THE EFFECT OF THERMOCOUPLE AND RECEPTACLE TYPE ON OBSERVED HEATING CHARACTERISTICS OF CONDUCTION-HEATING FOODS PACKAGED IN SMALL METAL CONTAINERS

Three different types of thermocouples and receptacles were studied to determine the effect on the observed heat penetration rate of a conduction-heating food packaged in 202 × 204 and 211 × 300 cans. The studies were conducted at two product initial temperatures (70 and 140F) and three retort temperatures (240, 250 and 260F) using an Allpax R&D retort. The results indicated that the Ecklund stainless steel receptacles and needle type thermocouples in 202 × 204 cans increased the apparent heat penetration rates significantly, which resulted in underestimated Ball Formula process times (≈5%) and overestimated process lethalities (≈27%). However, in the 211 × 300 cans only minimal effects were seen on the apparent heat penetration rates, Ball process times and resulting lethalities. The use of plastic Delrin receptacles and thermocouples in 202 × 204 and 211 × 300 cans produced results in close agreement with those obtained from thin-gauge flexible thermocouples having minimum conduction error.