Lipolysis and oxidation in subcutaneous adipose tissue during dry-cured ham processing

In southern countries where the consumers eat the adipose tissue of ham slices, adipose tissue contributes to the typical flavour of ham. The aim of this study was to investigate the changes in lipids of subcutaneous adipose tissue during dry-cured ham processing. Lipid hydrolysis and oxidation were followed in the adipose tissue of 30 hams (by groups of six) at different stages of processing (green ham, 6, 12, 18 and 24 months). The results showed that: (1) Adipose tissue of the green ham contained 89.7% triacylglycerols, 5.6% water and low amounts of free fatty acids (FFA) (0.1%), diacyl- and monoacylglycerols (traces). The main triacylglycerols were di-oleoyl-palmitoyl glycerol (POO) (36.6%), palmitoyl-stearoyl-oleoyl glycerol (PSO) (19.9%) and palmitoyl-oleoyl-linoleoyl glycerol (POL) (8.0%). Free fatty acids had a higher proportion of polyunsaturated fatty acids than triacylglycerols (17.7% vs 8.3%). (2) An intense lipolysis occurred during the first 6 months and continued at a slow rate up to 24 months. The amount of triacylglycerols decreased from 89.6 to 75.8% while FFA, diacyl- and monoacylglycerol amounts increased to reach 10.5, 4.5 and 1.3%, in the 24 month old hams, respectively. A preferential hydrolysis of triacylglycerols POO, POL and OOL was observed. Free fatty acid composition showed a sharp decrease in linoleic and stearic acids and an increase in palmitic acid. The decrease in linoleic content during the process suggested that this fatty acid acid was oxidised. Both lipolytic and oxidative changes in lipids of adipose tissue could affect its sensory traits, particularly colour and taste.