Reheating and Sterilization Technology for Food, Waste and Water: Design and Development Considerations for Package a

1. Reheating and Sterilization Technology for Food, Waste and Water: Design and Development Considerations for Package and Enclosure Soojin Jun, Brian Heskitt and Sudhir Sastry The Ohio State University Ritesh Mahna and Joseph Marcy Virginia Tech Michele Perchonok NASA/JSC

2. Introduction • Long-duration space missions • Food systems to provide the crew with a palatable, nutritious, and safe food system and minimize volume, mass, and waste • A thermal process in need of food reheating to serving temperature, or sterilization during in-transit and on evolved planetary base • Food package to pose a disposal problem after use

3. Introduction • Ohmic heating • Electrical energy to thermal energy with higher energy efficiency (close to 100%) • Reusable pouch • Sterilized to yield food quality with long shelf life • Enabled ohmic treatment in transit • Used to contain and sterilize waste post-food consumption

4. Objectives • Develop and optimize a pulsed ohmic heating system and reusable pouch • Minimize ESM • Eliminate gas generation • Eliminate electrode corrosion • Numerical Approach • Optimize electrode configuration • Most uniform, yet rapid heating thermal profiles • Predict and prevent worst-scenario during food heating

5. Output Isolation IGBT module Input TTL signal Pulsed ohmic heater IGBT output waveform Circuit diagram Ideal for minimizing electrochemical reaction Frequency: 10 kHz Pulse duty ratio: 0.2 Compact design

6. Ohmic heater enclosure and frame

7. Flexible package Foil electrodes Reusable pouch First realized version Newly designed version

8. Electrode materials • Degassing and ohmic treatment of NaCl solution to observe likely gas generation at the interface between solution and electrodes • Aluminum • Generate lots of gas • Serious self-corrosion • Stainless steel • Food grade 300 series • Little gas generation with ideal wave conditions

9. Secure bond in electrode-package construction • Hot press to seal stainless steel electrode pouches • However, electrodes unlikely to adhere to inner PE layer of pouches Sealant Multi-layered laminate

10. Secure bond in electrode-package construction • PE extruded on stainless steel foil • Contact select vendors • Use of food grade adhesive • Long curing time • Etching one side of foil to enhance the surface energy

11. Electrical conductivities and locations of temperature sensors Chicken noodle soup 1/2 L Y 3 2 1 Black beans X 1 2 3 4 5

12. 2D Electrode configuration and field distribution Pouch A Electrode V/m Pouch B Pouch C

13. Comparison of temperature profiles of chicken noodle soup between simulation and measurement data Pouch A Temperature (oC) Pouch C Temperature (oC) X Y Temperature (oC) Pouch B X Y  : Experimental data : Simulation data X Y

14. oC 80 40 12 2D temperature distribution and cold zones Pouch A Pouch B Pouch C

15. Predicted temperature distributions and cold zone in Pouch B with different electrode widths : Electrode

16. Optimization of electrode width with respect to cold zone ratio, power consumption, average temperature, and temperature variation

17. ESM estimation based on potential final product with optimized power consumption

18. Initiated sterilization experiment • Pressured environment • Counterbalance internal pressures developed due to heating • Installed air pressure regulator • Employed cooling system

19. Preliminary data Symmetry

20. Deliverables • Shelf life study of food package • Gassing, corrosion, and leakage • Minimize cold zones to ensure the sterility of treated product • System optimization with numerical approach • Study wastes related to human activities • Microbiological analysis, sterility testing