Given the danger of freeze burns (created by cooling air to below -320?F) and its tendency to crowd out oxygen in a confined space, liquid nitrogen requires special handling. Vacuum Barrier was founded in 1958 to make liquid-nitrogen handling equipment, and 30 years later the company was asked to develop a system that could maintain internal pressure in containers to offset the vacuum created during hot filling. Exposed to ambient air temperatures, liquid nitrogen instantly expands in a gaseous state to an area several hundred times its mass in liquid form, according to Ed Hanlon, Vacuum Barrier’s vice president of sales.
Until recently, snack food processors relied solely on nitrogen gas tunnels to reduce oxygen levels under 2 percent prior to package sealing to retard rancidity from fats and oils. Those systems use flushing tunnels. The tunnels require about 20 to 30 feet of floor space between filling and sealing. If seasoning is applied to the food, conveyor clean-up can pose sanitation issues.
Liquid nitrogen eliminates the need for a flushing tunnel, and the dosing system has proven more cost-efficient in terms of the nitrogen used by a copacker of nuts who has used Vacuum Barrier’s system, Hanlon maintains. The company has converted half a dozen lines at its plants, he adds, with more conversions likely.