This investigation was carried out in an attempt to find a reliable method which can be used in a quality control laboratory for the detection of lard adulteration in beef tallow. The laboratory technique is based on the Gas Liquid Chromatographic analysis of fatty acids composition in total extracted fat as well as in triglycerides and B-monoglycerides. The adulteration of the studied beef tallow samples with lard is made from some calculated ratios depending on the fatty acids composition of pure lard and beef tallow. The obtained results showed that lard contained more unsaturated fatty acids (66.53%) than beef tallow (45.38%), while total saturated fatty acids was much higher in beef tallow (52.59%) than in lard (31.97%). In addition, the stearic acid (C18:0) was lower in lard (12.33%) than in beef tallow (16.40%) and the linoleic acid (C18:2) in lard and beef tallow was found to be 14. 79% and 3.39%, respectively. The saturated fatty acids/unsaturated
fatty acids ratio was much higher in beef tallow TE (1.1) than in lard (0.48). Palmitic acid (C16:0) of Selard is mainly incorporated in B-monoglycerides
(85.37%), while oleic acid (C18:1) was the predominated acid in B-monoglycerides of beef tallow (48.33%). On the other side, oleic acid (C18:1) was highly concentrated in the triglycerides of either beef tallow and lard (46.23% and 47.41%), respectively. Palmitic acid enrichment factor was 0.85 and 2.06 in beef tallow and lard, respectively. The unsaturation ratio was rather low in lard 0.51 ) than in beef tallow (1.09), while the total C16/total C18 fatty acids in B-monoglycerides was much higher in lard (1.85) than in beef tallow (0.34), also the percent of saturated/unsaturated fatty acids in B-monoglycerides was rather high in lard (0.77) as compared with that in beef (0.51). Estimation of lard in unknown samples, is made by determining the percentage of linoleic acid content and taking the corresponding percentage of lard from the standard curve.