Effect of porphyrin structure on aroma sensing response based on DFT: A case study of black tea fermentation

Porphyrin-based colorimetric sensing arrays (CSA) are frequently used to evaluate the black tea quality, but the mechanisms behind the interaction between porphyrin structures and volatile organic compounds (VOCs) remain unclear. Six VOCs that can be used to distinguish the degree of fermentation in black tea were identified and analysed. Response surface optimisation revealed the optimal conditions for CSA: reaction temperature of 65 °C, reaction time of 8 min and dye volume of 5 μL. The predictive coefficients and relative predictive deviations of the simplified quantitative model ranged from 0.82 to 0.94 and 1.72 to 2.92, respectively. Finally, density functional theory (DFT) calculations were used to elucidate the intrinsic relationship between the structural features of porphyrin molecules and their responsiveness to sensing by analysing variations in binding energy, dipole moment, charge and bond length. This provides a theoretical basis for constructing targeted CSA to monitor aroma.