Effect of High‐Intensity Ultrasound on the Crystallization Behavior of High‐Stearic High‐Oleic Sunflower Oil Soft Stearin

The objective of this research was to evaluate the effect of high‐intensity ultrasound (HIU) and crystallization temperature (T_c) on the crystallization behavior, melting profile, and elasticity of a soft stearin fraction of high‐stearic high‐oleic sunflower oil. Results showed that HIU can be used to induce and increase the rate of crystallization of the soft stearin with significantly higher SFC values obtained in the sonicated samples, especially at higher T_c. SFC values were fitted using the Avrami model, and higher k_n and lower n values were obtained when samples were crystallized with sonication, suggesting that sonicated samples crystallized faster and through an instantaneous nucleation mechanism. In addition, the crystal morphology, melting behavior, and viscoelasticity were significantly affected by sonication.     

Cooling rate and dilution affect the nanostructure and microstructure differently in model fats

The effects of cooling rate and solid mass fraction on the polymorphism, nano and microstructure, thermal and rheological properties of binary mixtures of fully hydrogenated canola oil and canola oil at 20°C have been studied. The β‐polymorph was observed in fully hydrogenated canola oil (FHCO) when crystallized at slow cooling rates (0.1C°/min), however crystallization at higher cooling rates (0.7 and 10°C/min) resulted in the formation of the α form. The β‐polymorph was detected in all the binary mixtures of FHCO/canola oil and was not affected by crystallization at different cooling rates. Melting thermograms obtained from 100% FHCO displayed three melting peaks, associated with the development of the β‐polymorph via α→ β′→ β‐polymorphic transition in the DSC pan. Some solubilization of solid FHCO into canola oil was observed and the solubility was proportionally higher with increasing liquid oil fraction. The strong influence of the matrix concentration on micro/nanoscale structure was demonstrated by characterization of crystal size using cryogenic transmission electron (Cryo‐TEM) and polarized light microscopy (PLM). Crystallization under higher cooling rates lead to formation of smaller nano and meso‐structural elements. Furthermore, oscillatory rheology showed the influence of structural elements' size and polymorphism on material strength. The shear storage modulus (G′) of the mixtures was higher when crystallized at fast cooling rates (10°C/min). In contrast, for pure FHCO, G′ increased by lowering the cooling rate and the highest storage modulus was observed after crystallization at 0.1°C/min.     

Crystallization kinetics of palm stearin in blends with sesame seed oil

This study investigates the crystallization kinetics of palm stearin (PS), a palm oil fraction, in blends with sesame seed oil. The results indicate that the crystallization behavior of PS in sesame oil is mainly associated with the crystallization of tripalmitin. Therefore, crystallization of blends of 26, 42, 60, and 80% (wt/vol) PS in sesame oil was described by equations developed for simpler systems (e.g., Fisher and Turnbull equation). The isothermal crystallization, melting profile, and fitting of the kinetics of nucleation to the Fisher and Turnbull equation showed that the 26, 42, and 60% PS/sesame oil blends crystallized mainly in the β₁′ polymorph state. In contrast, the 80% blend crystallized in two different polymorph states (i.e., β₁′ at T⪯307.6 K and β₁ at T≽308.2 K). The data indicated that, in spite of the higher concentration of PS in the 80% PS/sesame oil system, crystallization in the β₁ state required more free energy for nucleation (δG _c ) than β₁′ crystallization in the 26, 42, and 60% PS/sesame oil. At the low cooling rate used (1 K/min) it was observed that, for a particular PS blend, the higher the effective supercooling the higher the viscosity of the oil phase and the smaller the induction time of crystallization (T_i). Additionally, the β₁′ crystals from PS, developed at the highest effective supercooling investigated, were smaller than the β₁ crystals obtained at lower effective supercooling.     

