Background: It has become increasingly clear that the current population averaged nutrition paradigm is not able to address the growing non-communicable disease (NCD) epidemics. Current approaches fail primarily for two reasons: firstly, poor adherence to public dietary advice and, secondly, individual health responses are not well reflected by population averages, as generic public health advice lacks relevance for individuals, personally and medically. Scope and approach: Personalized 'expert' systems are, potentially, powerful weapons against NCDs. Existing systems are, however, handicapped by both difficulty in measuring dietary intake reliably and that of tying population level nutritional knowledge to stochastic individual responses. In order to address these shortcomings, we propose an approach that no longer distinguishes between behavioural and physiological responses. Key findings and conclusions: We outline how a conceptual self-learning expert system could implement this approach, based on multifactorial lifestyle interventions, and give specific examples in the contexts of diabetes and obesity. Combining behaviour and physiological responses into a single entity removes the requirement to measure food intake, enabling users to map their individualised 'path of least resistance' to specific health outcomes. This new approach could be provided at minimal cost by leveraging users existing mobile devices, e.g. smart phones, watches, fitbits etc. The novelty in this concept is that the methodology purposely does not attempt to understand the complexity of the underlying physiological, metabolic and psychological responses. Despite requiring scientifically validated biomarkers, understanding the discrete influences of each of these factors is not required to drive improved individual-level outcomes.

Lipid self-assembled structures (SASs) have recently gained considerable interest for their potential applications, especially for sustained nutrient release and protein crystallization. An additional property, which is underexploited, is their ability to control chemical reactions in food products. Here, we concentrate on SASs formed by phospholipids (PLs) and monoglycerides (MGs), those compounds being the most natural surfactants and therefore, the best compatible with food products, in view of providing new functionalities through the formation of SASs. In this work, the phase behaviour of these amphiphiles when mixed with oil and water is described and compared. Subsequently, we address the influence of these structures to the oxidation and Maillard-type reactions. Finally, we show that SASs formed by MGs can strongly increase the yield of key aroma impact compounds generated by Maillard-type reactions when compared with the reaction performed in aqueous precursor solutions. Various SASs are compared. In particular, addition of oil to a reversed bicontinuous structure formed by MG leads to a reversed microemulsion, which, considering its low viscosity, is particularly suitable for food products and act as a very efficient reactor system. The influence of oil and precursors on phase behaviour is discussed and related to the efficiency of the Maillard reactions.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.

Surface layers of micro- and nanoparticles at fluid/liquid interfaces in absence and presence of surfactants are of large importance in the process of re-discovering Pickering systems, i.e. emulsions and foams stabilized by particles. The surface pressure/area isotherms of such layers can provide information about the properties of the used particles (dimensions, interfacial contact angles), the structure of interfacial layers, the interactions between the particles as well as about relaxation processes within the layers. For a correct description of Π-A isotherms of composite surface layers containing particles the significant difference in size of these particles to that of solvent and surfactant molecules should be taken into account. Corresponding equations can be derived on the basis of the two-dimensional solution theory. The gained equations provide satisfactory agreement with experimental data and predict realistic values for the area of particles at the interface. Also equations of state and of the dilational elasticity for composite surface layers containing particles can be obtained in the framework of the presented methodology.

Food manufacturers try to meet the rising expectations of consumers for nutritionally balanced and healthy foods.The current way to achieve this goal is based on "enhancing" nutritional functionality within a product by adding health beneficial bioactives such as probiotics, sterols, flavones, carotenoids, polyphenols to a common food base.Such enrichments are often linked to a health claim, supported by a clinical study, and aimed to prevent a potential health problem.The next major step in value addition to food will be to deliver food products adapted to the nutritional and health needs of an individual, as different people respond in different ways to similar diets and life styles.The current focus lies on nutrigenomics, studying how genetics and metabolic processes relate to nutrition.This approach will definitely help to better identify people who are statistically more likely to develop a particular disease and would require a personalized diet.A major challenge will be the translation of the obtained data into adequate nutrition solutions.The study and understanding of how the digestive system functions will play another important role in food personalisation.Humans (and most animals) digest their food extra-cellularly, that is, outside of cells, involving a complex interplay between bio-and colloidal transformations of the ingested food.Consequently, food scientists will have to provide food products adapted to the physiological, physico-chemical and colloidal processes involved in perception as well as nutrient transformation, liberation and absorption during digestion.In other words it will be important to master the kinetics and thermodynamics of a) nutrient incorporation into a food product, b) liberation during digestion and c) adsorption into the cells making use of food structures that facilitate the realization of the desired sensorial and nutritional benefits.Of particular interest is the question how food structure and composition (e.g.microstructure such as particle size and shape, self-assembly structures, molecular structure) are influencing the dynamics of nutrient uptake.We will review important physico-chemical and colloidal aspects regarding lipid digestion in relation to emulsion structure.Lipid digestion is a rather complex process, resulting in different intermediate self-assembly structures.We consider emulsions as ideal systems to study the relationship between food structure formation and lipid digestion, as they are easy to produce at different sizes and different internal self-assembly structures e.g. in form of cubosomes, hexosomes and isasomes.Moreover they can be loaded with lipo-and amphiphilic bioactives and can be easily evaluated using artificial or native digestion media such as saliva, gastric juices, lipolytic enzymes and bile.

