Compositional and thermal characterization of genuine and randomized lard: A comparative study

Composition and thermal characterization of genuine and randomized lard were investigated comparatively in an attempt to find common merits that assess lard detection. The investigation included compositional and positional distribution of fatty acids, triacylglycerol profiling by gas chromatography (CC) and reversed-phase high-performance liquid chromatography (RP-HPLC), as well as thermal behavior by differential scanning calorimetry (DSC) of both samples. Individual and total saturated and unsaturated fatty acid composition in total fats of both genuine and randomized lard were identical. On the other hand, the results of pancreatic lipolysis/GC analysis showed that the average percent palmitic acid [PAEF(%)] and myristic acid [MAEF(%)] enrichment factors of genuine (280 and 270) and randomized lard (110 and 98) were quite different. Thus, application of PAEF to detect randomized lard is of no value. However, normalization of fatty acid distribution by randomization in 2-monoacylglycerols made the individual and total saturated and unsaturated fatty acids almost identical to that of total fat and neutral triacylglycerols (TC) of lard. TC compositional analysis by GC revealed that both genuine and randomized lard had six dominant TG (C-46, C-48, C-50, C-52, C-54, and C-56) With quite different concentrations. TC with C-52 represent the major constituent of genuine and randomized lard. TC profiling of samples was also carried out by RP-HPLC with a refractive index detector. The same peaks were eluted in both samples, but the area % of major peaks changed due to randomization. 2-Palmitooleostearin (SPO) was found in high proportion in lard. However, the ratios of SPO to 2-palmitooleolinolein of both genuine and randomized lard are close (0.6 +/- 0.05) and significantly distinguishable from that of beef (4.24), mutton (6.17), chicken (0.21), and turkey (0.14) fats. The DSC thermogram and thermodynamics of phase transitions of both samples were quite different and do not reveal common characteristic(s) that could be used for immediate detection of lard substances in fat admixtures.