30E-7 |
Effect of discontinuous phases of rheological properties of strawberry jam |
V. SANTACRUZ-VÁZQUEZ1, C. Santacruz-Vázquez2, J. Torres-Merino1, O. Trujillo-Acevedo1, and J. Welti-Chanes3. (1) Facultad de Ingeniería Química, B. Universidad Autónoma de Puebla, Av. San Claudio s/n, Ciudad Universitaria, Puebla, 72570, Mexico, (2) Facultad de Ingeniería Química, B. Universidad Aut—noma de Puebla, Mexico, (3) Departamento de Ingeniería Química y Alimentos, Universidad de las Américas-Puebla, Santa Catarina Mártir, Cholula, Puebla, 72820, Mexico The knowledge of rheological properties of jams and fruit preserves during their processing, packed and distribution is fundamental for the equipment and processes design. These products present different properties which are function of their composition relationship (water/fruit/pectin/sucrose) and the temperature. The objective of this work was define the effect of the discontinuous phase and temperature on the viscosity of strawberry jam, using a sucrose solution (60%w/w) like a model system for a comparative analysis. A Brookfield DVII viscometer (Needles RV#2 and RV#7; 25 minutes, 120 rpm and torque of 70%) was used to evaluate the rheological properties of jam and sucrose syrups at 20, 30, 40, 50 y 60C. The syrups showed a Newtonian behaviour with a lineal relationship between viscosity (µ, cp) and the temperature (T,K) (µ=-4.54T†1577). At lower temperatures (20 and 30C), the jam showed a reopectic behaviour, while at 40, 50 and 60C the viscosity was not affected by the measuring time, the description of that different rheological behaviour was obtained using the fractal theory concepts. The effect of the type of discontinuos phase in the jam provoked a difference between the average viscosity of that product and the syrups of 35 times (at 20 C) to less of 6 times (at 50 and 60C). This last information is very important to define the rheological properties of the jam in function of the discontinuous phase quantity and the process temperature.
Session 30E, Food Engineering: Rheology and texture
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