The thermostabi
lity parameters of three tetracyc
line antibiotics at high and u
ltrahigh temperatures (110–140 °C) as we
ll as the inf
luence of treatment medium pH and water activity on their thermoto
lerance have been investigated. The therma
l degradation of the three antibiotics fo
llowed a first-order reaction kinetic within the 1.5–2
log
10 cyc
les investigated. A
linear re
lationship was observed between the
log of the
DT va
lues and the treatment temperature. The temperature dependence of the
DT va
lues was
simi
lar for the three mo
lecu
les (
z = 28
![](http://pubs.acs.org/images/entities/p<font color=)
lusmn.gif"> 2 °C).
DT va
lues of doxycyc
line were approximate
ly 1.5 and 3 times higher than those of tetracyc
line and oxytetracyc
line, respective
ly. Changes in the treatment medium pH (7.0–4.0) and water activity (0.99–0.93) scarce
ly varied the antibiotics’ therma
l stabi
lity. On
ly when doxycyc
line was heat-treated at pH 4.0 did its therma
l resistance increase by 3 times. The thermostabi
lity parameters obtained wou
ld a
llow the effect of different cooking and steri
lization procedures to be estimated. Whereas
low-temperature−
long-time treatments (conventiona
l steri
lization) wou
ld destroy >98% of the initia
l concentration of the residues of the three antibiotics, high-temperature−short-time treatments (UHT) wou
ld
leave una
ltered residues in the 50–90% range.