Solubilisation, fragmentation and precipitation of colloidal particles of cellulose as stabilising agents in foods

Cellulose is often referred to as the most abundant biopolymer on earth. It has many interesting properties and is dense, zero-calorie and tasteless, thus finding a wealth of applications across the food industry (including bulking, thickening and stabilising products). In light of upcoming legislation affecting products high in fat, salt and sugar (HFSS), there is huge necessity for the UK food industry to reduce calories and reformulate using sustainable, ‘clean-label’ ingredients. With the recent reassessment of its inherent amphiphilicity along the backbone, native cellulose has the potential to address some of these challenges if it can be suitably functionalised as a water-in-oil (W/O) emulsion stabiliser. Incorporation of water into confectionary products via an emulsion is a promising strategy for fat reduction, however both the lack of non-synthetic W/O emulsifiers and their low stabilities present issues. In this thesis, novel cellulose microgel particles (CMGs) have been produced based on a dissolution-reprecipitation method, adhering to clean-label restrictions where possible. An ionic liquid (IL) was investigated as a cellulose solvent and the properties of the cellulose-IL solutions were firstly characterised in detail, prompting the design of cellulose materials. CMGs were then fabricated from the solutions and various processing methods were employed, adopting different solvents and mechanical treatments. The best performing emulsifiers were CMGs with oil incorporated into the gel structure (‘oily’- CMGs), which were well-dispersed in hydrophobic media and stabilised W/O emulsions for at least 5 months. The cellulose-oil interaction was investigated in more detail, to further understand the origin of CMG- interfacial activity. In summary, this thesis addresses the need for replacement of synthetic surfactants in food, exploring the properties of native cellulose and its potential to be functionalised without chemical modification. These insights present an interesting opportunity for cellulose-based ingredients to be applied to reduced fat products, considering the upcoming HFSS requirements.