Heating and sterilization technology for long-duration space missions: transport processes in a reusable package

Long-duration space missions require a high-quality, shelf-stable food supply but must also contend with packaging waste after use. We have developed a package, adapted from a military pouch, that enables heating of foods to serving temperature. After the food is consumed, the package may be reused for containment and sterilization of waste, and, potentially, for packaging and sterilizing foods grown on a Mars base. Packages are equipped with electrodes to permit ohmic heating of internal constituents. Heat transfer within the package was modeled using the energy transport equation, coupled with the Laplace equation for electric field strength distribution. The model was verified by temperature measurements during a sample experimental run, and it was used to optimize the package design. Waste sterilization within the package was also studied and confirmed. Mass transfer (electrode component migration) was studied by inductively coupled plasma mass spectrometry; the findings have shown concentrations within products to be well below current daily dietary exposure levels. Microbiological studies for sterilization indicated the need for package redesign to ensure parallel electrode configuration, as well as the use of supplemental external heaters along the nonelectrode walls of the package. Temperature profiles during heating of these packages have been determined.