CONTAMINATION OF FLEXIBLE POUCHES CHALLENGED BY IMMERSION BIOTESTING

Immersion biotesting has long been used to challenge pack ages, partic ularly cans, for pinholes and channel leaks. Such testing for all type s of plastic packaging may not be appropriate because some packages (e .g., aseptic, hot fill) are not exposed to water. As the food-packagin g industry develops alternative environmental biotests there is a need to benchmark them against traditional immersion testing. The purpose of this research was to examine the threshold of critical-defect dimen sions using artifically created channel leaks of 10 and 20 mu m and 5- and 10-mm lengths sealed into plastic pouches which were subsequently tested by immersion at 10(2) and 10(6) CFU of motile and nonmotile Ps eudomonas fragi TM849 per mi. Forty-four percent (44%) of the pouches tested became contaminated, indicating the threshold defect value is b elow 10 mu m. Microbial ingress was significant (P < .05) for motile t est organisms with a concentration of 10(6) CFU/ml. The interaction of concentration and time was also significant at 10(2) CFU/ml at 30 min exposure and 10(6) CFU/ml at 15 min. Channel length was not statistic ally significant. The markedly greater contamination rate using immers ion testing versus that of aerosol testing highlights the importance o f using test methods that reflect environmental exposure conditions of the packages.