AC-2349 -- Thermal Diffusivity of Meats ✓ Most Recent

Solid and highly viscous foods are the most difficult to heat and cool rapidly because when
heat is transferred by only conduction, the food layers insulate the innermost portion from
the thermal processes applied at the food surface. For conduction heating of a given food,
heating and cooling times are directly proportional to the square of thickness. Consequently,
the foods most often involved in public health hazards are solid and viscous foods
of large geometry.

Most meats are cooked to enhance palatability, and under some conditions the cooking process
also inactivates vegetative pathogens such as Salmonella and Staphylococcus. To evaluate the
microbial lethality of a cooking process and the probability of excessive microbial growth
during cooling, the internal temperature-time relationship must be known. In the past, these
data have been obtained primarily by experimentation. Since new food products and processes
are in a continuous state of development, the experimental technique becomes cumbersome because
of the numerous combinations of foods, processing conditions, and geometries that must
be tested.

Temperature-time relationships can be computed for many food geometries if the thermal
properties of the food are known. Some thermal properties of foods are available,
but there are few data on thermal diffusivity of solid meats in the cooking range (43 to 95 C).
Hurwicz and Tischer reported an average thermal diffusivity of canned beef as 0.088
cm²/min during steri1ization and Smith, et a1. reported the thermal diffusivity of boneless
cooked hams as 0.057 cm²/min for the temperature range of 0 to 45 C. Riedel reported
data for corned beef, fish, and ham in the temperature range of 5 to 65 C.

The objective of this work is to measure thermal diffusivity of selected meats at temperatures
experienced by meat during usual cooking processes.