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Luis A García-Zapateiro

Universidad de Cartagena, Colombia

Title: The influence of thermic treatment on viscoelastic properties of squash (Cucurbita moschata) pulp

Biography

Biography: Luis A García-Zapateiro

Abstract

Statement of the Problem: The physicochemical properties of vegetables and fruits can change due to the storage condition, the operations and the thermic treatment applied. So in the food industry, i.e. 20ºC are used in storage and 60ºC in processes such as pasteurization and others. During pumping, in-pipe flow, mixing and stirring of liquid-like foods, shear rates in the range of 10–1000 s-1 may be experienced. Therefore, rheological experiments should preferably be done within the frequency and stress range that encompasses most applications. The purpose of this study is to describe the effect of thermic treatment on the viscoelastic properties of squash (Cucurbita moschata) pulp.

 

Methodology & Theoretical Orientation: Rheological measurements were carried out by using a stress-controlled rheometer Haake Mars 60 (TA Instruments, England), using roughened plate-plate geometries (diameter 35 mm, gap 1 mm, roughness 0.5 mm). Prior to measurement, all samples were allowed to stand for 600 seconds to relaxation of the same, the temperature of the samples was assured by Peltier system installed in the inferior plate of the rheometer. Oscillatory stress sweeps between 0.001 to 1000 Pa were performed to determine the linear viscoelastic range at a frequency of 1 Hz. Then, a frequency sweep between 0.01 and 100 Hz was performed to determine the mechanical spectra. All the rheological tests were performed at temperatures of 20, 40, 60, 80 and 100ºC.

 

Findings: The behavior of storage modulus G’ (elastic behavior) is higher and loss modulus G’’ (viscous modulus) in the frequency range of temperatures applied. According to this, the viscous and elastic properties of squash pulp are significantly different for temperatures of 20, 40, 60, 80 and 100ºC. On the other hand, no significant differences were found for 40 and 60ºC. So the lineal viscoelastic behavior of squash pulps is similar to mango, cherry and borojó, and is influenced by the temperature.

 

Conclusion & Significance: The present work has evaluated the viscoelastic properties of squash pulp. Product has shown a weak behavior, with storage modulus higher than loss modulus in the evaluated frequency.