Sonocrystallization of Interesterified Fats with 20 and 30% of Stearic Acid at the sn-2 Position and Their Physical Blends

Physical blends (PB) of high oleic sunflower oil and tristearin with 20 and 30% stearic acid and their interesterified (IE) products where 20 and 30% of the fatty acids are stearic acid at the sn-2 position crystallized without and with application of high intensity ultrasound (HIU). IE samples were crystallized at supercooling temperatures (ΔT) of 12, 9, 6, and 3 °C while PB were crystallized at ΔT = 12 °C. HIU induced crystallization in PB samples, but not in the IE ones. Induction in crystallization with HIU was also observed at ΔT = 6 and 3 °C for IE C18:0 20 and 30% and at ΔT = 9 °C only for the 30% samples. Smaller crystals were obtained in all sonicated samples. Melting profiles showed that HIU induced crystallization of low melting triacylglycerols (TAGs) and promoted co-crystallization of low and high melting TAGs. In general, HIU significantly changed the viscosity, G′, and G″ of the IE 20% samples except at ΔT = 12 °C. While G′ and G″ of IE 30% did not increase significantly, the viscosity increased significantly at ΔT = 9, 6, and 3 °C from 1526 ± 880 to 6818 ± 901 Pa.s at ΔT = 3 °C. The improved physical properties of the sonicated IE can make them good contenders for trans-fatty acids replacers.     

Dry fractionation of coconut oil by melt crystallization

Layer melt crystallization was applied for the dry fractionation of multi-component mixtures using coconut oil as a model substance. The aim of the experiments was to optimize the crystallization parameters (e.g. crystallization temperature, melt temperature, cooling rate, agitation speed) in order to obtain the solid fraction with a higher melting temperature and solid fat properties. The isothermal crystallization behavior of coconut oil was investigated via differential scanning calorimetry (DSC). The efficiency of the crystallization process was monitored by determining the melting point and solid fat content (SFC) of the fractionated products. The morphology of crystal layer was studied by a light microscope. Cool finger temperature was found to have the greatest impact on product properties. Applying a cooling rate of 0.2 K/h resulted in sufficient growth rates providing the required products. The micrographs of the solid fraction revealed lamellar particle arrangement compared to coconut oil possessing spherulites.     

Solvent Interesterification of Vegetable Oils III

Directed interesterification reaction in solvents of cottonseed, peanut and cottonseed containing peanut, sesame and safflower oils was investigated with special reference to the influence of amount of sodium methoxide catalyst, oil content in solvent, temperature during the reaction and the nature of solvent on the characteristics of the reaction. The parameters were first studied with cottonseed oil and the conditions that favoured the reaction were adopted for peanut oil and cottonseed oil mixtures.     

Cocoa Butter Substitute (CBS) Produced from Palm Mid-fraction/Palm Kernel Oil/Palm Stearin for Confectionery Fillings

This study investigated the physicochemical properties of ternary mixtures of palm mid-fraction (PMF):refined bleached deodorized palm kernel oil (RBDPKO):refined bleached deodorized palm stearin (RBDPS) for cocoa butter substitute (CBS). Fatty acid constituents, triacylglycerol constituents, solid fat contents (SFCs), melting behavior, polymorphism and crystal morphology were determined using gas chromatography (GC), high-performance liquid chromatography (HPLC), differential scanning calorimetry (DSC), pulsed nuclear magnetic resonance (p-NMR), X-ray diffraction (XRD) and polarized light microscopy (PLM), respectively. Eight blends of various ratios of ternary mixtures were investigated based on the previously studied binary fat mixtures. The composition of palmitic (P) and oleic (O), POP, and crystal morphology (size and shape) of the PMF/RBDPKO/RBDPS [14.9/59.6/25.5 (%w/w)] mixture were comparable to cocoa butter (CB), while its melting profile (18.5 and 37 °C), SFC at 20 °C and polymorphism were different from CB. The iso-solid diagrams of the mixture displayed a monotectic effect at 20–25 °C. Therefore, the 14.9/59.6/25.5 PMF/RBDPKO/RBDPS mixture could be used as a CBS in confectionery fillings because of the crystal morphology and monotectic behaviors comparable to those of CB.     

