Cereal Chem. 73 (5):625-627  |  VIEW ARTICLE

Miscellaneous

Stability of Uric Acid Used as an Indicator of Insect Contamination During Extrusion of Wheat Flour (1).

A. R. Ghaedian (2) and R. L. Wehling (2,3). (1) Published as Paper no. 11375, Journal Series, Agricultural Research Division, University of Nebraska, Lincoln, NE 68583-0704. (2) Department of Food Science and Technology, 143 Filley Hall, University of Nebraska, Lincoln, NE 68583-0919. (3) Author o whom correspondence should be addressed. Accepted June 12, 1996. Copyright 1996 by the American Association of Cereal Chemists, Inc. 

To determine the stability of uric acid during extrusion, wheat flours were spiked with uric acid such that the samples had a uric acid content of approximately 25 µg of uric acid per gram of flour. The samples were then extruded on a Brabender single-screw extruder at feed moisture contents of 28, 30, and 32% (db) and temperatures of 120, 140, and 160°C. Uric acid in the extrudates was quantified by reversed-phase high-performance liquid chromatography, using ion-pairing with tetrabutylammonium phosphate and ultraviolet detection. It was found that 62-80% of the uric acid in flour survived extrusion, depending on the extrusion conditions. On average, about 72% of the uric acid initially present was retained in extruded wheat flour. This high recovery level indicates that uric acid is relatively heat stable and could be used as an indicator of insect contamination in extruded products.