Transfer of Some Macrolide Group Antibiotics from Spiked Milk to Melting Cheese and Determination of Their Processing Factor with LC–MS/MS

The study is aimed at assessing residue levels and distribution of five macrolide antibiotics (erythromycin, neospiramycin, spiramycin, tilmicosin, and tylosin) in cheese and whey using liquid chromatography-tandem mass spectrometry (LC–MS/MS). In our study, to minimize the potential effects of variables such as moisture, lactose, protein, macro, and micro components from different milk samples on the results during validation analyses and cheese production, the same batch of raw cow milk sourced from the market was used throughout the entire production process. Macrolide residues were detected in all cheese and whey samples, varying in concentrations (from 179.92 to 99.36%). Erythromycin, tilmicosin, and tylosin were predominantly found in cheese, exceeding the maximum residue limit (MRL) of 50 µg/kg, except neospiramycin (49.83% residue level). The only antibiotic showing a decrease in cheese and whey compared to raw milk is neospiramycin. In contrast, spiramycin was concentrated in whey (226.17 µg/kg, surpassing the MRL), followed by tilmicosin (94.58%). Concentrations of four antibiotics (erythromycin, tilmicosin, neospiramycin, and tylosin) were higher in cheese than in whey, indicating a higher affinity for the casein matrix. Spiramycin, however, had higher concentrations in whey, suggesting lower affinity for the casein matrix. Pasteurization and cheese making did not significantly reduce macrolide levels. The processing factor, representing the ratio of antibiotic concentrations in the final dairy product to that in raw milk, exhibited variability based on antibiotic type and concentration. Generally, cheese demonstrated higher processing factors compared to whey, suggesting a greater antibiotic retention during cheese production. This study highlights the impact of the cheese-making process on antibiotic residue concentrations in dairy products, with the extent of influence varying by antibiotic type. The elevated retention percentages in cheese underscore the potential for consumers to be exposed to significant antibiotic levels through product consumption. This research offers valuable insights for assessing the risk of antibiotic residues in cheese and whey, as well as for developing strategies to mitigate or eliminate these residues in dairy products.