Improve your understanding of dairy product texture.

It is important to know at a fundamental level how texture is related to the organization of the components within a dairy-type food, such as yogurt, cheese or ice cream. This type of product typically contains protein and fat dispersed as colloidal particles-particles of a scale bigger than molecules, but still difficult or impossible to see under the microscope.

When these particles are joined together, they form the disordered aggregated structures that give food its complicated microstructure and textural features, e.g,. chewiness or creaminess. Relating the ingredients and the processing conditions more closely to microstructure and texture is the intent of researchers in Europe. Such information should be useful to ingredient companies that produce milk proteins and emulsifiers with a range of textures and stability characteristics.

Scientists have harnessed computer simulations, structure, rheology and protein-lipid interactions in their studies. They've been successful in relating the structure and rheology of simulated particle gels to the nature of interparticle interactions. Structural information on aggregated particle systems has been obtained using confocal laser scanning microscopy and transmission electron microscopy (casein gels and heat-set b-lactoglobulin gels); from observations of adsorbed layers in shear flow (polystyrene particles); and by diffusing wave spectroscopy (renneted skim milk particles).

Computer simulations and rheology experiments are providing insight into the control of structure by protein-protein and protein-lipid interactions. Data have also been collected on the rheology of concentrated caseinate solutions, concentrated latex dispersions, milk protein-stabilized emulsions, heat-set whey protein gels and emulsion gels, renneted casein dispersions, acid-induced casein-stabilized emulsion gels and heat-treated/acid-induced skim milk gels.

Scientists employed the computer simulations to interpret general features of behavior. Combined surface chemistry and spectroscopic techniques have been used to determine the influence of protein-protein and protein-lipid interactions on surface composition, structure and the viscoelasticity of adsorbed layers. The information shows how the rheology and stability of model milk protein-based colloidal systems are affected by emulsifier type, protein structure and solution conditions (pH and temperature).

Further information. E. Dickinson, Procter Department of Food Science, University of Leeds, Leeds LS2 9JT, England, U.K.; phone: [phone]; fax: [phone]; email: [e-mail].