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.     

Polymorphic behavior of some fully hydrogenated oils and their mixtures with liquid oil

Fully hydrogenated soybean oil, beef fat, rapeseed oil, a rapeseed, palm and soybean oil blend, cottonseed oil and palm oil were characterized by fatty acid composition, glyceride carbon number and partial glyceride content, as well as melting and crystallization properties. The latter were established by differential scanning calorimetry. Polymorphic behavior was analyzed by X-ray diffraction of the products in the flake or granulated form and when freshly crystallized from a melt. The hard fats were dissolved in canola oil at levels of 20, 50 and 80% and crystallized from the melt. Palm oil had the lowest crystallization temperature and the lowest melting temperature; rapessed had the highest crystallization temperature and soybean the highest melting temperature. All of the hard fats crystallized initially in the =00 form. When diluted with canola oil, only palm oil was able to maintain β′ stability.     

Crystallization Kinetics of Coconut Oil in the Presence of Sorbitan Esters with Different Fatty Acid Moieties

Sorbitan esters (SEs) are shown to strongly influence the solidification kinetics and fat crystal morphology, but not polymorphic behaviour, of coconut oil (CNO). Solid‐state SEs (sorbitan monopalmitate, monostearate, and tristearate) affect both the high‐ and low‐melting fractions of CNO by decreasing induction time and by increasing crystallization rate as well as the number concentration of crystals. Liquid‐state SEs (sorbitan monoleate and trioleate) and canola oil do not specifically influence the high‐ or low‐melting fraction of CNO but do slow crystallization and lengthen induction time. The influence of sorbitan monolaurate, the only SE with an acyl group similar to that of CNO, is shown to depend on the crystallization temperature. At temperatures below its melting point, it only affects CNO's high‐melting fraction; at temperatures above its melting point, crystallization of both fractions is extensively decelerated. The lack of influence in polymorphic behaviour by any SE confirms no alteration of subcell arrangement, suggesting a lack of complementarity with the crystallizing fat. Overall, these SEs significantly impact the crystallization kinetics of CNO; however, this largely depends on type and concentration.     

Effect of cooling rate on crystallization behavior of milk fat fraction/sunflower oil blends

The effect of cooling rate (slow: 0.1°C/min; fast: 5.5°C/min) on the crystallization kinetics of blends of a highmelting milk fat fraction and sunflower oil (SFO) was investigated by pulsed NMR and DSC. For slow cooling rate, the majority of crystallization had already occurred by the time the set crystallization temperature had been reached. For fast cooling rate, crystallization started after the samples reached the selected crystallization temperature, and the solid fat content curves were hyperbolic. DSC scans showed that at slow cooling rates, molecular organization took place as the sample was being cooled to crystallization temperature and there was fractionation of solid solutions. For fast cooling rates, more compound crystal formation occurred and no fractionation was observed in many cases. The Avrami kinetic model was used to obtain the parameters k _n and n for the samples that were rapidly cooled. The parameter k _n decreased as supercooling decreased (higher crystallization temperature) and decreased with increasing SFO content. The Avrami exponent n was less than 1 for high supercoolings and close to 2 for low supercoolings, but was not affected by SFO content.     

Palm oil and palm kernel oil in food products

Cocoa butter equivalent (CBE) formulation, especially the compatibility of palm oil based CBE with cocoa butter, is of special interest to chocolate manufacturers. Traditionally palm oil is fractionated to obtain high-melting stearin and olein with a clear point of around 25 C, the latter serving as cooking oil. Recently, palm oil has been fractionated to recover an intermediate fraction known as palm mid-fraction (PMF), which is suitable for CBE formulations. Generally, production of PMF is based on a three-step procedure. However, a dry fractionation system, which includes selective crystallization and removal of liquid olein by means of a hydraulic press, has been developed. Iodine value, solid content (SFI) at different temperatures, cooling curves (Shukoff 0°) and triglyceride/fatty acid composition determination confirmed effectiveness of the procedure followed. A direct relationship between yield, quality of PMF and crystallization temperature during fractionation has been achieved. Yield of 60% for olein of IV 64–67 has been achieved. Yield of 30% for PMF of IV 36–38 and 10% for high melting stearin of IV of 20–22 are also being achieved. High-melting stearin may be used in oleochemical applications, soaps, food emulsifiers and other industrial applications such as lubricating oil. Olein fraction, especially after flash hydrogenation thereby reducing the IV to 62/64, has excellent frying and cooking oil characteristics. Palm olein is also suitable as dietary fat and in infant formulation. Studies on interesterification of high-melting stearin with olein showed possibilities to formulate hardstocks for margarine and spread formulations, even without using hydrogenated fat components. Palm kernel and coconut fats or fractions or derived products are used for confectionery products as partial CB replacers and as ice cream fats and coatings. Coconut oil also serves as a starting material for the production of medium-chain triglycerides.     

