Kinetics of Thermal Destruction of Bacteriophages Active Against Streptococcus cremoris

Abstract

Heat inactivation of two bacteriophage races (el and rl) active against Streptococoons cremoris was determined in skimmilk and broth. For el phage, a single linear heat destruction curve was obtained with D values at 60 C in skimmilk and broth of 14 and 3.7 rain, respectively. For rl 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 rain in skinunilk and 3.4 and 6.S rain in broth, respectively. For the second component of 1'1 phage, the heat-protective properties of sldnnnilk as contrasted to broth decreased with increasing temperature, so that at 87 C the rate of inactivation was the same i1~ both media. Lack of linearity in rate of thermal destruction, differences in D values, reaction rate constants t/c), energy of activation (N,,), entropy change (aS), and free en-elNy change taP) between the first and second component of rl phage would support the conclusion that two separate mechanisms or chemical entities are involved in the thermal ilmctivation phenonlenon.