ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Physical and Chemical Changes during Microwave Drying of Rice

J. Kaasová, P. Kadlec, Z. Bubník, B. Hubáčková, and J. Příhoda

Institute of Chemical Technology, Department of Carbohydrate Chemistry and Technology, CZ-166 28 Prague

E-mail: jitka.kaasova@vscht.cz

Received: 11 April 2001

Abstract: Microwave drying of soaked rice was studied and compared with the conventional drying process. Soaked rice was treated in microwave oven at different processing microwave energy levels, initial moisture contents, and temperatures. The maximum value of drying rate for conventional hot air drying is up to 50 times lower than the rate observed for microwave drying. Amylographic gelatinization and pasting characteristics were used for the evaluation of microwave treatment influence on chemical and physicochemical characteristics of rice, parameters such as damaged and total starch content and water sorption capacity at 70ºC. It was found that microwave treatment did not affect the total starch content in rice, but the damaged starch content increased with the absorbed microwave energy and temperature of treatment, chiefly for the moisture content of 30 % and temperature of 100ºC. Amylographic characteristics and water sorption capacity showed minimal changes resulted from microwave drying of rice with the moisture content lower than 23 %. Compared to conventional drying, the course of rice microwave treatment was much faster and the main physical and chemical characteristics of rice were not changed.

Full paper in Portable Document Format: 561a32.pdf

Chemical Papers 56 (1) 32–35 (2002)