Measurement of micro-rheological properties of food structures

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A great many foods are made up of small (colloidal) particles.  Some are simply dispersions of particles (milks, creams, mayonnaises, cream liqueurs) that have to be kept in a stable condition until they are consumed.  On the other hand, some foods are created by causing their constituent particles to become unstable, so that they form curds or gels or other structures that provide acceptable textures for the consumer.  Well-known examples of these are cheese, yogurts, and ice cream.  The control of stability (or instability) of the basic particles in these products is clearly of considerable importance.  The particles are also of importance in the nanoengineering of foods, and can be used to carry important food ingredients such as flavours or nutritionally important molecules that must be protected from breakdown (such as by oxidation). The question we are trying to answer is: how is the stability of different types of particles maintained and how can it be controlled?  Especially, we are interested in how particles like the casein micelles of milk can be controllably destabilized to give defined curd structures.  One of the newest methods of studying this is the technique of Diffusing Wave Spectroscopy (DWS), which allows us to use the light scattered from a colloidal suspension to tell us about the way in which the particles interact.  Using the equipment we can look at the earliest stages of gel formation and at the interactions between the particles.  The technique also has the possibility of measuring the strengths of the very weak gels that are formed in these early stages.  It is at this stage that it may be possible to intervene to control the properties of the subsequent gel.  If we can understand what is happening at these early stages, we may be able to exercise a hitherto impossible control over the structures and properties of the final foods.  It is for this reason that we wish to improve the instrumentation we have, so that we can measure these very weak gels and learn even more about the mechanisms and control of gelation reactions in foods.