Discrimination between orange juice and pulp wash by H-1 nuclear magnetic resonance spectroscopy: Identification of marker compounds

The potential of NMR spectroscopy and multivariate analysis methods to dete ct the adulteration of orange juice with pulp wash is demonstrated. Princip al component analysis has been applied to H-1 NMR spectra of >300 orange an d pulp wash juices, and stepwise linear discriminant analysis was used to c lassify the samples. A model with six principal components gave a high succ ess rate of classification (94%) for both training and validation sets. An important principal component loading showed that dimethylproline played a key role in the discrimination between the two types of juice, with higher levels in pulp wash. Dimethylproline was not previously known as a marker c ompound for orange juice adulteration. An ANOVA test revealed at least 21 o ther NMR signals that differed significantly between the authentic and pulp wash groups. The compounds they represent could be seen as potential marke r compounds in addition to dimethylproline. This makes NMR with chemometric s an attractive screening tool with advantages in terms of rapidity, simpli city, and diversity of information provided.