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.     

Rapid synthesis of palm-based monoacylglycerols

Rapid synthesis of high-purity MAG from refined, bleached, and deodorized palm stearin (RBDPS) via chemical glycerolysis in the presence of pyridine was developed to obviate the conventional molecular distillation in the production of pure MAG. The optimal reaction for the sodium methoxide-catalyzed glycerolyis of RBDPS was recorded at 110°C using a 3 wt% catalyst concentration based on the weight of RBDPS, with an RBDPS/glycerol ratio of 1∶2 and an RBDPS/pyridine ratio of 1∶4. High yields of over 99% were achieved rapidly in 15 min, and increases in DAG and FFA were observed after a prolonged reaction time.     

A study on the crystal structure of palm oil-based whipping cream

The crystal structure of palm oil-based whipping cream was studied. Various proportions of refined, bleached, and deodorized palm oil (RBDPO) and palm kernel oil (RBDPKO) were prepared and their crystal structure and thermal profile were observed by an X-ray diffractometer and a differential scanning calorimeter, respectively. The results showed that all blends possessed a stable and shiny β′ polymorph at 25°C, which showed that RBDPO and RBDPKO were appropriate for producing a nondairy whipping cream. Some eutectic effect was observed in some blends, which was attributed to the complex combination of TAG in RBDPO and RBDPKO.     

Synthesis of a Cocoa Butter Equivalent by Enzymatic Interesterification of Illipe Butter and Palm Midfraction

This study aims to synthesize a cocoa butter equivalent (CBE)‐structured lipid from a blend of illipe butter (IB) and palm midfraction (PMF) by means of enzymatic interesterification using Rhizomucor miehei sn‐1,3 specific lipase, Lipozyme^® RM IM (Novozymes North America, Inc., Franklinton, NC, USA) as the biocatalyst. Physical and chemical attributes of the CBE and cocoa butter (CB) were analyzed. The synthesized CBE matched the triacylglycerol (TAG) profile range of a commercial CB and is therefore hypothesized to show similar physical and chemical characteristics to CB. The TAG profile, fatty‐acid constituents, melting and cooling behavior, polymorphism, and crystal morphology were determined using high‐performance liquid chromatography, gas chromatography, differential scanning calorimetry, X‐ray diffraction (XRD), and polarized light microscopy, respectively. Four enzymatically interesterified blends of IB:PMF at different weight ratios were analyzed for their TAG profiles, and a ratio of IB:PMF 10:3 (%, w/w) at 5% enzyme load and a reaction time of 30 min gave similar TAG results to CB. The TAG values of the IB:PMF 10:3 interesterified product (IP) were 1,3‐dipalmitoyl‐2‐oleoylglycerol at 19.1 ± 1.0%, 1‐palmitoyl‐2‐oleoyl‐3‐stearoylglycerol at 42.7 ± 1.0%, and 1,3‐distearoyl‐2‐oleoylglycerol at 29.9 ± 0.3%. The melting and the cooling profile of IP and CB showed no significant difference. XRD of IP and CB displayed similar dominant peaks at 4.6 Å, representing a β polymorph. Both CB and IP have similar granular spherulitic crystals.     

Thermal analysis of palm mid-fraction,cocoa butter and milk fat blends by differential scanning calorimetry

Commercial samples of anhydrous milk fat (AMF), Ivory Coast cocoa butter (CB) and palm mid-fraction (PMF) were blended in a ternary system. The melting characteristics of the blends were studied by differential scanning calorimetry (DSC). Results suggest that in the studies of interaction involving more than two fats, partial area (A_i) under the melting peak should be converted to partial enthalpy (ΔH_i) rather than to solid fat index. The ΔH values of the blends decreased as the amount of AMF was increased and increased as the amount of CB was increased. In general, the effect of PMF was less pronounced compared to the effect of the other two fats. Eutectic effects within the ternary system could be detected by measuring the deviation of melting enthalpy by DSC, and from the corresponding values that were calculated for the thermodynamically ideal blends. The deviation reached a maximum when the amount of AMF was about 33%. On the binary line of CB/PMF, the eutectic effect was maximum at about 50–75% PMF. The interaction effect in the system was more noticeable at 30 and 20°C than at lower temperatures. Evaluation at 30°C was preferred because both the effect of AMF in the ternary system and the effect of PMF on the binary line were more readily observed.     

