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\hypersetup{pdftitle={Thin"=layer Drying Behaviour of Celery Leaves (Apium Graveolens L. Var. secalinum)},pdfauthor={Franz Román, Oliver Hensel},pdfsubject={Tropentag 2010: Abstract},pdfkeywords={Apium graveolens, celery leaves, CIELAB, thin-layer drying},pdfpagemode=None,colorlinks=true}
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\begin{document}
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\parbox[b]{13.4cm}{\centering \large{\textbf{Tropentag, September 14-16, 2010, Zurich}}\\[1ex] \Large{``World Food System  ---\\A Contribution from Europe''\\[2ex]}}
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\begin{center}
\Large{\textbf{Thin"=layer Drying Behaviour of Celery Leaves (Apium Graveolens L. Var. secalinum)\footnote{\textbf{Contact Address:} Franz Román, University of Kassel, Agricultural Engineering, Nordbahnhofstr. 1a, 37213~Witzenhausen, Germany, \mbox{e-mail}: \email{franz.roman@uni-kassel.de}}\\[0.8ex]}}
\normalsize{\textsc{Franz Román$^{1}$, Oliver Hensel$^{2}$}}
\end{center}
\begin{itemize*}
\item[]{\small{\textit{$^{1}$University of Kassel, Agricultural Engineering, Germany}}}
\item[]{\small{\textit{$^{2}$University of Kassel, Agricultural Engineering, Germany}}}
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\index[author]{Román, Franz}
\index[author]{Hensel, Oliver}
\begin{center}
\vspace{1.1cm}
\textbf{Abstract}
\begin{abstract}
\normalsize{
Leaf celery (Apium graveolens L. var. secalinum), is a celery variety in which the usable parts are the dark"=green, glossy leaves. They may be eaten fresh or processed, mainly frozen or dried.



In general leaves require less time and energy for drying than other parts of plants, which makes celery leaves more suitable for the drying process compared to the stalk or root parts commonly used in the other varieties.



In this study, thin"=layer drying experiments were carried out on celery leaves to determine the influence of air temperature and air humidity on the drying rate. A through"=flow laboratory dryer was used, in which air temperature, humidity and speed can be regulated. Drying temperatures studied were 20, 30, 40 and 50° C and relative humidities of 15, 30, 45 and \mbox{60\,\%}. The air flow was set at \unitfrac[0.2]{m}{s}. Additionally, trials were conducted  at 40 and 50° C with cut leaves to observe the effect of this pretreatment on the drying time. Since colour is an important quality factor for herbs and spices and the drying conditions may have an impact on it, the colour change resulting from each treatment was measured by means of the CIELAB coordinates using a Colorimeter.



Drying curves were obtained, showing an important effect of both temperature and relative humidity on drying rate. Unlike previous studies on other products, in which relative humidity had a negligible effect below 50 or \mbox{60\,\%}, in this case the effect was important throughout the range studied. Cutting the leaves reduced the drying time at 40° C, but not at 50° C. At temperatures of 40° C or less, although colour varied with respect to the fresh samples, the change was not very significant and the leaves remained green. Although at 50° C the drying time is drastically reduced, the CIELAB coordinates in the end product showed a pronounced change, which was confirmed visually as a detrimental brownish tone, for which this drying temperature or higher ones should be avoided. 



  











}

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\noindent \textbf{Keywords:} Apium graveolens, celery leaves, CIELAB, thin"=layer drying
\index[key]{Apium graveolens}
\index[key]{Celery leaves}
\index[key]{CIELAB}
\index[key]{Thin"=layer drying}
\end{document}