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Determination of Rheological Properties of Liquid Food through Pilot Plant Testing

Due to a continuous increasing in the production’s volume, the food industry is now facing the problem to have fast techniques to gain reliable data about the quality of their production. In this context the most used parameters are the rheological parameters as, for example, shear and extensional viscosity. The interrelation between rheology and other product dimensions often makes the measurement of viscosity the most sensitive or convenient way of detecting changes in colour, density, stability, solids content, and molecular weight.
The determination of rheological data, in line, and in a fastest way, without compromising the high standard sanitary requirements leads to the development of new techniques able to satisfy the multiple requests of this important part of the industries horizon.

This MSc thesis was divided in two main parts. The first part was focused on the determination of shear and extensional rheological proprieties of a model fluid in a lab scale setup of hyperbolic contraction flow.
The second part was mainly focus on the determination of rheological proprieties in-line using pressure drop and ultrasonic velocity profiling (UVP-PD).

Velocity profiles acquired using the UVP-PD techniques have been compared with theoretical velocities profiles and the similarity has been found more than satisfactory.
Once the reliability of the UVP-PD technique have been proved, the gathered data were used to find rheological proprieties and then compared with values obtain in the classical way.
Shear viscosity has been found to be acceptable even if the data turned out to be degraded from small errors deriving from the new technique applied.

Extensional viscosity has been found difficult to calculate and further work is needed in order to overcome the difficulties encountered during the experimental data gathering.

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3 INTRODUCTION This MSc thesis work has been conducted at SIK, the Swedish Institute of Food and Biotechnology in Gothenburg (Sweden). It also part of the Ingegneria Meccanica per l’Industria Alimentare MSc program at Università degli Studi di Parma. 1.1 Background Rheology is by definition, a science dealing with the deformation and flow of matter (Marriane- Webster, 1929). All materials have rheological proprieties, for this rheology is relevant in many field of study, like food, polymer technology, mining, oil recovery, medicine and geology. Looking specifically in the food industry, the ability to gather data on material’s behaviour gives manufacturer an important “product dimension”. Knowledge of a material's rheological characteristics is valuable in predicting pumpability and pourability, performance in a dipping or coating operation, or the ease with which it may be handled, processed, or used. The interrelation between rheology and other product dimensions often makes the measurement of viscosity the most sensitive or convenient way of detecting changes in colour, density, stability, solids content, and molecular weight. (F. Bueche, 1960) Ascertained that rheological data are irreplaceable for some industry, companies had to face the problem to gather these data quickly trying, if it’s possible, to avoid the time needed by the internal laboratories to supply this data to the floor shop. This problem is more marked in the food industry where the demands of automated and real-time monitoring techniques coupled with high standard sanitary requirements have grown significantly over the past decade (J. CULLEN P., 2001). The classical way to obtain both shear and extensional viscosities’ data are no more considered enough quick and even the so-called in line rheometers have demonstrated to have some problem especially regarding the hygienic conditions, and the reproducibility of the measurement. (Dealy, 1990).

Laurea liv.II (specialistica)

Facoltà: Ingegneria

Autore: Davide Zatti Contatta »

Composta da 43 pagine.

 

Questa tesi ha raggiunto 97 click dal 07/07/2009.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.