Development of 5-(4,6-dichlorotriazinyl) aminofluorescein (DTAF) staining for the characterisation of low acyl gellan microstructures

AbstractAlthough hydrocolloids are used in a wide range of applications, understanding of microstructural interactions in the past have often based solely on mechanical properties. Systems which contain multiple polymers of similar properties are often, therefore, hard to fully understand since it is difficult to distinguish visually between the different phases. As such, the development of a novel staining method could aid our understanding of how microstructure relates to mechanical properties.This research has developed a method for the staining, and consequent visualisation, of low acyl gellan gum using 5-(4,6-dichlorotriazinyl) aminofluorescein (DTAF) without staining of a second polymer (gellan or PVA).The addition of DTAF on the gellan backbone was shown to affect mechanical properties, resulting in stronger gels. The influence of changing the ratios of DTAF stained gellan, and unstained gellan mixtures was also investigated. It was found; however, that these form phase separated networks. In conclusion, DTAF modification does enable fluorescent staining of gellan and allows the visualisation of microstructural interactions; however, since the modification influences the mechanical properties of the material, this staining method would be best employed as a validation method when used alongside other analytical techniques

The normal field instability under side-wall effects: comparison of experiments and computations

We consider a single spike of ferrofluid, arising in a small cylindrical container, when a vertically oriented magnetic field is applied. The height of the spike as well as the surface topography is measured experimentally by two different technologies and calculated numerically using the finite element method. As a consequence of the finite size of the container, the numerics uncovers an imperfect bifurcation to a single spike solution, which is forward. This is in contrast to the standard transcritical bifurcation to hexagons, common for rotational symmetric systems with broken up-down symmetry. The numerical findings are corroborated in the experiments. The small hysteresis observed is explained in terms of a hysteretic wetting of the side wall.Comment: accepted to New Journal of Physic

Fabrication, characterisation and stability of oil-in-water emulsions stabilised by solid lipid particles: the role of particle characteristics and emulsion microstructure upon Pickering functionality

Emulsifier-mediated wettability of solid lipid particles promotes the Pickering functionality in oil-in-water emulsions.</p

Self-structuring foods based on acid-sensitive low and high acyl mixed gellan systems to impact on satiety

This study investigated the in vitro acid-induced gelation of mixed systems of two biopolymers; low acyl and high acyl gellan gum. Rheological and texture analysis showed that these mixed gels displayed textures that lay between the material properties exhibited for the low and high acyl variants. DSC analysis showed that mixtures of the low acyl and high acyl forms exhibit two separate conformational transitions at temperatures coincident with each of the individual biopolymers. Various metabolically relevant pH environments and hydrocolloid concentrations were investigated. These resulted in very different acid gelled structures, which were characterised by texture analysis. The structures of the acid gels were shown to depend upon the pH, hydrocolloid concentration and proportion of each biopolymer used during their production. A selection of these mixed gellan structures were assessed post-production in terms of their response to prolonged exposure to an acidic (pH 1), stomach-like, environment. This resulted in a significant increase in the gel strength, regardless of the biopolymer proportions. The high acyl gellan was less acid-sensitive, and subsequently no evidence of acid gelation was observed with high acyl gellan at a proportion greater than 60% of the total biopolymer. The findings presented here demonstrate that structuring as well as de-structuring of mixed gellan acid gels can be controlled in acidic environments similar to those that are present in the stomach after food consumption

Whey protein fluid gels for the stabilisation of foams

AbstractThe ability of whey protein fluid gels to produce very stable foams was demonstrated. These systems were prepared by heat induced gelation within the turbulent flow field of a pin stirrer at pH 5 and 8. The effect of pH and final protein concentration on the morphology of the particles, the bulk, interfacial and rheological properties and finally the foaming properties of their aqueous suspensions were investigated. Whey protein fluid gels, when produced close to the isoelectric point, consist of small spherical protein aggregates without significant functionality. Micrographs taken suggest that the protein aggregates created have the ability to adsorb at the air/water interface. Nevertheless, the lack of further increase in interfacial viscosity or elasticity indicates that either the adsorption is easily reversible or that it is only partial due to lack of material available to provide complete coverage. By increasing the pH of these systems the protein entities present acquire a negative charge, which causes an increase to both the bulk and interfacial viscoelasticity and increase of the stability of foams. The proposed mechanism is that during foaming, the smaller and mobile protein entities diffuse fast to the interface and provide the necessary interfacial tension reduction to facilitate foam formation. Subsequently, the larger protein particles fill the free space between the air bubbles and increase the local bulk viscosity, which improves foam stability mainly by preventing drainage. Whey protein fluid gels were able to create the same amount of foam as non-treated whey proteins but with substantially increased stability