Bacillus cereus spores and Staphylococcus aureus sub. aureus vegetative cells inactivation in human milk by High-Pressure Processing

Abstract The effect of high hydrostatic pressure (HHP) on pathogen microorganisms is influenced by an important number of variables like treatment conditions, microorganism type and food matrix, among others. This technology could be an alternative to pasteurization in Human Milk Banks. In this study, a response surface methodology with a central composite design (CCD) was applied to determine the HHP conditions (pressure intensity and holding time) for the maximum inactivation of Staphylococcus aureus sub. aureus and Bacillus cereus in human milk. Precision and bias factors were calculated in order to validate the acceptance of predictions. These were considered within the acceptable range for vegetative cells models. The conditions to reach a maximum bacterial inactivation (within the ranges of this assay) were a pressure intensity of 593.96 MPa for 233 seconds. These conditions reached a decrease of 5.81 and 6.93 log cfu mL-1 in S. aureus sub. aureus and vegetative B. cereus, respectively. On the other hand, the decrease of B. cereus spores followed a trend that did not fit the model under study. Probably, the application of a second HHP treatment and/or the combination with higher temperature of processing would enhance the inactivation of this pathogen. This model could be a useful tool to increase milk safety by applying HHP treatments in human milk banks.