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This paper develops a finite element (FE) model of the single fibre fragmentation test designed for direct comparison with experimental results on an E-glass/epoxy system by McCarthy et al. (2015). Interface behaviour is modelled via a cohesive surface, and stochastic Weibull fibre strengths (determined by independent experiments) assigned at random to the elements along the fibre. Predictions from the model agree with experiment for a range of outputs: The evolution of the number of fibre breaks with strain is similar and breaks occur at random locations as required. The model also captures a transition to a Uniform (rather than Weibull) statistical distribution of break locations at later stages of the test consistent with recent experiments. The evolution of the cumulative distribution of fragment lengths is also similar to that of the experiment. In addition, fibre axial stress and interfacial shear stress distributions conform with experimental observation. Correct model predictions of break locations confirm the approach taken on assigning stochastic (Weibull) strengths along the fibre. The effectiveness of the FE model in capturing a number of key aspects of the fragmentation phenomenon suggest its usefulness as a tool in analysing and interpreting fibre fragmentation tests, including back-calculation of interfacial shear strength.

Stretchable Triboelectric Nanogenerators (TENGs) for wearable electronics are in significant demand in the area of self-powered energy harvesting and storage devices. Designing a suitable electrode is one of the major challenges in developing a fully wearable TENG device and requires research aimed at exploring new materials and methods to develop stretchable electrodes. This review article is dedicated to presenting recent developments in exploring new materials for flexible TENGs with special emphasis on electrode components for wearable devices. In addition, materials that can potentially deliver properties such as transparency, self-healability and water-resistance are also reviewed. Inherently stretchable materials and a combination of soft and rigid materials including polymers and their composites, inorganic and ceramic materials, 2D materials and carbonaceous nanomaterials are also addressed. Additionally, various fabrication strategies and geometrical patterning techniques employed for designing highly stretchable electrodes for wearable TENG devices are also explored. The challenges reflected in the present approaches as well as feasible suggestions for future advancements are discussed.

With electrical power generated from mechanical contact, triboelectric nanogenerators (TENGs) offer a promising route to realizing self-powered sensors. For effective usage, it is important to improve their limited power range (0.1–100 mW/cm2) and this can be achieved by optimizing the output performance. Among the factors that confer higher performance are materials with a strong triboelectric effect together with low permittivity, but it is challenging to optimize both within a single material. This paper presents a solution to this challenge by optimizing a low permittivity substrate beneath the tribo-contact layer. Results are simulated over a range of substrate permittivities. The open circuit voltage is found to increase by a factor of 1.6 in moving from PVDF to the lower permittivity PTFE. Two TENG devices have been fabricated with $100\boldsymbol {\mu m}$ PET and PTFE substrates to compare performance. The experiments confirm that lowering the substrate dielectric constant (i.e. PET to PTFE) raises the open circuit voltage in line with simulation predictions.

Triboelectric nanogenerators (TENGs) are flexible, efficient, and cost-effective energy harvesters. Here, we develop high-performance ferroelectric-assisted TENGs using electrospun fibrous surfaces based on P(VDF-TrFE) with dispersed BaTiO3 (BTO) nanofillers in either cubic (CBTO) or tetragonal (TBTO) form. TENGs with three types of tribo-negative surface (pristine P(VDF-TrFE), P(VDF-TrFE)/CBTO and P(VDF-TrFE)/TBTO) in contact with PET were investigated and output increased progressively from pristine (0.75 W/m2) to CBTO (2 W/m2) and to TBTO (2.75 W/m2). Accounting for contact pressure, the max output (Voc = 315 V & Jsc = 6.7 µA/cm2) is significantly higher than for TENGs having spin-coated P(VDF-TrFE)/BTO. It is hypothesized that electrospinning increases dipole alignment due to high applied voltages, but also aids the formation of a highly oriented crystalline β-phase via uniaxial stretching. Essentially, tribo-charge transfer is boosted due to increased surface potential owing to enhanced ferroelectric polarization. P(VDF-TrFE)/TBTO produced higher output than P(VDF-TrFE)/CBTO even though permittivity is nearly identical. Thus, it is shown that BTO fillers boost output, not just by increasing permittivity, but also by enhancing the crystallinity and amount of the β-phase (as TBTO produced a more crystalline β-phase present in greater amounts). Finally, the ferroelectric-assisted TENG was integrated with a flexible graphene electrode-based supercapacitor to produce a self-charging system capable of charging to 1.25 V in just 5 min. These results demonstrate that this technology can be valuable in wearable applications where higher power output, more efficient charging and flexibility are paramount.

