Ozonation as an Emerging Non-Thermal Technology for the Degradation of Sulfamethazine Residues in UHT Milk: Kinetics and Impact on Physicochemical Quality

Abstract The presence of antibiotic residues in dairy products is a food safety and public health concern, due to their potential contribution to antimicrobial resistance and adverse health effects. This study investigated ozonation as an emerging non-thermal technology for the degradation of sulfamethazine (SMT) residues in ultra-high temperature (UHT) milk and evaluated its effects on selected physicochemical properties. Milk samples spiked with SMT at 50, 100, and 200 µg/L were treated with ozone of 6.19 mg/L for up to 60 min, while oxygen-treated samples were used as controls to distinguish ozone-mediated oxidation from effects associated with gas sparging. SMT concentrations were quantified by LC–MS/MS. Ozonation promoted a significant time-dependent decrease in SMT concentration ( p < 0.001), with reductions of 59.1, 63.1, and 53.6% after 60 min for initial concentrations of 50, 100, and 200 µg/L, respectively. In contrast, no significant SMT reduction was observed in oxygen-treated samples, supporting the interpretation that the observed decrease was specifically associated with O 3 exposure. Concentration-based kinetic modelling showed that first-order kinetics adequately described the degradation profiles of the ozonated treatments ( R 2 ≥ 0.991), with rate constants ranging from 0.0125 to 0.0162 min⁻ 1 and estimated half-lives from 42.8 to 55.5 min. Although statistically significant differences were detected in some treatment–time combinations, pH and total soluble solids (°Brix) showed only limited variations under the evaluated conditions. Instrumental color parameters also varied, with some ΔE values reaching potentially perceptible levels, but without a consistent progressive trend with ozone exposure time. Overall, ozonation promoted degradation of SMT while inducing limited or variable changes in the selected physicochemical parameters evaluated. However, studies addressing transformation-product identification, toxicity, and broader quality attributes are required before application in dairy processing.