Effect of heat treatments on stability of β-lactams in milk

Abstract

The presence of residues of antimicrobial substances in milk may have serious toxicological and technical consequences. To date, few studies have been done to evaluate the effect of heat treatments on β-lactam residues in milk. However, the few studies that have been conducted estimate losses of antimicrobial activity under different combinations of temperature and time using microbiological methods. The aims of this study were to calculate the kinetic parameters for the degradation of β-lactam antibiotics in milk and to develop prediction models to estimate the concentration losses of these compounds in conventional dairy heat treatments. To do so, we employed a quantitative HPLC method to calculate losses in concentrations of 10 β-lactam antibiotics in milk with different combinations of temperature and time. Increasing the temperature from 60°C to 100°C decreased the half-life of amoxicillin (372 to 50 min), ampicillin (741 to 26 min), cloxacillin (367 to 46 min), and penicillin G (382 to 43 min). These increases in temperature caused further degradation in cephalosporins, which was accompanied by a decrease in half-life times to reach very low values; for instance, 4, 5, and 6 min for cefoperazone, cephurexime, and cephapirin, respectively. Kinetic equations were applied to different heat treatments used in dairy processing. Heat treatments at high temperatures and long times (e.g., 120°C for 20 min) led to a further degradation of β-lactam antibiotics with percentages close to 100% for cefoperazone and cefuroxime. In contrast, when milk was subjected to heat treatments at lower temperatures and times (e.g., 72°C for 15s), the degradation of β-lactam in milk did not exceed 1% for the 10 antibiotics tested.

Performance of Eclipse Farm Test Coupled to e-Reader for Antibiotic Residues Detection in Raw Milk

“…For instance, when incubation temperature is raised, thermal inactivation of the antibiotics could occur. This is in accordance with the low thermal stability of oxytetracycline and cefalexin reported by several authors (Hassani et al 2008;Roca et al 2011). Nevertheless, only the samples spiked with oxtetracycline had an impact on the false-negative rate when the temperature rose to 67°C.…”

Thermodynamic analysis of the thermal stability of sulphonamides in milk using liquid chromatography tandem mass spectrometry detection

“…Nevertheless, these coefficients were similar to those calculated by Roca et al (2011) in a study into thermal degradation of penicillins (amoxicillin, ampicillin, cloxacillin and penicillin), but lower than those determined for cephalosporins (cefoperazone, cefquinome, cephalexin, cephalonium, cephapirin and cephuroxime) at the same temperatures.…”

“…In previous studies (Roca, Castillo, Marti, Althaus, & Molina, 2010;Roca, Villegas, Kortabitarte, Althaus, & Molina, 2011), kinetic models of degradation to study quinolones and beta-lactam antibiotics in milk at various temperatures were established employing chromatographic methods. In both works, the results show that the analyzed substances are resistant to the pasteurisation (72°C; 15 s) and Ultra High Temperature sterilisation (140°C; 4 s), except for some cephalosporins which substantially degrade under the effect of these heat treatments.…”

Current bioanalytical methods for detection of penicillins

“…For example, heat inactivation of the β-lactams occurs, but only under extreme conditions, e.g. 120°C for 20 min caused degradation of 46.7 % for amoxicillin and 84 % for ampicillin in milk [19].…”