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Title: Waxy soft white wheat: extrusion characteristics and thermal and rheological properties

Author
item KOWALSKI, RYAN - Washington State University
item Morris, Craig
item GANJYAL, GIRISH - Washington State University

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2014
Publication Date: 4/27/2015
Publication URL: http://handle.nal.usda.gov/10113/60749
Citation: Kowalski, R.J., Morris, C.F., Ganjyal, G.M. 2015. Waxy soft white wheat: extrusion characteristics and thermal and rheological properties. Cereal Chemistry. 92:145-153.

Interpretive Summary: Extrusion is a common processing technique used in the food industry to produce direct snack food, cereal, and pet food. Extruded products are typically made by utilizing a raw material, often flour, and subjecting it to high temperatures while also creating a high shear environment using rotating screws. In this study soft white spring waxy wheat flour was compared to normal soft white wheat flour for its thermal properties and then both were extruded. After adjusting the screw profile to one with minimal mechanical energy, the waxy wheat was successfully extruded at low moisture and high screw speeds. The waxy wheat expanded much more than the normal wheat and its low energy requirements for extrusion processing were demonstrated. Waxy wheat may offer a unique solution to multiple problems in the food extrusion industry. The purpose of this study was to observe the differences in thermal properties and extrusion processing between a soft white waxy wheat flour and a commercial soft white wheat flour. If any specific benefits are identified in the extrusion processing of waxy wheat, it could find applications with numerous extruded products in the food industry.

Technical Abstract: Waxy wheat flour was analyzed for its thermal and rheological properties and extruded to understand its processing characteristics. Comparisons were made with normal soft white wheat flour to identify extrusion differences under the same conditions. The thermal and rheological properties through Rapid ViscoAnalyzer and DSC revealed the waxy wheat to have a higher gelatinization temperature, although it gelatinizes much quicker and with less thermal energy input. Preliminary extrusion experiments were conducted to determine the optimal screw profile for the waxy wheat. Extrusion experiments were then carried out with the optimum screw profile by varying flour moisture (15-25% w.b.) and extruder screw speed (200-400 rpm) while monitoring process conditions. Physical properties of the extrudates were then studied. The radial expansion ratios of the waxy wheat extrudates exceeded that of the normal wheat extrudates and it was observed that the waxy wheat flour took less energy to expand. The waxy wheat extrudates also exhibited significantly higher water solubility and less water absorption than the normal wheat extrudates. Our study shows that waxy wheat flour is a viable ingredient for creating direct expanded products using significantly less energy.