Rapid measurement of anthocyanin content in grape and grape Juice: Raman spectroscopy provides Non-destructive, rapid methods

Anthocyanins in grapes exhibit potent antioxidant properties, contributing significantly to human health. Exploring rapid, non-destructive, and in-situ measurement techniques for anthocyanin content in grapes and grape juice is essential for assessing their nutritional and health benefits. Traditional methods, which often involve chemical assays requiring sample pre-treatment, are not suitable for measuring anthocyanins in intact grapes. In this study, we present a Raman spectroscopy-based method to quantify anthocyanins effectively. We developed a univariate linear regression model utilizing the intensity of the anthocyanin Raman characteristic peak and a multivariate linear regression (MLR) model combined with feature engineering. The univariate model achieved a coefficient of determination (RP2) of 0.8949 and a root mean square error of prediction (RMSEP) of 0.2881 μmol/mg for grape skin. In contrast, the MLR model, optimized through Recursive Feature Elimination (RFE), showed superior accuracy with an RP2 of 0.9800 and an RMSEP of 0.1151 μmol/mg. For grape juice, which has a more complex composition, the RFE-MLR model yielded an RP2 of 0.9764 and an RMSEP of 0.2393 μmol/ml. Overall, our findings confirm that Raman spectroscopy is an effective method for the rapid and accurate in-situ measurement of anthocyanin content, offering a novel approach for on-site analysis in various fruits and their juices.