Influence of Fatty Acid Moieties of Sorbitan Esters on Polymorphic Occurrence of the Palm Mid‐Fraction

The influence of chain length and subcell packing of fatty‐acid moieties in sorbitan esters (SE) on the polymorphism of the palm midfraction (PMF) was examined. SE with different fatty‐acid moieties (sorbitan tripalmitate; sorbitan tristearate [STS]; and sorbitan tribehenate [STB]) were blended with PMF and PMF polymorph formation was examined using synchrotron radiation X‐ray diffraction and differential interference contrast microscopy. PMF without additives was crystallized in the β′ form under the isothermal condition at 22 °C; however, the addition of STS, which forms an α subcell structure, promoted the crystallization of PMF in the α form. In contrast, crystallization of PMF in the β′ form was accelerated by the addition of STB. These results showed that when the chain length of the fatty‐acid moiety between fat and emulsifiers was similar, the crystallization of PMF in the α form was promoted by the α subcell packing in STS crystals that were nucleated prior to PMF crystallization. In contrast, STB crystals, which have an α subcell packing, accelerated the crystallization of PMF in the β′ form because of the large difference between the chain lengths of STB and PMF. Therefore, structural similarities in both the chain length and the subcell packing are essential features that regulate the template effect, and the promotion of the crystallization of PMF in the β′ form by the addition of STB was caused by heterogeneous nucleation.     

Effect of Milk Fat Concentration on Fat Crystallization of Palm Oil-Based Shortenings

The effect of different dosages of anhydrous milk fat (AMF) (25%, 50% and 75%, w/w) on shear-crystallization of fat blends made of refined palm oil, refined palm stearin, and rapeseed oil was studied. Classical techniques as differential scanning calorimetry (DSC), pulsed field gradient nuclear magnetic resonance (pfg-NMR), rheometer, and X-ray diffraction (XRD) were applied to evaluate the crystallization kinetics of fat blends as well as the fat compatibility between components in rapid cooling (15 °C min⁻¹), isothermal crystallization (at 15 °C), and storage (5 °C). Obtained results revealed that the mixtures of palm oils and milk fat had a low compatibility. The co-crystallization between triacylglycerols (TAG) of milk fat and of palm oil occurred during isothermal crystallization and storage resulting in slower crystallization kinetics and the formation of some eutectic mixtures.     

Production of High-Melting Symmetrical Monounsaturated Triacylglycerol-Rich Fats from Mango Kernel Fat by Acetone Fractionation

1,3‐Distearoyl‐2‐oleoyl‐glycerol, 1‐palmitoyl‐2‐oleoyl‐3‐stearoyl‐glycerol and 1‐stearoyl‐2‐oleoyl‐3‐arachidoyl‐glycerol are typical high‐melting symmetrical monounsaturated triacylglycerols (Hm‐SMT) found in cocoa butter improver (CBI). These triacylglycerols help to increase the hardness of chocolate products in tropical climates. In the present study, natural CBI products were produced from mango (Mangifera indica, Linn) kernel fat (MKF) by selective three‐stage fractionation using acetone. The second stearin (fraction I) from the first precipitate of MKF by fractionation for 180 min at 15 °C contained 86.9% of Hm‐SMT, and the third stearin (fraction II) obtained from fraction I by further fractionation for 180 min at 18 °C was enriched with 94.4% Hm‐SMT. High percentages of such triacylglycerols in these products contributed to higher slip melting points (36.5–37.7 °C) than commercial cocoa butter and cocoa butter equivalent (26.7 and 27.9 °C). Also, their differential scanning calorimetry properties and solid fat content values were superior to those in traditional confectionery fats, indicating that the tailored stearins could be used as ideal CBI. In particular, the hard fat blends consisting of 55–70% cocoa butter (CB) and 30–45% fraction II were considered as the preferred heat‐resistant chocolate ingredients. In addition, the mixture of the oleins (fraction III) was rich in diunsaturated and triunsaturated triacylglycerols and showed similar thermal properties to super palm oil, thus making it more suitable as special fat ingredients and modified fat sources.     

