Rapid Evaluation of Succinic Acid in Sake Using Excitation-Emission Matrix and Chemometrics

Succinic acid, a major contributor to sake acidity, plays a key role in shaping the taste, mouthfeel. and aroma of sake. Accurate acidity control is essential to ensure consistent product quality and meet consumer expectations. However, traditional titration-based methods are destructive, time consuming, and require complex sample preparation. This study explored the use of excitation-emission matrix (EEM) fluorescence spectroscopy as a rapid, non-destructive alternative for predicting titratable acidity in sake. EEM spectra were collected from 100 sake samples, and acidity values, expressed as succinic acid equivalents, were determined via titration. Partial least squares regression (PLSR) models were developed using pre-processed spectral data, including Rayleigh scattering removal and logarithmic transformation, to enhance model performance. Among the evaluated spectral subregions. Region 1 (Ex: 270—310 nm / Em: 285-440 mn) yielded the best cross-validation results (R2cv = 0.5763. RMSECV= 0.0133 g/100 mL. RPDCV = 1.5994). suggesting a strong link between acidity and fluorescence signals from phenolic compounds, hi contrast. Region 3. which was dominated by riboflavin fluorescence, exhibited overfitting and instability. These results support the potential of EEM fluorescence combined with chemometrics as a semi-quantitative tool for acidity prediction in sake, although further refinement is required for precise quantification.