Nature-inspired humectants and plasticisers for use in aqueous confectionery fillings

With an ever-increasing global population and incidence of health-related non-communicable diseases (diabetes, cancer, cardiovascular disease), there is growing pressure on confectionery manufacturers to improve the nutritional profile of their products by reducing the content of undesirable free/added sugars. This is particularly challenging within aqueous confectionery fillings as sugars provide not only sweetness but also humectancy and plasticisation by lowering the water activity (aw) and glass transition temperature (Tg), which is necessary for maintaining product safety and quality. This thesis investigates both theoretical and practical aspects of replacing common confectionery sugars within model aqueous confectionery fillings using novel, nature-inspired approaches. Initial attention focussed on rationalising the aw of aqueous solutions containing archetypal or unheralded humectants via application of statistical thermodynamics. This revealed that aw manifests as a result of the interplay between the hydration (reduces aw) and clustering of solutes (increases aw). A second aspect of the thesis examined the humectant and plasticisation properties of two unheralded natural osmolytes; 2-O-α-D-glucopyranosyl glycerol (glycoin) and 2-O-α-D-galactopyranosyl glycerol (floridoside) and involved direct extraction of the latter from a natural biomass (Palmaria palmata). Both glycoin and the floridoside extract were found to exhibit low Tg values and effective aw reducing capacities that were equivalent or superior to common confectionery sugars (sucrose, fructose). Two previously unforeseen crystal forms of floridoside were also identified and subsequently characterised in detail. The development and characterisation of several novel ‘deep’ eutectic mixtures formed using naturally-occurring, food-grade components as ‘proof-of-concept’ humectant/plasticisers were also described. The performances of one such eutectic mixture, in addition to glycoin and the floridoside extract were evaluated within a model aqueous confection and found to be very comparable to D-fructose, suggesting that they all have potential as drop-in humectants and plasticisers for use within sugar-reduced confectionery and broader food sector applications.