The Water Activity Lowering Properties of Selected Humectants in Eggs

The high and intermediate moisture sorption isotherms of whole egg, egg white, and egg yolk at 25 and 45 C with and without the addition of selected food humectants (glucose, sucrose, glycerol, propylene glycol, sodium chloride) were determined. In the pure egg systems, dehydrated egg white exhibited the highest water activity (aw) lowering ability, dehydrated whole egg was intermediate, and dehydrated egg yolk was the lowest when used in liquid egg systems. The pattern was reversed when the humectants were employed as the aw controlling agents in the systems. On an equivalent weight basis, the aw depressing property of sodium chloride was the most effective, followed by that of glycerol, which was comparable to the moisture sorption characteristics of propylene glycol. Glucose was not as effective as glycerol or propylene glycol but was superior to sucrose as an aw lowering solute. The aw of the egg systems incorporated with egg solids, glucose, sucrose, or sodium chloride was lower at 45 than at 25 C. However, glycerol produced higher aw at the higher temperature when its level in the egg systems exceeded 30%.