Effects of High Intensity Ultrasound Frequency and High-Speed Agitation on Fat Crystallization

The objective of this research was to examine the effect of ultrasound frequency and high-speed agitation on lipid crystallization. Interesterified soybean oil was crystallized at 44 °C without and with the application of high intensity ultrasound (HIU—20 and 40 kHz) or with high-speed agitation (6000 and 24,000 rpm). Two tip amplitudes (24 and 108 µm) and three pulse durations were evaluated (5, 10, and 15 s) for the acoustic frequencies tested. Sonication at 20 kHz of frequency significantly reduced crystal size, increased (p < 0.05) elasticity (435.9 ± 173.3–80,218 ± 15,384 Pa) and SFC (0.2 ± 0.0–4.5 ± 0.4%). No significant difference was observed in the crystallization behavior of these samples when sonicated at different amplitudes for 5 and 10 s. The crystallization behavior was significantly delayed (p < 0.05) in samples sonicated using 108 µm amplitude for 15 s. Larger crystals were formed in samples sonicated at 40 kHz compared to those obtained with 20 kHz and lower SFC (3.7 ± 0.0%) and elasticity (3943 ± 1459 Pa) values were obtained. High-speed agitation at 24,000 rpm increased SFC (5.5 ± 0.1%) and crystallized area and decreased the elasticity (42,602 ± 11,775 Pa) compared to the samples sonicated at 20 kHz.     

Development of a Coconut- and Palm-Based Fat Blend for a Cookie Filler

Thirteen fat blends intended for cookie filler (CF) production that consist of 20–70 % palm mid-fraction (PMF), 20–70 % virgin coconut oil (VCO), and 0–10 % palm stearin (POs) were developed based on the solid fat contents (SFC) of the fat portions extracted from five commercial CF samples: A, B, C, D, and E. A mixture design was applied for fat blend optimization, and the combination that best approached the target SFC values was composed of 70 % PMF, 20 % VCO, and 10 % POs. The optimized coconut- and palm-based fat blend (O-CP) exhibited a steeper SFC profile, with 8.2 % (±0.2) SFC at 25 °C (room temperature) and 0.2 % (±0.2) SFC at 37 °C (body temperature); lower slip melting point of 34.0 °C (±0.0); and a lower iodine value (IV) of 40.25 g/100 g (±1.04). In addition, O-CP contained higher proportions of medium-chain fatty acids (MCFA) and lauric acid (C12:0) of 3.2 % (±0.18) and 9.7 % (±0.43), respectively. In terms of its thermal profile, O-CP showed no significant difference in terms of its crystallization range, 49.7 °C (±2.66) with the exception of sample C, but it exhibited a smaller melting range, 65.8 °C (±1.47), compared to the fat portions of the commercial samples. The ranges represented the span between the onset and offset temperatures of both crystallization and melting profiles as determined by differential scanning calorimetry.     

Application of High Intensity Ultrasound to a Zero-trans Shortening During Temperature Cycling at Different Cooling Rates

The objective of this work was to evaluate the effect of high intensity ultrasound (HIU) on the physical properties of a commercial shortening crystallized at a constant temperature and during temperature cycling at two different cooling rates (0.5 and 1 °C/min). Different ultrasound power levels and different durations were evaluated during crystallization at a constant temperature and the best conditions were used to evaluate the effect of HIU during temperature cycling. The physical properties tested were crystal microstructure, viscoelasticity, and melting profile. Results show that HIU is more efficient at changing crystal microstructure when used at 20 °C using a 1/2″ tip. No difference was found on the microstructure of the crystals formed when different durations of ultrasound exposure were tested. A significant increase (p < 0.05) was observed in the storage modulus (G′) of the lipid exposed to temperature fluctuations with the use of HIU. The G′ values increased from 662.6 ± 176.8 Pa (no HIU applied) to 3,365.5 ± 426.4 Pa (with HIU applied, 0.5 °C/min) and from 354.4 ± 49.7 Pa (no HIU applied) to 1,249.0 ± 19.8 Pa (with HIU applied, 1 °C/min).     

