TKPlate 1.0: An Open-access platform for toxicokinetic and toxicodynamic modelling of chemicals to implement new approach methodologies in chemical risk assessment.

This publication is linked to the following EFSA Supporting Publications articles: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2023.EN-8441/full, http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2023.EN-8440/full, http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2023.EN-8437/full.

Atypical phase behaviour of quinoa protein isolate in mixture with maltodextrin.

Consumers are increasingly looking for new plant-based alternatives to substitute animal proteins in their diets but for some applications it can be difficult to achieve the desired product microstructure using only plant proteins. One approach to facilitate structuring is to mix these plant-based ingredients with a polysaccharide. Here, the phase behaviour and microstructure of quinoa protein isolate (QPI) in mixture with maltodextrin (MD) of two dextrose equivalents (DE 7 and 2) were investigated. The binodals of both QPI-MD phase diagrams showed an atypical shape, where the concentration of MD in the QPI-rich phase and of QPI in the MD-rich phase increased with overall biopolymer concentration. Molecular weight distribution and microstructure analyses revealed that both maltodextrins fractionated between the phases and were probably entrapped within the volume-spanning protein network in the QPI-rich phase, indicating a depletion flocculation mechanism of phase separation. The pre-heating of QPI and the removal of salt from the systems resulted in similarly atypical phase diagrams. The approach presented contributes to our understanding of the phase behaviour of mixtures between plant proteins and polysaccharides, while the results suggest that the formulation of plant-based products of predictable properties may be more challenging than anticipated.

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.

Propolis particles incorporated in aqueous formulations with enhanced antibacterial performance.

In recent years, the use of natural bioactives in food, pharmaceutical and cosmetic industries has emerged as a global formulation development trend. Although natural bioactives exhibit promising properties, they are also associated with chemical instability or poor aqueous solubility. One such bioactive with beneficial functionalities but limited industrial applicability within industry is propolis. The purpose of this study was to investigate means to enable enhancement to the antibacterial activity of propolis-based aqueous formulations. Dry propolis was firstly extracted from crude material and the effect of common carrier phases used for dissolution of propolis for antibacterial assays was investigated. Consequently, the extract was formulated into propolis sub-micron aqueous dispersions via direct ultrasonication. Processing time was varied, and all formed particles were characterised immediately after production in terms of size, polydispersity and zeta potential, and then again after a month-long storage period. When tested on E. coli cells, 15% propolis dispersions caused a bactericidal effect, which was sonication time and time of exposure dependent. Particles formed at the shortest sonication period (4 min) resulted in higher cell injury while those processed the longest (10 min) caused greater cell death and with AFM imaging, cell membrane alterations were confirmed. Chemically, for whole dispersions and carrier phases alone, free radical scavenging activity and total phenol content were slightly enhanced at longer sonication times. Overall, the present work suggests that formulating propolis extract sub-micron aqueous dispersions via sonication enhances their antibacterial performance via a synergistic effect involving both their carrier and dispersed phases.

A flow velocity dependence of dynamic surface tension in Plateau borders of foam.

HYPOTHESIS: Liquid drainage through foams is a multiscale process, that primarily occurs through channels known as Plateau borders (PBs). Recent experimental studies of isolated PBs have observed variations in channel surface tension, γ, with liquid flow rate, Q, for systems containing soluble low molecular weight surfactant (LMWS). The current study proposes that the dynamic surface tension (DST) could be responsible for this effect, where the residence time of surfactant molecules in the PB is similar to the time required for their adsorption to the channel interface. EXPERIMENTS: Profile geometries of isolated 'ideal' PB's were created in a bespoke experimental setup at controlled forced liquid flow rates. Average surfactant residence times, τRes, were calculated for solutions of Sodium dodecylsulfate (SDS), Tween 20 (T20) and Tween 80 (T80), and used to calculate corresponding average DST values in discrete regions of measured PB profiles. DST values were combined with microscale drainage theory to assess the potential physical implications on liquid flow. FINDINGS: Significant variations in the magnitude of γ were calculated based on surfactant characteristics, where only the rapid adsorption of SDS was sufficient to produce DST values approaching equilibrium. These findings seriously question assumptions of near equilibrium surface tension in LMWS foam systems above their critical micelle concentration (CMC). Furthermore, the presence of surface tension gradients identified using this discrete approach, highlights the need to further refine the current theory to a continuous approach incorporating Marangoni effects.

Impact of Pickering Intervention on the Stability of W1/O/W2 Double Emulsions of Relevance to Foods.

