Preparative silver ion TLC/RP-HPLC determination of coffee triacylglycerol molecular species

Preparative silver ion thin layer chromatography (Ag-TLC) was utilized for the preparative isolation of triacylglycerol (TAG) classes from cherry coffee beans according to the degree of unsaturation. The isolated TAGs were chromatographically (Ag-TLC) pure and used as standards to identify TAG molecular species by RP-HPLC using a refractive index detector (RID). Acetonitrile/acetone (1:1, v/v) was used as the solvent at a flow rate of 2 mL/min. This methodology was used to determine the % of TAG molecular species in eight coffee samples to evaluate effects of bean type, drying procedures and geographic origin. The following nine TAG molecular species were identified in all the coffee samples: LLL, SLLn, OLL, PLL, StLL + POL, PPL + OOL, ALL, PStL + POO and PStO (in elution order) (Ln, linolenic; L, linoleic; O, oleic; P, palmitic; A, arachidic and St, stearic acid residues). Quantitative evaluation was based on the relative area percentages derived directly from the data-station. The data obtained were statistically compared by variance analysis. Although resolution with RP-HPLC/RID was poorer than the previously reported RP-HPLC/LSD (light scattering detector), the procedure can be useful for a number of applications, such as determine relative % of the resolved TAG molecular species, monitor relative % of TAG molecular species of coffee stored over prolonged period of time etc. RP-HPLC/RID offers several important advantages, such as lower cost and simpler instrumentation over RP-HPLC/LSD. In agreement with our previous studies, in general no effects of bean type, drying procedures and geographic origin on TAG composition were found (P > 0.05).