Modelling lipase‐catalysed transesterification of fats containing n‐3 fatty acids monitored by their solid fat content

Transesterification of fat blends rich in n‐3 polyunsaturated fatty acids (n‐3 PUFA), catalysed by a commercial immobilised thermostable lipase from Thermomyces lanuginosa, was carried out batch‐wise. Experiments were performed, following central composite rotatable designs (CCRDs) as a function of reaction time, temperature and media formulation. Mixtures of palm stearin, palm kernel oil and a commercial concentrate of triacylglycerols rich in n‐3 PUFA (“EPAX 2050TG” in CCRD‐1 and “EPAX 4510TG” in CCRD‐2) were used. The time‐course of transesterification was indirectly followed by the solid fat content (SFC) values of the blend at 10 °C, 20 °C, 30 °C and 35 °C. A decrease in all SFC values of the blends at 10 °C, 20 °C, 30 °C and 35°C was observed upon transesterification. The SFC_{10 °C} and SFC_{20 °C} of transesterified blends varied between 18 and 48 and SFC_{35 °C} between 6 and 24. These values fulfil the technological requirements for the production of margarines. Under our conditions, lipid oxidation may be neglected. However, the accumulation up to 8.3% free fatty acids in reaction media is a problem to overcome. The development of response surface models, describing both the final SFC value and the SFC decrease, will allow predicting results for novel proportions of fats and oils and/or a novel combination time‐temperature.     

Feasibility of Palm Oil as the Feedstock for Biodiesel Production via Heterogeneous Transesterification

The production of biodiesel has become popular recently as a result of increasing demand for a clean, safe and renewable energy. Biodiesel is made from natural renewable sources such as vegetable oils and animal fats. The conventional method of producing biodiesel is by reacting vegetable oil with alcohol in the presence of a homogenous catalyst (NaOH). However, this conventional method has some limitations such as the formation of soap, usage of significant quantities of wash water and complicated separation processes. Heterogeneous processes using solid catalysts have significant advantages over homogenous methods. Currently, more than 90 % of world biodiesel is produced using rapeseed oil. The production of biodiesel from rapeseed oil is considered uneconomical, considering the fact that palm oil is currently the world's cheapest vegetable oil. Therefore, the focus of this study is to show the feasibility of producing biodiesel from palm oil using montmorillonite KSF as a heterogeneous catalyst. The heterogeneous transesterification process was studied using design of experiment (DOE), specifically response surface methodology (RSM) based on a four‐variable central composite design (CCD) with α = 2. The transesterification process variables were reaction temperature, x₁ (50–190 °C), reaction period, x₂ (60–300 min), methanol/oil ratio, x₃ (4–12 mol mol^–1) and the amount of catalyst, x₄ (1–5 wt %). It was found that the conversion of palm oil to biodiesel can reach up to 78.7 % using the following reaction conditions: reaction temperature of 155 °C, reaction period of 120 min, ratio of methanol/oil at 10:1 mol mol^–1 and amount of catalyst at 4 wt %. From this study, it was shown that montmorillonite KSF catalyst can be used as a solid catalyst for biodiesel production from palm oil.     

