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The objective of this study was to determine the effect of high-temperature retorting process on the physical characteristics of the microchannel, to evaluate the significance of various processing parameters on microchannel penetration, and to determine the critical microchannel diameter in flexible pouches through the biotest using a retort.
Determining the critical microchannel size at which microbial contamination may occur is a prerequisite for establishing the lower limits of sensitivity required for nondestructive inspections of plastic package defects. A wide range of pinhole and microchannel leak sizes have been reported (10 to 33 µg) as the minimal diameters for microbial contamination. Experimental conditions have not been able to simulate the actual processing conditions experienced by food processors. A systematic approach to overcome these limitations is to use 'in situ' immersion biotesting on a pilot plant scale to evaluate the effect of risk parameters likely to be encountered by the packages through the retort cooling. This study was to establish the basic criteria for 100% nondestructive testing of flexible pouches to reduce the potential health risks. Given the conservative conditions described in this report for flexible retort pouches with 3 mm width seals and cooling water contamination levels of 106 CFU/ml, the selected microorganism can penetrate microchannels as small as 7 µm, but if the seal width is 6mm and the cooling water is chlorinated and the contamination level is lowered to 103 CFU/ml, the minimum microchannel diameter for penetration can be as large as 41 µm.