Expansion mechanism of extruded foams supplemented with wheat bran

Abstract Addition of bran reduces the expansion of extruded starchy foams. This may be attributed to changes in parameters driving expansion. Wheat flour was supplemented with wheat bran to achieve two levels of fibers (12.6% and 22.4%) and extruded under different conditions of barrel temperature (120 or 180 °C), water content in the feed (18% or 22%) or screw speed (400 or 800 rpm). Increasing the bran concentration decreased sectional and volumetric expansions and increased longitudinal expansion. Finer cellular structures consisting of an increased number of small cells with more spherical shapes were generated. This may be linked to an increased nucleation at the die. The reduction in volumetric expansion was associated with an increase in shear viscosity only at the highest bran concentration. At same extrusion conditions the glass transition temperature of starch was reduced by down to 15 °C by supplementation with bran. This may induce a decrease in the viscosity of the starch phase and counteract the matrix viscosity increase linked to the properties of bran. A higher surface porosity was observed in the bran containing recipe due to earlier burst of the bubbles during growth.

[1]  Tung-Ching Lee,et al.  Effect of Cysteine on the Functional Properties and Microstructures of Wheat Flour Extrudates , 1996 .

[2]  Margaret A. Brennan,et al.  Effect of inclusion of soluble and insoluble fibres into extruded breakfast cereal products made with reverse screw configuration , 2008 .

[3]  J. M. Harper,et al.  A General Model for Expansion of Extruded Products , 1988 .

[4]  S. Palzer,et al.  Starch transformation in bran-enriched extruded wheat flour , 2011 .

[5]  J. Kokini,et al.  A generalized theory linking barrel fill length and air bubble entrapment during extrusion of starch , 2002 .

[6]  John R. Mitchell,et al.  A computer simulation of the dynamics of bubble growth and shrinkage during extrudate expansion , 1994 .

[7]  S. Yanniotis,et al.  Effect of pectin and wheat fibers on quality attributes of extruded cornstarch , 2007 .

[8]  F. Hsieh,et al.  Expansion of corn extrudates containing dietary fiber: a microstructure study. , 1990 .

[9]  B. Launay,et al.  Twin-screw extrusion cooking of starches: Flow behaviour of starch pastes, expansion and mechanical properties of extrudates , 1983 .

[10]  J. Bouvier,et al.  Corn Grits Particle Size and Distribution Effects on the Characteristics of Expanded Extrudates , 1998 .

[11]  S. Palzer,et al.  Adjustable Twin‐Slit Rheometer for Shear Viscosity Measurement of Extruded Complex Starchy Melts , 2010 .

[12]  Jean-François Martin,et al.  Training and Sensory Judgment Effects on Mastication as Studied by Electromyography , 1998 .

[13]  S. Leung.  Mechanisms of Cell Nucleation, Growth, and Coarsening in Plastic Foaming: Theory, Simulation, and Experiment , 2010 .

[14]  Narpinder Singh,et al.  A comparison of wheat starch, whole wheat meal and oat flour in the extrusion cooking process , 1997 .

[15]  R. Hoseney,et al.  High-temperature short-time extrusion cooking of wheat starch and flour. II. Effect of protein and lipid on extrudate properties. , 1982 .

[16]  G. D. Valle,et al.  Relations between rheological properties of molten starches and their expansion behaviour in extrusion , 1997 .

[17]  J. Bouvier,et al.  Die design and dough expansion in low moisture extrusion-cooking process , 1996 .

[18]  Francis G. Giesbrecht,et al.  Planning, construction, and statistical analysis of comparative experiments , 2005 .

[19]  James S. Taylor,et al.  Ideal copolymers and the second‐order transitions of synthetic rubbers. i. non‐crystalline copolymers , 2007 .

[20]  Guy Della Valle,et al.  Extrusion, structure and mechanical properties of complex starchy foams. , 2010 .

[21]  L. Salvo,et al.  X-ray tomography study of the cellular structure of extruded starches and its relations with expansion phenomenon and foam mechanical properties , 2007 .

[22]  G. D. Valle,et al.  A specific slit die rheometer for extruded starchy products. Design, validation and application to maize starch , 1993 .

[23]  M. Hanna,et al.  Relationship between viscosity and expansion properties of variously extrusion-cooked corn grain components* , 1990 .

[24]  B. Bouchet,et al.  Individual contribution of grain outer layers and their cell wall structure to the mechanical properties of wheat bran. , 2003, Journal of agricultural and food chemistry.

[25]  S. Palzer,et al.  Online shear viscosity measurement of starchy melts enriched in wheat bran. , 2011, Journal of food science.

[26]  P. Rüegsegger,et al.  A new method for the model‐independent assessment of thickness in three‐dimensional images , 1997 .

[27]  Chi-Tang Ho,et al.  Food Extrusion Science and Technology , 1991 .

[28]  R. Landel,et al.  The Temperature Dependence of Relaxation Mechanisms in Amorphous Polymers and Other Glass-Forming Liquids , 1955 .

[29]  O. Campanella,et al.  Importance of extensional rheological properties on fiber-enriched corn extrudates , 2009 .

[30]  J. Blanshard,et al.  Food Structure: Its Creation and Evaluation , 1988 .

[31]  R. Parker,et al.  Aspects of the glass transition behaviour of mixtures of carbohydrates of low molecular weight. , 1990, Carbohydrate research.

[32]  J. Bouvier,et al.  Effect of Ingredients on Physical/Structural Properties of Extrudates , 1990 .