Although water-in-oil-in-water (W1/O/W2) double emulsions have been associated with a spectrum of potential applications in foods, their complex microstructure is significantly unstable. Pickering stabilization, reputed for superior and longer-term interfacial stabilization when compared to surfactant-stabilized systems, could provide the opportunity to enhance double-emulsion stability. The current work presents a systematic study on the impact of progressively adopting such a Pickering intervention onto one or both interfaces of W1/O/W2 emulsions relevant to foods. A range of surfactants/emulsifiers and particles have been used at the W1/O or O/W2 interface of the W1/O/W2 microstructure and, where appropriate, cross-compared with the equivalent interfaces of simple emulsions (W/O and O/W, respectively). As the aqueous compartments of all investigated systems were not osmotically balanced (at the point of formulating/forming these), any advantages in terms of double-emulsion stability enhancement can be directly attributed to the employed particle stabilization. It is demonstrated that, although partial Pickering intervention can encourage stability (particularly if that is introduced at the inner W1/O interface), only complete Pickering stabilization of the double microstructure can ensure that the oil globule size is maintained and the internal water phase is retained over a storage period of one month.

Measuring the impact of channel length on liquid flow through an ideal Plateau border and node system.

The phenomenon of foam drainage is a complex multi-scale process that unites molecular level interactions with bulk foam characteristics. Foam drainage is primarily governed by the flow of liquid in the channels and junctions that form between bubbles, which are known as Plateau borders (PBs) and nodes respectively. Existing theoretical work predicts the surface rheology of the PB and node air-liquid interface to influence liquid flow rates; however, direct experimental observations of this phenomenon remain scarce. This study recognises the clear need for a reproducible, accurate and standardised approach to directly studying liquid flow at the scale of a theoretically 'ideal' PB-node architecture. Measurements of PB geometric profiles and their apparent surface shear viscosities, µs, were made for an aqueous solution of Sodium Dodecyl Sulphate (SDS) at varying PB lengths, l1, and liquid flow rates in the range 10 µl min-1 ≤ Q ≤ 200 µl min-1. Geometric profiles displayed previously unobserved transitions between PB relaxation and expansion towards the node, with expansion dominating under conditions approaching conventional foam drainage. Average values of µs in the PB relaxation regions showed virtually inviscid behaviour, with magnitudes of 10-8 g s-1 < µs < 10-4 g s-1 for l1 in the range 27.5 mm ⪆ l1 ⪆ 8.0 mm. Decreasing magnitudes of µs and degrees of shear thinning were observed with increasing l1. This was attributed to a compressibility of the interface that was limited by an SDS concentration dependence on l1. Numerical evaluation predicted the appearance of Marangoni forces that scaled strongly with liquid shear rates, and could therefore have been responsible for the apparent shear thinning behaviour.

Production of Oil-in-Water Emulsions with Varying Dispersed-Phase Content using Confined Impinging Jet Mixers.

This work reports for the first time on the use of Confined Impinging Jet Mixers (CIJM) for the production of emulsions with dispersed-phase content up to 80 wt %, in both the surfactant-poor and -rich regimes, following the exposure to varying CIJM hydrodynamic conditions. It was observed computationally and experimentally that the CIJM capacity resulted strictly dependent on the mass jet flow rate (W jet > 176 g/min) and the pre-emulsion droplet size (>10 µm). CIJM emulsification performance remained (almost) unaffected by the variation in the oil mass fraction. All systems showed the lowest droplet size (∼8 µm) and similar droplet size distributions under the highest W jet. Conditionally onto the Tween20 availability, the emulsion d 3,2 was primarily determined by formulation characteristics in the surfactant poor-regime and by the CIJM energy dissipation rate in the surfactant-rich regime. In conclusion, this study offers further insights into the CIJM suitability as a realistic alternative to already-established emulsification methods.

Fabrication and Utilization of Bifunctional Protein/Polysaccharide Coprecipitates for the Independent Codelivery of Two Model Actives from Simple Oil-in-Water Emulsions.

Aside from single active microencapsulation, there is growing interest in designing structures for the coencapsulation and codelivery of multiple species. Although currently achievable within solid systems, significant challenges exist in realizing such functionality in liquid formulations. The present study reports on a novel microstructural strategy that enables the coencapsulation and corelease of two actives from oil-in-water emulsions. This is realized through the fabrication of sodium caseinate/chitosan (NaCAS/CS) complexes that in tandem function as encapsulants of one active (hydrophilic) but also as ("Pickering-like") stabilizers to emulsion droplets containing a secondary active (hydrophobic). Confocal microscopy confirmed that the two coencapsulated actives occupied distinct emulsion microstructure regions; the hydrophilic active was associated with the NaCAS/CS complexes at the emulsion interface, while the hydrophobic active was present within the oil droplets. Aided by their segregated coencapsulation, the two actives exhibited markedly different corelease behaviors. The hydrophilic active exhibited triggered release that was promoted by changes to pH, which weakened the protein-polysaccharide electrostatic interactions, resulting in particle swelling. The hydrophobic secondary active exhibited sustained release that was impervious to pH and instead controlled by passage across the interfacial barrier. The employed microstructural approach can therefore lead to the segregated coencapsulation and independent corelease of two incompatible actives, thus offering promise for the development of liquid-emulsion-based formulations containing multiple actives.

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.

Food-grade Pickering emulsions stabilised with solid lipid particles.

