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314 Part 3: Meat, Poultry and Seafoodsother dry-cured and cooked meat products when based on to-
tal protein carbonyls and fluorescence corresponding to protein
carbonyls. But a higher oxidation was reported in dry-cured
ham when usingα-aminoadipic semialdehyde andγ-glutamic
semialdehyde as indicators of protein oxidation (Armenteros
et al. 2009a).Oxidation to Volatile CompoundsAs mentioned previously, some oxidation is needed to gener-
ate volatile compounds with desirable flavor properties. For in-
stance, a characteristic aroma of dry-cured meat products is cor-
related with the initiation of lipid oxidation (Buscailhon et al.
1994, Flores et al. 1998). However, an excess of oxidation may
lead to off-flavors, rancidity, and yellow colors in fat.
The primary oxidation products, or hydroperoxides, are fla-
vorless, but the secondary oxidation products have a clear contri-
bution to flavor. There are a wide variety of volatile compounds
formed by oxidation of the unsaturated fatty acids. The most
important are (1) aliphatic hydrocarbons that result from autoxi-
dation of the lipids; (2) alcohols, mainly originated by oxidative
decomposition of certain lipids; (3) aldehydes, which can react
with other components to produce flavor compounds; and (4)
ketones produced through eitherβ-keto acid decarboxylation
or fatty acidβ-oxidation. Other compounds, like esters, may
contribute to characteristic aromas (Shahidi et al. 1987).
Oxidation rates may vary depending on the type of product
or the processing conditions. For instance, TBA (thiobarbituric
acid), a chemical index used as an indication of oxidation, in-
creases more markedly in products such as Spanish chorizo than
in French saucisson or Italian salami (Chasco et al. 1993). On
the other hand, processing conditions such as curing or smoking
also give a characteristic flavor to the product (Toldra 2006b). ́AntioxidantsThe use of spices such as paprika and garlic, which are rich
in natural antioxidants, protects the product from certain oxida-
tions. The same applies to antioxidants such as vitamin E that are
added in the feed to prevent undesirable oxidative reactions in
polyunsaturated fatty acids. Nitrite constitutes a typical curing
agent that generally retards the formation of off-flavor volatiles
that can mask the flavor of the product, and allows extended
storage of the product (Shahidi 1998). Nitrite acts against lipid
oxidation through different mechanisms: (1) binding of heme
and prevention of the release of the catalytic iron, (2) binding of
heme and nonheme iron and inhibition of catalysis, and (3) stabi-
lization of lipids against oxidation. Smoking also contains some
antioxidant compounds such as phenols that protect the external
part of the product against undesirable oxidations. The muscle
antioxidative enzymes also exert some contribution to the lipid
stability against oxidation. In the case of fermented meats, the
microbial enzyme catalase degrades the peroxides formed dur-
ing the processing of fermented sausages (Toldra et al. 2001). ́
Thus, this enzyme contributes to stabilizing the color and fla-
vor of the final sausage. Catalase increases its activity with cell
growth to a maximum at the onset or during the stationary phase,but it is mainly formed during the ripening stage. Large amounts
of salt exert an inhibitory effect on catalase activity, especially
at low pH values. The catalase activity is different depending on
the strain. For instance,S. carnosushas a high catalase activ-
ity in anaerobic conditions, whileS. warnerihas a low catalase
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