Crystallization Behavior and Kinetics of Chocolate-Lauric Fat Blends and Model Systems

Binary mixtures of cocoa butter and lauric fats have widespread use in chocolates and confections, yet incompatibilities between these fats can present formulation and processing constraints. This study examined the phase behavior and crystallization kinetics of cocoa butter-lauric fat model systems and chocolate-lauric fat blends. Solid fat content (SFC) profiles and isosolid diagrams confirmed eutectic and diluent interactions, indicating a softening of cocoa butter by lauric fat addition. Crystallization kinetics of model systems adhered to an exponential growth model. High lauric fat levels delayed crystal growth and reduced equilibrium SFC of cocoa butter. Coconut and palm kernel oils altered the solidification mechanisms of cocoa butter to a greater extent than fractionated palm kernel oil. Chocolate systems displayed multi-step crystal growth that contrasted with the exponential growth observed in the model systems. At high lauric fat levels (30%), crystallization onset was significantly lengthened. Blends with high lauric fat contents showed low \(G_{{\text {max}} }^{\prime }\) and did not achieve final equilibrium after 60 min of cooling, indicating incomplete crystallization.     

Relationship between oil binding capacity and physical properties of interesterified soybean oil

The objective of this study was to identify the physical properties of an interesterified soybean oil (EIESOY), containing 45% saturated fatty acids (SFA), that correlates with high oil binding capacity (OBC) and low oil loss (OL). In this study, three EIESOY samples were analyzed; a 100% sample, a 50% sample diluted with 50% soybean oil, and a 20% sample diluted with 80% soybean oil. All samples were crystallized using fast (7.78°C/min) and slow (0.1°C/min) cooling rates as well as with and without high-intensity ultrasound (HIU, 20 kHz). The 100%, 50%, and 20% samples were crystallized at 38.5, 27.0, and 22.0°C, respectively. HIU was applied at the onset of crystallization and all samples were allowed to crystallize isothermally for 90 min. After 90 min, physical properties such as crystal microstructure, hardness, solid fat content (SFC), elasticity, and melting behavior were evaluated. Physical properties were also measured after storage for 48 h at 22 and 5°C. Results show that OBC was positively correlated with hardness, G′, and SFC after 48 h (r = 0.738, p = 0.006; r = 0.639, p = 0.025; r = 0.695, p = 0.012; respectively), OL was negatively correlated with hardness after 48 h (r = −0.696, p < 0.001), G′ after 90 min and 48 h (r = −0.704, p < 0.001; r = −0.590, p = 0.002), and SFC after 90 min and 48 h (r = −0.722, p < 0.001; r = −0.788, p < 0.001). Neither OBC nor OL were correlated with crystal diameter or the number of crystals.     

Melting behavior of blends of milk fat with hydrogenated coconut and cottonseed oils

The melting behavior of milk fat, hydrogenated coconut and cottonseed oils, and blends of these oils was examined by nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). Solid fat profiles showed that the solid fat contents (SFC) of all blends were close to the weighted averages of the oil components at temperatures below 15°C. However, from 15 to 25°C, blends of milk fat with hydrogenated coconut oils exhibited SFC lower than those of the weighted averages of the oil components by up to 10% less solid fat. Also from 25 to 35°C, in blends of milk fat with hydrogenated cottonseed oils, the SFC were lower than the weighted averages of the original fats. DSC measurements gave higher SFC values than those by NMR. DSC analysis showed that the temperatures of crystallization peaks were lower than those of melting peaks for milk fat, hydrogenated coconut oil, and their blends, indicating that there was considerable hysteresis between the melting and cooling curves. The absence of strong eutectic effects in these blends suggested that blends of milk fat with these hydrogenated vegetable oils had compatible polymorphs in their solid phases. This allowed prediction of melting behavior of milk-fat blends with the above oils by simple arithmetic when the SFC of the individual oils and their interaction effects were considered.     

