Impacto de pretratamientos y uso de lacasa sobre la degradación de oxitetraciclina en leche y suero de quesería

Abstract

This work aimed to analyze the effect of different pretreatments and the use of laccase on the degradation of oxytetracycline residues in milk and whey. Milk samples containing 200 μM concentration of oxytetracycline were heat treated, coagulated to obtain whey, skimmed, or left untreated. In turn, these were divided into 3 subgroups, which were inoculated with 0.1, 0.2 or 0.3 mg L-1of laccase. Control samples were taken at time 0 and, after the addition of the enzyme, samples were taken every hour for 6 hours. Extraction and quantification of the antibiotic in the milk or whey samples were performed by high-performance liquid chromatography. Finally, a Repeated Measures ANOVA procedure was applied and the differences between groups were determined with the Bonferroni test. The thermal pretreatments and skimming did not substantially decrease oxytetracycline in milk, while acid coagulation resulted in whey with a reduction of more than 75% of the antibiotic. None of these treatments favored laccase activity. Using double or triple the concentration of laccase throughout the 6-hour study did not increase the degradation of the antibiotic. The use of laccase on raw milk or acid coagulation resulted in antibiotic residues below the limit established by the Codex Alimentarius so that the milk or whey could be disposed of directly into the environment or used for animal feed.

Keywords

• degradation
• laccase
• milk
• oxytetracycline
• pre-treatment