Lipid authentication of butter and margarine using Fourier transform infrared spectroscopy (FTIR)

Most consumers are unaware of the lipid composition of butter and margarine; they can buy an inauthentic product. Therefore, the objective of this study was to evaluate the lipid composition of two butters (A and B) and one margarine (C) of commercial brands, using FTIR at 400-4000 cm⁻¹ to determine their quality. Each of the samples was melted at 30°C for 1 min. Next, they were analysed by FTIR, and their aromatic (AC), carbonyl (CC), aliphatic (AP), aliphatic (long chain) (ALC) and sulfoxide (SC) compounds were quantified. The butters (A and B) and margarine (C), presented differences in their fingerprints (723 at 1465 cm⁻¹). The lipids with cis isomers were identified in wavenumbers at 723, 1417, 1654 and 3006 cm⁻¹, and trans isomers at 968 cm⁻¹. Chemical compounds which are desirable in these products, and were identified at wavenumbers at 1033 (thioester), 1105 (carbonyl), 1163 and 1238 (methylene), 1377 and 1465 (methyl), 1746, 2678 and 2730 (ester) and 3470 cm⁻¹ (hydroxyl). The authenticity of the butters and margarine was determined in the wavenumbers at 2853 and 2924 and 2953 cm⁻¹, which correspond to the functional groups, methylene and methyl, respectively; where margarine presented a higher value in AP (19.98 arbitrary units (au)) and ALC (124.22 au). Therefore, FTIR is an option for authenticity detection, in addition, it is a method of easy repeatability and fast response.