Abstract: A can container made of soft material such as aluminum having a wall thickness of less than 0.2 mm is used for low acid foods or drinks having pH of more than 5.0. A controlled quantity of liquified nitrogen is introduced into the can filled with the low acid foods or drinks and then the can is hermetically sealed off by double-seaming. The liquid nitrogen is soon gasified in the sealed can to increase internal pressure of the can to a level sufficient to prevent the can from being deformed. Then the can is subjected to retort sterilization treatment at a predetermined high steam temperature for a predetermined period of time for sterilization of any possible bacilli and bacteria in the low acid foods or drinks in the can. Prior to retort sterilization treatment, a thermal sensitive paint is applied to the can, which will change color when exposed to a steam of a predetermined temperature for a predetermined period.

Abstract: Pressurization of containers with liquid nitrogen to impart container strength and content protection is effected by injecting a small quantity of liquid nitrogen before sealing the container by the methods and apparatus including a gas pressure system wherein liquid nitrogen is maintained by control means at a constant pressure with nitrogen gas being separated from liquid nitrogen before dispensing and a recirculating pump pressure system wherein liquid nitrogen from a second of two supplies is pumped through a conduit to a dispensing gun and surplus liquid and gas is returned to the supply.