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

Abstract

Phenolic compounds play a critical role in red wine color, taste, flavor and mouthfeel sensory attributes. Additionally, they contribute to wine ageing and provide wine stability. This study evaluated the use of an attenuated total reflection (ATR) mid-infrared (MIR) spectroscopy for the measurement of phenolic compounds in Shiraz wine samples of different quality levels obtained from 24 Australian wine geographical indications (GIs). Partial least squares (PLS) regression using the second derivative of the whole MIR spectrum yielded the coefficient of determination (R²) in calibration and standard error in cross validation (SECV) for different attributes. In particular, SO₂ resistant pigments had R² = 0.58 (SECV=0.58 au), total anthocyanins had R² = 0.61 (SECV=32 mg/L), wine color density had R² = 0.51 (SECV=0.56 au) and total phenolics had R² = 0.60 (SECV=5.7 au). The potential use of ATR-MIR spectroscopy in combination with PLS regression as a rapid method to measure important parameters related to red wine phenolic composition and wine quality was demonstrated.