Heating Rates in Flexible Packages Containing Entrapped Air During Overpressure Processing

Abstract

ABSTRACT Experiments were performed in two steam/air retorts and one water immersion retort to test the influence of included air on heating rate index (f h ) values at the center of thin plastic bricks packaged in retort pouches and processed under various temperature and overpressure conditions. In general, high air overpressures (>80 kPa) allowed up to 30 mL air to be included with no detrimental effect on heating rates; however, even small amounts of entrapped air (<5 mL) degraded heat transfer when processed at low air overpressures (<40 kPa). Processing medium and retort type were important factors in the sensitivity of heating rate to increases of air volumes beyond a threshold value.