Nanoscale fibrillar crystals of PET from dilute quiescent solution

The crystallization behavior of poly(ethylene terephthalate) (PET, IV∼2 dL/g) from solution in biphenyl-diphenyl ether mixed solvent is examined. Reversible gelation of the polymer solution is observed during cooling of the solutions. Light scattering and DSC analysis are used to follow the heating and cooling processes, thus determining the crystallization temperature and the melting point, which are found to be nearly independent of the polymer concentration (0.25-5%). High degree of crystallization (>50%) is observed in the PET crystallized from the solution at 170 °C. Morphological characteristics of the crystals obtained after solvent removal are determined by WAXD, FTIR, SEM and TEM examination. The crystallization of PET into unique high aspect ratio fibrillar morphology during cooling of the solutions explains their gelation even at low PET concentration. Thin films made from the thus obtained PET could be drawn five times at 250 °C, resulting in only moderate values of modulus and strength.     

Physicochemical and Rheological Properties of Crystallized Blends Containing <Emphasis Type="Italic">trans</Emphasis>-free and Partially Hydrogenated Soybean Oil

Three vegetable oil blends, intended for formulation of high melting temperature confectionary coatings, were prepared by mixing different proportions of coconut oil, palm stearin, and either partially hydrogenated soybean oil (PH-SBO) or native soybean oil (i.e., trans-free SBO). The blends were crystallized under the same isothermal conditions and the crystallized systems evaluated by DSC, SFC, polarized light microscopy, and rheology under low [i.e., G′ and yield stress (σ*)] and high (i.e., creep and recovery profiles) stress forces. Overall, all trans-free blends showed lower SFC and heat of crystallization than the ones obtained with PH-SBO blends. These results showed that trans-fatty acids decrease the level of structural order of the crystals, and probably also the organization of the crystal network. As a result, most of the crystallized blends with PH-SBO showed lower σ* values and higher creep profiles (i.e., softer texture) than trans-free blends, particularly in systems crystallized at high supercooling and blends with saturated medium chain TAG. Nevertheless, at particular crystallization temperatures some trans-free formulations provided crystallized systems with rheological properties that would result in softer textures than the ones obtained with PH-SBO blends. Knowledge of the rheological properties under low and high stress forces is vital when comparing the functionality of crystallized TAG systems with and without TAG with trans-fatty acids.     

Physicochemical Characteristics and Aflatoxin Levels in Two Types of Sudanese Sesame Oil

The physicochemical characteristics and aflatoxin levels of two types of sesame oil [Walad (W) and Normal (N)] were determined. A total of 104 sesame oil samples were collected during two seasons (I and II) from traditional mills in five states of Sudan. Levels of aflatoxin B₁, B₂, G₁, and G₂ were determined using HPLC. The physicochemical characteristics of W and N samples were significantly (P ≤ 0.05) different: samples of W and N from the five states had fluctuations in physicochemical characteristics in the two seasons. The highest percentage of contamination (recorded in Khartoum followed by Kordofan state) by aflatoxin B₁ during season II occurred in normal sesame oil which was 80.77 %, followed by Walad sesame oil which was 76.92 %. These percentages of contamination in season I were lower than 59.26 % for normal sesame oil and lower than 52.0 % for Walad sesame oil in season II. Aflatoxin B₂ contamination recorded the highest incidence in season II (3 out of 26 samples, 11.54 %) of normal sesame oil, followed by Walad sesame oil (2 out of 26 samples, 7.69 %). These percentages were lower than the 7.40 and 4.0 % of normal and Walad sesame oils in season I, respectively. Aflatoxin B₁ and B₂ levels in sesame oil ranged from 0.5 to 9.8 and 0.5 to 1.3 μg/kg, respectively.     

