Reliability of destructive leakage detection methods for semirigid retort packages

Three different destructive testing methods for package integrity (biotesting, dye penetration and electrical conductance) were compared with each other using intact and leaking retort packages. In biotesting, both vegetative cells of Enterobacter aerogenes and spores of Bacillus subtilis were used as test microbes. The biotest results did not significantly differ from each other, most packages with a 50 μm channel leak through the seal area were contaminated. Biotesting with E. aerogenes was regarded as a more favourable method than testing with spores of B. subtilis since it was easier to perform and gas formation in the packages was a simple indicator for product contamination. The electrolytic test was able to discover most of the leaking packages more reliably than the biotests and the dye penetration test. The dye test had similar sensitivity in identifying leaks to that of the biotests. In conclusion, the microbial integrity of packages should not be estimated only by biotests, even if they are generally regarded as the most severe package integrity test methods.