Application Note: Improved yoghurt aroma analysis by Solvent-Assisted SBSE

Aroma compounds are determined in fatty high matrix foods by solvent-assisted SBSE coupled with Liquid Desorption-GC/MS, and sensory notes compared

Aroma and flavour profiles of dairy products generally consist of a large number of compounds spanning a wide range of concentrations, polarities, and functional groups. Further complicating the analysis, extraction takes place in competition with fats and other solid matrix compounds, in which critical flavour compounds are soluble. Stir Bar Sorptive Extraction (SBSE) and Solvent Assisted Stir Bar Sorptive Extraction (SA-SBSE) are firmly established techniques for extraction of flavour compounds. The solvent swollen PDMS stir bars used in SA-SBSE offer significant increased capacity for concentration of hydrophilic/polar compounds without performing direct solvent extraction of the sample. In this work, SBSE and SA-SBSE were used to extract a berry-flavoured yoghurt followed by GC-MS after liquid desorption of the stir bars.

The combination of MassHunter Unknowns Analysis and Aroma Office database search on the resulting data files was used to identify and document the compound profile differences. Four plain (non-flavoured) yoghurts were extracted by SA-SBSE and both GC-MS and sensory evaluations performed on the back extracts after liquid desorption. Multivariate analysis was then performed on the samples from the list of aroma compounds indicated, profiling them graphically in combination with the sensory characteristics. Finally, both SBSE and SA-SBSE were performed on one of the plain yoghurts to investigate the sensory differences in the back extracts. Results indicated that the increased extractive power of SA-SBSE resulted in an aroma profile closer to that of the original product than that produced by SBSE alone.