Tripalmitin-Driven Crystallization of Palm Oil: The Role of Shear and Dispersed Particles

While palm oil (PO) is a reliable ingredient in formulations for biscuits, cream fillings, and compound chocolates, our understanding of its crystallization behavior and physico-chemistry pales in comparison to many other fats and oils. Phase diagrams of triacylglycerol (TAG) mixtures may be used to elucidate fat crystal polymorphism and composition of such oils, yet conditions important to the food industry such as shear speed, relevant processing temperatures, and presence of secondary ingredients are regularly overlooked. Here, the effects of shear speed (n = 0–500 RPM), dispersion concentration (0–5 wt.%), and dispersed particle surface chemistry [silica or octadecyl-functionalized (C18) silica] on the thermal properties of commercial PO when cooled from 60 to 20 °C at 1 °C min⁻¹ were explored, with focus placed on PO's higher-melting fraction. Using a series of high-purity TAG standards, X-ray diffraction revealed PO's higher-melting fraction as mainly composed of tripalmitin (PPP) crystals and molecular compounds (MC) of PPP either with 1,3-dipalmitoyl-2-oleoyl-sn-glycerol (POP) or with POP and 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (PPO) in combination, all in a double chain-length β' (i.e., β'-2) conformation. Shear increased the formation of lower-melting α-2 POP and β'-2 MC_POP:PPO:PPP crystals while depleting the system of β'-2 MC_POP:PPP and β'-2 PPP crystals. This loss was further exacerbated by the addition of dispersed particles to the point where PPP was completely incorporated as MC and β'-2 PPP crystals were eliminated. While heterogeneous nucleation tends to favor kinetic products of fat crystallization, the interactions between shear and surface chemistry varied between crystal types.     

Lipase/acyltransferase‐catalysed interesterification of fat blends containing n‐3 polyunsaturated fatty acids

The lipase/acyltransferase from Candida parapsilosis is an original biocatalyst that preferentially catalyses alcoholysis over hydrolysis in biphasic aqueous/organic media. In this study, the performance of the immobilised biocatalyst in the interesterification in solvent‐free media of fat blends rich in n‐3 polyunsaturated fatty acids (n‐3 PUFA) was investigated. The interesterification activity of this biocatalyst at a water activity (a_w) of 0.97 was similar to that of commercial immobilised lipases at a_w values lower than 0.5. Thus, the biocatalyst was further used at an a_w of 0.97. Response surface modelling of interesterification was carried out as a function of medium formulation, reaction temperature (55–75 °C) and time (30–120 min). Reaction media were blends of palm stearin (PS), palm kernel oil and triacylglycerols (TAG) rich in n‐3 PUFA (“EPAX 4510TG”; EPAX AS, Norway). The best results in terms of decrease in solid fat content were observed for longer reaction time (>80 min), lower temperature (55–65 °C), higher “EPAX 4510TG” content and lower PS concentration. Reactions at higher temperature led to final interesterified fat blends with lower free fatty acid contents. TAG with high equivalent carbon number (ECN) were consumed while acylglycerols of lower ECN were produced.     

Structures and Binary Mixing Characteristics of Enantiomers of 1-Oleoyl-2,3-dipalmitoyl-sn-glycerol (S-OPP) and 1,2-Dipalmitoyl-3-oleoyl-sn-glycerol (R-PPO)

