Rapid evaluation of smoke exposure in grapes and wine by Raman spectroscopy and machine learning.

Raman Spectroscopy of Smoke Compounds

We have evaluated 10 different smoke compounds in synthetic wine using a 785 nm Wavelength Raman setup using defined parameters to gain spectra. Individual compounds, as well as different combinations, were tested to provide us with initial results showing the various Raman fingerprints of the smoke compounds and help determine any potential interferences between them.

Development of a Spectrum Collection Method using Gold Nanoparticle strips

We developed a method for data collection to improve the reproducibility of obtaining Raman spectrum, using the gold nano-strips and a 3D-Printed 3×3 grid. The nano-strips were cut into 9 identical pieces and then each piece was placed in a well of the 3×3 grid, then our sample was dropped onto the nano-strips for spectrum collection.

Our scan method involves obtaining 5 separate scans over the course of a set period to determine if signal enhancement improves as the nano-strip becomes more saturated. We are in the process of having an auto-sampling system created for the 785nm Raman to streamline our data collection as we are finalizing the enhancement protocols.

Surface Enhanced Raman Spectroscopy using Gold Nanoparticle Strips

Using the commercially produced gold nano-strips, we have obtained scans of smoke compounds in synthetic wine that show very strong Raman enhancement properties. Initial scans of smoke compounds were obtained to have benchmark results, and then the nano-strips were used to determine the effectiveness of enhancement with lower concentrations. Two significant results were obtained; a unique fingerprint for Guaiacol using the nano-strips was found in the form of a very strong peak at 576 cm-1, and we have been able to detect guaiacol at concentrations in synthetic wine as low as 100ppb (parts-per-billion) using the nano-strips

Removal of Anthocyanins and Tannins through different Extraction Methods

We have trialed many different extraction methods testing the removal of anthocyanins, tannins, and any other compounds present that interfere with obtained spectra of smoke compounds in wine. Various parameters were tested to determine the best method for removal while also recovering the smoke compounds present, to figure out how to obtain clean scans of smoke compounds in a wine matrix. Scans were obtained of two different types of wines spiked with smoke compounds prior to extraction, to see how well these extraction methods recovered the compounds when collecting Raman spectra. Un-spiked red wine was also treated through the extraction process and then spiked with smoke compounds, to see if there was any interference with scans taken post-extraction using an actual wine matrix rather than a synthetic wine matrix.