Prediction of Phenolic Composition of Shiraz Wines Using Attenuated Total Reflectance Mid-Infrared (ATR-MIR) Spectroscopy

Phenolic compounds play a critical role in determining red wine color, taste, flavor, and mouthfeel sensory attributes. Additionally, they contribute to wine aging and provide wine stability. This study evaluated the use of an attenuated total reflection (ATR) mid-infrared (MIR) spectroscopy to measure phenolic compounds in Shiraz wine samples of different quality levels obtained from 24 Australian wine geographical indications. Partial least squares (PLS) regression using the second derivative of the whole MIR spectrum produced the coefficient of determination (R-2) in calibration and standard error in cross-validation (SECV) for different attributes. In particular, SO2-resistant pigments had R-2 = 0.58 (SECV=0.58 au), total anthocyanins had R-2 = 0.61 (SECV=32 mg/L), wine color density had R-2 = 0.51 (SECV=0.56 au), and total phenolics had R-2 = 0.60 (SECV=5.7 au). These results demonstrated the potential use of ATR-MIR spectroscopy with PLS regression as a rapid method to measure important parameters related to red wine phenolic composition and wine quality.