Effect of irradiation on colour and lipid oxidation of dry-cured hams from free-range reared and intensively reared pigs

The effect of irradiation dose (0, 5 and 10 kGy) of vacuum-packaged Iberian dry-cured ham slices from pigs fed on concentrate (CON) or free-range reared (FRG) was studied in relation to TBA-RS, hexanal content and instrumental colour changes. TBA-RS values increased after irradiation in the two sets of hams and the increase was dose-dependent. FRG samples showed higher TBA-RS values than CON samples in all treatments, although differences in the rate of formation of thiobarbituric acid-reactive substances were different in the two types of hams, being higher in CON samples than in FRG ones. Irradiation of dry-cured ham slices significantly increased hexanal contents in both groups sets of hams. Irradiation produced statistically significant increases in vacuum-packed dry-cured ham slices lightness (L*-value), yellowness (b*-value) and chroma (C*-value). Irradiation resulted in significantly lower hue angle (h degrees) values and higher a*-values in both sets of hams indicating a redder colour of irradiated samples than non-irradiated, and these changes were greater in FRG samples than in CON samples. Differences in composition characteristics of raw material could play an important role in the irradiation-induced changes on colour and lipid oxidation of vacuum-packaged dry-cured ham slices. C) 2004 Elsevier Ltd. All rights reserved.