Biological Systems Engineering


Date of this Version



Published in Transactions of the ASAE Vol. 48(1): 287−303. Copyright 2005 American Society of Agricultural Engineers. Used by permission.


A two−dimensional axisymmetric transient heat conduction model was developed to simulate air chilling of large ready−to−eat meat products of ellipsoidal shape. A finite element scheme, using 1,600 linear triangular elements with 861 nodes, was implemented in Matlab 6.5 to solve the model. The model considered a variable initial temperature distribution and combined convective, radiative, and evaporative boundary conditions. Predicted values agreed well with experimental data collected in actual processing conditions. Validation of model performance resulted in maximum deviations of 2.54°C and 0.29% for temperature and weight loss histories, respectively. The maximum temperature deviation (2.54°C) occurred at the surface; however, for center temperature, the maximum deviation was lower (1.59°C). The validated model was used to assess the extent of deviations from stabilization performance standards established by the Food Safety and Inspection Service (FSIS) caused by unexpected equipment failure or electrical power outage. A total of 48 simulations were also carried out to establish critical product sizes and operating conditions for compliance with FSIS performance standards. It was concluded that, for cured meat products, small processors should be able to meet the stabilization requirements for any typical commercially available product size, under all simulated chilling conditions. Conversely, for non−cured meats, products should have a maximum weight of 2.25 kg (with typical dimensions of: major axis = 21.2 cm, minor axis = 13.9 cm) in order to comply with FSIS standards, particularly to meet the criteria of cooling between 54.4°C to 26.6°C. The validated model provides a useful quantitative tool for various food safety applications.