CONVECTIVE DRYING OF THE ROOT AND LEAVES OF THE PARSLEY AND CELERY

This paper shows the convective drying of the parsley and the celery (their roots and leaves). The root of the parsley and the celery are separately dried, and their leaves are separately dried, too. The temperature of the incoming air was 60 o C – 80 o C at both parts of the plants. The period of drying the root lasted 165 minutes, while the drying of the leaves took 75 minutes. Final results are compared in order to make the conclusion which parts of the plants are faster dried, and what are the reasons for that.


I n t r o d u c t i o n
Drying is the very old way of preserving food.People dried food in various ways.Today there are several procedures of drying the food.One of the most frequently used methods is the convective drying.The process of the convective drying is used in this research, and the results that are explained later in the text have been obtained after this procedure.What is relevant for the process of drying is to examine the method of work of the drying machine in which the process of drying is done.Every drying machine demands different inflow and circulation of the hot air.Prevailing influence on the process of drying has the air temperature (K r o k i d a et al., 2003).The air temperature determines the way of the drying of vegetables, because high temperatures can damage the material.
The convective drying of the roots and leaves of the parsley and the celery is done in this work.Their results are mutually compared.The purpose of this work is to show the change of the amount of moisture in the parsley and the celery, and to come to the conclusion why the leaves of the parsley and the celery are faster dried than the roots under the same conditions.

Material and Methods
The parsley and the celery belong to the group of tuberous vegetables, and they are very important for the nourishment of people; they have very important role.For those reasons in this work the parsley and the celery (the root and leaves) will serve as the material for the examination.
The name "parsley" comes from the Greek word "petros" which means "stone, rock" because it has grown on the slopes of the rocks.The parsley is rich with the vitamin C, carotene (pro-vitamin of the vitamin A), the vitamins of the B group (among which the greatest amount has the vitamin B12) and iron.It contains minerals Mn, Mg, Cu and the other ones.Because of the rich structure the parsley has the great appliance on keeping the health of the body and the organism, and it is greatly used in one's nourishment (A l e k s i c , 1984).
The celery also comes from the Greek territory.It is very rich with aromatic substances, about 40, it is also rich with carbon hydrates, salts K, Mg, Fe, albumens, pectin, fytoncides, aromatic oils, carotene, vitamin C, B1, B2, PP.With these very rich nutritive values the celery has found great appliance in food industry and health industry (A l e k s i c , 1984).What is characteristic for the celery and its preparation before drying is that the cleaned celery may be kept on air for only a short period of time, because there is the danger of fast darkening.
The process of drying the root and leaves of the parsley, so as the drying of the root and leaves of the celery is done in the laboratory of the Technological faculty in Leskovac.Three measurements have been done for drying the root and leaves of the parsley, and for the celery, too.Drying conditions were the same.The temperature of the incoming air for both plants was 60 -80 o C. The mass of both, the parsley and the celery, (the root) for all three measurements was at the beginning 250 g.The mass of vegetables on hurdles was 50 g.The time of selection, i.e. the measuring of the mass was done in 6 partial periods of 15, 45, 75, 105, 135 and 165 minutes and they were the same for all series.The amount of moisture of the root of the parsley and the celery was 89%.The parsley and the celery have been dried until they reach the amount of moisture of 4-6%.
For drying the leaves of the parsley the whole mass was 400 g, while the mass of the leaves of the celery was 200 g, and the mass of samples of leaves without stalks on hurdles was 20 g.Three measurements were done for the leaves of the parsley, and one measurement for the leaves of the celery.The time of selection, i.e. the measuring of the mass was done in 3 partial periods of 15, 45 and 75 minutes.The temperature of the incoming air was the same, 60 -80 o C. The amount of moisture of parsley's leaves was 82%, while the amount of moisture of celery's leaves was 87%.
The process of drying was done in the experimental drying machine of the convective type.The drying machine has a rectangular shape, and it has been made of zinced sheet iron, with 5 hurdles.It is a vertical type of the drying machine, with the flow of the air from the heater, and it is separated on 5 hurdles (frames that are made of laths and iron web).There is the movable bonnet on the drying machine itself which decreases the loss of moisture from the product.The working medium is the hot air which comes from the heater which is placed at the bottom of the drying machine.The method of drying in the convective type of the drying machine is such that hot and dry air is brought by the ventilator to a layer of the material which is going to be dried.In that way the air heats the surface of fruits, thus making the necessary conditions for the evaporation of water.Air comes above that surface and takes away the evaporated water, it becomes colder and wetter, while the products become warmer and with the smaller amount of water (Z l a t k o v i c , 2003).
The experimental part that is done in this work is based on: periodical change of the arrangement of hurdles on every 30 minutes, with the simultaneous control of the change of a mass, inletting and outletting temperature, and with defining the amount of moisture of a dry substance.During the work the aim was to check the temperature at the outlet of the drying machine, so as to measure the period of drying and the mass of the given materials.
The statistical analysis of these pieces of information is presented in the model of the polynomic dependence by using the program Origin Version 4.0.

