Supercritical CO₂ for the drying and microbial inactivation of apple’s slices

Abstract

Supercritical CO2 (Sc-CO2) drying has been recognized as a promising low temperature drying technique for food products. In this regard, this work focuses on the feasibility of Sc-CO2 drying of apple's slices: both the microbiological stability and mechanical behavior of the test product after the process have been investigated in dependence from different process parameters, namely drying time, pressurization time and depressurization time. The microbiological stability was determined for both inoculated pathogenic bacteria (E.coli O157:H7, Salmonella and Listeria monocytogenes) and naturally present microorganisms (yeasts and molds, mesophilic bacteria and spores and Enterobacteriaceae). Results demonstrated a complete inactivation of pathogenic bacteria under the detection limit (<1 CFU/g) just after the pressurization (10 min) and 2 depressurization (20 min) phases. After the same steps, a strong reduction of vegetative bacteria and yeasts and molds was also observed in comparison with air drying and freeze drying samples. As regards the mechanical behavior, the Young Modulus, measured before and after the CO2 processes to provide a measurement of samples' stiffness, resulted dependent from the final water activity, but independent from the length of pressurization and depressurization phases at longer drying time. Overall, these results are promising to foster the development of the technology at industrial level.

Contributions of supercritical fluid technology for advancing decellularization and postprocessing of viable biological materials

“…147 As a result, the drying process has been extensively explored for different materials such as silica, 148–156 cellulose aerogels, 157–159 chitosan nanoparticles, 160,161 and hydrogels, 162 and food products. 163–171 In the food industry, drying presents a crucial step for food preservation and microbial reduction. 163 The convectional air-drying techniques use high temperatures that compromise the quality of the final product.…”