AN INNOVATIVE PROCESS FOR SEPARATING WHEAT FLOUR INTO GLUTEN AND STARCH

An innovative process for separation of gluten and starch in a concentrated medium is presented. The process is based on the use of simple shear flow in a cone-and-cone device. The main objective of this study was to introduce a new mechanism for separating wheat flour into starch and gluten based on shear-induced migration of gluten. We also report on the effect of shearing time on the total protein concentration and the physical properties of glutenin macro-polymer (GMP) at different locations of the shearing device. It was concluded that at the moisture content used, shearing for 80 min yielded an optimum separation. At either very short or very long shear processing, separation did not occur or diminished. The wheat dough was separated into a protein-poor fraction, containing less than 4% protein, and a protein-rich fraction containing almost 50% protein on dry weight basis. The separation was achieved in two steps. Initially, shear-induced local segregation of gluten and starch into larger gluten patches occurred, followed by migration of the large gluten patches toward the apex of the cone. Obviously, the local gluten patches should have a minimum size before they are sufficiently influenced by inward forces to induce the large-scale separation. Too long processing led to redistribution of the gluten throughout the system. This effect can be explained by the fact that prolonged shearing influences the visco-elastic properties of the gluten negatively and thereby the driving force for separation. However, under the process conditions used, upon a very long shearing a redistribution of the aggregated gluten structures in the starch phase was observed, demonstrating a processing limit for the separation performance. Compared to traditional processing, the separation process presented shows opportunities for producing high quality gluten accompanied with significant water savings. Considering the fact that simple shear flow in steady rate is less harmful to gluten quality, such a separation process could benefit gluten quality.

Keywords:

Gluten , Starch , Flour , Separation , Shear