The impact of freezing and thawing processes on gel structure, bound states, and mobility of water in wheat and potato starch gels was investigated, using laser scattering granulometer, centrifugation, SEM, DSC, and thermogravimetrical analysis (TGA). Starch gel water syneresis was qualitatively and quantitatively correlated to the freezing-thawing process. Potato microstructure was mainly impacted by freezing rates whereas wheat was influenced by both freezing and thawing rates. The observations were confirmed by SEM. Indeed, the size of cavities created by ice crystals increased with higher freezing rates for both varieties. Microstructure modifications during thawing only appeared for wheat. The hypothesis to explain the difference between these two starch gels could be based on the structural feature of starch granules that induce modifications of the gel matrix hardness depending on the granule restructuration during the heating period of the preparation of these gels.

The aim of this study was to evaluate the impact of egg ageing on the surface properties of whole and fractionated yolk at the air-water interface. Eggs were stored at 4°C for 24 h, 1 week and 3 weeks after laying. A laboratory scale fractionation process was then applied at each ageing time. Egg yolk was separated into two fractions, plasma composed of low-density lipoproteins (LDLs) and livetins, and granules formed by highdensity lipoproteins (HDLs), phosvitins and LDLg (g = granule). Moreover, recombined plasma and granules fractions were investigated to highlight a potential synergic effect on surface properties. Results have shown the main contribution of LDLs on surface properties of yolk and an improvement of granules surface properties when they are disrupted. Moreover, ageing affected surface properties differently depending on the considered fractions. Broken LDLs and disrupted granules could explain this observed behaviour. Recombined fractions showed different compression isotherms at the air-water interface than whole yolk.