A discriminating microscopy technique for the measurement of ice crystals and air bubbles size distribution in sorbets.

In this work, a technique capable to distinguish between ice crystals and air bubbles in sorbets was developed in order to characterize the effect of operating conditions on their size distributions at the exit of the freezer. A pilot freezer was used to crystallize and aerate a commercial lemon sorbet mix. Crystals and bubbles sizes were measured using a light microscope technique under low temperature in a refrigerated glove box developed in the lab for that purpose. Results showed that the developed microscope technique allowed to distinguish them and to quantify their size distributions. Measurements showed that ice crystals size decreases with air flow rate while air bubbles size increases. The latter also increases with the cylinder pressure inside the scraped surface heat exchanger (SSHE).