14A-46

M. F. ALMEIDA, Food engineering, Cornell University, 175 Riley-Robb Hall, Ithaca, NY 14853, E. Ortega, Food Engineering, UNICAMP - State University in Campinas, SP, Brazil, FEA - School of Food Engineering, Caixa Postal 6121, Campinas - SP, 13083-970, Brazil, and P. R. Massaguer, Food Science, UNICAMP, School of Food Engineering, Cx. Postal 6121, Campinas-SP, 13081-970, Brazil.

JUSTIFICATION: Effective real-time monitoring of thermal sterilization of foods in trays will improve their microbiological safety and quality. Besides, it is known that semi-rigid packages present problem of maintaining package integrity during sterilization processes.

OBJECTIVES: To develop a computerized system for monitoring the temperature profile and accomplished lethality during sterilization of food in a thermo-resistant tray, and compare the results with those using an existing data acquisition system.

METHODS: Trays (PP/EVOH/PP) filled with chicken breast meals in a tomato sauce are heated. Temperature data were collected using type T thermocouples whose output are processed using an amplifier and a multiplexer board together with an A/D converter. Two in-water static processes were tested at temperatures of 115 ^oC and 118 ^oC. A real-time monitoring program was developed using the Genie commercial control software to display the transient temperature profile and the accomplished lethality at the coldest spot in the tray. Simpson's rule was used to integrate the lethality with time. The efficiency and accuracy of this data acquisition system was compared with an existing system (DORIC).

RESULTS: An empirical residual air - headspace relation in the trays was determined to allow the retort processing using counter-pressure in hot-water immersion. The data acquisition system was able to plot in real time the temperature and the calculated lethality. A set of six thermocouples was used in each tray. The thermocouple calibrations against an oil bath showed a standard deviation of 0.5 0C for both the new and the existing data acquisition systems. For the new system, the accomplished lethality had an estimated error of less than 11% compared with using calibrated temperature values. For the existing system, this estimated error was less than 4%.

SIGNIFICANCE: This work presents a novel and versatile real-time monitoring system for sterilization. By displaying the lethality in real time it can aid significantly in validation. New parameters such as residual air content in the package and the retort overpressure for sterilization of foods in trays were established.