SELECTION OF VARIABLE RETORT TEMPERATURE PROCESSES FOR CANNED SALMON

Variable retort temperature processes (VRT), in which retort temperatu re is a function of rime, were developed for sterilization of Pacific salmon in 307 x 115 steel cans, with objectives of minimizing loss of quality criteria such as surface quality or thiamine, or minimizing pr ocess time, all while maintaining constant center-point lethality (F-o ). A finite difference computer model of conduction within a finite cy linder was used to Zest different temperature-time profiles. Processes were constrained to include steam vent schedules and to exclude tempe rature decrease during the heating process as well as temperature modu lation during cooling, thereby improving compatibility with typical sa lmon canning facilities. Rho, the fraction of total lethality accumula ted at steam-off rime, was found to be a function of final unaccomplis hed temperature, retort temperature, salmon thermal diffusivity and co ntainer geometry. The search for favorable processes was aided by Rand om Centroid Optimization (RCO). Minimum surface cook in constant retor t temperature (CRT) processes varied with retort temperature and z of surface quality, but the best VRT process was consistently better than the best CRT process. VRT reduced operator's process time from 64 min to 54 min and maintained equal F-o and surface quality. Thiamine loss es were reduced from 19.6% loss by CRT to 16.8% loss by VRT.