Results and Discussion
The results of drying the root and leaves of the parsley and the celery are shown in the Table 1 and 2, while the graphical representations of these results are in the Pictures 1, 2, 3, 4 and 5.
Tab. 1. -The representation of the change of a mass (g), depending on the time of the treatment with the hot air while drying the root of the parsley and the celery.

time, min
The parsley-root The According to the experimental results that are presented in the chart 1, the amount of moisture while drying the root of the parsley and the celery is determined.The amount of moisture is graphically presented in the Pictures 1 and 2. According to the results that are presented in the Pictures 1 and 2, where the change of the amount of moisture is overlooked depending on the period of treating with the hot air by using the analysis of the morphological structure from the literature, one can come to the conclusion that the parsley and the celery are energetically dried.At the beginning of the drying in the intervals of 15, 45 and 75 minutes, we have the oscillations which are, above all, the cause of the nonstationary heating of vegetables.In time intervals 105, 135, and 165 minutes we have a small decrease of the percent of moisture until it reaches one constant value, which later shows the dryness.(V a l e n t, 2001) What is relevant to point out is that the raw materials were not bleached neither treated with the antioxidants before drying, and that their color matches with the color of the raw samples.
In the Picture 2, for the case the celeryroot, at the first phase of drying it is recommended the use of the maximum air temperature, in order to dry the surface of the material in the fastest way and to avoid the influences of oxidation.At further stages the drying is usual, gradual slowing of the rate of drying, in order to avoid making the hard crust on the surface.The same procedure is also used with drying the parsley -root Picture 1.
Tab. 2. -The representation of the change of a mass (g), depending on the period of a treatment with heated air while drying the leaves of the parsley, and the celery, too.If you compare the results from drying the leaves of the parsley and from drying the leaves of the celery (Table 1 and 2), you can come to the conclusion that you need twice less time for the drying of leaves than for the drying of roots.It is the logical conclusion because leaves have a simpler structure comparing to the structure of the roots which have a large number of fibres that demand longer drying.From the Table 2 we can see that only two completely identical measurements were done, so it was not necessary to note down the third measurement, because all other measurements under the same conditions gave the same results.Pictures 3 and 4 represent the graphical results of the change of the amount of moisture (%), and those results are got from the experimental results in the Table 2.In the Picture 3 the drying of the leaves of the parsley is presented, depending on the period of drying, and one can notice, if compares with the period of drying the leaves of the celery (Picture 4), that the parsley is faster dried, and it faster loses water, and the explanation for that is that the leaves of the parsley are thinner than the leaves of the celery.The Picture number 5 gives the parallel representation of the change of moisture of the leaves of the parsley and of the leaves of the celery.

C o n c l u s i o n
With the convective drying of the roots and leaves of the parsley and celery one can come to the conclusion that leaves are faster dried than roots.This is the logical conclusion because the structures of the leaves and the roots are different.According to the morphological structure, the roots are thicker and have strong, fat fibres and they also have a hard crust, so it is necessary to provide a longer period of drying.Apart from that, leaves have thin structure and thin fibres, and for that reason, they are faster dried.The hot air faster goes through the leaves, thus making the leaves to lose moisture in a faster way.

R E F E R E N C E S
The change of the amount of moisture (%) with the period of time, for the case the celeryroot for all three measurements The change of the amount of moisture (%) with the period of time, for the case the parsleyroot for all three measurements

- 4 .
The change of the amount of moisture (%), during a period of time, for the case the parsley -leaves, for all three measurements -The change of the amount of moisture (%), during a period of time, for the case the celery-leaves for two measurements

Picture 5 .
-The parallel representation of the middle values of the change of moisture (%) depending on the period of a treatments with the heated air for the leaves of the parsley and the celery.

1 .
A l e k s i c , M. (1984): Knowing the materials, pp.182-186, University in Nis, Technological faculty in Leskovac 2. Z l a t k o v i c , B. (2003): Technology of processing and preserving fruits, pp.104 -107, The Faculty of Agriculture, Belgrade -Zemun 3. Group of authors, redactor Petar V., (1982): The handbook for the industrial processing of the dried fruits and vegetables, pp. 25 -50, Belgrade