Effects of Tripalmitin and Tristearin on Crystallization and Melting Behavior of Coconut Oil

We investigated the crystallization behavior of coconut oil (CO) with tripalmitin (PPP) and tristearin (StStSt) as additives. The effects of cooling rates (2°C, 5°C, and 10°C min⁻¹) and triacylglycerol concentrations (0.3–10 wt.%) on crystallization and melting behavior of CO were studied using differential scanning calorimetry (DSC) and optical microscopy. The polymorph was also examined using synchrotron radiation X-ray diffraction (SR-XRD). From the DSC results, two exothermic peaks for CO crystallization indicated two compositions in CO. From the SR-XRD results, the α form crystallized first at a high crystallization temperature (HTc) followed by β′ crystallization at low temperature (LTc), after which both HTc-α and LTc-β′ transformed into the β′ form of CO (CO-β′) solid solution during heating. Although the addition of PPP increased crystallization temperature of CO, it did not change its polymorphic pattern. However, during slow cooling with the StStSt additive, CO-β′ crystallization was induced from the melt directly. Moreover, under isothermal conditions, the crystallized StStSt spherulites induced nucleation of CO more than did PPP. Therefore, PPP increased the crystallization temperature of CO in both HTc and LTc fractions without changing the polymorph of CO, while StStSt promoted crystallization of CO directly into CO-β′.     

Turbidimetry for crystalline fractionation of lard

Development of specific properties of lard, a well-known edible animal by-product and one which plays an important role in Chinese-style foods, was studied by means of multiple-step crystalline fractionation. A method for monitoring the crystallization temperature and crystallization time of lard by spectral turbidity was also studied. The capabilities of the proposed method were experimentally demonstrated through recovery of the fat crystal mass. Six significant changes in turbidity spectra, which correspond to the formation of fat crystals, were observed at various temperatures while cooling the melted lard from 50°C to the final vessel temperature at a constant cooling (0.5°C/min) and agitator rate (50 rpm). Crystallization time for each lard fraction was determined while the peak in turbidity was observed in the process of cooling at a specific temperature. Determination of crystallization time by means of turbidimetry correlated with the increase in deposition of fat crystals. No significant increase in fat crystal mass was observed when cooling prolongation after the turbidity peak for the sample was measured. Attributes of lard fractions were characterized by iodine value, saponification value, fatty acid composition, and melting profile of crystallization temperature. Based on the results, turbidimetry might be suggested as a fast and inexpensive method for monitoring the crystallization temperature and crystallization time for the routine crystalline fractionation process.     

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.     

Phase equilibrium and crystallization behavior of mixed lipid systems

As complex lipid systems, the phase and crystallization behavior of mixtures of a high-melting milk fat fraction with a low-melting milk fat fraction or canola oil was studied. A turbidity technique was developed to estimate solubility and metastability conditions of these lipid mixtures. Both solubility and metastability of the high-melting milk fat fraction in liquid lipids increased exponentially with temperature. At a given equilibration temperature, liquid phases and solid fractions with nearly identical melting profiles and TAG compositions were obtained regardless of the original concentration of the lipid mixture. The maximum melting temperature (MMT), as measured by DSC, of the liquid phase increased dramatically in the equilibrium temperature range of 27.5–35.0°C but did not change at temperatures below and above this range (down to 25.0°C and up to 40°C in this study). The content of long-chain TAG (C₄₆−C₅₂) increased and short-chain TAG (C₃₆−C₄₀) decreased in the liquid phases as the equilibrium temperature increased. A plot of the TAG group ratio (i.e, long-short-chain TAG) vs. equilibrium temperature was generated to illustrate the phase behavior of the complex lipid system and to represent a solubility curve, from which the supersaturation level for crystallization kinetics was determined. Higher supersaturation and lower temperature resulted in higher nucleation and crystallization rates. Compared to the system with a low-melting milk fat fraction, mixtures of the high-melting milk fat fraction with canola oil had higher nucleation and crystallization rates due to the lower solubility found for this system.     

