Thermostability of Oxytetracycline, Tetracycline, and Doxycycline at Ultrahigh Temperatures

Abstract

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.

Correlation analysis of heat stability of veterinary antibiotics by structural degradation, changes in antimicrobial activity and genotoxicity

“…Although heating in water did not reflect all cooking conditions, the results from simulated heating in liquid media could provide valuable information in interpreting results from certain actual cooking conditions (Moats, 1988). Moreover, heating in water avoids the lengthy lag phase of heating commonly encountered in the cooking of solid tissue and can thus easily assess the actual exposures of antibiotics to heat (Hassani et al, 2008).…”

“…For the past 50 years, many researchers have been interested in evaluating whether antibiotic residues can be destroyed by cooking procedures, pasteurization, or canning processes (Ibrahim and Moats, 1994;Rose et al, 1995;Isidori et al, 2005;Hassani et al, 2008). Traditionally, heat stabilities of antibiotics have been studied based on either the evaluation of the decrease in antimicrobial activity or by specific chromatographic analysis of change in concentration after heat treatments.…”

“…Previous studies have suggested that sulfamethazine (SMZ) (Rose et al, 1995;Papapanagiotou et al, 2005) oxacillin (OXA), chloramphenicol, aminoglycosides, quinolones, clindamycin, novobiocin, trimethoprim, vancomycin, and azlocillin are heat-stable (Traub and Leonhard, 1995) while oxytetracycline (OTC) (Hassani et al, 2008) and erythromycin were shown to be heat-labile. On the other hand, several β-lactams such as penicillin (PCN) G, ampicillin (AMP) and amoxicillin (AMX) appear partially heat-labile (Traub and Leonhard, 1995).…”

Termoestabilidad de sustancias antimicrobianas en la leche.

“…Hay que tener en cuenta de nuevo, que los resultados presentados en dicho Cuadro proceden de estudios realizados mediante bioensayos microbiológicos, aunque también se expone el trabajo realizado por Hassani et al (2008), donde se ha empleado la cromatografía líquida.…”

“…Muy recientemente, Hassani et al (2008), han evaluado la estabilidad térmica de la doxicilina, oxitetraciclina y tetraciclina en soluciones patrón sometidas a los tratamientos térmicos de esterilización convencional (118 ºC-30 min; 121 ºC-20 min) y UHT (145 ºC-15 s; 140 ºC-7 s) utilizando una técnica LC-PDA. Estos autores observan una pérdida de estabilidad >98% para los tres analitos bajo condiciones de esterilización convencional mientras que con los tratamientos UHT la reducción de la concentración inicial de cada solución patrón se encontraba entre el 50 y el 90%.…”