Low water activity and the glass state in dried foods restrict the growth of microorganisms and increase food stability. Vitrification of foods is related to the texture. Thus, hydration and vitrification are essential factors determining the physical properties and quality of foods. Inelastic neutron scattering (INS) is a promising research method for the analysis of water mobility and glass transition of food materials. Neutrons easily penetrate materials, and can be used to non-destructively investigate the molecular dynamics of food materials. INS generates information about the vibrational density of states, relaxation and diffusion processes, and mean-square displacement. Molecular dynamics (MD) simulation provides information regarding molecular structure and dynamics on an atomic scale, and is thus complementary to INS. It was found that the hydration level dependence of the onset of protein glass transition is correlated with the percolation transition of hydration water. In addition, the hydration water dynamics changed significantly at the transition temperature. The percolation of hydration water induces protein glass transition.