CLA‐Rich Soy Oil Shortening Production and Characterization

Conjugated linoleic acid‐rich soy oil (CLARSO) has been shown to have numerous health benefits, including anti‐obesity and anti‐carcinogenic properties. This oil was previously used to produce CLA‐rich margarine that showed physical characteristics similar to commercially available margarine. The objective of this study was to produce CLA‐rich shortening and analyze its physical properties relative to commercially available shortenings and soy oil control shortenings. The shortenings were prepared and their rheology, thermal behavior, and solid fat content (SFC) were determined and compared to the commercial samples. The CLA‐rich shortening samples showed similar rheological properties to the commercial samples and showed a better consistency (more solid‐like behavior) compared to the soy oil control samples. In addition, the CLA‐rich shortenings also have a higher SFC (% SFC) as well as higher latent heat of crystallization and melting than the soy oil controls indicating a comparatively higher crystalline fraction. Thus, CLARSO produced firmer shortenings than did conventional soy oil by interacting with the crystallizing stearin fraction and consequently increasing the crystalline mass fraction without significantly altering the microstructure kinetics of solid fat crystallization.     

Random interesterification of fat blends with alkali catalysts

Random interestification of fat blends, composed from vegetable oil and fully hydrogenated vegetable oil, catalyzed by sodium hydroxide and sodium methoxide, has been investigated. Sodium methoxide was used as a reference catalyst to evaluate the influence and the catalytic efficiency of NaOH on interesterification. Sodium hydroxide was found to be a suitable catalyst for this purpose. The choice of methods suitable for the investigation of interesterification reactions and characterization of the initial fat blends and their interesterified products is described. The randomization was followed by the changes in the triacylglycerol (TAG) composition of the fat blends determined by HPLC and high temperature GLC. This triacylglycerol composition of the original blends and the randomized products with the physical properties such as melting behaviour, crystallization and solid fat content were compared. The results show that the randomization of vegetable oil - fully hydrogenated vegetable oil fat blends in various ratios can be used to produce fats with desired physical and nutritional properties.     

Crystallization and fractionation of milk fat

Recent progress in understanding milk fat crystallization and fractionation is reviewed. Extent of fat solidification in butter can be altered by variations in thermal treatment of cream prior to churning. Because of its compositional complexity, milk fat rarely exhibits polymorphism. As with mixtures of closely related triglycerides, milk fat forms solid solutions. A typical milk fat begins melting below −40 C, maximum melting occurs at 15–18 C, and the highest melting fraction appears 20–37 C as a shoulder on the main peak. Dispersion of fat in emulsions increases its tolerance to supercooling, thereby altering the properties and composition of the solid phase. Most studies of milk fat fractionation have used progressive fractional crystallization, either of the melt or of solutions. Both procedures result in fractions showing larger changes in mp than in composition. The high melting glyceride fraction, ca. 5% total fat, influences crystallization out of proportion to concentration. The Alfa-Laval system, using an aqueous suspension of partially crystalline fat, produces two fractions. Typical high melting fractions have softening points ca. 3C higher than the original fat. The softening point of typical low melting fractions is lowered 10 C. Refractionation is easier with the high melting fraction. Melting thermograms of these fractions show them as resembling fractions prepared from melted fat. One of eight papers presented at the Symposium “Milk Lipids,” AOCS Fall Meeting, Ottawa, Canada, September 1972.     

Effect of processing conditions on physical properties of a milk fat model system: Rheology

The effect of processing conditions on rheological behavior of three blends of 30, 40, and 50% of high-melting fraction [melting point measured as Mettler dropping point (MDP)=47.5°C] in low-melting fraction (MDP=16.5°C) of milk fat was studied. The effects of cooling and agitation rates, crystallization temperature, chemical composition of the blends, and time of storage on complex, storage and loss moduli were investigated by dynamic mechanical analysis (DMA). Compression tests were performed on samples using frequency values within the linear viscoelastic range (1 to 10 Hz). Loss modulus was, on average, 10 times lower than elastic modulus and was generally not affected by processing conditions. Samples showed a more solid-like behavior that was better described by storage modulus. Storage modulus varied with all processing conditions used in this study, and even for the same solid fat content, different rheological properties were found. Storage and complex modulus increased with temperature of crystallization (25 to 30°C), even though solid fat contents of samples measured after 24 h at 10°C were the same. Moduli were higher for samples crystallized at slow cooling rate, decreased with agitation rate, and were lower for the 30–70% blend at all processing conditions used. Storage moduli also increased with storage time. Shear storage modulus was calculated from the DMA experimental data, and the results were in agreement with the values reported in literature for butter systems. Fractal dimensions calculated for these systems showed a significant decrease as agitation rate increased in agreement with the softening effect reported for working of butter.     

