Processing Effects on the Oxytetracycline and Tylosin Antibiotic Residues in Middle Eastern Dairy Products

Abstract

Antibiotics are used extensively in healthcare and veterinary fields to treat or prevent certain diseases caused by infectious agents. Their presence in food supply poses a human health threat and thus, can negatively affect the food industry. The main objective of our first-of-its-kind study in the Middle East was to assess the effect of different processes (skimming, pasteurization, curding, pressing, salting, cheese boiling, and whey acidification and heating) on two widely used antibiotics in Lebanon, Oxytetracycline (OTC) and Tylosin (TYL), in making commonly consumed Middle Eastern cheeses (Baladi, Double Crème, Halloum and Akkawi). This was done by spiking 450 Kgs of full-fat bovine milk with 25 ppm/kg of OTC and 8 ppm/kg of TYL, then skimming and pasteurizing using the two common pasteurization methods (Holder and High Temperature Short Time (HTST)), and processing the milk to different cheeses. Liquid Chromatography Mass Spectrometry (LCMS), the gold standard for the quantification of antibiotics, was used. OTC and TYL were not homogenously distributed between the dairy products. Skimming decreased significantly (p=0.015) TYL concentration by 68.6%. OTC degradation during Holder proved to be significant (p=0.015) and ranged from 40 to 48%, while that during HTST processing (18%) was not significant. As for TYL, HTST had a significant (p=0.012) effect with 32% degradation, while holder pasteurization did not cause a significant degradation (26%). Curding step had a significant (p=0.028) effect on OTC only with the concentration increasing by almost 1.5 folds. Acidification and heating of whey to produce Double Cream decreased significantly (p=0.037) OTC concentration by 14.7 to 46.3%, while TYL concentration increased significantly (p=0.000) by 300%. Pressing and salting did not have any significant effect on OTC and TYL, while cheese boiling in making Halloum significantly decreased the concentration of both antibiotics. The highest concentrations of OTC were measured in curd-based cheeses that did not undergo boiling (Baladi and Akkawi), making them of higher risk in this regard. As for TYL, the highest transfer level was for the whey-based Double Cream, making this cheese of higher concern for this antibiotic.