Detection of Phlorizin in Grape Juices: Development of a Rapid HPLC Method and Phenolic Characterization

This study compared the phenolic profile of integral grape juices against a control sample and developed a rapid liquid chromatography method for detecting apple juice adulteration using phlorizin as the official marker, as established by the Brazilian Ministry of Agriculture and Livestock. The method was validated, demonstrating excellent linearity (R² = 0.99998), low limits of detection (0.05 mg/L) and quantification (0.169 mg/L), both of which are below the official method values, as well as good precision (RSD ≤ 2.59%), accuracy (mean recovery of 110.66% ± 3.87%), and robustness. Ten commercial juices and one control juice prepared in the laboratory according to Embrapa protocols were analyzed. The phenolic profile revealed significant variations (p < 0.05) among samples. These differences were associated with origin, variety, and processing. Sample SUCO3 (São Francisco Valley) exhibited the highest levels of catechin (57.60 mg/L) and epicatechin (11.39 mg/L). Phlorizin was detected in all samples (0.21-0.60 mg/L), including the control sample (0.36 mg/L). These concentrations were all below the quantification limit of the official method (0.64 mg/L) and thus did not indicate adulteration. These findings suggest that phlorizin may occur naturally in grape juice at trace levels. The proposed method was found to be both rapid and reliable for regulatory monitoring and industrial quality control. This highlights the need for regulatory updates to account for the natural presence of this marker in grape juice. PRACTICAL APPLICATIONS: As the production and commercialization of industrialized juices increases, so does the demand for updated, rapid, and efficient analytical methods to ensure product authenticity. This study presents a modified and validated method involving a rapid chromatographic process with lower quantification limits than the official method. Phlorizin is used as an indicator of adulteration. The analysis of juices marketed in Sergipe also enabled characterization of the phenolic profiles in comparison with a control juice, revealing differences related to origin and processing. The developed methodology demonstrates direct applicability to the juice industry and provides valuable technical support for regulatory agencies, contributing to strengthened quality control and consumer protection.