Studying mixing in Non-Newtonian blue maize flour suspensions using color analysis.
BACKGROUND
Non-Newtonian fluids occur in many relevant flow and mixing scenarios at the lab and industrial scale. The addition of acid or basic solutions to a non-Newtonian fluid is not an infrequent operation, particularly in Biotechnology applications where the pH of Non-Newtonian culture broths is usually regulated using this strategy.


RESULTS
We conducted mixing experiments in agitated vessels using Non-Newtonian blue maize flour suspensions. Acid or basic pulses were injected to reveal mixing patterns and flow structures and to follow their time evolution. No foreign pH indicator was used as blue maize flours naturally contain anthocyanins that act as a native, wide spectrum, pH indicator. We describe a novel method to quantitate mixedness and mixing evolution through Dynamic Color Analysis (DCA) in this system. Color readings corresponding to different times and locations within the mixing vessel were taken with a digital camera (or a colorimeter) and translated to the CIELab scale of colors. We use distances in the Lab space, a 3D color space, between a particular mixing state and the final mixing point to characterize segregation/mixing in the system.


CONCLUSIONS
Blue maize suspensions represent an adequate and flexible model to study mixing (and fluid mechanics in general) in Non-Newtonian suspensions using acid/base tracer injections. Simple strategies based on the evaluation of color distances in the CIELab space (or other scales such as HSB) can be adapted to characterize mixedness and mixing evolution in experiments using blue maize suspensions.
Centro de Biotecnología-FEMSA, Tecnológico de Monterrey, Monterrey, Nuevo León, México; Centro de Investigación y Desarrollo de Proteínas (CIDPRO), Tecnológico de Monterrey, Monterrey, Nuevo León, México.
Grissel
G
Trujillo-de Santiago
Departamento de Ingeniería en Biotecnología, Tecnológico de Monterrey, Tlalpan, Distrito Federal, México.
Cecilia
C
Rojas-de Gante
Centro de Biotecnología-FEMSA, Tecnológico de Monterrey, Monterrey, Nuevo León, México.
Silverio
S
García-Lara
Centro de Biotecnología-FEMSA, Tecnológico de Monterrey, Monterrey, Nuevo León, México.
Adriana
A
Ballescá-Estrada
Centro de Biotecnología-FEMSA, Tecnológico de Monterrey, Monterrey, Nuevo León, México.
Mario Moisés
MM
Alvarez
D003116:Color; D005433:Flour; D012212:Rheology; D013535:Suspensions / Q000737:chemistry*; D003313:Zea mays / Q000737:chemistry*
D013535:Suspensions