Example 11
A mixed sugar solution comprising 200 g tagatose, and 50 g fructose was solvated in 120 g water by gently heating the solution with rotary agitation using a rotary evaporator (Eyela, N-1200BS) to a temperature of 60° C. Isothermal batch crystallization was performed by pulling vacuum of the evaporation flask to a constant pressure of 100 mmHg, then slowly evaporating water from the flask under constant vacuum over a 270 min period. Once 20 ml of condensate had been collected, the experiment was paused briefly, 0.25 g of pure tagatose seed crystals were added to the flask, and then vacuum conditions were restored, and the evaporation was continued. Slow crystallization was observed. The experiment was continued until 80 ml condensate had been collected, after which the flask was quickly disconnected from the rotary evaporator and the slurry of mother liquor and crystals was quickly filtered via a Buchner funnel fitted with a cellulose filter. The collected crystals were washed with 62.5 g of ice-cold water, then dried under vacuum at 60° C. for 2 h. The final tagatose crystals contained 98.51 wt % tagatose and 1.49 wt % fructose, a significant improvement versus the feed mixture.
