Emulsions: Stability, rheology and sensory perception
Emulsions can be encountered in many areas of daily life such as in food products, cosmetics, pharmaceutical and agricultural industry. A thorough understanding of their stability, rheology and sensory perception is needed as these are essential aspects in order to design and produce high quality emulsions. In this thesis, we describe our research findings and insights in these aspects of emulsions. Emulsions are thermodynamically unstable systems and thus require a stabilizer for prolonged stability. The most frequently used stabilizers are surface active agents (surfactants). However, due to their common release into the environment, surfactants are considered as unwanted pollutants in aquatic and terrestrial environments. One proposed substitute for traditional surfactants in stabilising emulsions are particles. Yet, their physicochemical behaviour and stabilisation mechanism is not yet well understood. A second important aspect of emulsions is their rheological behaviour. When making emulsions flow, we constantly deform their structure which leads to a response of fluid that depends on the rate of deformation. Although the rheology of emulsions has been a long lasting research subject, normal stress differences and the effect of polymers in the continuous phase on the rheology of emulsions are still poorly investigated. The sensory perception of emulsions is essential when developing products with further applicative interest. Linking sensory attributes to rheological parameters has shown much potential for the objective and efficient evaluation of the sensory perception of emulsions. However, this field is relatively ill explored and many sensory attributes are not yet linked to a rheology technique or property.