Distribution of Heat Penetration Parameters in a Single Basket Water Cascade Retort: Effect on Effective Pasteurization of Sous Vide Cooked Beef Pieces

ORMANDO PAULA; OURILLE CRISITAN; ROSSI NATALIA; SANCHO ANA M.; VAUDAGNA SERGIO R.

Ljubljana, Slovenia

Congreso; First European Food Congress (EFFoST 2008); 2008

European Federation of Food Science and Technology (EFFoST)

In sous vide products effective pasteurization should be demonstrated by the application at the food-core of a specific temperature-time combination or pasteurization value (1,2). A detailed study of the performance of the retort is required because a few profiles per batch are monitored in the commercial processing (1). The aim of this work was to evaluate the distribution of heat penetration parameters in a water-cascade retort and its effects on the effective pasteurization of sous vide cooked beef pieces. Standardized beef cylinders (20,8cm length; 10.5cm diameter) were packaged into cook-in pouches (CryovacTMCN-640). Core temperatures (CT) of cylinders were measured with type-T thermocouples. Each of the shelves (top, middle and bottom) of the basket was loaded with eight cylinders. Heating was carried out in a water-cascade retort (MicroflowTM Barriquand) at 75ºC for 135 min. Experiments were carried out in triplicates. The heating time from 10 ºC to 70 ºC at CT (deltatime) was calculated.  Heating rate index (fh) was obtained as in (3). Cylinders loaded on the top and bottom shelves heated significantly faster than ones on the middle shelf (Table I). The performance at the top shelf was expected, considering that the water is showered on this position (4). The lower heating rate in the middle shelf could be consequence of a minor heat transfer coefficient (h). However, h would be higher in the bottom shelf, due to a combined effect of water-cascade and water-bath flow pattern. The differences of deltatime  between the slowest and the fastest heating (Table II) are higher than the holding time (2min at 70 ºC) corresponding to 6D reduction of Listeria monocytogenes (5). Consequently, if a cylinder on the top/bottom shelves was held for 2min at 70 ºC, cylinders in the middle shelf would not have reached this CT. Hence, these cylinders would not achieve the recommend pasteurization target.