A nondestructive leak detection method for flexible food packages using hydrogen as a tracer gas

A nondestructive leak detection method developed at Technical Research Centre of Finland (VTT) was tested for both gas-flushed and vacuum flexible packages. In the method, agas package containing 0.5 to 5.0% (vol/vol) hydrogen in nitrogen was positioned in a test chamber, a controlled vacuum was pulled in the chamber through a pipe connected to a hydrogen sensor, and leaking packages were detected by the sensor as increased H-2 concentration. The H-2 tracer gas (0.5 to 5.0%) was introduced into leaking finished vacuum packages at 200 kPa pressure. Within 1 to 4 s the developed test method was able to detect leaks down to 10 to 15 mu m and 20 to 30 mu m in diameter in commercially manufactured gas-flushed packages filled with roasted meat balls and vacuum packages filled with ground coffee, respectively. Before leak testing, the vacuum packages were charged with H-2 for 30 s. The sensitivity and leak detection time of the test method were improved when the H-2 concentration in the package was increased and when the free space in the test chamber was decreased. The evaluated H-2 concentrations did not affect the sensory or microbiological quality of the roasted meat balls. This study clearly demonstrated that the hydrogen tracer gas leak detection method has potential to be further developed as a fast, nondestructive, on-line leak testing apparatus for flexible packages with or without a headspace.