Image of O₂ dynamics released by oak wood submerged in model wine with nanoparticle sensors

Oxidation of wine while in contact with oak wood is a well-known fact and recognized as an important process in wine ageing. The slow and continuous diffusion of oxygen from the oak wood entrapped in its porosity occurs and encourages the reactions usually related with wine aging. In this work, oxygen sensitive particles were used to study the oxygen dynamics from different anatomical regions of the oak wood and simultaneously the oxygen increasement because of the deoxygenation of the wood and the oxygen depletion due to its consumption by the tannins and other compounds released from the wood. To this end, core-shell-type PSPVP nanoparticles stained with Macrolex Fluorescence Yellow and Pt-TFPP were employed as reference and oxygen-sensitive particles respectively. Moreover, a Guppy Pro RGB camera was employed to monitor the particles performing ratiometric oxygen imaging, using the green and red channels to acquire the light emitted from the reference and the oxygen-sensitive particles respectively. Because the volume of nanosensors corresponding to each surface unit is very different from that of the wood region, different exposure times were chosen to obtain the images at each of the times. The results show the wood degassing process during the first minutes of the experiment, the oxygen release from different structural elements of the wood, its consumption by the released compounds from wood and the diffusion of the oxygen through the model wine.