Effect of oil unsaturation and wax composition on stability,properties and food applicability of oleogels

Oleogelation is emerging as one of the most exigent oil structuring technique. The main objective of this study was to formulate and characterize rice bran/sunflower wax-based oleogels using eight refined food grade oils such as sunflower oil, mustard oil, soybean oil, sesame oil, groundnut oil, rice bran oil, palm oil, and coconut oil. Stability and properties of these oleogels with respect to oil unsaturation and wax composition were explored. Sunflower wax exhibited excellent gelation ability even at 1%–1.5% (w/v) concentration compared to rice bran wax (8%–10% w/v). As the oleogelator concentration increased, peak melting temperature also increased with increase in strength of oleogels as per rheological studies. X-ray diffraction and morphological studies revealed that oleogel microstructure has major influence of wax composition only. Sunflower wax oleogels unveiled rapid crystal formation with maximum oil binding capacity of 99.46% in highly unsaturated sunflower oil with maximum polyunsaturated fatty acid content. Further, the applicability of this wax based oleogels as solid fat substitute in marketed butter products was also scrutinized. The lowest value of solid fat content (SFC) in oleogel was 0.20% at 25°C, resembling closely with the marketed butter products. With increase in oil unsaturation, oleogels displayed remarkable reduction in SFC. Depending upon prerequisite, oleogel properties can be modulated by tuning wax type and oil unsaturation. In conclusion, this wax-based oleogel can be used as solid fat substitute in food products with extensive applications in other fields too.     

Sintering of fat crystal networks in oil during post-crystallization processes

Several foods contain semi-solid fats that consist of solid crystals dispersed in a liquid oil. In oil-continuous margarine, butter, and chocolate, fat crystals determine properties such as consistency, stability against oiling-out, and emulsion stability. Trends toward foods with less fat and/or less saturated fat create a need for understanding and controlling the properties of fat crystal dispersions. Fat crystals form a network in oil due to mutual adhesion. One source of strong adhesion is formation of solid bridges (sintering), which has been studied in this work through sedimentation and rheological experiments. Results indicate that sintering may be created by crystallization of a fat phase with a melting point between that of the oil and the crystal. Generally speaking, β′ crystals were sintered by β′ fat bridges, favored by rapid cooling, and β crystals by β fat bridges, favored by slow cooling. The existence of the same polymorphic form of the crystal and bridge indicated that solid bridges, rather than bridges formed by small crystal nuclei, were formed. A maximum in sintering ability for an optimal sintering fat concentration occurred due to competition between bridge formation and other crystallization processes. Some emulsifiers influenced the sintering process. For example, monooolein made it more pronounced, while technical lecithin had the opposite effect.     

Cocoa Butter Alternatives from Enzymatic Interesterification of Palm Kernel Stearin,Coconut Oil,and Fully Hydrogenated Palm Stearin Blends

Structured lipids (SL) were produced from enzymatic interesterification (EIE) of palm kernel stearin (PKS), coconut oil (CNO), and fully hydrogenated palm stearin (FHPS) blends in various mass ratios. The EIE reactions were performed at 60 °C for 6 hours using immobilized Lipozyme RM IM with a mixing speed of 300 rpm. The physicochemical properties, crystallization and melting behavior, solid fat content (SFC), crystal morphology and polymorphism of the physical blends (PB), and the SL were characterized and compared with commercial cocoa butter and cocoa butter alternatives (CBA). EIE significantly modified the triacylglycerol compositions of the fat blends, resulting in changes in the physical properties and the crystallization and melting behavior. SFC and slip melting point of all SL decreased from those of their counterpart PB. In particular, SL obtained from EIE of blends 60:10:30 and 70:10:20 (PKS:CNO:FHPS) exhibited a high potential to be used as trans-free CBA as they showed similar melting ranges, melting peak temperatures, and SFC curves to the commercial CBA with fine needle-like crystals and desirable β' polymorph.     

