Inactivation of Escherichia coli K12 on raw almonds using supercritical carbon dioxide and thyme oil

The regulation of carbon dioxide on food microorganisms: A review

This review presents a survey of two extremely important technologies about CO2 with the effectiveness of controlling microorganisms - atmospheric pressure CO2-based modified atmosphere packaging (MAP) and high pressure CO2 non-thermal pasteurization (HPCD). CO2-based MAP is effectively in delaying the lag and logarithmic phases of microorganisms by replacing the surrounding air, while HPCD achieved sterilization by subjecting food to either subcritical or supercritical CO2 for some time in a continuous, batch or semi-batch way. In addition to the advantages of healthy, eco-friendly, quality-preserving, effective characteristic, some challenges such as the high drip loss and packaging collapse associated with higher concentration of CO2, the fuzzy mechanisms of oxidative stress, the unproven specific metabolic pathways and biomarkers, etc., in CO2-based MAP, and the unavoidable extraction of bioactive compounds, the challenging application in solid foods with higher efficiency, the difficult balance between optimal sterilization and optimal food quality, etc., in HPCD still need more efforts to overcome. The action mechanism of CO2 on microorganisms, researches in recent years, problems and future perspectives are summarized. When dissolved in solution medium or cellular fluids, CO2 can form carbonic acid (H2CO3), and H2CO3 can further dissociate into bicarbonate ions (HCO3-), carbonate (CO32-) and hydrogen cations (H+) ionic species following series equilibria. The action mode of CO2 on microorganisms may be relevant to changes in intracellular pH, alteration of proteins, enzyme structure and function, alteration of cell membrane function and fluidity, and so on. Nevertheless, the effects of CO2 on microbial biofilms, energy metabolism, protein and gene expression also need to be explored more extensively and deeply to further understand the action mechanism of CO2 on microorganisms.

Investigating the Effect of Rosemary Essential Oil, Supercritical CO2 Processing and Their Synergism on the Quality and Microbial Inactivation of Chicken Breast Meat

Fresh chicken meat is a very perishable good, even at refrigerated storage conditions, due to psychrophilic microbial growth and physicochemical changes. The present study focuses on the use of rosemary (Rosmarinus officinalis L.) essential oil (REO), supercritical CO₂ processing and their synergism to increase the microbial inactivation in chicken breast meat. E. coli and L. innocua were inoculated on the chicken breast surface, and the inactivation effects of two different processes, namely SC-CO₂ and SC-MAPCO₂, were compared with or without the addition of REO. Moreover, the impact of the treatments on the superficial color of the meat was considered. The study demonstrated a synergic effect with 1% REO and supercritical CO₂ for the inactivation of E. coli on chicken meat, while for L. innocua, there was no synergism. Regarding SC-CO₂ treatment, the E. coli reduction was 1.29 and 3.31 log CFU/g, while for L. innocua, it was 1.42 and 1.11 log CFU/g, respectively, without and with the addition of 1.0% of REO. The same amount of REO allowed us to obtain a reduction of 1.3 log CFU/g of E. coli when coupled with SC-MAPCO₂. For L. innocua, no reduction was obtained, either with SC-MAPCO₂ or together with REO. The synergism of SC-MAPCO₂ with 1% REO was confirmed for the total psychrophilic bacteria, demonstrating a strong dependence on the microorganism. The color modification induced by the SC-MAPCO₂ process was lower than the SC-CO₂ treatment. Overall, this study demonstrated a possible synergism of the technologies which can support the development of innovative methods to improve the safety and shelf-life of chicken breast meat.