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

Trujillo-de Santiago G, Rojas-de Gante C, García-Lara S, Ballescá-Estrada A, Alvarez MM - PLoS ONE (2014)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: 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.

ABSTRACT

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.

Methodology and findings: 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.

Conclusion and relevance: 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.

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Blue maize flour suspensions exhibit different rheological behavior at different pH values.(A) Plot of apparent viscosity versus shear rate (in the range from 250 to 1500 s−1) for blue maize suspensions prepared at different pH values. Gray dotted lines correspond to power-law fits to experimental data based on the Ostwald-de Waele model [η = K (γ)n–1] using the parameter values reported in Table 1. (B) Plot of apparent viscosity versus shear rate (in the range from 250 to 1500 s−1) for blue maize suspensions prepared at different pH values. (C) Log-log version of the plot of apparent viscosity versus shear rate (in the range from 250 to 1500 s−1) for blue maize suspensions prepared at different pH values. Straight dotted lines have been used to connect the experimental data points.
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pone-0112954-g003: Blue maize flour suspensions exhibit different rheological behavior at different pH values.(A) Plot of apparent viscosity versus shear rate (in the range from 250 to 1500 s−1) for blue maize suspensions prepared at different pH values. Gray dotted lines correspond to power-law fits to experimental data based on the Ostwald-de Waele model [η = K (γ)n–1] using the parameter values reported in Table 1. (B) Plot of apparent viscosity versus shear rate (in the range from 250 to 1500 s−1) for blue maize suspensions prepared at different pH values. (C) Log-log version of the plot of apparent viscosity versus shear rate (in the range from 250 to 1500 s−1) for blue maize suspensions prepared at different pH values. Straight dotted lines have been used to connect the experimental data points.

Mentions: The non-Newtonian behavior of flour suspensions has been characterized in the context of food engineering applications [29]–[31]. We conducted determinations of shear stress and apparent viscosity at different shear rate values for the blue maize flour suspensions used in our experiments using an automatic Rheometer (Physica MCR Anton Paar, Austria). Figure 3a shows the apparent viscosity values in the range of shear rates from 20 to 1520 s−1; we observe non-Newtonian behavior across various pH values (Figure 3a, 3c). At low shear rate values (Figure 3b), except under very acidic conditions (3.3> pH >1.6), suspensions displayed an evident non-Newtonian behavior with apparent viscosities varying drastically as a function of shear rate.


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

Trujillo-de Santiago G, Rojas-de Gante C, García-Lara S, Ballescá-Estrada A, Alvarez MM - PLoS ONE (2014)

Blue maize flour suspensions exhibit different rheological behavior at different pH values.(A) Plot of apparent viscosity versus shear rate (in the range from 250 to 1500 s−1) for blue maize suspensions prepared at different pH values. Gray dotted lines correspond to power-law fits to experimental data based on the Ostwald-de Waele model [η = K (γ)n–1] using the parameter values reported in Table 1. (B) Plot of apparent viscosity versus shear rate (in the range from 250 to 1500 s−1) for blue maize suspensions prepared at different pH values. (C) Log-log version of the plot of apparent viscosity versus shear rate (in the range from 250 to 1500 s−1) for blue maize suspensions prepared at different pH values. Straight dotted lines have been used to connect the experimental data points.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4234479&req=5

pone-0112954-g003: Blue maize flour suspensions exhibit different rheological behavior at different pH values.(A) Plot of apparent viscosity versus shear rate (in the range from 250 to 1500 s−1) for blue maize suspensions prepared at different pH values. Gray dotted lines correspond to power-law fits to experimental data based on the Ostwald-de Waele model [η = K (γ)n–1] using the parameter values reported in Table 1. (B) Plot of apparent viscosity versus shear rate (in the range from 250 to 1500 s−1) for blue maize suspensions prepared at different pH values. (C) Log-log version of the plot of apparent viscosity versus shear rate (in the range from 250 to 1500 s−1) for blue maize suspensions prepared at different pH values. Straight dotted lines have been used to connect the experimental data points.
Mentions: The non-Newtonian behavior of flour suspensions has been characterized in the context of food engineering applications [29]–[31]. We conducted determinations of shear stress and apparent viscosity at different shear rate values for the blue maize flour suspensions used in our experiments using an automatic Rheometer (Physica MCR Anton Paar, Austria). Figure 3a shows the apparent viscosity values in the range of shear rates from 20 to 1520 s−1; we observe non-Newtonian behavior across various pH values (Figure 3a, 3c). At low shear rate values (Figure 3b), except under very acidic conditions (3.3> pH >1.6), suspensions displayed an evident non-Newtonian behavior with apparent viscosities varying drastically as a function of shear rate.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: 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.

ABSTRACT

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.

Methodology and findings: 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.

Conclusion and relevance: 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.

Show MeSH
Related in: MedlinePlus