Rapid development in apple wine industry has raised a growing need for effective fermentation process
monitoring. The alcohol strength and titratable acidity have been used as indicators for process control
and optimization in apple wine making. The objective of this study was to investigate the efficacy of
using near-infrared (NIR) spectroscopy to monitor and assess the process parameters during apple wine
fermentation. A simple and rapid NIR spectroscopy method was developed for simultaneous determination
of alcohol strength and titratable acidity in apple wine. The selected spectral regions of 6101.9
e5446.2 cm1, and 11,995.4e7498.1 cm1 were pretreated by second derivative (SD) and straight line
subtraction (SLS) for alcohol strength and titratable acidity, respectively, prior to developing calibration
models using partial least squares (PLS) regression with cross-validation. The highest R2c
and the lowest
RMSECV in the calibration set were obtained for the alcohol strength (0.923 and 4.63 mL/L) and for the
titratable acidity (0.930 and 0.264 g/L). The NIR calibration models showed good correlation of determination
and low predictive errors. Application of the NIR calibration models demonstrated the feasibility
of NIR spectroscopy to be used as a quality control tool for monitoring the apple wine fermentation
process.