Effect of Palm Oil Enzymatic Interesterification on Physicochemical and Structural Properties of Mixed Fat Blends

The physicochemical properties of binary and ternary fat systems made of commercial samples of palm oil (PO) blended with anhydrous milk fat (AMF) and/or rapeseed oil (RO) were studied. Physical properties such as solid fat content by pulsed‐Nuclear Magnetic Resonance (p‐NMR), melting profile by differential scanning calorimetry (DSC), and polymorphism of the blends were investigated. Palm oil was then batch enzymatically interesterified for 27 h, using Lipozyme^® TL IM as biocatalyst, and further blended with AMF and/or RO in the same way. The objective of the present work was to evaluate the effect of batch enzymatic interesterification (B‐EIE) of palm oil on physical characteristics of the investigated fat blends. For that purpose, iso‐solid diagrams have been constructed from p‐NMR data. It was shown that B‐EIE of palm oil modifies its melting behaviour, but also its polymorphic stability and miscibility with other fats. Under dynamic conditions, after B‐EIE, the non‐ideal behaviour (eutectic) detected at low temperatures in the ternary PO/AMF/RO system disappears in the corresponding EIE‐PO/AMF/RO. After static crystallization followed by a tempering, the hardness of palm oil is increased after B‐EIE, as well as the hardnesses of the blends containing this fat compared to the native one. Polymorphism stability of the binary and ternary fat systems is also modified after B‐EIE compared to the corresponding native systems.     

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.     

Formation of Granular Crystals in Margarine with Excess Amount of Palm Oil

Crystallization behavior of palm oil and tripalmitin (PPP) in a model margarine system was investigated. The model margarine was held in a programmable oven, heated to 5 °C for 12 h and then 20 °C for a further 12 h. After 3 weeks, the model margarine was evaluated by polarization microscopy. Granular crystals were observed in the margarine containing an excess amount of palm oil and PPP. The concentration of higher-melting fatty acids was higher in the crystals relative to the surroundings. Likewise, the presence of lower-melting fatty acids was lower in the crystals. The polymorphic structure of the margarine with excess palm oil and PPP was determined to be all β′ by X-RD spectra. The result suggested that the agglomeration of higher-melting point triglycerides (TAGs), such as PPP in this study, led to the formation of granular crystals in the margarine without β polymorphic emergence.     

Physical Properties of <Emphasis Type="Italic">trans</Emphasis>-Free Bakery Shortening Produced by Lipase-Catalyzed Interesterification

Lipase-catalyzed interesterified solid fat was produced with fully hydrogenated soybean oil (FHSBO), and rapeseed oil (RSO) and palm stearin (PS) in a weight ratio of 15:20:65, 15:40:45 and 15:50:35. The interesterified fats contained palmitic (27.8–44.6%), stearic (15.6–16.2%), oleic (27.5–36.5%) and linoleic acids (8.0–13.5%). After interesterification of the blends, the physical properties of the products changed and showed lower melting points and solid fat contents, different melting and crystallization behaviors as well as the formation of more stable crystals. The produced interesterified fats (FHSBO:RSO:PS 15:20:65, 15:40:45 and 15:50:35 blends) contained desirable crystal polymorphism (β′ form) as determined by X-ray diffraction spectroscopy, a long plastic range with solid fat content of 51–63% at 10 °C to 4–12% at 40 °C, and melting points of 39 (15:50:35), 42 (15:50:45) and 45 °C (15:20:65). However, a reduction in tocopherols (α and γ) content and a reduced oxidative stability were observed in the interesterified fats. The physical properties of the interesterifed fats were influenced by the amount of PS, resulting in more hardness and higher solid fat contents for 15:20:65 than 15:40:45 and 15:50:35 blends. The present study suggested that the produced interesterified fats containing trans-free fatty acids could be used as alternatives to hydrogenated types of bakery shortenings.     

Rheological and Microscopic Properties of Fat Blends with Similar Solid Fat Content but Different Trans Composition

In this study, two different groups of fat samples were prepared in a way that samples of each group had different trans fatty acid (TFA) composition but similar solid fat content (SFC). Samples of the first group (named group A) had TFA between 0.0 and 56.23 %, while the samples of the second group (group B) contained trans isomers ranging from 0.0 to 44.4 %. A polarized microscope was used to monitor the differences between the samples in terms of crystal size and crystal number during isothermal crystallization. In general, increasing TFA resulted in formation of larger crystals in a shorter time. Similar findings were also observed when small deformation time and frequency sweep experiments were conducted. A higher TFA content led to higher complex modulus values during isothermal crystallization. On the other hand, when the samples were stored at 4 °C for 48 h, the samples with the lower trans isomer had higher hardness values.     

