Determination of ochratoxin A in Vitis labrusca musts: analytical performance and occurrence in Southern Brazil

Ochratoxin A (OTA) is a mycotoxin of major concern in grape-derived products; however, information on its occurrence in fresh grape must remain limited. This study aimed to evaluate and adapt a high-performance liquid chromatography with fluorescence detection (HPLC-FLD) method recommended by the International Organisation of Vine and Wine, originally validated for wine and grape juices, for the determination of OTA in fresh grape musts obtained from Vitis labrusca cultivars grown in Southern Brazil. Must samples from Bordô, Concord, Niagara Rosada, and Isabel were collected and characterised in terms of °Brix, °Babo, and total titratable acidity to assess maturity-related physicochemical attributes. Adaptation was required only for sample clarification, whereas sequential filtration was employed to overcome the high turbidity and soluble solids that may interfere with analytical reliability. The adapted method showed excellent linearity (R² ≥ 0.999), satisfactory recoveries (83.75-104.6%), and limits of detection and quantification of 0.02 and 0.07 µg/L, respectively, in agreement with the Brazilian regulations. Only trace OTA peaks were detected, with no association observed between mycotoxin occurrence and grape cultivar or physicochemical maturity parameters. Overall, the proposed sample preparation proved suitable for routine monitoring at the pre-fermentation stage, supporting the safety and quality assessment of grape-derived products.