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 (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). 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.
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