PHYSICAL CHEMISTRY OF FOOD
Learning outcomes of the course unit
The aims of the course are the following:
1. to show that thermodynamics is the foundation for understanding the main machinery related to food preservation;
2. to give an outline of colloidal chemistry, foundation of structural and functional features of foods.
No preliminary examinations are requested.
Course contents summary
1. Equilibrium thermodynamics applied to chemical, biological and food systems with a statistical thermodynamics outline. Variables and state functions. The laws of thermodynamics. The temperature and pressure dependence of thermodynamic quantities. Thermochemistry. Calorimetry. Outline of statistical Thermodynamics. Exercises.
2. Changes of state: physical transformations of pure substances. Phase diagrams. Clapeyron and Clausius-Clapeyron equations. Gibbs phase rule
3. Changes of state: physical transformations of simple mixtures. Open systems and partial molar quantities. Ideal and real solutions. Raoult and Henry laws. Fugacity and activity. The water activity in foods and food preservation. Regular solutions. Ideal mixing and excess functions. Phase equilibria in binary systems. Fractional distillation. Azeotropes, eutectic, partially miscible liquids, binary mixtures compounds forming. Phase transition in food materials. The glassy state and the glass transition.
4. Solutions of macromolecules. Solvent chemical potential. Colligative properties. Osmotic pressure. Molecular weight measurements. Membrane equilibria. Dialysis equilibrium. Donnan equilibrium.
5. Equilibria of chemical reactions. Thermodynamics of chemical equilibrium. Gibbs free energy and equilibrium constant. Activity and ionic strength. Exergonic and endergonic reactions. Coupled reactions.
6. Non-equilibrium thermodynamics and transport processes. Order out of caos. Force and flow. Phenomenological equations. Theorems. Onsager law. Dissipation function. Steady state concept. Mobility of the ions in solution. Electrophoresis. Diffusion. Sedimentation. Viscosity.
7. Colloidal Systems. Dispersed systems. Size and shape of colloidal particles. Ostwald classification. Surface tension and surface free energy. Van de Waals forces. Lennard-Jones potential. Intermolecular forces in colloidal systems. DLVO theory. Hydrophobic interactions, hydrophobic hydration and Hydrophobic effect : model for the interpretation. Structure and classification of surfactants. Micelle formation. Casein Micelles. Emulsifiers and stabilizers in foods. Cohesion and adhesion work, spreading coefficient, wettability. Ostwald ripening. Gibbs isotherm. Laplace pressure. The most common food colloids: Emulsions, foams, dispersions and suspensions, gels. Methods of preparation. Examples: beer, whipped cream, ice-cream, meringue, butter, mayonnaise. Marangoni effect. Physico-chemical properties of a food colloid. Micro-emulsions. Lyotropic and thermotropic liquid crystals.
- Pieter Walstra, Physical Chemistry of Foods, Marcel Dekker, Inc, New York (2003)
- Eric Dickinson, An Introduction to Food Colloids, Oxford Science Publications (1992)
Lectures by means of computer presentations, available to the students before classes.
Written examinations on the whole syllabus during normal examination sections.
Assessment methods and criteria