Starch extrudates are currently an important industrial process, resulting in a product with a cellular foam structure that can be used for diverse applications [1]. Numerous studies have been done to understand expansion in extruded products [2]. A common theme is an incomplete understanding of what happens to a cross section of extrudate upon the release of pressure. However, experimental studies are frequently inconvenienced by the lack of suitable methods [3] to capture the phenomena as it happens inside the mass of expanding liquid.

In this research, experimental analysis of the lateral expansion of a thin section of dough as well as growth of bubbles inside the cross-section is performed. The dough was initially saturated with CO2 generated through fermentation and subjected to a high CO2 pressure before sudden release. The effect of various conditions affecting the expansion like initial concentration of dissolved CO2, CO2 pressure, section thickness, temperature and moisture content are studied. A better understanding of extrudate expansion is expected through a modeling of the lateral growth of the dough section. In addition, the experimental procedure developed is expected to assist further research in lateral expansion during related processes like baking [4-6], which has attracted little research.

References

1. Wang L, Ganjyal GM, Jones DD, Weller CL and Hanna MA (2005) Modeling of Bubble Growth Dynamics and Nonisothermal Expansion in Starch-Based Foams During Extrusion Advances in Polymer Technology 24 1 29–45

2. Moraru CI and Kokini JL (2003) Nucleation and Expansion During Extrusion and Microwave Heating of Cereal Foods Comprehensive Reviews in Food Science and Food Safety 2 120-138

3. Elmehdi HM, Page JH and Scanlon MG (2003) Monitoring Dough Fermentation using Acoustic Waves, Transactions of the Institution of Chemical Engineers 81(C) 217-223

4. Lee S and Inglett GE (2006) Rheological and physical evaluation of jet-cooked oat bran in low calorie cookies International Journal of Food Science and Technology 41 553–559

5. Zoulias E, Oreopoulou V and Kounalaki E (2002) Effect of fat and sugar replacement on cookie properties Journal of the Science of Food and Agriculture 82 1637–1644

6. Swanson RB, Carden LA and Parks SS (1999) Effect of a carbohydrate-based fat substitute and emulsifying agents on reduced-fat peanut butter cookies Journal of Food Quality 22 19–29