The aim of this work has been to assess the influence of freeze drying parameters, i.e. the pressure in the drying chamber and temperature of the heating panel of the sublimation dryer on the change of colour coordinates of dried celery leaves. In the research the leaves of Apium graveolens L were used. The drying process was conducted in a freeze dryer with a one-sided contact way of providing heat, in temperature range between 20–70°C and under the pressure of 30 Pa, 63 Pa, 125 Pa, 198 Pa. The measurement of colour was conducted according to the reflective method with the use of spherical spectrofotometer X-Rite 8200. The colour coordinates were marked according to the CIElab system. A significant influence of the temperature of the heating panels and pressure in the drying chamber on the change of parameters L*, a* and b* of dried celery leaves was found. The change of colour was assessed on the basis of the difference in colour saturation (C*) and tone (h*). The smallest difference in colour saturation and tone in comparison to fresh leaves was recorded in dried material kept in the temperature of 20°C on each of the pressure levels. Due to a small range of colour coordinates, the method of freeze drying should be regarded as conservative because of this qualitative feature.

9-17