Czech J. Food Sci., 2009, 27(2):88-94 | DOI: 10.17221/170/2008-CJFS

Influence of process parameters and pre-treatments on quality and drying kinetics of apple samples

Stela JOKIĆ, Darko VELIĆ, Mate BILIĆ, Jasmina LUKINAC, Mirela PLANINIĆ, Ana BUCIĆ-KOJIĆ

Department of Process Engineering, Faculty of Food Technology, University J. J. Strossmayer of Osijek, Osijek, Croatia

The aim of this research was to determine the influence of the process parameters and pre-treatment methods on the quality and drying kinetics of apple samples of the Florina variety using standard analytical methods: thermo-gravimetry, rehydration, colorimetry. The Apple samples were dried in a laboratory tray drier at different temperatures (50, 60, and 70°C), airflow velocities (1.5 m/s and 2.75 m/s), and pre-treatment methods (dipping in 0.5% ascorbic acid solution; 0.3% L-cysteine solution; 0.1% 4-hexyl resorcinol solution; 0.5% sodium metabisulfite solution; mixed solution of 0.05% 4-hexyl resorcinol and 0.5% sodium metabisulfite; blanching in hot water at 85°C). According to the drying time, rehydration and colour characteristics, the optimal drying parameters found were: temperature of 60°C and airflow velocity of 2.75 m/s. The drying kinetic equations were estimated using Page's mathematical model. The results of the estimation showed a good agreement with the experimental data. The best results were achieved when the samples were pre-treated with 4-hexyl resorcinol. Blanching in hot water resulted in a higher drying rate and higher rehydration ratio, but also in unacceptable changes in the colour appearance of the apple samples.

Keywords: drying kinetics; convection drying; apple; pre-treatment; rehydration; colour

Published: April 30, 2009  Show citation