Functionalization of Non-interesterified Mixtures of Fully Hydrogenated Fats Using Shear Processing

Multiscale assessment of the effect of a stearic-palmitic sucrose ester on the crystallization of anhydrous milk fat

Anhydrous milk fat (AMF) is a flavorful, but particularly complex fat containing a wide variety of fatty acids (FAs) and triglycerides (TGs), resulting in an extended melting range of -40 °C to 40 °C. The functionality of this fat can be steered by the addition of sucrose esters (SEs). In this study, the crystallization behavior of AMF in the presence of a stearic-palmitic SE was assessed. Samples were cooled at 1 °C/min (slow cooling) or 20 °C/min (fast cooling) to 0 °C, 20 °C or 25 °C and kept isothermal for one hour. At each of these temperatures, AMF was found to crystallize via different polymorphic pathways and chain length structures, as studied by wide- and small-angle X-ray scattering. The addition of the SE (0.5 wt%) accelerated nucleation and allowed crystallization to start at higher temperatures. Polymorphic transitions were accelerated, but not changed. For fast-cooled samples, ultra-small-angle X-ray scattering provided insights into the mesoscale behavior of the crystal nanoplatelets (CNPs). It was observed that CNPs formed at 20 °C were smaller than those at 25 °C. The addition of the SE did not change the size nor the shape of CNPs. Polarized light microscopy (PLM) and cryo-scanning electron microscopy (cryo-SEM) gave insight into the microstructure of the networks. Addition of the SE resulted in more fine and dense fat crystal networks at 0 °C and 20 °C. At 25 °C, large separate floc structures were encountered, with and without the addition of the SE.

Effect of Water Content and Pectin on the Viscoelastic Improvement of Water-in-Canola Oil Emulsions

This study aimed to investigate gelation in glycerol monooleate (GMO)-stabilized water-in-canola oil (W/CO) emulsions by increasing water content (20–50 wt.%) and the addition of low methoxyl pectin (LMP) in the aqueous phase. A constant ratio of GMO to water was used to keep a similar droplet size in all emulsions. Hydrogenated soybean oil (7 wt.%) was used to provide network stabilization in the continuous phase. All fresh emulsions with LMP in the aqueous phase formed a stable and self-supported matrix with higher viscosity and gel strength than emulsions without LMP. Emulsion viscosity and gel strength increased with an increase in water content. All emulsions showed gel-like properties (storage moduli (G’) > loss moduli (G’’)) related to the presence of LMP in the aqueous phase and increased water content. Freeze/thaw analysis using a differential scanning calorimeter showed improved stability of the water droplets in the presence of LMP in the aqueous phase. This study demonstrated the presence of LMP in the aqueous phase, its interaction with GMO at the interface, and fat crystals in the continuous phase that could support the water droplets’ aggregation to obtain stable elastic W/CO emulsions that could be used as low-fat table spreads.

Influence of sonication, temperature, and agitation, on the physical properties of a palm-based fat crystallized in a continuous system

High-intensity ultrasound (HIU) has been used in the past to change fat crystallization and physical properties of fat crystalline networks. The objective of this work was to evaluate how HIU placed on different positions in a scraped surface heat exchanger (SSHE) using different processing conditions affect the physical properties of an interesterified palm olein. The sample was crystallized at two temperatures (20 °C and 25 °C) and two agitation rates (344/208 rpm and 185/71 rpm, barrels/pin worker). HIU (12.7 mm-diameter tip, 50% amplitude, 5 s pulses) was placed at three different positions within the SSHE. After processing, samples were stored at 25 °C for 48 h and analyzed according to the crystal morphology, solid fat content (SFC), oil binding capacity (OBC), melting behavior, viscoelasticity, and hardness. Physical properties were affected by crystallization conditions, by sonication, and by HIU position. The greatest improvement obtained was at 20 °C using low agitation when HIU was placed at the beginning of the SSHE. These conditions result in a sample with 98.9% of OBC, 274 kPa of viscoelasticity and 31 N of hardness. These results show that HIU can be used as an additional processing tool to improve physical properties of a palm-based fat and that the best improvement was obtained as a combination of crystallization conditions and HIU position.

Rheo-NMR to investigate fat crystallization under shear

It is well known that shear has an effect on fat crystallization. Whereas rheo-NMR has been used to study the impact of shear on the crystallization kinetics in the past, these methods mostly used a simple Teflon mixing shaft inside a sophisticated NMR instrument to apply shear to the sample. However, this method did not enable the determination of rheological parameters. In this work, a custom made low-field rheo-NMR device was evaluated, consisting of a commercial rheometer combined with a low-field permanent magnet to enable simultaneous rheological and NMR measurements. Two fats, i.e. partially hardened sunflower oil (PHSO) and soft palm mid fraction (sPMF), were submitted to several rheo-NMR experiments. The results of these experiments clearly indicated that these fats crystallized differently. First, PHSO crystallized faster than sPMF. Moreover, the latter seemed to crystallize in two steps. Initially a weak structure was formed when a low amount of solids was present, but this structure was replaced by a stronger network once more crystals were present. Both fats were studied under stagnant conditions, but also when submitted to low shear rates (1 s⁻¹ and 5 s⁻¹). It was shown that the amount of solids necessary to obtain a viscosity of 10 ​Pa ​s was higher when the shear rate was higher. The strength of the formed crystal network at a given percentage of solids was also weaker as the shear rate during crystallization increased. Whereas these experiments were done non-isothermally, it was shown that rheo-NMR can also perfectly be used for isothermal measurements.

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A recently developed custom-made rheo-NMR set p was used.

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The amount of solids and rheological parameters were simultaneously determined.

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Crystallization at a lower shear rate produced a stronger crystal network.

