Extraction properties and absorption spectra of dry cured hams made with and without nitrate

The spectral and extraction properties of nitrate-free dried hams (Parma hams) were studied as a function of maturing time and muscle type (semimembranosus and biceps femoris muscles). To understand the red colour of the processed meat, a three-step extraction using water, acetone and tetrahydrofuran (THF) as solvents was employed and the extracts from each step were submitted to spectrophotometric (visible) analysis while the corresponding residues underwent instrumental (CIE L* a* b*) colour evaluation. Results showed that the drier the meat the more the pigment is soluble in organic solvents, THF proving a major extractant in matured hams, regardless of muscle type. When Parma hams were compared with hams made using nitrate, the former displayed more intense (P<0.05) absorption in the red region in the aqueous solution, lower intensities in acetone and higher values in THF solution. Major differences in spectral characteristics were found between water and organic extracts of Parma hams, with both acetone and THF solutions exhibiting a doublet at 544-584 nm, and water extracts displaying two distorted peaks at 551 and 595 nm. It is concluded that dry curing of meat without nitrate yields a lipophylic stable red pigment whose hydrophobicity increases with ageing.