FT–IR studies on polymorphism of fats: molecular structures and interactions

Chocolate Tempering: A Perspective

Tempering is a critical step in chocolate production, ensuring desirable properties such as gloss, snap, and bloom resistance. Traditionally, tempering has been understood through the lens of cocoa butter polymorphism, with a predominant focus on achieving Form V crystals, due to their sharp melting profile and associated macroscopic physical properties. However, this Perspective challenges the notion that Form V alone guarantees high-quality, bloom-resistant chocolate. Recent research suggests that polymorphism is only one aspect of chocolate quality. Multiscale structural analyses-including small-angle X-ray scattering (SAXS), ultrasmall-angle X-ray scattering (USAXS), small-angle neutron scattering (SANS), and microcomputed tomography (μCT)-reveal that nanostructural to microstructural properties are key indicators of bloom susceptibility and can vary significantly, despite identical polymorphic phases. This Perspective proposes that tempering should be viewed as a hierarchical crystallization process, where nucleation rate, structural homogeneity, and microstructural organization play critical roles. A broader approach to tempering assessment-integrating microstructural probes alongside traditional solid-state characterization-may provide deeper insights into chocolate's mechanical stability and long-term bloom resistance. As supply chain fluctuations increasingly impact cocoa butter composition, this multiscale perspective could help manufacturers mitigate quality inconsistencies and adapt to cost-driven formulation changes that may otherwise compromise bloom resistance in tempered chocolate.

How triacylglycerol thermal history impacts film removal by surfactant solution

HYPOTHESIS

The physical and mechanical properties of triacylglycerols (TAGs), or 'fats', depend on their composition and thermal history which, in turn, impact crystal structure and morphology. We examine whether thermal history can be mechanistically related to film removal by a surfactant solution.

EXPERIMENTS

Model TAG mixtures, comprising triolein:tripalmitin:tristearin 0.5:0.3:0.2, were subjected to a range of cooling profiles from the melt (0.5-80°C/min, Newtonian and annealed), and the resulting solid films characterised by microscopy, X-ray diffraction, infrared spectroscopy, and contact angle measurements. Film removal from a model glass substrate by an aqueous surfactant solution of sodium dodecylsulphate and dodecyldimethylamine oxide at room temperature fixed at 25°C was examined under quiescent flow conditions.

FINDINGS

Quantitative relations are established between TAG cooling profile, crystal structure and morphology, surface energy γSFE, and removal (or 'cleaning'). In general, films cooled slowly from the melt yield heterogeneous morphologies with predominantly β1' phase, higher polar γSFE, and faster removal timescales. By contrast, rapid cooling results in homogeneous films, rich in β2' phase, low polar γSFE, and long removal times. Our results elucidate the non-trivial impact of TAG thermal history, connecting the multiscale semi-crystalline structure to surface energy, and eventually to film delamination by micellar solutions.

Temperature-dependent properties of fat in adipose tissue from pork, beef and lamb. Part 1: microstructural, thermal, and spectroscopic characterisation

We investigated the temperature-dependent microstructure and thermal properties of back fat adipose tissue from pork, beef and lamb. Microstructural characterisation via electron, confocal and light microscopy showed that the back fats were structurally similar and consisted of fat dispersed as discrete units within a protein matrix akin to a closed cell foam. Differential scanning calorimetry showed distinct fat melting profiles for each of the tissues, which were ascribed to differences in fatty acid profile. Fat crystal organisation, melting and re-solidification signatures unique to each adipose tissue were found via X-ray diffraction and Raman spectroscopy. Overall, we found that the temperature-dependent microstructure of adipose fat was intricately linked to the fat phase melting behaviour, and importantly, to its protein matrix at elevated temperatures. Such understanding is necessary to provide the required insights to effectively replicate the functionality of adipose tissue using plant-based materials.

The effects of interesterification on the physicochemical properties of Pangasius bocourti oil and its fractions

Soft and solid fats which were fractionated from Pangasius bocourti oil (PBO), namely, Pangasius bocourti olein (PBOL) and Pangasius bocourti stearin (PBST), respectively, were introduced as new base oils for plastic fats. The physicochemical properties of PBO and its fractions were modified after interesterification. Enzymatic interesterification (EIE) reduced the sn-2 palmitic acid content attributed to the occurrence of acyl migration. The PBO solid fat content (SFC) at 20-40 °C increased after chemical interesterification whereas under similar range of temperature, the SFC of PBST decreased after EIE and a steep melting curve was obtained. The effect of interesterification on the crystal polymorphisms was less prominent whereby the initial and interesterified samples exhibited similar crystal forms. The solid state of PBOL was improved after interesterification but post-hardening was observed. Free fatty acids were produced via partial hydrolysis during EIE which contributed to the reduced oxidative stability in the EIE fats.

