical properties. It will be necessary to formulate
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