Understanding the mechanical performance of raw and cooked potato cells.

The micromechanics of individual potato cells comprising of cell wall and embedded native or gelatinised starch were explored. Micromanipulation can be used to compare cells of distinct strengths and study (bio)mechanical issues related to industrial processing (e.g. heat treatment). Two commercial types of potato, 'baking' and 'Maris Piper' were selected to conduct microcompression experiments. Cells isolated from 'Maris Piper' raw tubers appeared to be more resistant to deformation than the respective ones from the 'baking' cultivar. Cooked cells suffered a decrease in their turgidity which resulted in clusters of observed behaviours, with force-deformation curves showing a single or multiple bursting events. This study provides fundamental work and an insight on the behaviour of potato cells via an exploratory investigation of how different elements of the potato tissue can be measured. The results obtained can be used to relate cellular biology to mechanical properties and could also pave the way to understanding other starch-containing cells (e.g. pea, lentils, wheat).

Mechanical properties of starch-filled alginate gel particles.

The aim of this work was to investigate the mechanical behaviour of alginate-based composite particles. Alginate gel beads with entrapped starch were used as the replicates of storage cells of plant tissue. Beads were formulated using different ratios of both ingredients and were produced using two methods, resulting in particles in the macro- and micro-scale size range. Compression tests revealed an effect of bead size on mechanical properties and a dominant role of the alginate on the material properties. Starch was successfully encapsulated as native granules in the beads and once encompassed, it suffered restricted swelling, up to 45 % of its original size, after undergoing heating. Force versus displacement data were fitted to both an empirical and the Hertz model and Young's modulus was found to increase only with heated starch inclusions. Microscopy was deemed crucial for the interpretation of mechanical measurements.

Independent co-delivery of model actives with different degrees of hydrophilicity from oil-in-water and water-in-oil emulsions stabilised by solid lipid particles via a Pickering mechanism: a-proof-of-principle study.

HYPOTHESIS: The development of vehicles for the co-encapsulation of actives with diverse characteristics and their subsequent controllable co-delivery is gaining increasing research interest. Predominantly centred around pharmaceutical applications, the majority of such co-delivery approaches have been focusing on solid formulations and less so on liquid-based systems. Simple emulsions can be designed to offer a liquid-based microstructural platform for the compartmentalised multi-delivery of actives. EXPERIMENTS: In this work, solid lipid nanoparticle stabilised Pickering emulsions were used for the co-encapsulation/co-delivery of two model actives with different degrees of hydrophilicity. Lipid particles containing a model hydrophobic active were prepared in the presence of either Tween 20 or whey protein isolate, and were then used to stabilise water-in-oil or oil-in-water emulsions, containing a secondary model active within their dispersed phase. FINDINGS: Solid lipid nanoparticles prepared with either type of emulsifier were able to provide stable emulsions. Release kinetic data fitting revealed that different co-delivery profiles can be achieved by controlling the surface properties of the lipid nanoparticles. The current proof-of-principle study presents preliminary data that confirm the potential of this approach to be utilised as a flexible liquid-based platform for the segregated co-encapsulation and independent co-release of different combinations of actives, either hydrophobic/hydrophilic or hydrophobic/hydrophobic, with diverse release profiles.

Formulation design, production and characterisation of solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) for the encapsulation of a model hydrophobic active.

Lipid nanoparticles have been widely investigated for their use as either carriers for poorly water soluble actives or as (Pickering) emulsion stabilisers. Recent studies have suggested that the fabrication of lipid nanostructures that can display both these performances concurrently, can enable the development of liquid formulations for multi-active encapsulation and release. Understanding the effects of different formulation variables on the microstructural attributes that underline both these functionalities is crucial in developing such lipid nanostructures. In this study, two types of lipid-based nanoparticles, solid lipid nanoparticles and nanostructured lipid carriers, were fabricated using varying formulation parameters, namely type of solid lipid, concentration of liquid lipid and type/concentration of surface active species. The impact of these formulation parameters on the size, thermal properties, encapsulation efficiency, loading capacity and long-term storage stability of the developed lipid systems, was studied. Preliminary lipid screening and processing conditions studies, focused on creating a suitable lipid host matrix of appropriate dimensions that could enable the high loading of a model hydrophobic active (curcumin). Informed by this, selected lipid nanostructures were then produced. These were characterised by encapsulation efficiency and loading capacity values as high as 99% and 5%, respectively, and particle dimensions within the desirable size range (100-200 nm) required to enable Pickering functionality. Compatibility between the lipid matrix components, and liquid lipid/active addition were shown to greatly influence the polymorphism/crystallinity of the fabricated particles, with the latter demonstrating a liquid lipid concentration-dependent behaviour. Successful long-term storage stability of up to 28 weeks was confirmed for certain formulations.

The role of surface active species in the fabrication and functionality of edible solid lipid particles.

Lipid particles are very promising candidates for utilisation as Pickering stabilisers, and fabrication of these species has been attracting considerable academic and industrial research. Nonetheless, current understanding of these systems is hindered by the fact that, as a whole, studies reporting on the fabrication and Pickering utilisation of lipid particles vary significantly in processing conditions being utilised and formulation parameters considered. The present study investigates, under well-controlled processing and formulation conditions, the fabrication of edible lipid particles from two lipid sources in the presence of two different types of amphiphilic species (surfactant or protein) via melt-emulsification and subsequent crystallisation. Fabricated solid lipid particles were assessed in terms of their particle size, interfacial and thermal behaviour, as well as stability, as these microstructure attributes have established links to Pickering functionality. Lipid particle size and stability were controlled by the type and concentration of the used amphiphilic species (affecting the melt emulsification step) and the type of lipid source (influencing the crystallisation step). Interfacial behaviour was closely linked to the type and concentration of the surface active component used. Finally, the types of lipid and amphiphilic agents employed were found to affect lipid particle thermal behaviour the most.