Whipped oil stabilised by surfactant crystals

We describe a protocol for preparing very stable air-in-oil foams starting with a one-phase oil solution of a fatty acid (myristic acid) in high oleic sunflower oil at high temperature. Upon cooling below the solubility limit, a two-phase mixture consisting of fatty acid crystals (length around 50 μm) dispersed in an oil solution at its solubility is formed which, after whipping, coat air bubbles in the foam. Foams which do not drain, coalesce or coarsen may be produced either by increasing the fatty acid concentration at fixed temperature or aerating the mixtures at different temperatures at constant concentration. We prove that molecular fatty acid is not surface-active as no foam is possible in the one-phase region. Once the two-phase region is reached, fatty acid crystals are shown to be surface-active enabling foam formation, and excess crystals serve to gel the continuous oil phase enhancing foam stability. A combination of rheology, X-ray diffraction and pulsed nuclear magnetic resonance is used to characterise the crystals and oil gels formed before aeration. The crystal-stabilised foams are temperature-sensitive, being rendered completely unstable on heating around the melting temperature of the crystals. The findings are extended to a range of vegetable oil foams stabilised by a combination of adsorbed crystals and gelling of the oil phase, which destabilise at different temperatures depending on the composition and type of fatty acid chains in the triglyceride molecules

Linking the yield stress functionality of polyglycerol polyricinoleate in a highly filled suspension to its molecular properties

Polyglycerol polyricinoleate (PGPR) is a food emulsifier with a unique yield stress reducing efficacy in fat-based suspensions. There are many commercially available PGPRs, and the different products vary in their impact on the yield stress. Choosing the right PGPR for a specific formulation is often based on empirical data and the experience of the formulator. Lack of fundamental understanding of why these differences exist hampers reformulation efforts to replace PGPR. Therefore, this study aimed to link the yield stress reducing efficacy of PGPR to its molecular properties. Five commercial PGPR samples were studied (3 g/kg) in a concentrated suspension of icing sugar (650 g/kg, ≈ 530 mL/L) in sunflower oil (with naturally-occurring surface-active molecules removed). Rheological analysis revealed Herschel-Bulkley yield stress variations of between 0.90 ± 0.06 Pa and 1.90 ± 0.18 Pa, compared to 57.6 ± 15.8 Pa in the absence of PGPR. Yield stress was correlated to critical micelle concentration, obtained from oil-water interfacial tension data. Applying molecular characterisation techniques revealed that the presence of a hydroxyl group on the fatty acid at the end of the polyricinoleate estolide chain could be linked to inferior yield stress reducing efficacy

Fast Field Cycling NMR relaxometry studies of molten and cooled cocoa butter

Due to its relevance in the confectionery industry, cocoa butter (CB) has been extensively studied. However, most studies focus on its crystallisation properties, whilst studies of its liquid state are lacking. Here, and for the first time, a study of the self-diffusion of CB at different temperatures is presented, using fast field cycling (FFC) nuclear magnetic resonance (NMR) further validated using pulsed field gradient stimulated echo (PGSTE) NMR. Measurements were performed upon heating CB to either 50 or 100 °C and cooling it to 22 °C. No hysteresis was found between the different thermal treatments. However, the activation energy (28.7 kJ/mol) estimated from the cooling protocol of the 100 °C treatment, was the closest to that reported in literature for similar systems. This suggests that measurements using a wider range of temperatures, and starting with a liquid material are advisable. Additionally, samples were measured during isothermal crystallisation at 22 °C, showing that the region below 1 MHz is the most sensitive to phase change

Cabotagem brasileira: avaliação do segmento de carga conteinerizada

O Brasil apresenta condições favoráveis à utilização do transporte aquaviário, cujo potencial para navegação é elevado em função das características geográficas do território nacional. O trabalho desenvolvido objetivou avaliar o segmento de carga conteinerizada da cabotagem brasileira, sob a ótica dos usuários. A metodologia utilizada foi a multicritério de apoio à decisão (MCDA). Para tanto, elaborou-se um modelo multicritério de avaliação com o apoio de uma equipe de especialistas em cabotagem. A avaliação global atingiu a nota 6,0, o que demonstra uma certa insatisfação dos usuários com os serviços que lhe são prestados pelas empresas brasileiras de navegação

