Rapid Monitoring of Key Quality Indicators of Red Wines Based on UV-Vis Spectroscopy

Consumer demand for high-quality and safely produced wines requires high standards in terms of quality assurance and process control methods, which in turn requires proper analysis of wines during and after production. The role of phenolics and color characteristics in ensuring wine quality at all stages of the production process is gradually gaining recognition and importance. However, traditional chemical analysis methods required cumbersome pre-treatment, expensive instrumentation requirements, time-consuming determination procedures, and harsh operating conditions. The evolution of phenolics and color was monitored, as well as UV-Vis absorption spectral characteristics, and a partial least squares regression（PLSR） model was developed for phenolics and color parameters based on UV-Vis spectroscopy during wine fermentation and aging. The results showed that the content of total phenols, total tannins and total flavanols were increased continuously during fermentation and decreased gradually during aging. In contrast, total flavonoids were increased and then decreased during fermentation and gradually decreased during aging. In addition, the maceration process and the early stage of fermentation were the critical periods for color formation, while the color was gradually aged during the aging. The calibration set correlation coefficients R_cal~2 and validation set correlation coefficients R_val~2 of the UV-Vis spectroscopy-based phenolic and color parameter prediction models were both no less than 0.84, and the residual predictive deviation（RPD） was no less than 2.54, thus the models could achieve the prediction purpose. Therefore, UV-Vis spectroscopy combined with chemometrics was a simple, economical and efficient way to monitor phenolic compounds and color evolution during red wine fermentation and aging.