Elemental Changes in Riesling Wines Following Controlled Apple Juice Addition: An ICP-OES-Based Model Study

Wine adulteration with inexpensive fruit juices remains a significant authenticity issue. Apple juice, due to its neutral sensory properties, can be added to white wines without visual detection. While elemental analysis is widely applied in wine authentication, its suitability for detecting adulteration with low-mineral juices has not been systematically evaluated. In this study, 60 commercial white wines representing seven grape varieties and 45 Riesling samples intentionally adulterated with 5%, 10%, and 20% (v/v) apple juice were analyzed for 24 elements using ICP-OES. The data were evaluated using nonparametric statistical tests, including Mann-Whitney U, Wilcoxon signed-rank, and Friedman tests, with Holm correction for multiple comparisons, as well as Pearson correlation analysis and principal component analysis. Apple juice addition caused a decrease in most evaluated elements, especially Ca, Mg, Mn, P, S, and Sr, reflecting dilution of the wine matrix, whereas Na showed an opposite trend, particularly at the highest adulteration level. The reduced PCA model based on selected diagnostic variables provided clearer visualization of the adulteration-related pattern than the model based on all variables and highlighted the separation of samples adulterated at 20% (v/v). Apple juice addition also increased wine pH. The results demonstrate that ICP-OES data combined with statistical and chemometric analysis can reveal compositional changes associated with apple juice adulteration in a Riesling wine model.