Publications in year 2016

Vol. 23, Issue 4



Sorption properties of selected species of rice

International Agrophysics
Year : 2016
Volumen : 23
Issue : 4
Pages : 681 - 694
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Authors: Zbigniew Pałacha1, Aleksandra Sas1

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

In the study presented in the paper water adsorption and desorption isotherms were determined for selected species of rice at 25°C over a range of water activity from 0.113 to 0.932 (adsorption) and from 0.810 to 0.113 (desorption) by static gravimetric method. The study used long-grain white rice, brown, red, black and parboiled. The water adsorption and desorption isotherms of the tested species of rice had a course compatible with type II of isotherms according to the Brunauer classification. For the description of the water adsorption and desorption isotherms the Oswin, GAB, Lewicki and Peleg models were used. The GAB, Lewicki and Peleg models gave very good fit to the experimental sorption data. The calculated root mean square error (RMS) did not exceed 6.5%. All isotherms show hysteresis loop, while the highest hysteresis loop characterised parboiled rice and the smallest – black rice. The water content in the monolayer determined in the GAB model was higher than the desorption process in adsorption for all species of rice. White rice had the highest water content in the monolayer in both processes (7.182 g water 100 g–1 d.m. – adsorption; 11.162 g water 100 g–1 d.m. – desorption). The largest specific surface area was noted for the white rice (254.7 m2 g–1 d.m.) while parboiled rice had the smallest value of that parameter (158.0 m2 g–1 d.m.).

Keywords : rice, adsorption and desorption isotherms, sorption hysteresis
Language : polish