4. Conclusions
Speed of sound measurements are widely accepted to
be highly sensitive to crystallization processes, but to
our knowledge this is the first attempt to measure progressive
water crystallization during freezing. The two
methods of data interpretation proposed offer slightly
different estimates of the degree of freezing. Which is
more appropriate in any given situation will depend on
both the ease of data acquisition and which gives a
better measure of food stability. Both approaches can be
used to give an estimate of the progress of a freezing
process. The key applications of this work will be in
developing sensors to control the operation of a food
freezer. Comparing two measurements on a single food
item at different times during a freezing operation would
give a good indication of the freezing kinetics and allow
an estimate of the freezing time. A single measurement
on a series of similar food items exiting a freezer could
also be used for freezer control.