30E-4 |
Rheological characterization of fruit nectars by mixer viscometry |
L. G. MONTOYA-AYÓN1, S. Vargas-García, and J. A. I. Romero-Espinoza. (1) Departamento de Ingenierías Química y Bioquímica, Instituto Tecnológico de Durango, F. Pescador 1830 Ote., Col. Nueva Vizcaya, 34080 Durango, 34080, Mexico Many products derived from fruits and vegetables are suspensions or dispersions in which solids settle more or less rapidly. Rheological properties of these foods are useful in applications related to their handling, their quality control and their sensory analysis; however, these properties can not be appropriately determined by traditional means because those substances may exhibit slip and settling of their solid particles. Under these circumstances, mixer viscometry is a reliable technique. The purpose of this work was to characterize the rheological behavior of liquid foods containing suspended particles by using a mixer viscometer. Mixer rheometer data were collected using a rotational viscometer equipped with a cup and flag impeller. As a calibration fluids, hydrocolloids at different concentrations were used and, using a cone and plate rheometer, rheological properties (K and n) of these fluids were determined. For calculation of mixer viscometer constants (A y k’), measurements of torque and angular speed were done, For rheological characterization some commercial fruit nectars were analyzed. For calibration fluids, behavior index values ranging between 0.1735 and 0.9982 were obtained. By means of regression analysis, the values of viscometer constants (A y k’) were obtained and they were 3.604 and 1.6576 rad-1, respectively. Because of the operation range of the equipment, only mango nectar and apple nectar were characterized and the behavior index values (n) were 0.288 and 0.730, respectively as obtained by the mixer viscometer and 0.292 y 0.763 by the cone and plate rheometer. The corresponding values of consistency coefficient (K) showed significative differences. The behavior index values, as obtained in conventional rheometer and mixer viscometer, were very close and the consistency coefficient values were different; however the similarity is good enough for the main applications of that information
Session 30E, Food Engineering: Rheology and texture
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