When using fluorescence microscopy for the investigation of beta-lactoglobulin (BLG) stabilized thin liquid films and monolayers, it is necessary to label the protein sample with a fluorescent dye. In the present study, we discuss the effect of labeling beta-lactoglobulin with either Rhodamine iso-thiocyanate (RITC) or Fluorescein iso-thiocyanate (FITC) on the BLG properties at the air-water interface and in thin films. RITC and FITC are the two most frequently used dyes in fluorescence microscopy. Two different Rhodamine concentrations were used, namely the concentration conventionally used in fluorescence microscopy, and a two times higher Rhodamine concentration. Interfacial tension and rheology measurements, and thin film investigations using X-ray reflectivity or the diminishing bubble method showed that the labeling procedure of the beta-lactoglobulin using Rhodamine at the lowest concentration does not change the viscoelastic properties of the air-water interface, as well as the film thickness and gas permeability. However, when taking the higher Rhodamine concentration the films are thicker and more permeable for gas. Similarly, Fluorescein at a concentration equivalent to the highest concentration of Rhodamine induced also a modification of the protein film properties. However, the labeling did not influence the BLG monolayer viscoelastic characteristics.Labeling beta-lactoglobulin with Rhodamine allows now using confocal fluorescence microscopy (CSLM) for the elucidation of structure formation in thin films and at water-air surfaces. As an example, images from thin films as formed in the diminishing bubble experiment and stabilized with labeled BLG show that the formed BLG aggregates are highly surface active, i.e., enriched at the water-air interface. The obtained images reveal that the aggregates are also present in the film. In general, CSLM combined with the diminishing bubble method seems to be an excellent experimental set-up to visualize the distribution of labeled components throughout a thin film and its adjacent monolayers. This is not possible using the diminishing bubble method in combination with conventional microscopy. (c) 2006 Elsevier B.V. All rights reserved.

The thermodynamic model of a 2D solution developed earlier for protein monolayers at liquid interfaces is generalized for monolayers composed of micro- and nanoparticles. Surface pressure isotherms of particle monolayers published in the literature for a wide range of particles sizes (between 75 microm and 7.5 nm) are described by the theoretical model with one modification. The calculations of surface pressure pi on area A provide satisfactory agreement with the experimental data. The theory also yields reasonable cross-sectional area values of the solvent molecule water in the range between 0.12 and 0.18 nm2, which is almost independent of particle size. Also, the area per particle in a closely packed monolayer obtained from the theory is quite realistic.

Insoluble monolayers of commercially available sodium stearoyl lactylate (SSL) spread at the air/water interface were studied by recording pressure–area (Π–A) isotherms simultaneously with the morphology via Brewster angle microscopy (BAM). Whereas a strong hysteresis on the Π–A isotherms was observed for the first compression–expansion cycle, the second and further cycles show a strongly reduced hysteresis. The BAM images show significant changes in the surface textures during compression/expansion reflecting 2D-heterogeneities in the monolayer. The most probable explanation of these phenomena can be given when taken into account the composition of the SSL sample consisting of two components of different interfacial activity—so-called SSL1 and SSL2. The less surface-active component was assumed to be pushed out of the monolayer at higher surface pressures. Additional compression experiments performed separately on the systems enriched by either of these compounds, respectively, confirm the explanation.

Monoglyceride molecules spontaneously self-assemble into various liquid crystalline structures when present in an aqueous environment. The various phases can be used to achieve different functionalities, e.g. to protect molecules from chemical degradation, to solubilize drugs and nutrients, to control release of flavours and drugs or to increase the yield in Maillard reactions. We will review (1) the typical characteristics of monoglyceride self-assembly structures, (2) the most common characterisation techniques, (3) how introduction of guest molecules influences the self-assembly structures, (4) their use for drug delivery and (5) how commercial food grade monoglycerides obtained from sunflower oil can be applied to achieve unique delivery functionalities in food systems.

Application of emulsifiers for water-based or water-contained heterogeneous food systems is often restricted by their very low solubility in aqueous media and, therefore, by their very low equilibrium bulk concentration. As a consequence, only very slow adsorption rates can be attained. On the other hand, the rate of adsorption from micellar solutions is found to be very fast because of the significant enhancement of matter transfer by means of micelles as containers. In this way, even surfactants with a very low critical micelle concentration (CMC) or non-micellar surfactants could be involved in such adsorption enhanced processes due to mixed micelles formation existing for many binary systems composed of substances with different micellization ability. This general mechanism of micellar promoted adsorption is realized in binary systems having great importance for applied food science and food industry.

