Application of FT-NIR Spectroscopy to Apple Wine for Rapid Simultaneous Determination of Soluble Solids Content, pH, Total Acidity, and Total Ester Content

The feasibility of rapid simultaneous analysis of soluble solid content (SSC), PH, total acidity, and total ester content in apple wine by Fourier transform near-infrared (FT-NIR) spectroscopy together with partial least squares (PLS) models was studied in this work. A set of 380 apple wine samples were scanned in a quartz cuvette with a 1-mm path length in the NIR region (4,000-12,000 cm(-1)) in transmission mode. Calibration models were established by PLS with full cross-validation. The NIR spectra were pretreated with different methods, and the effective wave number range together with the number of PLS factors used in the model calibration was optimized. The optimal models yielded the determination coefficients of 0.91, 0.93, 0.98, and 0.92 and the root mean standard error of prediction (RMSEP) of 0.601, 0.077, 0.021, and 0.096 for SSC, pH, total acidity, and total ester content, respectively. This work demonstrated that NIR spectroscopy was a rapid and convenient technique for analyzing and predicting SSC, pH, total acidity, and total ester content simultaneously during apple wine fermentation process.