process of enzymatically converting glucose to fructose wherein a glucose - containing solution is passed , under specific conditions , through a bed composed of an immobilized glucose isomerase in a fine , particulate form and non - porous beads or granular inert material such as polystyrene beads . the porous beads and granular inert material comprise between 40 % and about 75 % of the bed by volume . the bead &# 39 ; s presence exerts a buoyant effect which prevents bed packing and promotes desirable flow patterns with no observable channelling . this helps to minimize the formation of undesired or undesirable carbohydrates such as psicose .