Monensin residues in the production of Minas Frescal cheese: Stability, effects on fermentation, fate and physicochemical characteristics of the cheese.

Considering the widespread use of the antibiotic monensin (MON) in the Brazilian livestock and the possibility of residues in milk, this paper aimed to study the stability and fate of this drug during the production of Brazilian Minas Frescal cheese, its effects on milk fermentation and on the physicochemical characteristics of this product. For that, samples of raw milk were fortified with MON at three different nominal concentrations (1.0, 2.0 and 8.0 μg/kg), passed through heat treatment and used to produce Minas Frescal cheese. Pasteurization efficiency was certified by alkaline phosphatase and peroxidase enzyme tests and cheese samples were evaluated for pH, moisture and total protein and fat content. MON residues were determined by LC-MS/MS in the following steps: raw milk, heat-treated milk, whey and cheese. No significant degradation of MON due to heat treatment was observed, suggesting that the drug is resistant to high temperatures. Moreover, the residue levels quantified in cheese and whey demonstrated a concentration of this antibiotic in the curd by about 5-fold, with a small amount of MON being lost during draining. There were no significant differences (p > 0.05) considering the physicochemical parameters evaluated in cheese samples. Fermentation was also not affected by the presence of the drug. The results showed that residues of MON in milk are stable during cheese production and may be concentrated in the final product, as well as indicate the need to establish a MON safe residue level for this food commodity.