Kinetics of Thermal Destruction of Bacteriophages Active Against Streptococcus cremoris

Abstract

Heat inactivation of two bacteriophage races (c1 and r1) active against Streptococcus cremoris was determined in skimmilk and broth. For c1 phage, a single linear heat destruction curve was obtained with D values at 60 C in skimmilk and broth of 14 and 3.7 min, respectively. For r1 phage, a nonlinear curve was obtained which could be integrated into two components varying in rate of inactivation and having D values at 65 C of 16 and 64 min in skimmilk and 3.4 and 6.8 min in broth, respectively. For the second component of r1 phage, the heat-protective properties of skimmilk as contrasted to broth decreased with increasing temperature, so that at 87 C the rate of inactivation was the same in both media. Lack of linearity in rate of thermal destruction, differences in D values, reaction rate constants (k), energy of activation (Ea), entropy change (ΔS), and free energy change (ΔF) between the first and second component of r1 phage would support the conclusion that two separate mechanisms or chemical entities are involved in the thermal inactivation phenomenon. © 1967, American Dairy Science Association. All rights reserved.