The direct method ofoptica l microscopy with
episcopic coaxial lighting has the advantage to characterize,
in situ, the ice cream structure by preserving at
best the original properties ofthe frozen overrun ice
cream sample.
Firstly, this technique was compared with other
classical techniques more largely used for the characterization
of this type of frozen food texture. The data
derived with this new original method were found in
agreement with each other. Besides, it has the great
advantage to be easy to implement with low running
costs.
Secondly, we applied this technique to analyse the
influence ofpor osity on the ice crystals distribution and
the influence ofthe freezer exit temperature of the mix
on the air bubbles size distributions. The results
presented in this study are in agreement with the last
literature data. Nevertheless, for the purpose of heat
transfer modelling during ice cream freezing, more
experimental data and more advanced analyses ofthe
air bubbles size distribution are necessary to estimate
precisely the air porosity which is an important
parameter influencing the apparent thermal conductivity
ofthe mix.
Finally, this methodology could be extended to other
ice cream formulations and to other frozen food types
(vegetables, fruits, etc.) for routine exploitation in
industrial control laboratories.