isomerization and decomposition of galactose. In contrast, the
yield and selectivity of talose were hardly affected by the change
in ethanol concentration. Vourinen and Sjostrom (1982) also
reported that ethanol promoted both the isomerization and
decomposition of monosaccharides in an aqueous alkaline solution,
and they attributed the promotion ability of ethanol to its
increasing the ionization constant of monosaccharides. In this
study, there is a possibility that a similar mechanism acted on
the promotion of the isomerization. Ethanol also promotes the
isomerization of saccharides by changing the conformation and
configuration of the monosaccharides, thus shifting the apparent
reaction equilibrium to product formation (Angyal, 1969). The contribution
of ethanol to the isomerization of these saccharides in
subcritical aqueous ethanol is still unclear. Under subcritical conditions,
the role of ethanol in promoting the isomerization reaction
may be more complicated.