Numerical modeling of a food analog, and heat transfer parameters and nutrient retention of selected foods thermally processed in retortable semi-rigid plastic trays

Numerical procedures, using the finite difference method, to describe heat transfer into semi-rigid retortable plastic trays have been developed using non-biological material as food simulants. Research is needed to characterize heat transfer into plastic trays using bio-polymer food model systems, as well as to assess the influence of heat sterilization on thermal characteristics and nutrient retention in conduction-heated foods. The objectives of the study were to (1) model heat transfer in plastic trays using starch suspension; and (2) evaluate the effects of experimental variables on process parameters, quality factors and nutrient retention in chili con carne and pork sausage links. Plastic trays filled with pregelatinized corn starch, chili, and pork sausage were processed in a commercial Water Cascading Static retort at 121.1°C before cooling under air overpressure. For heat transfer modeling using starch, different headspace volumes and lid orientations were employed, while for chili and pork sausage processing, a lid-down orientation with zero headspace volume was used. Proximate composition and amino acid profile were determined for both food products before and after processing.; For 10% starch, the heating (f_h and j_h) and cooling (f_c and j_c) response parameters were influenced (P < 0.05) by lid orientation and headspace volume. The f_c value was 1.57× greater (P < 0.05) than f_h. The j_c value was 7.8% higher than the Ball's assumed value of 1.41. There was no significant (P > 0.05) difference between experimental and model F_o values. For chili, the f_c was equal to 1.12f_h. Lethality decreased (P < 0.05) with increases in residual air volume. The C_o, C _AV and Q_D values increased (P < 0.05) with process time. For pork sausage links, process parameters and quality factors were influenced (P < 0.05) by thermocouple location in the tray (geometric vs nongeometric center), and the f_c was always higher than the f_h. Lethality at the nongeometric was higher (P < 0.05) than at the geometric center. None of the thermal processing conditions caused destruction of essential amino acids.; Thermal sterilization of conduction-heated high-protein foods in plastic trays, when done properly, would not significantly impair the product quality. Thus, this type of containers may be suitable for processing military-type rations at optimal time-temperature parameters.