The application of GC-C-IRMS to the authentication and characterisation of foods and beverages

The second study was of greater analytical complexity than the first study as 4 fatty acids (FA) δ13C values were analysed in polar (PL) and neutral (NL) lipids of the intramuscular fat of lambs. The lambs (24) were fed 4 different diets supplemented with oil and Cistus ladanifer L. (a tanniferous shrub). The research question was to understand whether the increase in intramuscular fat for lambs fed a diet supplemented with both oil and C. ladanifer, could be explained mostly by the incorporation of diet preformed FA or by increased de novo FA synthesis. It was shown that, with respect to 16:0, the increase of intramuscular FA was due to continual de novo FA synthesis for lambs fed a diet supplemented with oil and C. ladanifer. The results also showed that diets supplemented with oil prevented de novo FA synthesis from occurring; therefore, the inclusion of C. ladanifer to the diet repressed the oil effect. The last study, of even greater analytical complexity, focussed on the analysis of 9 amino acids δ15N and δ13C values for the differentiation between tomatoes grown organically and conventionally. Amino acids are involved in many metabolic pathways in the plant; therefore, tracing the N uptake from the fertilizer to the plant and subsequent fruit could be possible. Glx functioned as an internal standard to remove the effects of external factors. The analysis of the amino acids Ala, Val, Ileu, Leu, Gly, Pro, Thr, Glx and Phe for δ15N and δ13C with particular focus on Glx for δ13C, provided separation between tomatoes grown organically and tomatoes grown conventionally.