Fat crystallite thickness distribution based on SAXD peak shape analysis

Understanding of the multiscale structuring capability of triacylglycerols (TAGs) can be enhanced through knowledge of the crystallite thickness distribution (CTD), which can be obtained through X‐ray diffraction peak shape analysis. The Fourier‐transformation‐based Bertaut–Warren–Averbach (BWA) method provides an approach to resolve CTDs in TAGs, where molecules are packed in repeating layers. The feasibility of using the BWA method is demonstrated for small angle X‐ray diffraction (SAXD) measurements on both laboratory equipment and a synchrotron beamline for model TAG systems and real food products such as margarines. Practical Applications: The CTDs enable discrimination of margarines produced by different processing routes and may be used as a signature of network structures that underlie product texture

Shear Modulus of Sintered 'House of Cards'-Like Assemblies of Crystals

A cell model of a 'house of cards'-like assembly of crystals is used for the study of the evolution of the shear modulus during sintering. The crystals are assumed to have a lozenge shape. The cell model takes different crystal-crystal contacts into account. The force needed to separate two sintered crystals is calculated using the minimum surface area (MSA) approximation. By varying the thickness, long axis, and short axis of the crystals, it is possible to make space-filing configurations which have a nonzero shear modulus at crystal volume fraction that can be as low as Ø= 0.03. This is significantly lower than the volume fractions Ø > 0.52 that are found in studies where the MSA approximation is applied to assemblies of spherical particles. It is found that sintering may cause a nonlinear volume fraction dependence of the shear modulus, which depends on the shape of the crystals, the type of crystal-crystal contacts, and the character of the crystal assembly. The calculated shear modulus is analyzed using the phenomenological expression (Ø -Ø 0)beta, where 0 represents the volume fraction at the start of sintering. The exponent beta is found to vary between 1 and 2. The interpretation of the shear modulus using a fractal model is also discussed

Quantitative Assessment of Triacylglycerol Crystallite Thickness by 1H Spin-Diffusion NMR

Properties and consumer appreciation of fat containing food products are greatly influenced by the growth of thefat crystalline domains and their morphology. Various analytical methods can be exploited to provide insight into the multilengthscale microstructure of fat networks, but very few are able to discriminate structural features between different ways of processingfats. We selected in this work methods that highlight the mesostructure of fat crystalline systems. In this respect, 1H spindiffusionNMR and XRD methods were employed to determine the fat crystallite thicknesses (crystalline domain size). This isthe first attempt to quantify the mesostructure domains of triglyceride-based fat crystals by means of 1H spin-diffusion NMR experiments. The crystalline domain sizes determined by spin-diffusion NMR were found to be in good agreement with the crystallite thickness determined by the Scherrer analysis of the first order diffraction line from SAXS data. These resultsdemonstrate the ability of the NMR technique to characterize the mesostructure of fats in a quantitative manner. This method is of particular interest for the structure analysis of fats, especially because of the possibility to quantify the size of the crystalline domains in diluted systems where scattering techniques struggle with the amount of diffracting material

Structuring edible oil with lecithin and sorbitan tri-stearate

The gelation of edible oil by a mixture of lecithin and sorbitan tri-stearate (STS) was studied. The two components individually in oil do not give structure at concentrations between 6% and 20% w/w: viscous, pourable solutions are obtained. A synergetic effect is observed with their mixture, at specific ratios of lecithin:STS, between 40:60 and 60:40, when firm gels are obtained. The interaction of the two structurants was studied by varying concentration and ratio of lecithin:STS and evaluated through microscopy, texture analysis, X-ray diffraction (XRD), rheology and nuclear magnetic resonance (NMR). The gels are shear-sensitive, they irreversibly lose their firmness upon deformation. The gels collapse at about 30 °C but this phenomenon is reversible, since upon cooling they regain their firmness. Under polarised light, the microstructure of 50:50 lecithin:STS mixture in oil is given by needle-like crystals. Oil with pure STS and oil with lecithin and STS at a ratio 50:50 show similar X-ray scattering patterns. Both X-ray scattering patterns and NMR relaxation curves show that no solid or crystalline matter is present in samples containing only lecithin in oil. The analytical results lead to the hypothesis that the structure is mainly given by STS crystals, assuming needle or plate shape due to the lecithin action and connected by weak junctions, also due to lecithin. Keywords: Organogel; Low-molecular-weight organic gelator; Oil; Food; Texture; Crystallisation; Lecithin; Sorbitan tri-stearat

Crystal network for edible oil organogels: Possibilities and limitations of the fatty acid and fatty alcohol systems

The textural and structural properties of organogels made by structuring liquid oil with mixtures of stearic acid (octadecanoic acid) and stearyl alcohol (octadecanol) have been studied. Optical, rheological and X-ray diffraction measurements have been used to investigate the influence of temperature, time and composition on the pseudo-binary system. The aim of these experiments is to relate the observed macroscopic behaviour of the organogels to the microscopic molecular ordering within the crystals that form a network. Oscillating strain measurements have been performed on mixtures with various acid to alcohol ratios. A synergetic effect in structuring was obtained by applying a 3:7 (acid:alcohol) ratio. Hardness and elastic modulus were significantly higher compared to samples with other ratios, at the same overall structurant concentration. Microscopy showed that the crystal habit of the structurant strongly depends on the composition of the mixture. X-ray diffraction experiments, which show that mixed crystals are formed when structurant mixtures are used, confirmed this result. The observed behaviour of the elastic modulus is likely the result of the difference in the microstructure of the interlinked crystals

Crystal network for edible oil organogels: Possibilities and limitations of the fatty acid and fatty alcohol systems

The textural and structural properties of organogels made by structuring liquid oil with mixtures of stearic acid (octadecanoic acid) and stearyl alcohol (octadecanol) have been studied. Optical, rheological and X-ray diffraction measurements have been used to investigate the influence of temperature, time and composition on the pseudo-binary system. The aim of these experiments is to relate the observed macroscopic behaviour of the organogels to the microscopic molecular ordering within the crystals that form a network. Oscillating strain measurements have been performed on mixtures with various acid to alcohol ratios. A synergetic effect in structuring was obtained by applying a 3:7 (acid:alcohol) ratio. Hardness and elastic modulus were significantly higher compared to samples with other ratios, at the same overall structurant concentration. Microscopy showed that the crystal habit of the structurant strongly depends on the composition of the mixture. X-ray diffraction experiments, which show that mixed crystals are formed when structurant mixtures are used, confirmed this result. The observed behaviour of the elastic modulus is likely the result of the difference in the microstructure of the interlinked crystals