Fat crystallization of blends of palm oil and anhydrous milk fat: A comparison between static and dynamic-crystallization

The application of dynamic-crystallization (a combination of shear with rapid cooling) often plays an important role in the production of industrial fat-based products such as shortenings/margarines but has been rarely reported. In this study, three blends of palm oil (PO) with anhydrous milk fat (AMF) (0, 25 and 50% AMF, w/w) were rapidly crystallized under static (using freezer) and dynamic conditions (using a benchtop scraped surface heat exchanger). Various techniques including differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarized light microscopy (PLM), rheology and texture analysis were applied to investigate physicochemical properties of fat blends as well as their crystal morphology upon the long-term storage (4 weeks) at 5 °C and 15 °C. The results revealed that high cooling rate of dynamic-crystallization not only affected melting behavior of fat blends but also prevented the polymorphic transformation from β' to β crystals. Besides, the application of shear during fat crystallization helped to improve significantly the gel strength of produced shortenings. Although post-crystallization of low melting triacylglycerols (TAGs) occurred for all produced shortenings during storage at 5 °C which was accompanying with a firmness increase, it was more considerable for samples owning higher AMF content. Moreover, this phenomenon promoted the sintering as well as Ostwald ripening between fat crystals of dynamic-crystallized fat blends resulting in the formation of unwanted large aggregates (or granular crystals) with the size ranging from 100 to 500 μm.

Advances in our understanding of the structure and functionality of edible fats and fat mimetics

The reasons for the increased world-wide incidence of obesity, type-2 diabetes, and cardiovascular disease include sedentary lifestyles and poor food choices. Regulatory agencies in several countries now require companies to add unattractive front of package labels to their products where salt, sugar and fat (or saturated fat) levels are prominently displayed. After the demise of partially hydrogenated fats, saturated fat has become the new target. Consumption of saturated fat over polyunsaturated oil has been clearly shown to increase cholesterol levels in humans. However, saturated fats provide the functionality required in many food products. To complicate matters, concerns over sustainability, veganism, genetically modified organisms, animal welfare, as well as religious beliefs, severely limit our sources of saturated fat. In this review we will discuss recent advances in our understanding of the nano and mesoscale structure of fats, responsible for their physical functionality and contrast it to that of fat mimetics. Fat mimetics include polymeric networks of ethylcellulose, emulsion-templated networks of proteins and polysaccharides, colloidal and self-assembled fibrillar networks of polar lipid crystals, as well as solid o/w emulsions of oil trapped within crystallized lamellar mesophases. Clean label and economic considerations will also be touched upon.

Manipulation of Recrystallization and Network Formation of Oil-Dispersed Micronized Fat Crystals

A detailed investigation was carried out on the modulation of the coupling between network formation and the recrystallization of oil-dispersed micronized fat crystal (MFC) nanoplatelets by varying oil composition, shear, and temperature. Sunflower (SF) and bean (BO) oils were used as dispersing media for MFC nanoplatelets. During MFC dispersion production at high shear, a significant increase in the average crystal thickness (ACT) could be observed, pointing to recrystallization of the MFC nanoplatelets. More rapid recrystallization of MFC occurred in the SF dispersion than in the BO dispersion, which is attributed to higher solubility of MFC in the SF oil. When the dispersions were maintained under low shear in narrow gap Couette geometry, we witnessed two stages of recrystallization (measured via rheo-SAXD) and the development of a local yield stress (measured via rheo-MRI). In the first stage, shear-enabled mass transfer induces rapid recrystallization of randomly distributed MFC nanoplatelets, which is reflected in a rapid increase in ACT (rheo-SAXD). The formation of a space-filling weak-link MFC network explains the increase in yield stress (assessed in real time by rheo-MRI). In this second stage, recrystallization slows down and yield stress decreases as a result of the formation of MFC aggregates in the weak link network, as observed by confocal Raman imaging. The high fractal dimension of the weak-link network indicates that aggregation takes place via a particle-cluster mechanism. The effects of oil type and shear on the recrystallization rate and network strength could be reproduced in a stirred bowl with a heterogeneous shear stress field, which opens perspectives for the rational manipulation of MFC thickness and network strength under industrial processing conditions.

Design of yield-stress fluids: a rheology-to-structure inverse problem

We present a paradigm for the design of yield-stress fluids, using six archetypal materials for demonstration. By applying concepts of engineering design, we outline a materials design paradigm that includes (i) morphological organization based on jammed versus networked microstructures, (ii) collected scaling laws for predictive design, (iii) low-dimensional descriptions of function-valued flow data, (iv) consideration of secondary properties including viscous behavior, and (v) a strategy for material concept synthesis based on the juxtaposition of microstructures. By explicitly specifying these design strategies, we seek to create an ontology and database for the engineering of yield-stress fluids. Our proposed design strategy increases the likelihood of finding an optimal material and prevents design fixation by considering multiple material classes to achieve a desired rheological performance. This flips the typical structure-to-rheology analysis to become the inverse: rheology-to-structure with multiple possible materials as solutions.

Nanostructured fat crystal systems

A new understanding of the nature and organization of fat crystalline supramolecular structure, in particular at the nanoscale, has arisen in the past three years. These new findings have helped establish that the first step in the formation of a triacylglycerol network is the creation of nanocrystalline platelets that aggregate into polycrystalline clusters in the micrometer range, ultimately forming a three-dimensional network. This review explains how fat nanostructure can be characterized and highlights recent findings on how crystallization parameters influence the formation of fat nanocrystals. For instance, shear has been shown to modify not only nanoplatelet size but also their aggregation, affecting some macroscopic properties such as porosity and, therefore, the ability of the network to effectively bind liquid oil. This new information on fat nanostructure is relevant from scientific and technological standpoints and has opened up the possibility of nanoengineering material properties as well as developing new products and processes.