Estimating the efficacy of mild heating processes taking into account microbial non-linearities: A case study on the thermisation of a food simulant

Traditional and novel approaches for the calculation of the heat treatment efficiency are compared in this work. The Mild Heat value (MH-value), an alternative approach to the commonly used sterilisation, pasteurisation and cook value (F, P, C-value), is calculated to estimate the efficiency of a mild heat process. MH-value is the time needed to achieve a predefined microbial reduction at a reference temperature and a known thermal resistant constant, z, for log-linear or specific types of non-log-linear microbial inactivation kinetics. An illustrative example is given in which microbial inactivation data of Listeria innocua CLIP 20-595 are used for estimating the inactivation parameters under isothermal conditions of 58, 60, 63 and 66 °C by the use of the log-linear and the Geeraerd et al. (2000) model. Thereafter, dynamic temperature profiles (targeting at 54 and 57 °C) representing milk thermisation are exploited for illustrating the application of MH-value. Finally, the equivalent holding times of different temperatures are calculated taking into account the observed non-linearity.