ARS | Publication request: PHYSICOCHEMICAL PROPERTIES OF STARCH IN EXTRUDED RICE FLOURS

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 2002
Publication Date: August 1, 2002
Citation: Kadan, R.S., Pepperman, A. 2002. Physicochemical properties of starch in extruded rice flours. Cereal Chemistry. 79(4):476-480.

Technical Abstract: The effects of extruding temperatures and subsequent drying conditions on X-ray diffractionpatterns (XRD) and differential scanning calorimetry (DSC) of long grain (LG) and short grain (SG) rice flours were investigated. The rice flours were extruded in a twin-screw extruder at 70-120degreesC and 22% moisture, and either dried at room temperature, transferred to 4degreesC for 60 hr, or frozen and then dried at room temperature until the moisture was 10-11%. The dried materials were milled without the temperature increasing above 32degreesC. XRD studies were conducted oil pellets made from extruded and milled flours with particle sizes of 149-248 mum DSC studies were conducted from the same material. DSC studies showed that frozen materials retrograded more than the flours dried at room temperature. The LG and SG samples had two distinct XRD patterns. The LG gradually lost its A pattern at >100degreesC, while acquiring V patterns at higher temperatures. SG gradually lost its A pattern at 100degreesC but stayed amorphous at the higher extruding temperatures. DSC analysis showed that retrograded flours did not produce any new XRD 20 peaks, although a difference in 20 peak intensities between the LG and SG rice flours was observed. DSC analysis may be very sensitive in detecting changes due to drying conditions, but XRD data showed gradual changes due to processing conditions. The gradual changes in XRD pattern and DSC data suggest that physicochemical properties of the extruded rice flours can be related to functional properties.