Lipid migration in multicomponent food products such as chocolate

Oral presentation given at the DGP Verhandlungen, held in Berlin (Germany) on March 15-20th, 2015.Tetracosane (C24 , TCS) o/w nanoemulsions stabilized by the lecithin 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were prepared by high-pressure melt homogenization. The droplets (diameters of about 65 nm as measured by photon correlation spectroscopy) exhibit a strong super-cooling (Δ about 20 K) and crystallize in a for TCS unusual orthorhombic crystal structure (space group Pca21 as verified by wide-angle x-ray scattering). Using small-angle x-ray and neutron scattering and nanodispersions with different neutron scattering contrasts for the TCS core and the DMPC stabilizer layer, the molecular arrangement of DMPC in the interfacial layer was studied. For the nanoemulsions a dense monolayer of DMPC with a thickness of about 16.2 Å was found with only a minor interpenetration between TCS and the acyl chains of DMPC. For the nanosuspensions a monolayer thickness of 10.5 Å is found, indicating a more flat arrangement of the DMPC molecules at the interface. This could be explained by the expanded surface of the nanocrystals with respect to the emulsion droplets. The structure of the interfacial stabilizer layer of lipid emulsions and suspensions is highly relevant with regard to lipid oxidation of bioactive compounds in food and the crystallization of nanoemulsions. Our aim is to obtain a deeper understanding of the preferred pathways of lipid molecule migration in multicomponent food materials. A profound understanding of the mechanisms is the basis for controlling undesired fat migration leading to degradation of the material quality, e.g. fat blooming of chocolate, resulting in large sales losses for the food industry. Synchrotron X-ray tomography revealed voids in an industrial chocolate sample, which are considered as having a strong impact on the plausible migration pathways. In addition, oil migration into particles with cocoa butter, which resulted in structural changes, were tracked using spatially resolved small angle X-ray scattering (SAXS). Oil migration has been observed in artificial pores produced in cocoa butter matrices with embedded particles and the analysis of wetting properties of the material has provided further insights into the migration mechanism. Although we have not yet elucidated the exact migration mechanism, our results suggest that migration could occur through the pores of the material. Future research will further clarify the role of the porous structure in chocolate fat blooming

Tracking Structural Changes in Lipid-based Multicomponent Food Materials due to Oil Migration by Microfocus Small-Angle X-ray Scattering

One of the major problems in the confectionery industry is chocolate fat blooming, that is, the formation of white defects on the chocolate surface due to fat crystals. Nevertheless, the mechanism responsible for the formation of chocolate fat blooming is not fully understood yet. Chocolate blooming is often related to the migration of lipids to the surface followed by subsequent recrystallization. Here, the migration pathway of oil into a cocoa butter matrix with different dispersed particles was investigated by employing microfocus small-angle X-ray scattering and contact angle measurements. Our results showed that the chocolate powders get wet by the oil during the migration process and that the oil is migrating into the pores within seconds. Subsequently, cocoa butter is dissolved by the oil, and thus, its characteristic crystalline structure is lost. The chemical process provoked by the dissolution is also reflected by microscopical changes of the surface morphology of chocolate model samples after several hours from the addition of oil to the sample. Finally, the surface morphology was investigated before and after oil droplet exposure and compared to that of water exposure, whereby water seems to physically migrate through the particles, namely cocoa powder, sucrose, and milk powder, which dissolve in the presence of water

Synchrotron X-Ray microtomography reveals interior microstructure of multicomponent food materials such as chocolate

The current contribution discusses the structure analysis of a solid multicomponent food product (which is in this case dark chocolate) using microtomography. The material consists of a continuous solid lipid phase, in which particles are suspended. A detailed analysis of the microstructure is needed to understand migration processes, which are e.g. responsible for major problems in the confectionery industry such as chocolate blooming. In this study it was possible to clearly distinguish the particles from the continuous phase. Particle arrangement and structural imperfections within the sample were made visible by using synchrotron radiation. The observed imperfections, which arise during the manufacturing process, might act as migration pathways, since they propagate throughout the entire sample. The captured microtomographic images proof the presence of cracks and voids within a common industrial made chocolate. Future research has to show if migration is happen along the identified microstructural defects

Brazilian cabotage : evaluation of the containerized cargo segment

O Brasil apresenta condições favoráveis à utilização do transporte aquaviário, cujo potencial para navegação é elevado em função das características geográficas do território nacional. O trabalho desenvolvido objetivou avaliar o segmento de carga conteinerizada da cabotagem brasileira, sob a ótica dos usuários. A metodologia utilizada foi a multicritério de apoio à decisão (MCDA). Para tanto, elaborou-se um modelo multicritério de avaliação com o apoio de uma equipe de especialistas em cabotagem. A avaliação global atingiu a nota 6,0, o que demonstra uma certa insatisfação dos usuários com os serviços que lhe são prestados pelas empresas brasileiras de navegação.Brazil has favorable conditions for the use of water transport, whose potential for navigation is high due to the geographic characteristics of the national territory. The work developed aimed to evaluate the segment of containerizedcargo of Brazilian cabotage, from the perspective of users. The methodology used was the multicriteria decision support (MCDA). To this end, a multi-criteria evaluation model was developed with the support of a team of cabotage specialists. The global assessment reached a score of 6.0, which demonstrates a certain dissatisfaction of users with the services provided by Brazilian shipping companies.Faculdade de Economia, Administração, Contabilidade e Gestão de Políticas Públicas (FACE)Departamento de Administração (FACE ADM