Unilever's Krassimir Velikov and Eddie Pelan reveal the design behind innovative, nutritious and tasty foods.

Colloids can enhance the flavour, texture, appearance and nutritional benefits of food

Product functionality is a complex product description that covers the formulation, structure, texture, stability, appearance, taste, flavour and bioavailability of food ingredients. To design nutritious foods, we need to introduce the nutrients, known as micronutrients and nutraceuticals, in a proper form to assure the stability, as well as good taste, of the final product. Micronutrients, such as vitamins and minerals, are essential for growth and development whereas nutraceuticals are not essential for life but have a positive effect on health. Unfortunately, they often cause problems due their own physico-chemical properties or their interaction with other ingredients present in the food. As a result, the food functionality is often compromised.

Incorporation of soluble active ingredients in food products can cause a bitter taste, lipid oxidation, colour changes, and chemical instability. Use of the insoluble salts can lead to physical instability and insufficient bioavailability. We need a balance between solubility and dispersibility of the active ingredient. Furthermore, we need control over this balance in order to have flexibility in solving technical issues. A generic solution for these problems is to use colloidal delivery systems, which are insoluble in the product but dissolve in the gastrointestinal tract upon consumption. Colloidal dispersions are small enough not to cause physical instabilities like sedimentation. Unfortunately, there are not readily available natural colloidal delivery systems for most micronutrients and nutraceuticals so custom-made delivery systems are required.

Colloidal dispersions can be used to design and fine tune product structure and enable new product formats. Both nutraceuticals and micronutrients are used in relatively low concentrations, so ability to alter product structure can be limited. Nevertheless, particles like rods and platelets can be used as alternatives to biopolymers to increase viscosity or create gels at sufficiently low volumes. Colloidal particles can also provide stabilisation of fluid-in-fluid dispersions meaning that emulsions can be formed using little or no surfactant.

Taste and flavour are crucial for the success of any food product. Changes in flavour are often linked to the inherited taste of the ingredients or to unwanted chemical interactions, for example oxidation. Colloidal dispersions offer control on solubility and, as a result, control on taste.

Because a colloid's optical properties vary depending on its size and shape, colloidal dispersions offer great opportunities for fine tuning product appearance - they can deliver translucency, complete transparency or a desired colour.

Bioavailability of functional ingredients is a rapidly growing issue in the area of functional food design. Often ingredients are poorly soluble, crystalline solids at room temperature and are poorly absorbed from the gastrointestinal tract. There are several common approaches to improve their bioavailability: chemical modification; size reduction; hydrophilisation of particle surfaces to improve the solubility; crystallinity reduction; or polymorph alteration.

The successful application of colloidal delivery systems in foods requires a broad knowledge of molecular, ionic, and colloidal interactions in the product, as well as knowledge of the biological function and metabolism of the micronutrients or nutraceuticals. Since these processes are not independent, successful application in industrial products requires an integrated approach. An approach where the ingredients are pre-formulated to allow easy incorporation and stabilisation in the product is likely to be most useful. This approach also requires linking the in-product and in vivo function of the delivery systems. Finally, in this approach all aspects of product functionality, like stability, texture, taste, appearance, and bioavailability, are simultaneously considered and addressed to achieve a balanced and consumer acceptable solution.

The strategy is valid not only for food systems but also home and personal care products, drug formulations, agricultural compositions and paints. Importantly, many micronutrients and nutraceuticals are also cosmeceuticals in skin care products. Depending on the type of industry, one or another aspect of the product functionality will be of higher importance.

Read more in 'Colloidal delivery systems for micronutrients and nutraceuticals' in issue 10 of Soft Matter.