3D imaging analysis method to measure ice crystal size.

International audienceImportant notes: Do NOT write outside the grey boxes. Any text or images outside the boxes will be deleted. Do NOT alter the structure of this form. Simply enter your information into the boxes. The form will be automatically processed – if you alter its structure your submission will not be processed correctly. Do not include keywords – you can add them when you submit the abstract online. Title: 3D imaging analysis method to measure ice crystal size. Abstract: (Your abstract must use Normal style and must fit in this box. Your abstract should be no longer than 300 words. The box will 'expand' over 2 pages as you add text/diagrams into it.) Freezing is widely used in the food industry to preserve product quality thanks to the low storage temperature. It is well known that a faster freezing enhances frozen food quality while forming smaller ice crystals. Indeed large ice crystals damage cells membranes. However fast freezing processes are energy demanding. It is therefore a challenge to reduce process cost without increasing ice crystals size or to reduce ice crystal size without a dramatically increase of cost. Some experimental studies have shown that it is possible to obtain smaller ice crystals by using electromagnetic waves assisted freezing [1,2]. The freezing process could thus be carried out with less intensive conditions. To evaluate the impact of this innovative process on frozen product quality, a method had to be developed. Methylcellulose was chosen as a model gel. A 9 g sample of 2.6 cm height was frozen with gaseous nitrogen at-40°C on its top surface. Other surfaces were insulated to consider unidirectional freezing. The non-porous gel was then freeze-dried to sublimate ice crystal so that crystals phantoms size can then be measured by X-ray tomography [3]. The ice crystal distribution was measured along height by dividing the sample in 8 sub-volumes from VOI1 to VOI8 (Figure 1). The results obtained showed a logarithmic correlation between crystal diameters and depth (Figure 2). The distribution of crystal size was Gaussian. To evaluate temperature without invasive measurement a predictive model [4] was used to perform numerical simulation from the gaseous nitrogen temperature. It permitted to find correlations between ice crystal sizes, characteristic freezing times and freezing rate. The coherence of the results allows to validate this analysis method for methylcellulose. In the context of the European project FREEZEWAVE (FP7-ERA-Net_SUSFOOD), the impact of low energy microwave pulses during freezing on ice crystal size will then be investigated. [1] M. Anese, L. Manzocco, A. Panozzo, P. Beraldo, M. Foschia, M.C. Nicoli, Effect of radiofrequency assisted freezing on meat microstructure and quality, Food Res. Int. 46 (2012) 50– 54