3.5. Rheological behavior
In SPC system with vitamins behavior was similar to a Newtonian fluid (Fig. 4) because the shear stress was virtually proportional to the shear rate (McClements, 1999). This result was manifested by the values of n (before and after pasteurization),even though they were lower than 1, they were very close to this value (Table 3). The Newtonian behavior remained after pasteurization, which confirms that heat treatment did not modify the viscosity of the system. This was corroborated with the apparent viscosity measurements which did not show a significant difference before and after pasteurization. These results are also related to the morphology and size distribution: when a low aggregation tendency was observed, favors a Newtonian behavior.
Before pasteurization the SPC:SA formulation with vitamins showed an increment of aggregation corroborated by the high D4,3 value, morphology and multimodal particle size distribution. This result is related to a pseudoplastic behavior; as the n value was lower than 1. However, after pasteurization this system showed less aggregation, corroborated by a decrease of the D4,3 value and reduction of aggregation observed by morphology and multimodal particle size distribution. This effect is related with the decrease of viscosity and a Newtonian behavior since the n value was close to
1 respect to the same unpasteurized system (Table 3).
3.5. Rheological behaviorIn SPC system with vitamins behavior was similar to a Newtonian fluid (Fig. 4) because the shear stress was virtually proportional to the shear rate (McClements, 1999). This result was manifested by the values of n (before and after pasteurization),even though they were lower than 1, they were very close to this value (Table 3). The Newtonian behavior remained after pasteurization, which confirms that heat treatment did not modify the viscosity of the system. This was corroborated with the apparent viscosity measurements which did not show a significant difference before and after pasteurization. These results are also related to the morphology and size distribution: when a low aggregation tendency was observed, favors a Newtonian behavior.Before pasteurization the SPC:SA formulation with vitamins showed an increment of aggregation corroborated by the high D4,3 value, morphology and multimodal particle size distribution. This result is related to a pseudoplastic behavior; as the n value was lower than 1. However, after pasteurization this system showed less aggregation, corroborated by a decrease of the D4,3 value and reduction of aggregation observed by morphology and multimodal particle size distribution. This effect is related with the decrease of viscosity and a Newtonian behavior since the n value was close to1 respect to the same unpasteurized system (Table 3).
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