Page 381 - Natural Antioxidants, Applications in Foods of Animal Origin

360 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir the tests followed for activity assessment, and the antioxidant activity in rela-

tion to reference antioxidants such as butylated hydroxytoluene (BHT), or
reference EO such as those from age or bush-basil. Some EO from oregano,
thyme, or clove has good antioxidant activity, comparable to that of BHT.
In general, however, the antioxidant activity of EOs is medium or low; on
the other hand, some concrete EOs have no antioxidant or even prooxidant
activity.
EOs are promising food antioxidants when their particular aroma
compatible with the organoleptic characteristics of the foods in which they
are applied. EO from oregano seems to be the most successful one. Goulas et
al. (2007) reported that this EO in combination with modified atmospheres
and salting extend the shelf life of sea bream. Oregano EO is also able to
protect the extra virgin olive oil from oxidation during storage (Asensio et
al., 2012) and to protect minced meat from auto-oxidation (Fasseas et al.,
2008). Very recent and encouraging applications of EOs were described in
active packaging and in edible coatings as we will treat later.

9.3.1.5 PEPTIDES

Despite the fact that all the amino acids naturally present in the proteins can
react with free radicals if these have high energy, the free amino acids are in
the practice not generally effective in the prevention of oxidation processes
in foods and biological systems (Samaranayaka & Li-Chan, 2011). Some
peptides, however, possess antioxidant capacity based on their chem-
ical structure determined by the presence of some concrete amino acidic
sequences. Most of the peptides derived from food proteins having antioxi-
dant activity show molecular weights from 0.5 to 1.8 kDa and often they
have hydrophobic amino acids (as Val or Leu) in the amino-terminal posi-
tion and they include the amino acids Pro, His, Tyr, Trp, Met, and Cys in
their sequences.
The mechanism of action of the antioxidant peptides is generally based
on the free radical scavenging; the tripeptides possessing Trp or Tyr in the
carbonyl-terminal position have a strong free radical scavenging activity
(Saito et al., 2003). In other cases, the action is based in the scavenging of
oxygen-containing compounds. Some peptides act as antioxidants though
the chelation of metal ions such as Cu or Fe. The peptides chelating Cu have
the amino acid His in their sequence, being the imidazole ring of this amino
acid responsible for the union with the Cu ion. Finally, it has been proven
that antioxidant peptides can show synergistic affects with some other