The Mutarotation of Fructose and the Invertase Hydrolysis of Sucrose

Studies by GLC and GLC/MS of the mutarotation of fructose in water have been made to determine equilibrium composition as a function of temperature. The major components are β-fructo-pyranose, β-fructofuranose and α-fructofuranose in agreement with studies in the literature. There are small amounts of the α-fructopyranose and the open-chain ketone form. The major change during mutarotation is the ring size change for β-fructopyranose → β-fructofuranose, but other changes contribute. For this reason, polarimetric rate studies of this system as a simple first-order equilibrium process are not valid. Hydrolysis of sucrose catalyzed by invertase has been accomplished to the extent of 99% in 1 min. The mutarotation of glucose and fructose were then studied without the complication of further production of the products from sucrose. The enzymatic cleavage is stereo-specific to provide retained configuration in α-glucopyranose and β-fructofuranose which each mutarotate to equilibrium. The mutarotation lag was demonstrated and its importance to sucrose hydrolysis discussed.