This work presents a triboelectric nanogenerators (TENG) based wide-range, self-powered flexible pressure sensor. The fabricated TENG can detect wide range of applied pressure from 3.2 to 1176 kPa. By analyzing the open-circuit voltage versus pressure curve, the sensitivity in three pressure regimes, namely low (1-10 kPa), medium-high (10-500 kPa) and ultra-high (>500 kPa) is extracted. The obtained sensitivities for these three pressure regimes are 3.16, 0.023 and 0.031 V•kPa-1, respectively. The origin of such a stable response of TENG at all of 3 pressure regimes lies in the use of real contact area of the interface pair. To the best of our knowledge, this is the first time a TENG as self-powered pressure sensor has been characterized over such a wide pressure range covering both low and super high pressures. These results show the potential of TENGs for a wide range of applications such as detecting the pressure in wearables, self-powered e-Skin for sole of humanoid robot to help them walk and stand, and the impact of wave energy.

Triboelectric nanogenerators (TENGs) have attracted significant interest as the alternative source of renewable energy. Their performance is believed to depend on the contact force, but its origin is yet to be established. Herein, we show that the origin lies in the real contact area A r , probed with novel experiments specifically designed for this purpose. The open circuit voltage V oc , short circuit current I sc and A r for a TENG, having two nominally flat tribo-contact surfaces, were found to increase with contact force/pressure. The A r is notably small at low pressures (0.25% at 16 kPa) that are typically experienced in wearable applications. However, it increases 328 fold to as much as 82% when it saturates beyond about 1.12 MPa pressure - achievable for impact with ocean waves. Critically, V oc and I sc saturate at the same contact pressure as A r suggesting that electrical output follows the evolution of the A r . Assuming that tribo-charges can only transfer across the interface at areas of real contact, it follows that an increasing A r with contact pressure should produce a corresponding increase in the electrical output. These results underline the importance of accounting for real contact area in TENG design to boost their performance, the distinction between real and nominal contact area in tribo-charge density definition, and the possibility of using TENGs as a self-powered pressure/load sensors. Crucially, the results indicate that the large contact pressures, readily available in applications such as road-tyre contact and wave energy, alone could be enough to boost the performance, thus avoiding the need for costly surface engineering to increase A r .

Abstract An approach to producing interfaces with tailored and repeatable normal contact stiffness using micropatterned surfaces is developed. A finite element model is first used to design square wave interfaces having a range of stiffnesses, and these are fabricated in polycarbonate via a microfabrication process. Results demonstrate that the contact stiffnesses of the fabricated interfaces are both tailorable and repeatable. The approach can be broadened to other materials and is useful for applications requiring specified interface stiffness. Finally, even with these deterministic interfaces, we show that low levels of roughness on the surface features are sufficient to produce a load-dependent contact stiffness at lower loads. Therefore, tailorability is mostly applicable above this limit where total contact stiffness converges to a load-independent value. Graphic Abstract

The viability of using induction heating to facilitate the wrinkle-free forming of multi-axial pre-consolidated advanced thermoplastic composites over complex geometries is explored. The research focuses on the use of tin as a medium to both heat and lubricate the forming laminate. Initial tests demonstrate the viability of the fundamental ideas of the process; induction heating is used to melt the tin sheet, which is then shown to melt the matrix phase of carbon-nylon composite laminates when stacked in a hybrid composite/tin layup. A novel low-cost reconfigurable multi-step forming tool is used to demonstrate how most of the tin can be squeezed out of the layup prior to consolidation. The multi-step tool can be augmented with segmented tooling to rapidly manufacture composite parts of high geometric complexity. In this investigation, a 'ripple' geometry containing three 'cavities' is used to demonstrate the technique. Tests demonstrated that at least three sheets of inter-laminar tin can be simultaneously melted using the induction heating system. Initial results indicate complex geometries can be formed with minimal wrinkling while removing interlaminar tin.