Aqueous dispersions of tripalmitin particles (with a minimum size of 130 nm) were produced, via a hot sonication method, with and without the addition of food-grade emulsifiers. Depending on their relative size and chemistry, the emulsifiers altered the properties of the fat particles (e.g. crystal form, dispersion state and surface properties) by two proposed mechanisms. Firstly, emulsifiers modify the rate and/or extent of polymorphic transitions, resulting in the formation of fat crystals with a range of polarities. Secondly, the adsorption of emulsifiers at the particle interface modifies crystal surface properties. Such emulsifier-modified fat particles were then used to stabilise emulsions. As the behaviour of these particles was predisposed by the kind of emulsifier employed for their manufacture, the resulting particles showed different preferences to which of the emulsion phases (oil or water) became the continuous one. The polarity of the fat particles decreased as follows: Whey Protein Isolate > Soy Lecithin > Soy Lecithin + Tween 20 > Tween 20 > Polyglycerol Polyricinoleate > no emulsifier. Consequently, particles stabilised with WPI formed oil-in-water emulsions (O/W); particles stabilised solely with lecithin produced a highly unstable W/O emulsion; and particles stabilised with a mixture of lecithin and Tween 20 gave a stable W/O emulsion with drop size up to 30 µm. Coalescence stable, oil-continuous emulsions (W/O) with drop sizes between 5 and 15 µm were produced when the tripalmitin particles were stabilised with solely with Tween 20, solely with polyglycerol polyricinoleate, or with no emulsifier at all. It is proposed that the stability of the latter three emulsions was additionally enhanced by sintering of fat particles at the oil-water interface, providing a mechanical barrier against coalescence.

Designing food structures for nutrition and health benefits.

In addition to providing specific sensory properties (e.g., flavor or textures), there is a need to produce foods that also provide functionality within the gastrointestinal (GI) tract, over and above simple nutrition. As such, there is a need to understand the physical and chemical processes occurring in the mouth, stomach, small intestine, and large intestine, in addition to the food structure-physiology interactions. In vivo techniques and in vitro models have allowed us to study and simulate these processes, which aids us in the design of food microstructures that can provide functionality within the human body. Furthermore, it is important to be aware of the health or nutritional needs of different groups of consumers when designing food structures, to provide targeted functionality. Examples of three groups of consumers (elderly, obese, and athletes) are given to demonstrate their differing nutritional requirements and the formulation engineering approaches that can be utilized to improve the health of these individuals. Eating is a pleasurable process, but foods of the future will be required to provide much more in terms of functionality for health and nutrition.

Advances in membrane emulsification. Part B: recent developments in modelling and scale-up approaches.

Membrane emulsification is a promising process for formulating emulsions and particulates. It offers many advantages over conventional 'high-shear' processes with narrower size distribution products, higher batch repeatability and lower energy consumption commonly demonstrated at a small scale. Since the process was first introduced around 25 years ago, understanding of the underlying mechanisms involved during microstructure formation has advanced significantly leading to the development of modelling approaches that predict processing output; e.g. emulsion droplet size and throughput. The accuracy and ease of application of these models is important to allow for the development of design equations which can potentially facilitate scale-up of the process and meet the manufacturer's specific requirements. Part B of this review considers the advantages and disadvantages of a variety of models developed to predict droplet size, flow behaviour and other phenomena (namely droplet-droplet interactions), with presentation of the appropriate formulae where necessary. Furthermore, the advancement of the process towards an industrial scale is also highlighted with additional recommendations by the authors for future work.

Advances in membrane emulsification. Part A: recent developments in processing aspects and microstructural design approaches.

Modern emulsion processing technology is strongly influenced by the market demands for products that are microstructure-driven and possess precisely controlled properties. Novel cost-effective processing techniques, such as membrane emulsification, have been explored and customised in the search for better control over the microstructure, and subsequently the quality of the final product. Part A of this review reports on the state of the art in membrane emulsification techniques, focusing on novel membrane materials and proof of concept experimental set-ups. Engineering advantages and limitations of a range of membrane techniques are critically discussed and linked to a variety of simple and complex structures (e.g. foams, particulates, liposomes etc.) produced specifically using those techniques.

Designing colloidal structures for micro and macro nutrient content and release in foods.

We report on how edible nano-emulsions can be designed and produced in order to remain stable on storage. Edible nano-emulsions can potentially be used to target and control delivery of micronutrients to the human gastrointestinal tract. A class of microstructures that offers enormous potential in foods is duplex (or double) emulsions. In this paper we report the ability to design and construct particle and low molecular weight emulsifier stabilised edible duplex emulsions; i.e. Pickering-in-Pickering emulsions. This novel design opens up routes for significant fat replacement in a way that is imperceptible to the consumer. Having demonstrated the ability to design novel emulsion structures for food applications, we finally present data on how fluid gel structures can be designed and used in foods to give fat-like lubrication properties in the absence of fat.