Intermittent dynamics of bubble dissolution due to interfacial growth of fat crystals

Foams are inherently unstable objects, that age and disappear over time. The main cause of foam aging is Ostwald ripening: smaller air bubbles within the foam empty their gas content into larger ones. One strategy to counter Ostwald ripening consists in creating armored bubbles, where solid particles adsorbed at the air/liquid interface prevent bubbles from shrinking below a given size. Here, we study the efficiency of coating air bubbles with fat crystals to prevent bubble dissolution. A monoglyceride, monostearin, is directly crystallized at the air/oil interface. Experiments on single bubbles in a microfluidic device show that the presence of monostearin fat crystals slows down dissolution, with an efficiency that depends on the crystal size. Bubble ripening in the presence of crystals exhibits intermittent dissolution dynamics, with phases of arrest, when crystals jam at the interface, followed by phases of dissolution, when monostearin crystals are ejected from the interface. In the end, crystals do not confer enough mechanical strength to the bubbles to prevent them from fully dissolving.

An Insight into the Solid-State Miscibility of Triacylglycerol Crystals

The crystallization properties of triacylglycerols (TAGs) strongly determine the functional properties of natural lipids. The polymorphic and mixing phase behavior of TAG molecules have long been, and still are, a hot topic of research with special relevance for the cosmetic, pharmaceutical, and food industry. To avoid the difficulties arising from the study of whole real fats, studies at the molecular level on mixtures of a limited number of TAGs has become an indispensable tool to identify the underlying causes of the physical properties in lipid systems. In particular, phase diagrams of binary mixtures of TAGs exhibiting a different degree of heterogeneity (monoacid or mixed fatty acids; molecular symmetry; the presence of cis or trans double bonds) have resulted in a significant breakthrough in our knowledge about structure-interaction-function relationships. The present work aims to provide an overview of the main reports regarding binary and ternary TAG systems, from the early studies to the most recent developments.

The Application of FT-IR Spectroscopy for Quality Control of Flours Obtained from Polish Producers

Samples of wheat, spelt, rye, and triticale flours produced by different Polish mills were studied by both classic chemical methods and FT-IR MIR spectroscopy. An attempt was made to statistically correlate FT-IR spectral data with reference data with regard to content of various components, for example, proteins, fats, ash, and fatty acids as well as properties such as moisture, falling number, and energetic value. This correlation resulted in calibrated and validated statistical models for versatile evaluation of unknown flour samples. The calibration data set was used to construct calibration models with use of the CSR and the PLS with the leave one-out, cross-validation techniques. The calibrated models were validated with a validation data set. The results obtained confirmed that application of statistical models based on MIR spectral data is a robust, accurate, precise, rapid, inexpensive, and convenient methodology for determination of flour characteristics, as well as for detection of content of selected flour ingredients. The obtained models' characteristics were as follows: R² = 0.97, PRESS = 2.14; R² = 0.96, PRESS = 0.69; R² = 0.95, PRESS = 1.27; R² = 0.94, PRESS = 0.76, for content of proteins, lipids, ash, and moisture level, respectively. Best results of CSR models were obtained for protein, ash, and crude fat (R² = 0.86; 0.82; and 0.78, resp.).

Development of a coarse-grained model for simulations of tridecanoin liquid-solid phase transitions

Novel coarse-grained models for molecular dynamics of tridecanoin melts are here proposed as results of a coarse-graining step procedure. The procedure is implemented to develop three coarse-grained models of increasing number of particle types from two to four. Force fields are computed by minimization of the deviations of appropriate distribution functions of the coarse-grained models from those of a reference atomistic one. Density, diffusivity and shear viscosity are computed by numerical simulation and compared with experimental values. The ability of each model to describe liquid-solid transitions is also analyzed. In particular, the model with four types of coarse-grained beads shows a transition from a liquid to a crystal phase.

Physicochemical, textural and viscoelastic properties of palm diacylglycerol bakery shortening during storage

BACKGROUND

Diacylglycerol (DAG), which has health-enhancing properties, is sometimes added to bakery shortening to produce baked products with enhanced physical functionality. Nevertheless, the quantity present is often too little to exert any positive healthful effects. This research aimed to produce bakery shortenings containing significant amounts of palm diacyglycerol (PDG). Physicochemical, textural and viscoelastic properties of the PDG bakery shortenings during 3 months storage were evaluated and compared with those of commercial bakery shortening (CS).

RESULTS

PDG bakery shortenings (DS55, DS64 and DS73) had less significant increments in slip melting point (SMP), solid fat content (SFC) and hardness during storage as compared to CS. Unlike CS, melting behaviour and viscoelastic properties of PDG bakery shortenings remained unchanged during storage. As for polymorphic transformation, CS contained only β crystals after 8 weeks of storage. PDG bakery shortenings managed to retard polymorphic transformation for up to 10 weeks of storage in DS55 and 12 weeks of storage in DS64 and DS73.