Triboelectric nanogenerators (TENGs) allow generation of electricity based on charge transfer during repeated contact of suitably chosen surfaces. Recently, rapid advances have been made in boosting their performance, but advancement in fundamental understanding has progressed more slowly. Currently, the most popular TENG models assume idealized flat surfaces that guarantee complete contact and a contact force (or load)-independent response. However, all real surfaces possess some level of surface roughness which is known to produce a load-dependent contact area. We develop a new unified model (for dielectric-to-dielectric TENGs) which adds consideration of surface roughness to the established distance-dependent electric field model. We account for surface roughness by applying Persson's contact theory to determine the load-dependent contact area. The model is applicable from first touch to nearly complete contact provided deformation remains elastic. Compared to load-independent approaches, the presented model is a better predictor of TENG performance. It captures the load-dependent nature of TENG performance apparent in recent tests. It predicts that the electrical output can be expected to be tiny at low contact loads, but should converge to an upper-bound at higher loads as the contact area approaches complete contact. Comparison with test results reveal substantially better prediction of open circuit voltage V O C compared to load-independent models which tend to overestimate V O C considerably. By assisting the designers with better predictions of TENG output, the developed unified theory has huge potential for advancing the use of TENGs in applications such as wearables (i.e. low loads) to tidal or wave energy (i.e. large loads).

Nutritional beverage emulsions contain water and oil, stabilised by surfactants, and are both diverse and complex. Their susceptibility to changes induced by manufacturing processes and on storage, results in challenges with their stability, quality and shelf-life. An understanding of the relationship between structure and stability of an emulsion is essential to designing and competently formulating food products with the desired nutritional functionality and sensory properties, while achieving the required shelf-life. This article critically reviews a selection of commonly-used analytical approaches focused on characterisation of emulsion structure in the context of emulsion formation, techno-functional properties and stability to intrinsic and environmental factors.

Conjugation of whey protein isolate (WPI) and maltodextrin (MD, dextrose equivalent of 6) was achieved by dry-heating at an initial pH of 7.0, at 60 °C and 79% relative humidity, with WPI: MD6 ratio of 1:1, for up to 24 h. Conjugation was achieved with limited development of colour and advanced Maillard products on 24 h of heating. Conjugation increased the protein solubility at pH 4.5, by 7.1–8.5%, compared to the unheated and heated WPI controls. Conjugation of WPI with MD6 enhanced the stability and retention of clarity in protein solutions heated at 85 °C for 10 min with 50 mM added NaCl.

Syntactic foams with hollow glass microspheres embedded in an epoxy matrix are\ud used in marine, aerospace and ground transportation vehicle applications. This\ud work presents an in situ experimental study of failure mechanisms in syntactic\ud foam based on X-ray microcomputed tomography with uniaxial compression.\ud Under different levels of compressive strain, the material was scanned using X-ray\ud microcomputed tomography to obtain three-dimensional (3D) images of its\ud internal microstructure. Experiments with the same parameters were carried out\ud to investigate repeatability. The microscopic observations have suggested that\ud damage nucleation occurs at the weakest microspheres. When applied strain\ud increases, shear collapse bands (SCBs) develop local to the fragmented microspheres\ud due to stress concentration and bending deformation around SCBs occurs.\ud After significant strain, the thickness of the SCBs increases owing to the accumulation\ud of the broken microspheres. The relationship between the volume\ud fraction of microspheres and applied bulk strain has been characterised.