Accelerated Fat Bloom in Chocolate Model Systems: Solid Fat Content and Temperature Fluctuation Frequency

Chocolate model systems were designed with high‐melting fat (cocoa butter stearin, CB‐S) mixed with low‐melting fats (sunflower oil, canola oil, cottonseed oil, peanut oil) to give 45, 55, and 65 % solid fat content (SFC). Defatted cocoa powder provided a 50 % particulate level in the model chocolates. The effects of SFC, low‐melting fat type and storage temperature fluctuation frequency on bloom whiteness were investigated. Both SFC and storage condition had significant influences on bloom whiteness (p < 0.0001), although the type of low‐melting fat did not (p = 0.1223). Increasing the SFC significantly reduced bloom formation, as did more rapid temperature fluctuations.     

Mixtures of palm kernel oil with cocoa butter and milk fat in compound coatings

Thermal behavior of binary mixtures of palm kernel oil (PKO), cocoa butter (CB), and anhydrous milk fat was used to study mixed-lipid crystallization. This study was related to the physical properties of compound coatings made with these fats. Phase behavior was studied by evaluating changes in melting behavior with composition and time, by creating isosolid diagrams, and by monitoring polymorphic behavior. For binary mixtures, multiple melting peaks and eutectic formation were observed for 30–50% addition levels of CB to PKO, but not for addition of milk fat to PKO. For compound coatings and binary mixtures, made with the same fat composition, hardness of compound coatings increased as solid fat content (SFC) at 25°C of binary mixtures increased. Also, as SFC at 25°C of the binary mixtures increased, induction time for bloom formation and time to fully bloom for compound coatings decreased. Observation of eutectic behavior for binary mixtures indicated softness in a compound coating with the same fat composition, but the converse was not necessarily true.     

Sonocrystallization of Interesterified Fats with 20 and 30% C16:0 at <Emphasis Type="Italic">sn</Emphasis>-2 Position

The objective of this study was to induce crystallization in enzymatically interesterified fats (IE) with 20 and 30% palmitic acid at the sn-2 position using high intensity ultrasound (HIU). The physical blends (PB) used to prepare these two IE were consisted of tripalmitin and high oleic sunflower oil and contained 13.2 and 27.1% tripalmitin, respectively. Crystallization behavior of IE was compared with PB at supercoolings of 9, 6 and 3 °C. Results show that the melting point, SFC, and crystallization rate of PB were higher than IE and were driven mainly by tripalmitin content. HIU induced crystallization and generated small crystals in the IE samples. At 9 °C supercooling, sonication did not increase the viscosity of IE C16:0 20%, while that of the IE C16:0 30% increased significantly from 192.4 ± 118.9 to 3297.7 ± 1368.6 Pa·s. The elastic modulus (G’) for IE C16:0 30% increased from 12521 ± 2739.8 to 75076.7 ± 18259 Pa upon sonication at 9 °C supercooling, while the G’ of the IE C16:0 20% did not increase. Similar behavior was observed for the other supercoolings tested. This research suggests that HIU can improve the functional properties of IE with low content of C16:0 creating more viscous and elastic materials. These fats with low C16:0 content and improved functional properties could be used as trans-free fat alternatives.     

Influence of Temperature and Time on Isothermal Crystallization of Poly-L-lactide

The thermal behavior of poly-L-lactide (PLLA) isothermal crystallization upon cooling from the melt was investigated using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing microscope (POM) by changing the crystallization temperature and time. It was indicated that 110°C should be a critical temperature for PLLA melting crystallization. The melting point of crystallized PLLA discontinuously changed with crystallization temperature, increased with temperature, but decreased at about 110°C, and thereafter again increased with higher crystallization temperatures. At 110°C a multiple endothermic peak was observed. PLLA crystals of higher perfection form when crystallized under higher temperature, which reflects the effects of high chain mobility in higher temperatures. During isothermal crystallization, PLLA crystallites become increasingly perfect, and thicken with prolonged time, leading to an increasing melting point.