The performance of a new horizontal retort (Steriflow Standard 1-Basket Model, Barriquand, Paris, France) was evaluated on the basis of temperature, heat and lethality distribution. Time-temperature data for these studies were obtained from bare thermocouples (type T), and rectangular bricks fabricated from Teflon$ sp{ rm TM}$ and Lexan$ sp{ rm TM}$ with thermocouples positioned at their geometrical centres. / The effect of entrapped air on processing parameters for bricks packaged in retort pouches was determined using silicone rubber bricks (10 x 14.5 x 2 cm), containing 5 thermocouples with their junctions positioned from the geometrical centre to near the top surface. The processing media employed were steam/air at two temperatures (121.1$ sp circ$C and 115.6$ sp circ$C) and two levels of superimposed air over-pressure, corresponding to 65% and 75% steam content. / With the exception of the highest level of over-pressure (116 kPa), 60 ml of entrapped air caused the heating rate index (f$ sb{ rm h}$) to double. At low levels of air over-pressures, the slowest heating region (often assumed to be the geometrical centre) in the brick was shifted to a height equivalent to 3/4 of the brick thickness from the centre when the entrapped air volume was 60 ml. For similar conditions, the location receiving the least combined lethality during heating and cooling was near the top surface of the brick.

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