Studying mixing in Non-Newtonian blue maize flour suspensions using color analysis

• Published in: PloS one Vol. 9; no. 11; p. e112954
• Main Authors: Trujillo-de Santiago, Grissel, Rojas-de Gante, Cecilia, García-Lara, Silverio, Ballescá-Estrada, Adriana, Alvarez, Mario Moisés
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 17.11.2014; Public Library of Science (PLoS)
• Subjects: Acids; Analysis; Anthocyanins; Biotechnology; Blood vessels; Broths; Color; Computational fluid dynamics; Corn; Digital cameras; Engineering and Technology; Evolution; Evolution (Biology); Experiments; Flour; Flow (Dynamics); Fluid flow; Fluid mechanics; Food; Hydrogen ions; Newtonian fluids; Non Newtonian fluids; pH effects; Physical Sciences; Rheology; Surfactants; Suspensions - chemistry; Technology application; Tomography; Zea mays - chemistry
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0112954

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. 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. 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.