Our study indicates that under typical test conditions, the surface temperature of the primary food pack was measured to be -8.7 ± 0.5°C at the end of 24 hours since packaging and the temperature continues to rise linearly with time even beyond 30 hours since packaging without plateauing out. This indicates that the contents of the food pack continue to remain completely frozen since the temperature measurements would have remained constant if the contents within the pack had started thawing, until the thawing process is complete.
The frozen state was best preserved in the box with dry ice lined with foil lining. Gel pack with foil and dry ice without foil were comparable and the food remained frozen after 24 hours. Ice packs with foil lining of the box was also effective, but after 24 hours, the periphery of the containers showed partial thawing.