J.E. Norton

Designer colloids—towards healthy everyday foods?

Dietary related diseases are on the increase. Colloids play an important role in food structuring, stability through the distribution chain, and delivery of in use properties, taste and flavour, and nutrition. In the future it is imperative that foods are constructed to deliver the desired performance and sensations, but with reduced calorific content and the ability to modulate food intake. This will require the design and construction of colloids with increasingly complicated structures and complex production processes.

Fat crystallisation at oil-water interfaces.

This review focuses on recent advances in the understanding of lipid crystallisation at or in the vicinity of an interface in emulsified systems and the consequences regarding stability, structure and thermal behaviour. Amphiphilic molecules such as emulsifiers are preferably adsorbed at the interface. Such molecules are known for their ability to interact with triglycerides under certain conditions. In the same manner that inorganic crystals grown on an organic matrix see their nucleation, morphology and structure controlled by the underlying matrix, recent studies report a templating effect linked to the presence of emulsifiers at the oil/water interface. Emulsifiers affect fat crystallisation and fat crystal behaviour in numerous ways, acting as impurities seeding nucleation and, in some cases, retarding or enhancing polymorphic transitions towards more stable forms. This understanding is of crucial importance for the design of stable structures within emulsions, regardless of whether the system is oil or water continuous. In this paper, crystallisation mechanisms are briefly described, as well as recent technical advances that allow the study of crystallisation and crystal forms. Indeed, the study of the interface and of its effect on lipid crystallisation in emulsions has been limited for a long time by the lack of in-situ investigative techniques. This review also highlights reported interfacial effects in food and pharmaceutical emulsion systems. These effects are strongly linked to the presence of emulsifiers at the interface and their effects on crystallisation kinetics, and crystal morphology and stability.

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.

A comparative study on the capacity of a range of food-grade particles to form stable O/W and W/O Pickering emulsions

Whilst literature describing edible Pickering emulsions is becoming increasingly available, current understanding of these systems still suffers from a lack of consistency in terms of the (processing and formulation) conditions within which these structures have been studied. The current study aims to provide a comparative analysis of the behaviour of different edible Pickering candidates and their ability to stabilise emulsion droplets, under well-controlled and uniform experimental conditions, in order to clearly identify the particle properties necessary for successful Pickering functionality. More specifically, an extensive investigation into the suitability of various food-grade material to act as Pickering particles and provide stable oil-in-water (O/W) and water-in-oil (W/O) emulsions was carried out. Polysaccharide and flavonoid particles were characterised in terms of their size, ζ-potential, interfacial activity and wettability, under equivalent conditions. Particles were subsequently used to stabilise 20% w/w O/W and W/O emulsions, in the absence of added surfactant or other known emulsifying agents, through different processing routes. All formed Pickering emulsions were shown to resist significant droplet size variation and remain stable at particle concentrations between 2 and 3% w/w. The main particle prerequisites for successful Pickering stabilisation were: particle size (200nm - 1μm); an affinity for the emulsion continuous phase and a sufficient particle charge to extend stability. Depending upon the employed emulsification process, the resulting emulsion formation and stability behaviour can be reasonably predicted a priori from the evaluation of specific particle characteristics.

Effect of emulsifier type and concentration, aqueous phase volume and wax ratio on physical, material and mechanical properties of water in oil lipsticks

Water‐in‐oil emulsions in lipsticks could have the potential to improve moisturizing properties and deliver hydrophilic molecules to the lips. The aims of this work were (i) to investigate the effect of emulsifier type (polymer vs. monomer, and saturated vs. unsaturated chain) and concentration on droplet size and (ii) to investigate the effect of wax ratio (carnauba wax, microcrystalline wax, paraffin wax and performalene) and aqueous phase volume on material properties (Youngs modulus, point of fracture, elastic modulus and viscous modulus).

Coconut and sunflower oil ratios in ice cream influence subsequent food selection and intake

The effect of coconut oil (CO, containing mainly medium chain triglycerides - MCTs) and sunflower oil (SO, containing mainly long chain triglycerides - LCTs) used as fat source (10% fat ice cream) in different ratios (25% CO and 75% SO - 25CO:75SO, 50% CO and 50% SO - 50CO:50SO, 75% CO and 25% SO - 75CO:25SO) was investigated to assess differences in appetite and ad-libitum (evening and snack) food intake using a single blind design. 36 healthy female participants consumed a fixed portion (150g) of ice cream 45min before an ad-libitum dinner and snacks. Appetite sensations were tracked across the day. Participants ate significantly less fat after 75CO:25SO than 25CO:75SO (p=0.007) and there was also a trend for lower fat intake in this condition as compared to 50CO:50SO (p=0.068). High fat savoury snack intake significantly decreased after 75CO:25SO in comparison with both 25CO:75SO (p=0.038) and 50CO:50SO (p=0.008). Calorie intake from snacks was also found to be significantly lower after 25CO:75SO and 50CO:50SO than 75CO:25SO (p=0.021 and 0.030 respectively). There was no effect of condition on appetite or desire ratings over the day. Eating a standard portion of ice cream containing different ratios of MCTs and LCTs can modestly influence acute food selection and intake, with MCTs manifesting their effect earlier and LCTs later due to differences in the absorption and metabolism of these lipids. However, the differences evident in the present study were small, and require further research before firm conclusions can be drawn.

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.

Formulation Engineering of Foods

All three editors are based in the University of Birmingham, base of the largest Chemical Engineering-based food research group in the UK, incorporating research into structured foods, flavour delivery and food hygiene. Research in food processing is carried out in partnership with key companies such as Nestlé, Unilever and Cadbury, as well as through funding from research councils and DEFRA. Joint research and collaboration has been carried out with Food Science departments at Nottingham, Leeds and Reading.

The acoustics of friction and microstructure of model and apparel fabrics

Apparel fabrics are constructed of large numbers of fibers, spun into thread and woven and treated with sizing into final structures, giving rise to a number of different surface properties. A method to record and analyze the friction sound emitted from model fabrics (uniform, single-fiber polyester meshes) and apparel fabrics was developed and the relationship between microstructure and the sound emitted was established. The effect that surface modification (conditioning) has on sound emission was also investigated. Fabric sounds were captured as a result of friction, producing sound spectra (frequency versus amplitude), from which total noise could be calculated. This was compared to the fabrics’ microstructure. The shape of the sound spectra varied as a result of the structure of the model fabrics, with experimentally measured frequencies being comparable to predicted frequencies calculated. It is possible to produce a ‘fingerprint’ of acoustics, based on the thread diameter and aperture size of single-fiber structures. Spectra produced for apparel fabrics were broader than for the model fabrics (possibly as a result of the multifiber structure), and the level of total noise differed between the three fabrics, with total noise being strongly correlated to surface roughness and weight. A relationship between the total frictional noises emitted from surfaces of different materials has previously been investigated. Conditioning fabrics, no treatment and desizing the fabrics did not have a significant effect on surface roughness, weight or total noise.