Submitted to: International Journal of Food Properties
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/27/2008
Publication Date: 1/1/2009
Citation: Gajula, H., Liu, S., Alavi, S., Herald, T., Tilley, M., Bean, S., Madl, R. 2009. Pre-cooked Fiber-enriched Wheat Flour Obtained by Extrusion: Rheological and Functional Properties. International Journal of Food Properties. 12:27-44. Interpretive Summary: Obesity is a major concern in the U.S. and globally, and the problem is reaching epidemic proportions. Consumption of dietary fiber has been recommended as a safe and practical approach for reduction of serum cholesterol and coronary artery disease. Extrusion cooking is widely used to modify functional properties, such as paste viscosity, water solubility and water absorption of cereal flours and starches. The purpose of this project was to examine the feasibility of utilizing extrusion technology for producing pre-cooked whole-wheat flours with increased functionality for baked products like cookies and tortillas at the same time having a reduced glycemic index. Significant differences in functional, rheological properties, and quality parameters of extruded wheat flour cookies and tortillas were observed. As the percent fiber content was increased, the quality parameters deteriorated for both non-extruded and extruded wheat flour cookies. No significant difference was observed in the rollability of non-extruded wheat flour tortillas whereas a significant difference was observed in extensibility values for extruded wheat flour tortillas.
Technical Abstract: Functional and rheological properties of different process conditions of extruded wheat flour with 0%, 10%, 20% and 30% fiber levels were studied in the production of cookies and tortillas. Functional and rheological properties were evaluated using Rapid Visco Analyzer and Mixograph equipment. Results showed that peak viscosity increased for the 20% fiber level of extruded wheat flour (123.1cP) and non-significant difference was shown for all other fiber level extruded wheat flour for lower process conditions and to non-extruded wheat flours. The pasting properties for the high processing treatment (treatments are explained above) were decreased from 98.2cP to 52cP with increasing fiber level content. Mixograph peak time was observed similar for all fiber levels in high processing extruded wheat flour and non-extruded wheat flour and decreased in low processing extruded wheat flour. Peak height (66.6cm) was higher in high processing extruded wheat flour as compared to low processing extruded wheat flour (26.8cm) and non-extruded wheat flour (44.6cm). Quality parameters including weight, height, width, width/thickness, spread factor, rollability, and extensibility were evaluated for cookies and tortillas made from pre-cooked wheat flour and compared with those of non-extruded wheat flour. As the percent fiber content was increased, the quality parameters deteriorated for both non-extruded and extruded wheat flour cookies. The deterioration was more significant in the high processing tortillas. No significant difference (p<0.05) was observed in rollability of non-extruded wheat flour tortillas whereas a significant difference (p<0.05) was observed in extensibility values for extruded wheat flour tortillas.