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

摘要

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 x 204 and 211 x 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 x 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 x 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 x 204 and 211 x 300 cans projuced results in close agreement with those obtained from thin-gauge flexible thermocouples having minimum conductionerror.