Long-duration space missions require the development of improved foods and novel packages that do not represent a significant disposal issue. In addition, it would also be desirable if rapid heating technologies could be used on Earth as well, to improve food quality during a sterilization process. For this purpose, a package equipped with electrodes was developed that will enable rapid reheating of contents via ohmic heating to serving temperature during space vehicle transit. Further, the package is designed with a resealing feature, which enables the package, once used, to contain and sterilize waste, including human waste for storage prior to jettison during a longduration mission.
Ohmic heating is a technology that has been investigated on and off for over a century. Literature indicates that foods processed by ohmic heating are of superior quality to their conventionally processed counterparts. This is due to the speed and uniformity of ohmic heating, which minimizes exposure of sensitive materials to high temperatures. In principle, the material may be heated rapidly to sterilization conditions, cooled rapidly, and stored.
The ohmic heating device herein is incorporated within a package. While this by itself is not novel, a reusable feature also was developed with the intent that waste may be stored and re-sterilized within the packages. These would then serve a useful function after their use in food processing and storage.
The enclosure should be designed to minimize mass (and for NASA’s purposes, Equivalent System Mass, or ESM), while enabling the sterilization function. It should also be electrically insulating. For this reason, Ultem® high-strength, machinable electrical insulator was used.
Because the pouch would expand when exposed to heating to sterilization temperatures (greater than 121 °C), it is necessary to prevent seal rupture by applying air pressure into the enclosure. To enable cooling of the package in the enclosure, a water inlet and outlet are provided. The electrode tabs could be modified to form a larger pair of electrodes, which will also allow heating of water within the enclosure if necessary.
Under normal reheating conditions, temperatures will not need to go above 100 °C, thus the air overpressure feature will be unnecessary. The plan is to provide a user interface with a keypad that will enable users to dial in the heating protocol depending on the product that is within the chamber. This feature could be automated.
The incidence of electrolysis will be minimized using a solid-state IGBT power supply at 10 kHz. This is critical in a space application, since bubble formation at the electrodes can stop the heating unless electrolysis can be suppressed.
This work was done by Sudhir K. Sastry, Brian F. Heskitt, Soojin Jun, Joseph E. Marcy, and Ritesh Mahna of Ohio State University for Johnson Space Center. For further information, contact the JSC Innovation Partnerships Office at (281) 483-3809.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
Office of Technology Licensing
1960 Kenny Road 2nd floor
Columbus, OH 43210-1063
Phone No.: (614) 292-1315