Glycation of milk proteins and peptides can be achieved by Maillard-induced conjugation of reducing carbohydrates with the available amino groups of proteins/peptides during the early stages of the Maillard reaction. This conjugation can be achieved under wet or dry heating conditions, with the choice of heating mode influencing the rate and extent of conjugation, in addition to the functionality of the conjugated protein/peptides. Conjugation has been shown to modify the technological and nutritional properties of a range of milk protein/peptide-based ingredients. This review focuses mainly on modifications to physicochemical properties and technological functionality (i.e., solubility, heat stability, emulsification, foaming and gelation properties) of milk proteins and peptides by conjugation. Particular emphasis is placed on understanding of the relationships between changes in protein/peptide molecular structure/conformation, physicochemical properties and technological functionality, as influenced by glycation.

Whey proteins may be modified by conjugation with carbohydrates through the Maillard reaction, a process that can occur naturally during thermal processing and storage. However, most academic and industrial interest is in the exploitation of conjugation as a means to modify, extend, and control the technological and nutritional functionality of whey proteins in premium nutritional applications such as protein beverages. This chapter provides an overview of the work to date on this rapidly expanding topic, focusing on a review of the substrates used for conjugation and a comparison of the different approaches used for production of conjugated ingredients. It also contains a detailed investigation of the impact of conjugation on selected technological and nutritional properties of whey proteins. Approaches under investigation for the enrichment and purification of whey protein conjugates are discussed and several thought-provoking topics are presented in the final section on perspectives and future research needs.

Mass production of microfluidic devices commonly relies on injection molding. Injection molding requires a master surface made using micro or nanofabrication. Conventionally, electroplating from a silicon master is used for mold insert production, but this is expensive and cannot be used with masters produced via the Bosch process as interlocking of the scalloping between polymer and metal insert hinders part ejection. Here, an alternative to the electroplating process is developed by adapting a nanoimprint route to produce flexible micro-structured polymer inserts capable of molding using a Bosch process-produced master. An optimized fabrication approach using silicon masters with smooth sidewalls (produced using the mixed process) is used to characterize the limits of the process. Aspect ratios of 1 and below are successfully replicated. Feature spacings down to 20 µm are successfully produced with minimal variation between repeated parts. Masters produced using two different Bosch etches exhibiting both coarse and fine nanometer scalloping are also studied. Parts are successfully ejected with retained nanometer scalloping in all samples although inlay damage occurred after >10 replicas. A proof-of-concept microfluidic device is successfully produced vindicating the use of this approach as an efficient and cost-effective approach for the rapid prototyping of complex micro-structured designs.

The potential to improve the mechanical properties of adhesive joints via micro-structured interlocking features is investigated. The micro-structured surfaces were fabricated in polycarbonate via injection moulding from a master template. The specimens were then bonded in an interlocking configuration to form single lap joints and tested to failure in tension. Planar untreated (i.e. un-abraded) and planar roughened (i.e. abraded) samples were also tested to provide benchmarks. Compared to the planar roughened case, results show that micro-structuring the interface can yield up to a 95.9% increase in strength and up to 162% increase in work to failure. Increases in strength and work to failure beyond the planar roughened level are attributed to mechanical interlocking of features. As deformation proceeds, progressive bending of each pair of interlocking features develops an increasing resistive load which allows the total load to significantly exceed that of the planar roughened case. Work to failure is increased via a combination of increased maximum force, increased displacement enabled by microfeature bending and a more torturous crack path. Low clearances between interlocking features were found to be favourable for mechanical properties owing to reduced bending stiffness of the repeating periodic unit at the interface.

