A COMPARATIVE STUDY OF HEAT PENETRATION DATA USING REMOTE SENSORS AND NEEDLE OR ROD-IN-TUBE THERMOCOUPLES

Using 5% w/v bentonite suspension as model food, studies were conducted to evaluate the performance of internally mounted remote sensors relative to thermocouples in 300 × 407 cans. These studies were done to essentially evaluate the impact of remote sensors on heat penetration parameters, mainly j_h (the lag factor) and f_h (the heating rate index), for different retort rpm, container headspace (HS) and mode of agitation in FMC's Steritort (FMC Food Tech, Madera, CA) and/or the Allpax R&D retort (Model 2402, Covington, LA). The criterion used for evaluating the performance of the sensors was the Ball process time (B_b), which combines both j_h and f_h. Generally, some variations in heat penetration data were observed between remote sensor types and thermocouples. With some exceptions, calculated mean B_b values for the remote sensors and thermocouples were statistically insignificant (P > 0.05). The exceptions depended on the remote sensor type and mode of container agitation, but generally, variations in measured parameters from that of the reference thermocouple were attributed to container HS, retort rpm, sensor configuration and mounting fixture design. For axial agitation in the Steritort using 300 × 407 two‐piece cans, the average Ball process times were generally higher (i.e., longer process times) for thermocouples compared to the remote sensors with the percentage difference ranging from 2 to 7%. The range was 2 to 8% for end‐over‐end agitation with water immersion, and 1 to 6% for still cook in steam using the Allpax R&D retort using 300 × 407 three‐piece cans. Given the unusually high percentage differences found for some of the experimental conditions, caution must be exercised in using these variations as correction factors in adjusting remote sensor data without a thorough understanding of the behavior and interaction of that specific sensor with HS and retort rpm.