The main objective ofthis study was to develop and to set up a new optical direct microscopy method, based on the reflected light
flux differences, with episcopic axial lighting to characterize the different phases structure of commercial overrun ice creams. Firstly,
the results obtained have been validated by two others methods, a destructive method by dispersion and observation by light
microscopy and, an indirect method, by scanning electron microscopy after freeze-drying sample. It was observed that the three
methods were in agreement and led to the same conclusions concerning the main freezing parameters influence.
So, this technique has been principally used to investigate the effects of the freezing conditions on the ice crystal structure. One of
the most important parameters is the freezing rate that governs not only the size, but also the ice crystals texture of the ice cream.
The air introduction (overrun) tends to limit the ice crystal growth. Besides, by this method, it was also possible to observe and to
quantify the air bubbles size distribution. This direct microscopy method could be extended to other frozen food structure analysis.
r 2003 Swiss Society ofFood Science and Technology. Published by Elsevier Ltd. All rights reserved.