The relationship between material failure and surface roughness has been investigated using two titanium alloys: Ti64 and the more ductile Ti407. Three surface types were created (polished, sandblasted and scratched) with instances spanning a wide range of average roughness. The surfaces were tested in three-point bending with the imparted roughness on the tensile under-surface of a rectangular beam specimen. Results showed failure of Ti64 to be highly sensitive to both magnitude and orientation of roughness. High roughness in the maximum tensile stress direction (and scratch like features perpendicular to this direction) were most detrimental. Thus, strain-to-failure (and work-to-failure) in Ti64 dropped off significantly with increasing surface roughness in the tensile direction. Finite element modelling of the test indicated that cracks initiate at zones of high plastic strain at the tips of roughness valleys due to high local surface curvature. Thus, roughness can be considered as a series of blunt crack-like features where larger crack tip curvature induces greater likelihood of crack propagation. Contrastingly, the mechanical response of Ti407 was insensitive to surface roughness owing to its significantly greater ductility. Thus, designers need to be aware of the sensitivity of failure of particular materials to surface roughness. The insensitivity of Ti407 is advantageous, but the sensitivity of failure to surface roughness in a material like Ti64 is potentially serious if not properly accounted for.

The titanium alloy Ti-407 (Ti407) is a new alloy being considered for single load to failure applications where energy absorption is a key requirement. This work characterised the deformation and failure mechanisms of Ti407 in uniaxial tension and compression at quasi-static and increased strain rates. The results are compared with equivalent tests on Ti-6Al-4 V (Ti64) to provide a benchmark. The stress-strain data under each condition reveals reduced strength but significantly increased ductility in the Ti407 alloy compared to Ti64. The reduced aluminium content in Ti407 is thought to allow additional dislocation motion and delay crack initiation and propagation. The crystallographic texture analysis on deformed specimens further suggests that in response to an applied stress, Ti407 proves more sensitive to texturing and exhibits greater grain elongation and rotation in comparison to Ti64. Its ability to accommodate significantly more deformation before failure (than Ti64) will provide opportunities for improved impact energy absorption performance, as well as improved machinability and formability (and potentially lower manufacturing cost).

The dry friction of surfaces with nanoscale roughness and the possibility of using micropatterning to tailor friction by manipulating contact area is investigated. Square wave patterns produced on samples from silicon wafers (and their unstructured equivalent) were slid against unstructured silicon counter surfaces. The width of the square wave features was adjusted to vary the apparent feature contact area. The existence of nanoscale roughness was sufficient to ensure Amontons’ first law (F = μP) on both structured & unstructured samples. Somewhat counterintuitively, friction was independent of the apparent feature contact area making it difficult to tailor friction via the feature contact area. This occurred because, even though the apparent feature contact area was adjusted, the surface roughness and nominal flatness at the contact interface was preserved ensuring that the real contact area and thereby the friction, were likewise preserved. This is an interesting special case, but not universally applicable: friction can indeed be adjusted by structuring provided the intervention leads to a change in real contact area (or interlocking)– and this depends on the specific surface geometry and topography.

Model infant formula emulsions containing 15.5, 35.0 and 70.0 g L−1 protein, soybean oil and maltodextrin (MD), respectively, were prepared. Emulsions were stabilised by whey protein hydrolysate (WPH) + CITREM (9 g L−1), WPH + lecithin (9 g L−1) or WPH conjugated with MD (WPH–MD). All emulsions had mono-modal oil droplet size distributions post-homogenisation with mean oil droplet diameters (D4,3) of

The impact of conjugation with maltodextrin on selected functional properties (i.e., solubility and thermal stability) of intact whey protein isolate (WPI) and whey protein hydrolysate (WPH) was determined. Conjugation of WPI and WPH (degree of hydrolysis 9.3%) with maltodextrin (MD) was achieved by heating solutions of 5% WPI or WPH with 5% MD, initial pH 8.2, at 90 °C for up to 24 h. The WPH had 55.4% higher levels of available amino groups compared with the WPI, which contributed to more rapid and extensive conjugation of WPH-MD, compared with WPI-MD. The WPI-MD and WPH-MD solutions heated for 8 h had significantly higher (P m added NaCl.

