1H NMR-based metabolomic profiling and chemometric discrimination of authentic and adulterated Brazilian grape juices

Grape juice is widely consumed in Brazil and worldwide, but authenticity control and the detection of adulteration remain challenging. This work examined the metabolomic composition of grape juices from southern Brazil and evaluated the use of 1 H Nuclear Magnetic Resonance (NMR)-based metabolomics for detecting adulteration with apple juice. Sixty-five samples were analyzed, including authentic grape juices, apple juices, and commercial juice formulations. 1 H NMR spectra were acquired on a 300 MHz NMR spectrometer and then processed for spectral and chemometric analyses. Principal component analysis (PCA), permutational multivariate analysis of variance (PERMANOVA), and partial least squares discriminant analysis (PLS-DA) supported the discrimination between grape and apple juices. Malic acid at 2.59 ppm was the main discriminant metabolite associated with apple juice, whereas carbohydrate-related signals were primarily linked to formulation and processing effects. Significant differences among juice categories were verified by ANOVA followed by Tukey’s post hoc test (p < 0.05). The results indicate that 1 H NMR-based metabolomics combined with chemometric analysis may provide a fast, reproducible, and non-destructive method for grape juice authentication and adulteration detection, with possible application in routine quality control and food authenticity verification.