Foam stability: formation and stability of interfaces in complex foods
Aerated foods, such as foams, are important food products because people enjoy their taste and mouthfeel. Foams, however, are unstable and suffer from deterioration due to creaming, drainage, aggregation, coalescence and disproportionation. A challenge for the food industry is to control these mechanisms. Food foams, such as beer foam, whipped cream, cappuccino toppings, mousses, bread and foamed sweets consist of various components exhibiting different properties. The role of these components, in the formation and stability of foams, is not yet sufficiently understood.
This project aimed to identify the key relationships that control the physical and chemical properties of air bubbles and their interfaces in complex food matrices and foams, over time. We studied the relationship between the properties of the ingredients (such as proteins, low-molecular-weight surfactants and organic and/or inorganic particles), the properties of the air/water interface and the properties of the foam (such as stability and bubble-size distribution). Unique to the project is its multi-scale approach: we mapped and combined the overall effects of ingredient combinations on molecular, interfacial, thin-film and foam properties. New insight was obtained into how to get particles into the air-water interface at which they can form a jammed-colloidal shell, which results in air bubbles that remain stable for more than a year. Single-protein-stabilised bubbles were made using a relatively new technique known as coaxial electrohydrodynamic atomisation. Important insights into protein-surfactant interactions were obtained that are relevant to foam stability and foam formation.
This project has successfully linked food properties, such as mechanical and sensory characteristics, to oral-processing behaviour. This has advanced our understanding of the eating process, and bridged the knowledge gap between oral-processing behaviour and food structure. The fundamental knowledge provided by the project will assist the food industry to provide products that are low in fat, salt or sugar and retain excellent sensory performance.