US EPA

4957430 

Journal Article 

Pore formation in apple during air-drying as a function of temperature: porosity and pore-size distribution 

Rahman, MS; Al-Zakwani, I; Guizani, N 

2005 

1 

Journal of the Science of Food and Agriculture
ISSN: 0022-5142
EISSN: 1097-0010 

85 

6 

979-989 

10.1002/jsfa.2056 

WOS:000228405900014 

Characteristics of air-dried apple produced by drying at 50, 80 and 105 degrees C were studied by measuring apparent porosity, open pore porosity and pore-size distribution with a helium gas pycnometer and mercury porosimetry. Apparent porosity increased with the decrease of moisture content as well as with the increase of drying temperature. Fresh apple showed negligible closed pores, whereas drying caused collapse of surface pores, and consequently reduced open pores. Pore-size distribution for fresh apple showed two sharp peaks, one at 5.8 mu m and another at 3.6 mu m. Apple rings, dried for 20h, showed only one sharp peak at 3.6 mu m while samples dried for 30h showed three peaks, at 10, 5.8 and 3.6 mu m, respectively. Application of high pressure (0.12-414MPa) resulted on negligible intrusion of mercury into the sample. Fractal analysis indicated the formation of more micro-pores on the surface caused by air-drying. (c) 2005 Society of Chemical Industry. 

air drying; porosity; density; fractal dimension; shrinkage; hysteresis; apple