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Author
Armengol Casali, Roger
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In this project, 3 types of gels were studied: whey protein, stranded, and opaque gels.
In the experimental part, the gels are synthesized, put in a swelling solution to reach the swelling equilibrium, and then they are tested with magnetic resonance and in the oven. Magnetic resonance imaging (MRI) is a very powerful non-invasive technique used in food engineering, medicine, etc., where the local water content is quantified. Homogeneous whey protein hydrogels were used as a model system, easier to understand than other foods. The normalized intensity of the proton density of the hydrogels was studied using experimental correlations of the spin-lattice and spin-spin relaxation times. Using a typical resonance time of 20 ms, the intensity is highest at a volumetric swelling ratio of 15, and magnetic resonance is suitable for studying the drying of hydrogels at lower swelling ratio values. Swelling can be studied by changing the resonance time to reach the swelling ratio range, for example around 200 ms. An interesting correlation is found between the predicted normalized intensities and the drying and swelling experiments. Swelling deviations are observed at high NaCl concentrations, also at high alkaline pH. Opaque hydrogels can be studied and compared to beached clear ice. The inflation of the ice is evaluated by weight and by measuring the diameter before and during the inflation of the ice.
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