Fibres made from carbon nanotubes (CNTs) have not yet achieved strengths approaching that of individual CNTs. The problem is that load is not effectively transferred between the constituent, discontinuous CNTs. High energy irradiation has shown promise on small CNT bundles, in creating covalent cross-links to enhance load transfer, but cannot sufficiently penetrate real CNT fibres, which typically contain 106 or more CNTs. Here, we suggest that the “draw-twist” process for producing CNT fibres from forests offers an opportunity for CNT bundles to be individually treated with irradiation before being twisted to form a fibre. We use molecular dynamics to examine the effectiveness of low energy (1 eV) carbon ion irradiation (or deposition) in this context. We find that very small amounts of deposition can significantly enhance both intra-bundle and inter-bundle load transfer. Within bundles, deposition atoms mediate covalent links between both the sides and ends of neighbouring CNTs. Inter-bundle load transfer is improved as under-coordinated carbon adatom branches formed during deposition, spontaneously form inter-bundle cross-links as the bundles are forced together by the twisting action. The effects of varying fluence and twisting angles are examined, and the potential to add a prior higher energy irradiation step to penetrate larger bundles is explored. The possibility to produce an amorphous carbon/CNT composite fibre is also discussed.

Internal porosity of metallic parts manufactured by laser powder bed fusion (LPBF) is governed by processing parameters including laser power, scanning speed, scan spacing and layer thickness. To fully understand the influence of processing parameters it is important to categorise the shape of process defects (pores) in 3D beyond the degree of sphericity alone. In the present paper, AlSi10Mg samples were manufactured using 30 unique LPBF parameter combinations and analysed using high resolution X-ray micro computed tomography (XμCT). The shapes of individual pores are classified and studied using an approach based on the similarity of 3D pore descriptors with simplified artificial objects. Porosity within high as-fabricated densification builds can be reduced to virtually negligible by hot isostatic pressing (HIPping), which was found to fully or partially close (flatten) pores. Subsequent T6 treatment causes pores to reopen and resemble their original shape. The effects of treatment are sensitive to pore size.

With electrical power generated from mechanical contact, the triboelectric nanogenerators (TEN Gs) have attracted attention recently as a promising route to realising self-powered sensors (e.g. tactile sensors, biomedical sensors etc.). Due to their limited power range (0.1-100 mW/cm2), it is important to optimise the output performance of TENGs. Among the factors that confer higher performance are materials with a strong triboelectric effect and materials with low permittivity. It can be difficult to realize these two benefits in a single contact material. This paper presents a solution to this challenge by optimising a low permittivity substrate beneath the tribo-contact layer. Results are simulated over a range of both substrate permittivity and thickness. The open circuit voltage is found to increase by a factor of 1.8 in moving from PVDF to the lower permittivity PTFE and by a further factor of 37.2 when the substrate thickness is reduced from 200 to $\pmb{1\ \mu}\mathbf{m}$ . For PTFE with $\pmb{1\ \mu}\mathbf{m}$ thickness, this amounts to 12.2 kV, as against 327V known from simulations up to now. These results clearly indicate that optimized low permittivity, low thickness substrates represent a potential route to self-powered sensors.

Whey protein hydrolysate (WPH)-based oil-in-water (O/W) emulsions containing lecithin (0–5%, w/w, oil) were produced and stored at 4 °C for 14 days. Surface tension and interfacial tension of these systems were measured for formulation development. Fat globule size distribution (FGSD) analysis and confocal laser scanning microscopy (CLSM) were used to assess the physical stability of emulsions during storage and identify mechanisms of instability. Lecithin decreased interfacial tension between oil and aqueous phases of model emulsions and allowed formation of smaller oil droplets on homogenisation. However, low-intermediate levels (1–3%) of lecithin caused coalescence and shift to bimodal FGSD during storage of emulsions.

