Mutarotational Kinetics and Glass Transition of Lactose

Ronan Lefort (1) , Vincent Caron (2) , Jean-François Willart (2) , Marc Descamps (2)

1 GMCM - Groupe matière condensée et matériaux
2 LDSMM - Laboratoire de dynamique et structure des matériaux moléculaires

We report for the first time real time in situ and quantitative measurements of the mutarotation reaction of lactose in the solid state. The experiments have been performed by 13C NMR. We show that mutarotation is initiated on heating the amorphous state, and reaches chemical equilibrium close above the glass transition temperature Tg. We do not observe this transformation when starting from stable crystalline states. The final ratio of and anomers is 1:1, which suggests that the energy profile of the mutarotation reaction pathway in the solid state is actually different from the mechanism proposed for aqueous solution. This chemical equipartition is reached before the crystallization into the corresponding 1:1 molecular compound. These new data clearly illustrate the interrelation between the chemical molecular properties, the physical state of the material, and the relaxational dynamics of the glass.

Mots clés: Lactose; Mutarotation; Glass Transition; Ball Milling; Solid State Nuclear Magnetic Resonance

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Ronan Lefort, Vincent Caron, Jean-François Willart, Marc Descamps. Mutarotational Kinetics and Glass Transition of Lactose. Solid State Communications, 2006, 140, pp.329-334. ⟨10.1016/j.ssc.2006.09.003⟩. ⟨hal-00073118v2⟩