CONCLUSION

PDG bakery shortenings had similar if not better storage stability as compared to CS. This is mainly due to the ability of DAG to retard polymorphic transformation from β' to β crystals. Thus, incorporation of DAG improved physical functionality of bakery shortening.

Critical review of techniques and methodologies for characterization of emulsion stability

The efficient development and production of high quality emulsion-based products depends on knowledge of their physicochemical properties and stability. A wide variety of different analytical techniques and methodologies have been developed to characterize the properties of food emulsions. The purpose of this review article is to provide a critical overview of the most important properties of emulsions that are of interest to the food industry, the type of analytical techniques that are available to measure these properties, and the experimental protocols that have been developed to characterize the stability of food emulsions. Recommendations are made about the most suitable analytical techniques and experimental protocols needed to characterize the stability and properties of food emulsions.

Characterization of the triacylglycerol crystal formation in adipose tissue during a vehicle collision

The unusual appearance of crystalline fat structures was observed during the postmortem examination of a motor vehicle accident victim. The crystal structures were characterized using Fourier transform infrared spectroscopy and x-ray diffractometry. The structures were found to be made of triacylglycerols, a dominant lipid structure found in human adipose tissue, capable of forming various polymorphic structures. The morphology of the crystalline material was found using both techniques to be predominantly the beta' form of triacylglycerols. The accelerated growth of such triacylglycerol morphology has been observed as a result of shear stresses in other studies involving edible fats. As a result of the findings of this study, it is proposed that increased shear forces may be responsible for the formation of the unusual fat structure found in the victim. An understanding of the effect of forces on the structure of body fat in high-impact collisions can potentially assist in verifying a high-velocity impact.

Structural and thermal characterization of glyceryl behenate by X-ray diffraction coupled to differential calorimetry and infrared spectroscopy

Physical and thermal properties of glyceryl behenate (Compritol 888 ATO) used as sustained-release matrix in pharmaceutical applications are studied by coupled time-resolved synchrotron X-ray diffraction and Differential Scanning Calorimetry combined with Infrared Spectroscopy. With these techniques, all polymorphs formed in glyceryl behenate, analyzed as received and after various thermal treatments from quenching to slow crystallization, are characterized. By using different well-controlled mixtures of mono-, di- and tribehenate, we identify each lamellar phase observed in the glyceryl behenate. Finally the influence of the crystallization rate on the formation of preferential conformations was also analyzed in order to bring insights into the polymorphism of glyceryl behenate. By changing the crystallization rate of the sample, it was shown that one can favor the formation of preferential polymorphs in the sample. In particular the crystallization at 10 degrees C/min seems to be well adapted for producing a single lamellar phase with a period of 60.9 A while a crystallization rate of 0.4 degrees C/min produces three different lamellar phases.

Structures of the High-Temperature Solid Phases of the Odd-Numbered Fatty Acids from Tridecanoic Acid to Tricosanoic Acid

Crystal structures of the high-temperature phases of odd-numbered fatty acids (C(n)H(2n-1)OOH) from tridecanoic acid (C(13)H(25)OOH) to tricosanoic acid (C(23)H(45)OOH) are presented in this article. They have been determined from high-quality X-ray powder-diffraction patterns. Two types of high-temperature phases are adopted: one monoclinic A2/a with Z=8 for the fatty acids with n=13 and n=15, denoted as C'', and one monoclinic P2(1)/a with Z=4 for the longer-chain fatty acids, denoted as C'. It appears that the packing arrangement of the alkyl chains and of the carboxyl groups is similar in all of the structures. However, the arrangement at the methyl-group interface differs between the C' and C'' forms. A survey of the intermolecular interactions involved in these polymorphs coupled with a study of the effects of temperature on the structures have led us to a better understanding of the arrangement of the molecules within the high-temperature solid phases of odd-numbered fatty acids.