The microstructural breakdown properties of heat-induced whey protein (WP) gels prepared at pH 7.0 or 5.4 and containing emulsified sunflower oil (7%, w/w) were studied using notch propagation tensile testing in combination with dynamic confocal laser scanning microscopy (CLSM). In addition, the microstructural breakdown properties of stirred acid milk gels containing added emulsified oil (0–15%, w/w) or Konjac glucomannan (0.05%, w/w) were studied using compressive rheological deformation in combination with dynamic CLSM imaging. The structural breakdown properties (Young's modulus and stress/strain at fracture), the microstuctural behaviour of the protein phase, the emulsified oil phase and the pattern of notch propagation during large deformation tensile testing of the WP emulsion filled gel prepared at pH 7.0 (fine stranded gel) differed from that of the WP emulsion filled gel prepared at pH 5.4 (particulate gel). The protein aggregates, emulsified oil droplets and the Konjac phase in the stirred acid milk gels flowed on compression; however, the flow pattern changed from “frictional” flow with no emulsified oil or Konjac to “slip” flow in the presence of emulsified oil or Konjac. Also, compression of stirred acid milk gels below a certain critical height led to disintegration of the aggregated protein structure, serum release and reduced stability of the oil droplets in the stirred gels. The critical compression height was influenced by emulsified oil level and the presence of added Konjac.

Sodium caseinate was hydrolysed to a limited, moderate or extensive degree. The hydrolysates were conjugated with maltodextrin by a Maillard-type reaction by dry-heat treatment at 60 °C and 79% relative humidity for 2 or 4 days. Conjugates were characterised by SDS–PAGE and gel permeation chromatography. In comparison with the hydrolysates themselves, the conjugated hydrolysates had improved solubility, particularly around the isoelectric pH of the protein. The emulsifying properties of these conjugates were assessed in oil-in-water (o/w) emulsions; on emulsion formation, each conjugate-stabilised emulsion had lower mean fat globule size than the corresponding hydrolysate-stabilised emulsion. After storage for 7 days under accelerated shelf life testing conditions, the limited and moderate hydrolysate conjugate–stabilised emulsions had improved storage stability compared with hydrolysate-stabilised emulsions; however, further research is required to optimise the hydrolysate fraction prior to conjugation for the production of novel low molecular weight emulsifiers.

The objective of this study was to compare the drying performance and physicochemical properties of model infant formula (IF) emulsions containing 43, 96 and 192 g L−1 protein, oil and maltodextrin (MD), respectively, prepared using different emulsifier systems. Emulsions were stabilised using either whey protein isolate (WPI), whey protein hydrolysate (WPH; DH 8%), WPH + CITREM (9 g L−1), WPH + lecithin (5 g L−1) or WPH conjugated with maltodextrin (DE 12) (WPH-MD). Homogenised emulsions had 32% solids content and oil globules with mean volume diameter WPH + LEC > WPH > WPH- MD > WPI, WPI > WPH > WPH- MD > WPH + LEC > WPH + CIT and WPH- MD > WPI > WPH > WPH + LEC > WPH + CIT, respectively. Additionally, differences in wettability, surface topography and oil globule distribution within the powder matrix and in reconstituted powders were linked to the emulsifier system used. Inclusion of the WPH-MD conjugate in the formulation of IF powder significantly improved drying behaviour and physicochemical properties of the resultant powder, as evidenced by lowest powder build-up during drying and greatest emulsion quality on reconstitution, compared to the other model formula systems.

A finite-element model of the interaction of an elastic-plastic asperity junction based on cylindrical or spherical asperities is used to predict sliding friction coefficients. The modelling differs from previous work by permitting greater asperity overlaps, enforcing an interface adhesional shear strength, and allowing material failure. The results of the modelling were also used to predict friction coefficients for a stochastic rough surface. The asperities were based on the titanium alloy Ti-6Al-4V, and the magnitudes of the predicted friction coefficients were generally representative of experimental measurements of sliding friction. The results suggest that friction arises from both plasticity and tangential interface adhesion. © 2011 Elsevier Ltd. All rights reserved.

