EEG and fNIRS Evidence for Brain Responses to Three Tannins: Implications for Astringency Surface Sub-quality in Red Wine

The astringency surface sub-quality is pivotal to red wine perception, yet its neural bases remain unclear. The approaches of non-invasive neurophysiological techniques, sensory analysis, LC-MS analysis, and molecular docking were applied to examine the astringency surface sub-quality responses to three tannins—tannic acid, grape tannin and wine tannin—standardized to equivalent astringency intensity. The results showed that the three tannins at iso-intensity evoked distinct brain activity and sensory responses. The EEG(electroencephalography) results showed that differential frontal delta-band power, while fNIRS(functional near-infrared spectroscopy) revealed corresponding changes in oxygenated hemoglobin within the ventromedial prefrontal cortex, most prominently at channel 6 (wine tannin > tannic acid > grape tannin; p  < 0.05). LC-MS analysis of tannins indicated that higher levels of polymeric pigments and free anthocyanins were associated with finer astringency sub-quality and stronger neurophysiological responses. This investigation suggested a rapid, objective of non-invasive neurophysiological approach to complement sensory evaluation of wine.