Publications in year 2013

Vol. 20, Issue 4



Mechanical and sorption properties of two-stage dried apples

International Agrophysics
Year : 2013
Volumen : 20
Issue : 1
Pages : 195 - 205
  PDF 176.4 KB
Authors: Magdalena Śledź1, Małgorzata Nowacka1, Artur Wiktor1, Magdalena Selke1, Dorota Witrowa-Rajchert1

1Department of Food Engineering and Process Management, Faculty of Food Science, SGGW – Warsaw University of Life Sciences ul. Nowoursynowska 159C, 02-776 Warszawa
Abstract :

The purpose of the study was the analysis of texture and the water adsorption properties of two-stage dried apples: microwave-convective with convective finishing drying method, and convective with microwave-convective finishing drying technique. In the first stage apples with a water content of 30 or 50% were obtained, afterwards they were dried in the second stage until equilibrium water content was reached. Convective drying was carried out at the temperature of 70°C and air velocity 2.5 m s-1, while during microwave-convective drying the following parameters were applied: microwave power 300 W, air temperature 40°C and air velocity 3.5 m s-1. In order to analyse the mechanical properties, the cutting test was performed. Sorption properties were determined based on the mass changes of dried apples kept for 72 hours in an exsiccator over saturated NaCl solution (in an environment with aw= 0.75). The method of two-stage drying significantly influenced the mechanical and sorption properties of apples. The maximum cutting force and cutting work fell in ranges of 159-222 N and 178-290 mJ, respectively. The relative mass gain after 72 hours amounted to 11-24%, depending on the drying method. The highest values were obtained for microwave-convective dried apples with convective finishing drying from 50% of water content. In turn, materials dried using the convective technique and the microwave-convective with convective finishing drying method (from 30% of water content) were characterised by significantly lower values of maximum cutting force and cutting work, as well as value of water vapour adsorption.

Keywords : apple, two-stage drying, microwave-convective drying, convective drying, mechanical properties, sorption properties
Language : Polish