Weak gel model for foods

Autori: D. Grabiele, B. de Cindio, P. D'Antona
Presentato al: Southern Europe Conference on Rheology
Anno: 1999
Volume: 2
Issue: Unico
Casa Editrice: SIR-Cuen Napoli
Lingua: English


Abstract
In the last decades researchers have focussed their attention on the rheological behaviour of foods because its knowledge is essential for the proper design and operation of unit operations, as well as for the understanding of the pertinent properties relevant for both transport processes during operations and organoleptic perception during eating. This is due to the capability of rheology to make a bridge between structural aspects and continuous macroscopic parameters. During a long period questionable and sometime wrong approaches have been proposed to fulfil the lack of knowledge of both experiments and theories. Experiments based on empirical tests such as penetrometers, pencil test, FIRA extruder etc., or theories based on correlation models such as Maxwell model, Voigt model or their combinations have been widely used, and literature is very rich of data performed and interpreted in this way. It is clear that such approaches renounce “a priori” to understand and increase the knowledge because they have the aim to produce data or fitting models that in general hardly link with the structure of the considered food. We should admit that this situation was also determined by the relative high cost of rheometers, compared to the expected results. But one of the main advantages stated for the use of rheology was just the possibility to achieve this link between structure and continuum, therefore a more general approach has to be designed from both an experimental and a theoretical point of view. The availability of new basic instruments at realistic costs occurred in the last decade, capable to give suitable fundamental measurements, finally justifies considering again the problem under a more general standing point. Thus regarding to experiments it has become more and more usual to measure the dynamic moduli G’ and G’’ obtained during a small amplitude oscillatory shear test, as a function of frequency or temperature, instead of the infinite old empirical techniques. It is an opinion of the authors that to achieve the proposed main objective, and to avoid making the same previous even if justified mistakes, it is still needed to put also these measurements into a fundamental theoretical frame.
In this work are presented the last achievements obtained by our research group in this field, respect to both theory and experiments. The aim is to obtain a unique predictive model that should be as general as possible to be applied to many foods systems. This implies that the rheological characterisation as to be tailored on the theoretical model.


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