Impact of heat treatment on the antimicrobial residues in raw goat's milk

Abstract

Although antibiotics are valuable drugs for treatment of bacterial and some parasitic infections, their presence in animal products have a potential public health hazard. This study investigated antibiotic residues in goat raw milk and thermal effect on residues. Samples were collected randomly from different farms and retail outlets in Erbil city from January 1st to June 30th 2019. The residues were detected by disc diffusion assay against Bacillus subtilis bacteria on Muller Hinton agar. The occurrence rates among milk samples was 14.9%, also these residues in the samples was 13.5% and 16.4% in farm samples and retail store samples, respectively. No significant differences were found between sampling sites (farms vs sale points). Regarding the seasonal variations, spring was found to be associated with gradual decrease in antibiotic residues frequency in milk. Boiling for 5 minutes was the most effective treatment (among pasteurization and microwave heating) that inactivated antibiotic residues in 57.7% of positive samples. Such occurrence rate of residues is alarming and require authorities to observe and validate the quality of raw milk introduced to markets for consumers. Further evaluation of antibiotic stability period in raw milk is highly recommended.

Keywords

• b. subtilis
• disc diffusion assay
• winter
• thermal stability