CRYOCONCENTRATION OF VOLATILE COMPOUNDS I N WATER - A STUDY ON A MODEL AQUEOUS-SOLUTION

Vacuum distillation is a safe and powerful way to extract flavour comp ounds from food. Cryoconcentration of this vacuum distillate allows a gentle concentration of volatile compounds while avoiding thermal degr adation and the use of solvents. The resulting concentrate is, moreove r, perfectly suitable for a sensory analysis after incorporation into a neutral medium. Cryoconcentration involves crystallization of a frac tion of the water, and separation of the crystals from the liquid phas e containing the dissolved flavour compounds. The present experiment a imed to determine the best conditions to cryoconcentrate, on the labor atory scale, an aqueous model solution simulating a distillate. Three final levels of ice (0.5, 0.7, and 0.9 of the initial weight of the so lution), and three different programs for temperature of freezing (a c onstant temperature of -2.6 degrees C, a temperature decreasing at a r ate of -1 degrees C.h(-1), or -5 degrees C.h(-1)) were tested. At a fi nal level of crystallized water equal to 0.9 of the initial weight of the water, the recovery of all volatile compounds experimental was hig her than 75%, corresponding to a final concentration factor of 8.