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

Katryna van Leeuwen

Research output: ThesisDoctoral Thesis

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Abstract

Traceability and authenticity perform an important role in keeping the food and beverage industries honest for the protection of the general consumer and for the decent producer. The process to investigate the authenticity and traceability of food and beverages is through analytical techniques and methods. One such technique is the gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) and compound specific isotopic analysis (CSIA) to analyse different compounds in a variety of matrices, as the name suggests, for isotope ratios of C and N.

The purpose of this thesis was the implementation GC-C-IRMS to develop methods to detect adulterations in distillates using δ13C for vanillin; to trace dietary effects on intramuscular fat in sheep using δ13C of fatty acid methyl esters; and to differentiate between different farming systems (organic vs. conventional) with δ13C and δ15N of amino acids from tomatoes.

The first study was the development of a method for a single compound, vanillin, for δ13C. The determination of whether a distillate has been adulterated, by the addition of synthetic vanillin, to enhance the overall quality of the beverage could be detected. Vanillin ranges were determined and compared with those in literature for synthetic, natural and ex-lignin vanillin. Distillate samples, rum, whisky etc, were analysed for their δ13C vanillin value, which were compared against the determined vanillin ranges. The vanillin in 32 distillates were in the δ13C range for ex-lignin, there was one spirit, however, which was found to have synthetic vanillin.

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.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Charles Sturt University
Supervisors/Advisors
  • Ryan, Danielle, Principal Supervisor
  • Prenzler, Paul, Principal Supervisor
  • Camin, Federica, Principal Supervisor, External person
Publication statusPublished - 2017

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