F. Makki et Td. Durance, THERMAL INACTIVATION OF LYSOZYME AS INFLUENCED BY PH, SUCROSE AND SODIUM-CHLORIDE AND INACTIVATION AND PRESERVATIVE EFFECT IN BEER, Food research international, 29(7), 1996, pp. 635-645
Thermal stability of lysozyme in aqueous buffer solutions was studied
at selected temperatures (73-100 degrees C), pH values (4.2-9.0) and l
evels of sucrose (0%, 5%, 15%) and sodium chloride (0, 0.1M, 1M). The
results, fitted to a first-order model and expressed in terms of decim
al reduction time (D), inactivation rate constant (k), decimal reducti
on temperature (z) and Arrhenius activation energy (E(a)) indicated th
at lysozyme was most stable at pH 5.2, and thermal stability decreased
sharply as the pH increased to 9.0. A regression equation for predict
ion of k as a function of pH and temperature was derived, with the bes
t fit obtained for the model in the pH range of 5.2-7.2 (adjusted mult
iple r(2)=0.98). At pH 7.2 and 9.0, sodium chloride had a clear stabil
izing effect against heat inactivation of lysozyme. Sucrose stabilized
lysozyme against heat inactivation at 75 degrees C but not at 91 degr
ees C. Thermal inactivation kinetics of lysozyme and its potential to
prevent or delay microbial growth were investigated in beer. Lysozyme
at concentrations of 10 and 50ppm appeared to delay growth of the spoi
lage bacteria L. brevis and P. damnosus in beer, but did not prevent g
rowth of the bacteria. (C) 1997 Canadian Institute of Food Science and
Technology. Published by Elsevier Science Ltd.