Rheology,polymorphic crystal transformation,thermal, and mechanical properties of long-chain branched isotactic poly(1-butene)

Effects of long-chain branches (LCBs) on the rheology, crystal polymorphism, polymorphic transformation, and corresponding thermal and mechanical properties at different crystallization conditions, of isotactic poly(1-butene) (iPB-1) are systematically studied. The complex viscosity decreases and tangent increases with the increase of LCB concentration, and they inversely correlate with gels. The low branched samples crystallize into pure Form II by compression molding and cooling the melt to room temperature at a low crystallization cooling rate, whereas the moderate-to-highly branched samples crystallize into mixtures of Forms II and III, with a 1–30% fraction of crystals of Form III. The transformation of Form II into Form I in low branched iPB-1 was not significantly decelerated at different crystallization cooling rates, which is important in thermoforming, foaming, and extrusion blowing processes. Upon heating, Form III in highly branched iPB-1 with gels does not cold-crystallize into Form II even at a low heating rate. The low-to-highly branched samples mainly in Form I exhibit high yield strength, high melting temperature, and lower ductility, while the highly branched iPB-1 containing gels and mixtures of Forms I, III, and I′ possess brittleness. Under stretching, Form III predominantly transforms into Form I via a solid–solid crystal transition. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48411.     

Miscibility and crystallization behavior of biodegradable blends of two aliphatic polyesters. Poly(butylene succinate) and Poly(ε-caprolactone)

Poly(butylene succinate) (PBSU) and poly(ε-caprolactone) (PCL) blends, both biodegradable chemosynthetic semicrystalline polyesters, were prepared with the ratio of PBSU/PCL ranging from 80/20 to 20/80 by co-dissolving the two polyesters in chloroform and casting the mixture. The miscibility and crystallization behavior of PBSU/PCL blends were investigated by differential scanning calorimetry and optical microscopy. Experimental results indicated that PBSU was immiscible with PCL as evidenced by the composition independent glass transition temperature and the biphasic melt. However, during the crystallization from the melt at a given cooling rate, the crystallization peak temperature of PBSU in the blends decreased slightly with the increase of PCL, while that of PCL in the blends first increased and then decreased with the increase of PBSU. Moreover, both the crystallization peak temperature of PBSU and PCL shifted to the low temperature range with the increase of the cooling rate for a given blend composition. Double melting peaks or one main melting peak with a shoulder were found for both PBSU and PCL after the complete crystallization cooled from the melt, and were ascribed to the melting-recrystallization mechanism. It was found that the subsequent melting behavior of PBSU/PCL blends was influenced apparently by the blend composition and the cooling rate used.     

A comparison of crystallization behavior for melt and cold crystallized poly (l-Lactide) using rapid scanning rate calorimetry

A unique rapid scanning rate differential scanning calorimeter is used to examine the differences in melt and cold crystallized poly (l-Lactide) (PLLA), a biodegradable semi-crystalline polymer. After isothermal melt and cold crystallization at various temperatures, both melt and cold crystallized PLLA are characterized by similar melting temperatures (T_m) and exhibit multiple melting behavior on heating at 500 °C/min. However, cold crystallization results in a higher degree of crystallinity (w_c) compared to melt crystallization. While the overall amorphous fraction is higher for melt crystallization, the mobile amorphous fraction (w_a) is found to be higher for cold crystallization. The rigid amorphous fraction (w_raf) in PLLA is determined to be higher for melt crystallization than for cold crystallization at almost all temperatures. The higher values of w_raf also appear to result in higher values of the glass transition temperature (T_g) for melt crystallized samples due to a reduction in mobility of amorphous phase. These dramatic differences depending on whether the material is brought to the crystallization temperature from the melt or the glassy state, could have profound implications for processing and optimizing the properties of PLLA.     

熔分赤泥熔渣纤维化过程中熔体性能研究

以熔分赤泥为研究对象,探究熔分赤泥熔渣纤维化过程中熔体性能的变化规律,采用炉渣熔点熔速测定仪研究熔分赤泥熔化过程及熔化温度,采用FactSage热力学软件模拟熔分赤泥熔渣冷却过程中矿物析出种类、含量及开始析晶温度,采用X射线衍射仪和场发射扫描电子显微镜研究熔分赤泥熔渣不同温度下矿物组成与显微形貌,采用熔体物性综合测定仪研究熔分赤泥熔渣降温过程中的黏度变化。结果表明,熔分赤泥的熔化温度为1 236 ℃,熔分赤泥熔渣冷却过程中,1 300 ℃开始析出晶体,首先析出晶相为镁铝尖晶石(MgAl₂O₄)。此外,综合分析熔分赤泥熔渣熔体性能,明确利用熔分赤泥熔渣纤维化制备无机纤维时的温度应高于1 433 ℃。