Exploring the efficacy of a novel high-pressure carbon dioxide method for food microbial inactivation on a synthetic matrix

Abstract

This study investigated the microbial inactivation performance of a novel CO₂-based method for food applications on a wide range of process conditions using LB agar cubes. Four different microbial strains, Escherichia coli, Listeria innocua, Pseudomonas fluorescens, and Saccharomyces cerevisiae, were homogenously inoculated on the surface of an agar cube and treated with the novel method. The initial microbial loads were 7.46 ± 0.27, 7.38 ± 0.24, 7.47 ± 0.24, and 5.13 ± 0.18 Log CFU/g, respectively. Results showed a similar trend to that of traditional High-Pressure Carbon Dioxide (HPCD) processes in terms of inactivation degree as a function of time and temperature. Notably, greater microbial inactivation occurred at subcritical or near-critical pressure values. Specifically, for P. fluorescens and S. cerevisiae the inactivation rates increased from −0.039 and − 0.094 Log CFU/g/min at 12 MPa to 0.029 and 0.046 Log CFU/g/min at 6 MPa, respectively. At 45 °C and 6 MPa, P. fluorescens and S. cerevisiae were inactivated to undetectable levels after 40 min, while a 60-min treatment was needed for E. coli. L. innocua was more resistant, achieveing after 60 min at 45 °C only 1.32 Log CFU/g inactivation, and requiring a higher temperature to achieve a significant inactivation. Moreover, the gas-to-product volume ratio was proven to affect the inactivation efficiency, a low ratio could represent a limit for achieving high inactivation levels. Future studies will explore the impact of the product's nature, volume and shape, and the use of antimicrobial substances to enhance process performance and apply it to food products, mainly fresh-cut fruit and vegetables, and meat.

Industrial relevance

High-Pressure Carbon Dioxide (HPCD) processes have shown considerable potential in enhancing food safety and shelf life while preserving nutritional and sensory qualities. However, the industrial implementation of HPCD for solid food processing presents some challenges, especially regarding the potential risk of post-process contamination. This study presents a novel patented process that aims at exploiting the power of HPCD on pre-packed solid food products, facilitating the industrialisation of the method.