Thermostability of oxytetracycline, tetracycline, and doxycycline at ultrahigh temperatures.
The thermostability parameters of three tetracycline antibiotics at high and ultrahigh temperatures (110-140 degrees C) as well as the influence of treatment medium pH and water activity on their thermotolerance have been investigated. The thermal degradation of the three antibiotics followed a first-order reaction kinetic within the 1.5-2 log(10) cycles investigated. A linear relationship was observed between the log of the DT values and the treatment temperature. The temperature dependence of the DT values was similar for the three molecules (z=28+/-2 degrees C). DT values of doxycycline were approximately 1.5 and 3 times higher than those of tetracycline and oxytetracycline, respectively. Changes in the treatment medium pH (7.0-4.0) and water activity (0.99-0.93) scarcely varied the antibiotics' thermal stability. Only when doxycycline was heat-treated at pH 4.0 did its thermal resistance increase by 3 times. The thermostability parameters obtained would allow the effect of different cooking and sterilization procedures to be estimated. Whereas low-temperature-long-time treatments (conventional sterilization) would destroy >98% of the initial concentration of the residues of the three antibiotics, high-temperature-short-time treatments (UHT) would leave unaltered residues in the 50-90% range.
Hassani
Mounir
M
Produccion Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, C/Miguel Servet 177, 50013 Zaragoza, Spain.
Lázaro
Regina
R
Pérez
Consuelo
C
Condón
Santiago
S
Pagán
Rafael
R
D000900:Anti-Bacterial Agents / Q000737:chemistry*; D004318:Doxycycline / Q000737:chemistry*; D004355:Drug Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010118:Oxytetracycline / Q000737:chemistry*; D013752:Tetracycline / Q000737:chemistry*
D000900:Anti-Bacterial Agents; D013752:Tetracycline; D004318:Doxycycline; D010118:Oxytetracycline