Figure 2 Product centre temperatures and freezer air
temperatures for one production cycle from the
example freezer test.
From the test example, not one of the product centre temperatures reached 10F (-12C) in the desired 40 hours.
Extended freezing times are most often caused by the plant increasing product throughputs without increasing the capacity of the refrigeration system (thus resulting in higher-than-designed air temperatures). Increasing the carton depth or changing the cardboard material to one with poorer heat transfer properties are also common causes.