Utilization of nanoemulsion gels for novel structure and functional properties of food

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Emulsions play a key structural role in numerous natural and processed foods (e.g., milk, mayonnaise, and beverages). Nanoemulsions are a relatively new class of emulsions with an average droplet radius typically less than 100 nm. Due to their extremely small droplet size, nanoemulsions have a number of functional properties that can be advantageous in food formulations; for example, they can significantly improve stability or act as an efficient delivery medium with high bioavailability of bioactive compounds. So far, applications of nanoemulsions in food have been limited to liquid-based products. Recently, it has been shown that by reducing droplet size an oil-in-water nanoemulsion can be transformed into a solid-like matrix, called a nanogel, at a much lower oil volume fraction (~20% oil) than conventional emulsion gels (>60% oil). These nanogels could provide a novel structure that may significantly improve stability and health-promoting properties of a number of emulsion-based foods, including yoghurt, mayonnaise-type spreads and cheese. However, a lack of understanding of the influence of nanodroplet size, charge, and interfacial chemistry is limiting their use in the food industry. *The long-term objective of the proposed research program is to develop an in-depth understanding of the interfacial and interdroplet interactions in oil-in-water nanoemulsions so that nanogels with tunable physicochemical properties can be created to improve the structure, functionality, and health-promoting properties of foods and related soft materials. The short-term objectives to be addressed over the next five years are to: 1) Optimize the influence of size and interdroplet interactions on the formation of a random-jammed network of nanodroplets; 2) Investigate the multi-scale structure and mechanism of formation of nanogels; 3) Optimize elasticity and flow behaviour of nanogels; 4) Demonstrate stability and applications of nanogels in food and related soft materials. Two different approaches of nanogel formation will be investigated: increasing the effective oil phase volume fraction so that nanodroplets can form a random-jammed structure by reducing their droplet size and increasing their interfacial shell thickness; and inducing attractive interactions among the nanodroplets so that strong aggregates can be formed. The internal nanostructure and mechanism of nanodroplet gelation will be investigated using small angle X-ray scattering techniques. The bulk and interfacial rheological behaviour of the nanogels will be studied in order to understand how the nature of interdroplet forces and interfacial rigidity controls their elasticity and flow behavior. This information will be used to develop a universal model for prediction of elastic behaviour and long-term stability of nanogels. Finally, the applications of nanogels in delivery and rapid release of bioactive compounds and replacement of high fat containing conventional emulsion gels will be demonstrated.*Food-grade nanogels represent a potential new class of ingredients to improve the structure of processed foods (e.g., yoghurt, mayonnaise-type spreads, cheese). At present, these foods are made out of conventional emulsion gels. The successful application of low-oil containing nanogels to reduced-fat foods and the rapid release of bioactive compounds is expected to lead to significant improvements in health-promoting properties of processed foods. The major discoveries, impact, patent applications, and future technology transferred from this research will directly benefit the Canadian agricultural and food sectors, with potential advantages for pharmaceutical and cosmetic industries.