4 °C - the National Sea Grant Library

technique would reduce the potential for recontamination of product after steaming
by decreasing the time that meat is exposed to the plant environment (i.e., air).
Special crab meat was chosen for the purpose of this comparative study.
Cooling rate profiles of crab meat were obtained for air-cool and hot-fill process
techniques, respectively, according to procedures described in Part II. Due to the
difficulty in handling crab meat at high temperatures, no samples were packed by hand
with temperatures exceeding 65.5°C.
Model simulations
In order to simulate temperatures greater than 65.5°C , a mathematical
spreadsheet (Quattro Pro for Windows, Version 5.0, Borland International) and
model generator (MathCAD 2.0, Addison-Wesley) were used to curve fit cooling data
and extrapolate initial meat temperatures outside the experimental range obtained at
the processing plant. By generating models for these cooling rates a better
understanding of how to improve the atmospheric steam process could be obtained.
Models were developed using the following exponential equation:
T t = T sur+ T 0 * e -(K*t) (1)
T t is the meat temperature at any time, t. T sur is the surrounding temperature. T o is the
initial temperature minus the surrounding temperature. K is the rate constant and t is
time. This model clearly shows that the temperature at any time t is dependent not
only on the surrounding temperature but also on the initial meat temperature.
The constant K which determines exactly how fast the meat will cool can be
calculated with the following equation:
ln(T t - T sur)
T 0
t
= K (2)
It can be seen from equation (2), that if time remains constant and the
surrounding temperature is constant then crab meat with the higher initial temperature
will have a faster cooling rate. This translates simply into the fact that the hotter a
body is the faster that it cools. Knowing this, the question now becomes at what initial
meat temperature does this make a significant difference in the cooling time? Since
only a small difference in cooling time was actually observed between air-cool and
hot-fill packing of meat, it was further hypothesized that there must be an optimum
temperature in which to pack crab meat to obtain the maximum cooling rate and