Polysaccharides at fluid interfaces of food systems

Abstract

Fabrication of next generation polysaccharides with interfacial properties is driven by the need to create high performance surfactants that operate at extreme environments, as for example in complex food formulations or in the gastrointestinal tract. The present review examines the behaviour of polysaccharides at fluid food interfaces focusing on their performance in the absence of any other intentionally added interfacially active components. Relevant theoretical principles of colloidal stabilisation using concepts that have been developed for synthetic polymers at interfaces are firstly introduced. The role of protein that in most cases is present in polysaccharide preparations either as contaminant or as integral part of the structure is also discussed. Critical assessment of the literature reveals that although protein may contribute to emulsion formation mostly as an anchor for polysaccharides to attach, it is not the determinant factor for the long-term emulsion stability, irrespectively of polysaccharide structure. Interfacial performance of key polysaccharides is also assessed revealing shared characteristics in their modes of adsorption. Conformation of polysaccharides, as affected by the composition of the aqueous solvent needs to be closely controlled, as it seems to be the underlying fundamental cause of stabilisation events and appears to be more important than the constituent polysaccharide sugar-monomers. Finally, polysaccharide adsorption is better understood by regarding them as copolymers, as this approach may assist to better control their properties with the aim to create the next generation biosurfactants.

Emulsifying properties of Ghanaian grewia gum

“…Similarly, PBP with lower protein than SMBP exhibits smaller d 4,3 values and uniform particle size distribution at the early stages of ageing although both samples destabilise at the end of the storage period. This is in accordance with the findings in other polysaccharide‐stabilised emulsions where conformation of polysaccharides and adsorption strength at the interface seem to be the main mechanism behind their functionality at the oil‐water interface (Kontogiorgos, ).…”

“…Other studies have also reported that increasing molecular weight enhanced emulsion stability by forming thicker polysaccharide layers, which protected the coated oil droplets and reduced coalescence and aggregation (Liu et al , , Funami et al , , Jung & Wicker, ). However, adsorption strength, interfacial rheology and conformational rearrangements may also influence the behaviour of polysaccharides at the interface (Kontogiorgos, ). Consequently, molecular weight cannot alone account for emulsion stability, as for example, SMBC samples with substantially higher Mw than the rest of samples do not perform particularly well during long‐term storage.…”

“…In polysaccharide extracts with substantial protein concentration, examination of the interface composition may disclose further details into their stabilisation mechanisms. Frequently, hydrophobic protein moieties act as anchoring points for polysaccharides although the relative contribution of each biopolymer to the overall stability may vary depending on the system (Kontogiorgos, ). Consequently, in the next part of the present investigation we examined the interfacial load of fresh grewia‐stabilised emulsions).…”

“…One of the functional properties that is very frequently exploited is their capacity to stabilise oil‐in‐water emulsions (Porto & Cristianini, ; Dickinson, ), as some polysaccharides may play an essential role as surface active agents that facilitate emulsion stability by lowering the interfacial tension between immiscible phases (Grein et al , ). The surface activity of polysaccharides that contributes to emulsion stability is largely attributable to the presence of hydrophobic groups for molecular attachment at the oil interface and to chain branching to sterically stabilise oil droplets (Kpodo et al , , Dickinson, , Alba & Kontogiorgos, , Kontogiorgos, ).…”

“…To that end, polysaccharide‐based delivery systems may resist both proteolytic enzymes and the acidic gastric environment that limit the functionality of protein and surfactant‐based formulations. Nevertheless, polysaccharides need to be tailored to enhance their adsorption strength and overall functionality at the interface (Kontogiorgos, ).…”