Publication no. C-1997-0201-02R |  VIEW ARTICLE

Changes in Water Absorption and Swollen Volume in Extruded Alkaline Peroxide Pretreated Rice Hulls.

M. A. Larrea (1), M. V. E. Grossmann (1,2), A. P. Beléia (1), and D. Q. Tavares (3). (1) Londrina State University Food Science Department. Caixa Postal 6001 - 86051-970 - Londrina, PR, Brazil. (2) Corresponding author. E-mail: <victoria@npd.uel.br> (3) Campinas State University. Department of Nutrition. Caixa Postal 6001 - 13081-970 - Campinas, SP, Brazil. Cereal Chem. 74(2):98-101. Accepted December 23, 1996. Copyright 1997 by the American Association of Cereal Chemists, Inc.

Rice hulls were pretreated with an alkaline (pH 11.5) solution of hydrogen peroxide (1%) and then extruded. Pretreatment of rice hulls (4% db) at 50°C for 12 hr promoted 94.4% silica reduction, caused lignin solubilization and increased water absorption index (54%) and swollen volume (44%). The effects of temperature (125, 175, and 225°C), moisture content (25, 30, and 35%) and screw speed (120, 140, and 160 rpm) on water absorption and swollen volume of rice hulls fiber were evaluated after extrusion in a single-screw extruder. Operational conditions that produced the most modified product with regard to the functional properties were: 125°C, 35% moisture, and 120 rpm. Extruded fiber had a water absorption index 95% higher and swollen volume 138% higher than the unprocessed material. Microscopic examination showed a slight effect on the hulls epidermis after pretreatment, while extrusion promoted cellular structure disruption.