We performed differential scanning calorimetry (DSC) and synchrotron radiation X-ray diffraction (SR-XRD) experiments of polymorphic structures and binary mixing characteristics of the enantiomers of 1-oleoyl-2,3-dipalmitoyl-sn-glycerol (S-OPP) and 1,2-dipalmitoyl-3-oleoyl-sn-glycerol (R-PPO). In the two enantiomers, oleic and palmitic acid moieties are asymmetrically connected at the sn-1 and sn-3 positions of the glycerol groups, with palmitic acid moiety at the sn-2 position. Pure enantiomer samples (>99 %) were synthesized and employed throughout this study. The following results were obtained. (1) A basic feature of the mixture systems of S-OPP and R-PPO is of a eutectic nature due to different polymorphic structures of two enantiomers and the racemic compound of PPO (rac-PPO). (2) Polymorphic behavior of S-OPP and R-PPO was quite similar, both having α-2 and β′-3, whereas rac-PPO contained α _rac-3, β′_rac-2, and β′_rac-3. The DSC measurements showed that the melting points of β′-3 (S-OPP = 35.3 °C and R-PPO = 34.9 °C) were higher than that of β′_rac-3 (31.0 °C). β was not crystallized in the pure enantiomers, and rac-PPO. (3) α_rac-3 was crystallized at low cooling rates (~2 °C/min), whereas α-2 of the two enantiomers was crystallized only with very rapid cooling (~10 °C/min). (4) Triple-chain-length structures were formed in α_rac-3, β′_S-3 (=β′_R-3), and β′_rac-3; α-2 with a double-chain-length structure was formed in both enantiomers. These results indicate the importance of the relationship between subcell packing and glycerol conformation in the polymorphism and mixing characteristics of asymmetric unsaturated–saturated-saturated mixed-acid triacylglycerols.     

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.     

Cold stability of red palm oleins

Cold stability of crude and refined red palm oleins was investigated. Single- and double-fractionated crude as well as refined single- and double-fractionated red palm oleins were stable against crystallization for more than 1 h but less than 2 h, whereas commercial red palm oleins remained stable for more than 5 h at 5°C. At 20°C, refined red palm oleins had better resistance to crystallization than crude palm oleins. Red palm oleins with lower amounts of saturated fatty acids (C_16:0 and C_18:0), lower levels of POP and POS triacylglycerols, and lower cloud points have increased resistance to crystallization and result in better cold stability.     

Refining of rice bran oil by neutralization with calcium hydroxide

The applicability of calcium hydroxide (lime) in the neutralization of rice bran oil (RBO) was investigated. Crude RBO samples of three different free fatty acids (FFAs) (3.5–8.4 wt%) were degummed, dewaxed, bleached, and neutralized with lime and deodorized. The oils obtained thus were characterized by determining the color, peroxide value (PV), content of unsaponifiable matter (UM), and FFA. Conventionally practiced caustic soda neutralization (at 80–90°C) of FFA has in the present investigation been replaced by a high temperature (150–210°C) low pressure (2–4 mm Hg) reaction with lime. It was observed that neutralization with Ca(OH)₂ at high temperature (210°C) and under low pressure (2–4 mm Hg pressure) may substantially reduce the FFA content (0.8 wt%, after 2 h). The deodorized oil was found to be of acceptable color, PV, and content of UM and FFA. Neutralization of oil was also carried out by using NaHCO₃ and Na₂CO₃, nonconventional alkalies for neutralization, and the results were compared with NaOH and Ca(OH)₂. Overall recovery of oil in Ca(OH)₂ refining process (88.5 ± 0.6 wt%, for Sample 1 containing 8.4%‐wt FFA) was found to be more than other competitive processes studied.     

Effect of Different Deacidification Methods on Phytonutrients Retention in Deacidified Fractionated Palm Oil

Crude red palm oil of 11.4 % free fatty acid content was dry fractionated to obtain liquid crude red palm olein which was deacidified using enzyme (lipase from Rhizomucor miehei), solvent (ethanol), and chemical (aqueous sodium hydroxide), and its effect on physicochemical characteristics and phytonutrients retention was evaluated. Enzymatic deacidification showed 100 % product yield and no neutral lipid loss, whereas yields of 78 and 62 % and neutral lipid loss of 12 and 30 % were observed for solvent and chemical deacidification, respectively. Variation in viscosity (25.3–37.2 cSt at 40 °C), slip melting point (15–36 °C), monoacylglycerols (1.7–3.3 %), and diacylglycerols (5.8–27.9 %) were also observed. Carotenoid content was slightly reduced by enzymatic (535 mg/kg), solvent (556 mg/kg), and chemical (526 mg/kg) deacidification. Retention of phytonutrients such as phytosterols (1,235 mg/kg), total tocopherols (965 mg/kg), squalene (301 mg/kg), coenzyme Q₁₀ (25.9 mg/kg), and total phenolics (3 mg/kg) was highest following enzymatic deacidification. The IC₅₀ value of the enzymatic deacidified sample (21.8 mg/ml) indicates more radical scavenging activity than in samples obtained using solvent (42.0 mg/ml) and chemical (28.8 mg/ml) methods.     

