and the presence of moisture and/or metallic cations. The next step in oxidation is the formation of peroxide radicals (propagation), by reaction of free radicals with oxygen. The formed hydroxyperoxides (primary oxidation products) are flavorless but very reactive, giving secondary oxidation products that contribute to flavor (59). Oxidation is finished when free radicals react with each other. Main products from lipid oxidation (60-62) are aliphatic hydrocarbons (poor contribution to flavor), alcohols (high odor threshold), aldehydes (low odor threshold), and ketones. The last two groups are related to the aroma of dry-cured ham in French-type hams (63) and Spanish hams (64,65). Alcohols may interact with free carboxylic fatty acids, giving esters, especially when nitrate is not used, as in Parma ham, in which esters are generated in greater amounts and are well correlated with its aged odor (66).
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