Effect of Handling Procedures on the Post‐process Contamination of Retort Pouches

Abstract

The effect of handling flexible retort pouches has been studied in relation to their integrity and resistance to post‐process contamination (‘leaker spoilage’). Tests were made using a pilot‐plant processing line on which pouches were filled with broth, sealed, heat‐processed and subjected to three post‐process handling treatments. Using Enterobacter aerogenes as an indicator organism, it was shown initially that rough instead of careful handling during loading of the retort increased the proportion of punctured pouches from 0.06 to 0.27%. The effect of post‐process handling procedures on leaker spoilage was studied using pouches deliberately punctured with a needle of 100 μm diameter. When these pouches were cooled in tap water, unloaded manually from the retort and stored wet, the incidence of post‐process contamination was 90%. With similar pouches which were dried immediately after manual unloading and stored dry, the contamination rate was only 10%, whereas cooling in chlorinated water and drying before manual unloading reduced the contamination rate of punctured pouches to less than 1%. It was concluded that manual handling of dry pouches presents an acceptable alternative to complete mechanical handling of freshly heat‐processed pouches, which was proposed in a Code of Practice for retort pouches formulated in 1971.