Impact of freezing and thawing processes on wheat and potato starch gel syneresis

Abstract

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.