Monitoring ethanol and glucose during wine fermentation is essential for quality control, yet current analytical tools are often costly and confined to laboratories. Affordable and portable solutions are needed to support real-time decision-making in wineries. This work presents a near-infrared (NIR) LED–photodiode device designed for the simultaneous determination of ethanol and glucose, highly relevant for enological analysis. The system integrates four LEDs (860, 950, 1200, and 1300 nm) with dedicated photodetectors. Its compact format makes it suitable for routine use and adaptable to future automated monitoring.
Calibration strategies were tested to optimize performance. Univariate models with single-analyte standards (ethanol or glucose) showed limited accuracy. Multiple linear regression (MLR) improved predictions, and results further benefited when combined ethanol–glucose standards were used, better reproducing fermentation conditions. As an additional calibration strategy, the standard addition method was applied in commercial wines, yielding results consistent with MLR and confirming reliability in real matrices.
With optimized wavelength combinations, the system achieved relative errors of 2–3% for ethanol and about 10% for glucose, values adequate for fermentation monitoring. Repeatability was satisfactory, with coefficients of variation between 3% and 5%. Both MLR and standard addition produced results comparable with reference methods for ethanol and glucose determination, validating the robustness of the device.
Overall, compact NIR LED–based technology provides a reliable, low-cost, and field-deployable solution for enology. Its portability, affordability, and novelty in quantifying ethanol and glucose simultaneously make it a promising tool for real-time fermentation control and more sustainable winemaking.