Thermodynamic and kinetic aspects of fat crystallization

Naturally occurring fats are multi-component mixtures of triacylglycerols (TAGs), which are triesters of fatty acids with glycerol, and of which there are many chemically distinct compounds. Due to the importance of fats to the food and consumer products industries, fat crystallization has been studied for many years and many intricate features of TAG interactions, complicated by polymorphism, have been identified. The melting and crystallization properties of triacylglycerols are very sensitive to even small differences in fatty acid composition and position within the TAG molecule which cause steric hindrance. Differences of fatty acid chain length within a TAG lead to packing imperfections, and differences in chain lengths between different TAG molecules lead to a loss of intersolubility in the solid phase. The degree of saturation is hugely important as the presence of a double bond in a fatty acid chain causes rigid kinks in the fatty acid chains that produce huge disruption to packing structures with the result that TAGs containing double bonds have much lower melting points than completely saturated TAGs. All of these effects are more pronounced in the most stable polymorphic forms, which require the most efficient molecular packing. The crystallization of fats is complicated not just by polymorphism, but also because it usually occurs from a multi-component melt rather than from a solvent which is more common in other industrial crystallizations. This renders the conventional treatment of crystallization as a result of supersaturation somewhat meaningless. Most studies in the literature consequently quantify crystallization driving forces using the concept of supercooling below a distinct melting point. However whilst this is theoretically valid for a single component system, it can only at best represent a rough approximation for natural fat systems, which display a range of melting points. This paper reviews the latest attempts to describe the sometimes complex phase equilibria of fats using fundamental relationships for chemical potential that have so far been applied to individual species in melts of unary, binary and ternary systems. These can then be used to provide a framework for quantifying the true crystallization driving forces of individual components within a multi-component melt. These are directly related to nucleation and growth rates, and are also important in the prediction of polymorphic occurrence, crystal morphology and surface roughness. The methods currently used to evaluate induction time, nucleation rate and overall crystallization rate data are also briefly described. However, mechanistic explanations for much of the observed crystallization behaviour of TAG mixtures remain unresolved.

Raman spectroscopy investigation of various saturated monoacid triglycerides

A study of the vibrational behavior of five saturated monoacid triacylglycerides is performed by Raman spectroscopy at room temperature in the 3100-500 cm(-1) spectral range. The splitting of the CO stretching mode leads to conclude on the existence of two or three geometries of CO in the "knot" group OCO. The CO stretching mode seems to be a good tool for distinguishing the polymorphic forms of the studied triglycerides. The assignments of the different CH stretching modes are performed in the 1500-500 cm(-1) spectral range. The I(2845)/I(2880) (in the CH stretching spectral region) and I(1445)/I(1296) intensity ratios (between the maximal intensity I(1445) of the CH(2) scissoring mode and the maximal intensity I(1296) of the skeletal vibration of (CH(2))(n) in-phase twist) seem to depend on the type of polymorphic forms of these molecules.

FT-IR spectrometry analysis of plasma fatty acyl moieties selective mobilization during endurance exercise

This study was designed to describe changes in plasma fatty acyl moieties during a 2-h endurance exercise. Sixteen endurance-trained subjects cycled 2 h at 55% of maximal power output and capillary blood was sampled every 15 min. Fourier-transform infrared (FT-IR) spectrometry was used to determine correlated changes between plasma fatty acyl moieties (FAM) structural characteristics and metabolic parameters (oxygen consumption, respiratory exchange ratio, glucose, lactate, TG, glycerol, and albumin). Opposite changes were found between carbohydrate and fatty acid metabolism during the second hour of exercise, i.e., a decrease of glucose and lactate concentrations while albumin, FAM, and TG increased. For fatty acid metabolism, FAM and TG did not showed the same pattern of changes at the end of exercise, i.e., TG remained constant after 90 min while FAM continued to increase. This late FAM concentration increase was correlated to the changes in albumin concentration and the nu C=C-H/nu(as) CH3 and nu(as) CH2/nu(as) CH3 ratios. These ratios clearly showed that FAM unsaturation increased while chain length decreased. It was hypothesized that PUFA from TG adipose lipolysis ketone bodies (beta-hydroxybutyric acid) from liver may have been released in higher amounts as glycogen stores became depleted after 90 min of exercise.

Determination of stress-induced changes in plasma molecular species by two-dimensional correlation Fourier transform infrared spectrometry

For determining exercise-induced changes in plasma molecular species, we investigated the feasibility of using two-dimensional correlation spectra (2D-COS) on 21 series of plasma samples obtained from progressive exercise tests. Intensities of 2D synchronous and asynchronous correlation peaks were compared to concentration evolutions of glucose, lactate, triglycerides (TG), glycerol, fatty acyl moieties, amino acids, proteins, and albumin [determined from plasma Fourier transform infrared (FTIR) spectra] and to performance and training levels of athletes. Synchronous 2D-COS allowed us to determine the linear relationship between protein and fatty acid concentration evolutions as exercise intensity increased (nu1-nu2; 2959 vs 1656 and 1543 cm(-1)). Asynchronous 2D-COS allowed differentiation of fibrinolysis level in subjects during intense exercise, as well as parameters of fatty acid metabolism specifically related either to performance or to training levels. Furthermore, unexpected correlated evolutions of molecular species were highlighted by this method, showing that 2D spectrometry may also be used for experimental investigations on human physiology. This study has demonstrated that 2D-COS may be used for the treatment of complex biological samples, such as plasma.