Analiza kinetyki sublimacyjnego suszenia liści lubczyku ogrodowego (Levisticum officnale Koch.)

Celem przeprowadzonych badań była ocena wpływu temperatury i ciśnienia podczas sublimacyjnego suszenia liści lubczyku ogrodowego na kinetykę procesu. Zamrożone w całości liście lubczyku suszono sublimacyjnie w temperaturach: 20°C, 45°C, 70°C oraz pod ciśnieniem 30 Pa i 198 Pa. Proces suszenia przeprowadzono w suszarce sublimacyjnej Alpha 1-4 firmy Christ o jednostronnym, kontaktowym sposobie dostarczania ciepła. Kinetykę suszenia oznaczono na podstawie ubytku masy próbek, a następnie opisano modelami matematycznymi. Stwierdzono, że czas sublimacyjnego suszenia liści lubczyka ogrodowego zmieniał się w zależności od wartości parametrów procesu. Wzrost temperatury liofilizacji z 20°C do 70°C powodował ponad dwukrotne skrócenie czasu suszenia, niezależnie od zastosowanego ciśnienia. Ponadto stwierdzono, że w całym zakresie zmienności temperatury, czas suszenia ulegał skróceniu wraz ze wzrostem ciśnienia w komorze liofilizatora. Kinetykę sublimacyjnego suszenia liści lubczyku najdokładniej opisuje model Page, z wyjątkiem procesu suszenia w temperaturze 45°C, przy ciśnieniu 198 Pa, który najlepiej odwzorowuje model logarytmiczny.

The traditional use of lovage (Levisticum officinale Koch.) in different diseases has been thoroughly documented in several publications. It is a well-known aromatic plant that has been commonly used in foods, flavorings, and medicinal preparations. The aim of the work was the evaluation of drying temperature and pressure in the freeze-drying chamber on the lyophilization kinetics of loveage garden leaves. The material for the study were fresh lovage leaves from an industrial plantation. Whole healthy leaves with the same degree of vegetative maturity were frozen for 24 hours at a temperature of –30°C, in convection-free conditions. The freeze-drying process was performed in ALPHA 1-4 freeze-dryer (Martin Chrits Company) equipped with one-sided contact heat supply system. The frozen samples of leaves were put on the heating plates and freeze-dried at 20°C, 45°C, 70°C, and with a pressure 30 Pa and 198 Pa. During the process the changes of leaves mass were recorded after each 60 seconds using weight balance with the accuracy 0.01 g. The drying process was stopped when the moisture of sample reach about 5% (wb.). The experiment was performed in triplicate. Based on the measurements of mass loss taken in the course of the experiment, drying curves were charted as functions of water ratio (MR) versus time. During the determination of MR, the value of equilibrium water content was omitted. With a view to selecting the most appropriate mathematical equation for the description of the freeze-drying of lovage leaves, six potential equations commonly mentioned in literature were examined. Measurement scores were subjected to an analysis of variance. When significant differences in were detected, the means were compared using Tukeys test. Statistical analysis was performed at a significance level of significance level of α = 0.05 using Statistica 10.0 by Statsoft. A regression analysis was also performed. The coefficient of determination R², root mean square error (RMSE), and the reduced χ² values were calculated. The results of regression analyses for the six considered models showed that each of the was characterized by a good fit for the experimental data. Specifically, all the calculated R² values fell in the 0.983–0.999 interval, whereas the RMSE changed from 0.0123 to 0.0002, and the value of reduced χ² not exceed 0,00016. The Page model provided in the most cases the best fit to the experimental data. Besides, the results revealed that an increase of heating plates temperature and the pressure in the drying chamber significantly decreased the time of freeze-drying.