PTCR characteristics of poly(styrene‐co‐acrylonitrile) copolymer/stainless steel powder composites

Positive temperature coefficient of resistivity (PTCR) characteristics of poly(styrene‐co‐acrylonitrile) copolymer (SAN)/stainless steel (SS) powder (80 wt %) composites prepared by melt‐mixing method has been investigated with reference to SAN/carbon black (CB) composites. The SAN/CB (10 wt %) composites showed a sudden rise in resistivity (PTC trip) at 125°C, above the glass transition temperature (T_g) of SAN (T_g ≈ 107°C). However, the PTC trip temperature of SAN/SS (80 wt %) composites appeared at 94°C, well below the T_g of SAN. Addition of 1 phr of nanoclay increased the PTC trip temperature of SAN/CB (10 wt %) composites to 130°C, while SAN/SS (80 wt %)/clay (1 phr) nanocomposites showed the PTC trip at 101°C. We proposed that the mismatch in coefficient of thermal expansion (CTE) between SAN and SS played a key role that led to a disruption in continuous network structure of SS even at a temperature below the T_g of SAN. The dielectric properties study of SAN/SS (80 wt %) composites indicated possible use of the PTC composites as dielectric material. DMA results showed higher storage modulus of SAN/SS composites than the SAN/CB composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of Sucrose Esters on Isothermal Crystallization of Palm Oil‐based Blend

The effects of sucrose esters (SEs) with different acyl chain lengths, namely, lauryl (L‐195), palmitoyl (P‐170), stearoyl (S‐170), oleoyl (O‐170), and erucyl (ER‐190), on isothermal crystallization of a palm oil‐based blend (PO–PS) were studied. From this study, it was found that both α‐ and β′‐crystals coexisted following crystallization of PO–PS from melt to room temperature. Addition of SEs P‐170 and S‐170, which had saturated acyl chains similar to PO–PS, resulted in an accelerating crystallization rate, promoting the appearance of α‐crystals and transition to β′‐crystals and increasing viscosity of PO–PS blend. SE O‐170, which is liquid at room temperature, had little effect on blend crystallization. SEs L‐195 and ER‐190, with an acyl chain dissimilar to PO–PS, inhibited triacylglycerol bonding or further integration to the surface of crystals and reduced the crystallization rate and viscosity of the PO–PS blend. The PO–PS blend with SE L‐195 and ER‐190 contained large crystals and resulted in slower formation of α‐crystals and transformation to β′‐crystals. Results from this study indicate that crystallization of PO–PS was greatly influenced by acyl–acyl interactions between acyl chains of SEs and triacylglycerols.     

Phase Transition of Sunflower Oil as Affected by the Oxidation Level

The influence of the oxidation level on the phase transition behavior of sunflower oil was evaluated by differential scanning calorimetry (DSC) and synchrotron X-ray diffraction (XRD) at both small and wide angles. The crystallization was monitored at a cooling/heating rate of 2 °C/min from 20 to ?80 °C and vice versa applying both techniques. The triacylglycerols organize in two double-chain length structures: α 2L (61.87 Å) and β′ 2L (82.89 Å). The crystalline structure changes upon oxidation. In particular, the intensity of the XRD peak associated with the double-chain structure of β′, as well as its crystallization and melting enthalpy, significantly decreases as the oxidation level increases.