Helium Leak Test for Micron-Sized Holes in Canned Foods

Abstract

A helium leak test for canned foods was developed to provide a more sensitive method than existing ones and to reduce dependence on operator judgment for detecting leaking cans. The test forced helium through holes into cans filled with foods. Can headspace gas was sampled, and the helium content was measured by gas chromatography. An approximately linear (r = 0.81) relationship existed between the helium content of the headspace and the hole size in the can. The method detected holes as small as 1 μm in diameter (the smallest hole tested). Measurements of direct holes and dented seam holes in metal cans indicated that most holes tested smaller upon retesting. However, some seam openings did become larger. Some holes closed completely, probably as a result of clogging by particles. Cans with direct holes of known size were processed in a canning retort, and the cooling water was inoculated with ca. 106 bacteria/ml. Cans with holes greater than 5 μm became contaminated as exhibited by gas production during incubation at 37°C. The described helium test was compared with two modified conventional leak tests. When comparing cans with direct holes of known size, there was no difference between the methods. However, when comparing cans with leaks caused by dented seams, the helium test was found to be the most sensitive method for detecting leaks in cans of food. In order of their sensitivity, the tests for leaking cans were the helium test, the modified fluorescent dye test, and the modified vacuum test.