Whey protein isolate (WPI) solutions, with different levels of aggregated protein, were prepared by heating (5% protein, pH 7, 90 °C for 30 min) WPI solutions with either 20 mM added NaCl (WPI + NaCl), 5 mM N-ethylmaleimide (WPI + NEM) or 20 mM added NaCl and 5 mM NEM (WPI + NaCl + NEM). Gel electrophoresis demonstrated that the heated WPI and WPI + NaCl solutions had higher levels of aggregated protein, due to more covalent interactions between proteins, than the heated WPI + NEM and WPI + NaCl + NEM solutions. There were marked differences in the levels of amino groups between all heated WPI solutions when measured by the OPA and TNBS methods, with lower levels being measured by the TNBS method than by the OPA method. These results demonstrate that the measurement of available amino groups by the OPA method is less impacted than by the TNBS method after heat-induced structural changes, arising from disulfide or sulfhydryl-disulfide bond-mediated aggregation of whey protein molecules.

The tangential contact stiffness of frictional interfaces affects both the vibration response and structural integrity of structures comprising frictional joints. Vibration and structural response of monolithic structures can be predicted very accurately; however, when assemblies of components involve frictional interfaces, additional damping and compliance are present due to these interfaces. These features make it more challenging to predict the vibration characteristics of assemblies with the same degree of accuracy as can be achieved for single components. If these interface properties can be determined, it should then be possible to significantly enhance current models of the vibration of engineering assemblies. Measurements of both force and displacement in the tangential direction are obtained from a series of in-line fretting tests involving flat pads with rounded corners clamped against the flat surface of a specimen which is oscillated by a hydraulic tensile testing machine. In order to measure the local displacement field very close to the contact interface, the digital image correlation (DIC) method is employed. The effect of normal contact pressure on tangential contact stiffness is investigated. Multiple experiments with the same parameters show good repeatability given the number of variables involved. © (2011) Trans Tech Publications, Switzerland.

The present paper describes an experimental technique to accurately measure the tangential contact stiffness between two rough contacting surfaces manufactured from the titanium alloy Ti6Al4V. The digital image correlation method is employed to measure the local displacement field. The effect of normal contact pressure, nominal contact area and fretting wear on tangential contact stiffness is investigated. The experiments indicate that the tangential contact stiffness is approximately proportional to the nominal contact area and the normal pressure raised to the power of 0.64. Multiple experiments with the same parameters show good repeatability given the number of variables involved. © 2011 Elsevier Ltd. All rights reserved.

Liqueurs are a diverse family of strong, sweet, alcoholic beverages, usually containing distilled spirits such as brandy, whiskey, and rum, which are made by combining spirits with sugar and flavorings. A cream liqueur is a specific type of liqueur that is a dairy-based oil-in-water emulsion containing sufficient alcohol to inhibit microbial growth; cream liqueurs typically contain cream, protein, sugar, alcohol, flavors, colors, and emulsifiers. Physical instability during storage is the main problem facing cream liqueurs, and a key technological step is homogenization to produce cream liqueurs with fat globules of very small diameters and thereby ensure the long-term stability of the product. This article reviews the principles of formulation and production of liqueurs in general, with particular focus on the case of cream liqueurs.

The effect of conjugating konjac glucomannan with fluorescein isothyocyanate (FITC) via covalent labelling on selected physicochemical properties of FITC and konjac was investigated using spectrophotometry, rheometry, and size exclusion chromatography (SEC). The binding of the lectin concanavalin A (ConA) to sugar residues of konjac was investigated using SEC. Covalent conjugation of konjac with FITC led to a shift in the absorbance spectrum peak of FITC to a lower wavelength and a decrease in the average molecular weight distribution of konjac. Furthermore, covalently labelled konjac showed reduced apparent viscosity compared to unlabelled konjac. ConA bound to the sugar residues in konjac. The potential of konjac–FITC covalent labelled conjugate or konjac–lectin labelled ConA complexes as fluorescent markers for localisation of konjac in a phase separated micellar casein–konjac mixture was investigated using confocal laser scanning microscopy. Results indicated that covalently labelled konjac has microscopic phase behaviour similar to that of un-labelled konjac and are therefore suitable for localising konjac glucomannan in a phase-separated micellar casein–konjac system.