Surface enhanced Raman spectroscopy (SERS) based detection schemes for food analysis

The development of food industry over the last century broadened the range of available food products and increased the awareness of society regarding the importance of a healthy diet. As a direct consequence of this, norms and regulation regarding the composition of different products were formulated and are enforced. Still, different food products have a very short shelf-life (i.e. fruits and vegetable) and accordingly, their analysis should be performed in a time and price effective way, while maintaining a high standard for the quality and reliability of the analysis. The current gold standard analytical technique for most of the food products is high performance liquid chromatography (HPLC) combined with different detection schemes such as UV-Vis spectroscopy, fluorescence spectroscopy or mass spectrometry. There are, however, analytes where HPLC-based measurements encounter difficulties and research is still needed in order to overcome these. For those molecules, analysis based on biological assays are applied as reference analytical method. The objective of the present thesis was to investigate the applicability of surface enhanced Raman spectroscopy (SERS) for the analysis of food products. In order to evaluate the potential and limitations of SERS toward these applications, the thesis is divided in two parts. First, different SERS-active substrates were tested and characterized in order to decide on the best-suited substrate for the development of the analytical procedure. While doing this, the substrates’ homogeneity and not their enhancement properties was prioritized. This is thoughtfully discussed in the first part of the results section of the thesis. Second, two selected applications, with increasing degree of complexity, were developed. In both situations a complete analytical procedure is introduced, starting from a thoughtfully understanding of the molecules fingerprint and ending with the measurements and analysis of food extracts. In the first application the tested food product was a market-available fortified cereal and in the second application, different garden-grown tomatoes were analyzed.