Acacia gum is a complex mixture of three main components, the arabinogalactan (AG), the arabinogalactan-protein complex (AGP) and the glycoprotein (GP). In the present study, the influence of complex formation between the protein β-lactoglobulin and the Acacia gum and its two major components, the AG and AGP, on the formation of vertical macroscopic thin liquid films were investigated by means of X-ray reflectivity measurements. This method allows the determination of the thickness of the formed film and its nano-structural features. The experimental results revealed that the main effect of adding Acacia gum to a 1g/l β-lg solution at a pH of 5.3, i.e., near the protein's pI value, is related to the formation of soluble and insoluble β-lg – arabinogalactan (AG) complexes. Addition of Acacia gum to the protein solution significantly decreased the film thickness of the formed film before it ruptured. Film experiments with fractionated Acacia gum mixtures (an AG-rich and an AG-poor, i.e., AGP-rich, fraction) or with a dialyzed Acacia gum preparation allowed to conclude that the observed influence of the Acacia gum on the thickness of the β-lg stabilized films and film stability is primarily due to the extent of complex formation between the negatively charged AG component and the β-lg. This complex formation reduces the ‘free’ β-lg concentration in the bulk which is stabilizing the two water-air surfaces in the film. The degree of complex formation considerably depends on the ionic strength in the solution. At low ionic strength, the negative charges on the AG are not screened by the salt ions leading to extensive electrostatic complex formation (formation of soluble and/or insoluble complexes) with the β-lg, even at the isoelectric point of the protein. However, if the ionic strength in the β-lg – Acacia gum mixture is in the sub-millimolar range, significant charge screening effects are occurring keeping the arabinogalactan component away from complexation with the β-lg molecules and allowing the formation of stable thin liquid films up to a β-lg – Acacia gum weight ratio of 2:1. Addition of more Acacia gum under these ionic strength conditions resulted again in the formation of unstable thin films.

Low molecular weight surfactants, for example monoglycerides and phospholipids, form a multitude of self-assembled structures, such as inverted cubic or hexagonal mesophases, if brought into contact with water/oil. These mesophases can be dispersed in water using adequate surface-active materials such as low molecular weight surfactants or surface active polymers. In order to use such mesophase particles for incorporating drugs and aromas, it is essential to determine their internal crystallographic structure and to understand their mechanism of stabilization. Cryo-transmission electron microscopy was used to investigate the internal structure of different dispersed particles at various temperatures and oil contents. It is shown here that cryo-trans mission electron microscopy, in combination with fast Fourier transform and tilting experiments, is effective in obtaining information on crystallographic structure, space group and morphology of particles with reversed bicontinuous cubic and hexagonal structures. In particular, using the presence or the absence of the {111} reflections and viewing the same particle under different axes of observation allows one to discriminate between the Im3m and Pn3m space groups. A major advantage of cryotransmission electron microscopy is the ability to analyse single particles. This allows the identification of particles present at very low concentrations and the coexistence of particles with different internal self-assembly structures. With this technique we have obtained strong evidence for the presence of two cubic internal self-assembly structures with different space groups within the same dispersion. In addition, we found that cryo-transmission electron microscopy combined with tilting experiments enables the analysis of internal particle morphology, allowing the discussion of mechanisms for hexosome stabilization.

The capillary pressure technique is the method of choice for any tensiometry measurements in microgravity, as all bubbles and drops have a spherical shape. A combination of fast drop formation based on a known constant liquid flow and fast data acquisition of measured capillary pressure gives access to dynamic interfacial tensions in the range of milliseconds. Also the maximum drop pressure method, an equivalent to the maximum bubble pressure technique as fastest dynamic surface tension method, can be practised by the same set-up. The technique was developed already 15 years ago [ii] and now further refined during the MAP FASES* supported by the European Space Agency [ii]. Besides a detailed description of the technical parameters, experimental results for emulsion relevant systems are presented. The set-up presented here is based on a commercial drop and bubble profile analysis tensiometer which appears to be a kind of in-situ technique for membrane emulsification processes. The instrumental set-up is suitable also for oscillating drop and bubble experiments up to frequencies of several hundreds Hz.

It is shown experimentally that the desorption of sodium decyl sulphate from the liquid/air interface is purely diffusion controlled, while the desorption of higher surface active surfactants such as the non-ionic surfactants Triton X-100 and tridecyl dimethyl phosphine oxide obeys a mixed mechanism. The desorption kinetics of β-lactoglobulin (BLG) and β-casein is, however, determined by a barrier mechanism. From the analysis of the BLG and β-casein desorption kinetics at different temperatures the activation energy of desorption is calculated. The values obtained are rather close to the free energy of adsorption. The theoretical model of desorption kinetics predicts that these two energetic parameters are similar if the adsorption activation energy is low. This explains why substances with a higher adsorption activity have a lower desorption rate. Adsorption kinetics studies for β-casein with and without forced convection show the same equilibrium surface tension values. This leads to the conclusion that the protein adsorption at liquid interfaces is thermodynamically reversible, although the slow desorption kinetics would allow to assume it to be an irreversible process.

The general theoretical model by Garrett and Joos proposed in 1976 for the estimation of the dilational elasticity of mixed surfactant solutions, and also the theoretical model proposed by Joos for the limiting elasticity of such mixtures, demonstrate quite satisfactory agreement with experimental results obtained from the oscillating bubble shape method for mixtures of a nonionic surfactant and a protein, that is, beta-lactoglobuline and decyl dimethyl phosphine oxide, C10DMPO.