Melting and Solidification Properties of Palm Kernel Oil,Tallow, and Palm Olein Blends in the Preparation of Shortening

Ternary systems composed of palm kernel oil (PKO), tallow, and palm olein (POo) were studied in terms of their physical properties such as solid fat content (SFC), melting characteristics by DSC and polymorphism by X-ray diffraction. Ternary phase behavior was analyzed with isosolid diagrams. The results showed that as the POo content of the blends was increased the SFC value decreased, while the increase of tallow content increased the SFC value. Eutectic effects within the ternary system were confirmed from the deviation of the measured SFC from the calculated SFC for corresponding thermodynamically ideal blends. The deviation reached a maximum when the amounts of PKO and POo are both about 45%. X-ray diffraction results showed that addition of PKO into the blends promoted stabilization in the β′ crystalline form.     

Preparation and Characterization of Human Milk Fat Substitutes Based on Triacylglycerol Profiles

Human milk fat substitutes (HMFS) having similarity in (TAG) composition to human milk fat (HMF) were prepared by Lipozyme RM IM‐catalyzed interesterification of lard blending with selected oils in a packed bed reactor. Four oil blends with high similarity in fatty acid profiles to HMF were first obtained based on the blending model and then the blending ratios were screened based on TAG composition similarity by enzymatic interesterification in a batch reactor. The optimal ratio was determined as lard:sunflower oil:canola oil:palm kernel oil:palm oil:algal oil:microbial oil = 1.00:0.10:0.50:0.13:0.12:0.02:0.02. This blending ratio was used for a packed bed reactor and the conditions were then optimized as residence time, 1.5 h; reaction temperature, 50 °C. Under these conditions, the obtained product showed high degrees of similarity in fatty acid profile with 39.2 % palmitic acid at the sn‐2 position, 0.5 % arachidonic acid (n‐6) and 0.3 % docosahexaenoic acid (n‐3) and the scores for the degree of similarity in TAG composition was increased from 58.4 (the oil blend) to 72.3 (the final product). The packed bed reactor could be operated for 7 days without significant decrease in activity. The final product presented similar melting and crystallization profiles to those of HMF. However, due to the loss of tocopherols during deacidification process, the oxidative stability was lower than that of the oil blend. This process for the preparation of HMFS from lard with high similarity in TAG composition by physical blending and enzymatic interesterification, as optimized by mathematical models in a packed bed reactor, has a great potential for industrialization.     

Crystallization Kinetics of Cocoa Fat Systems: Experiments and Modeling

Isothermal crystallization kinetics of unseeded and seeded cocoa butter and milk chocolate is experimentally investigated under quiescent conditions at different temperatures in terms of the temporal increase in the solid fat content. The theoretical equations of Avrami based on one-, two- and three-dimensional crystal growth are tested with the experimental data. The equation for one-dimensional crystal growth represents well the kinetics of unseeded cocoa butter crystallization of form α and β′. This is also true for cocoa butter crystal seeded milk chocolate. The sterical hindrance due to high solids content in chocolate restricts crystallization to lineal growth. In contrast, the equation for two-dimensional crystal growth fits best the seeded cocoa butter crystallization kinetics. However, a transition from three- to one-dimensional growth kinetics seems to occur. Published data on crystallization of a single component involving spherulite crystals are represented well by Avrami’s three-dimensional theoretical equation. The theoretical equations enable the determination of the fundamental crystallization parameters such as the probability of nucleation and the number density of nuclei based on the measured crystal growth rate. This is not possible with Avrami’s approximate equation although it fits the experimental data well. The crystallization can be reasonably well defined for single component systems. However, there is no model which fits the multicomponent crystallization processes as observed in fat systems.     

Isothermal Crystallization of Palm Oil-Based Fats with and without the Addition of Essential Oils

The objective of study was to evaluate the crystallization behavior of palm oil-based fats processed with and without the addition of essential oils (5% w/w) obtained from the flowers (EsOF) and stems (EsOS) of Pituranthos scoparius. Palm oil (PO) and a mixture of PO, soybean oil, and sunflower oil (Mix) were tested. The addition of the essential oils did not change the melting points of the fats but affected their crystallization behavior. A delay in crystallization was observed, evidenced by lower crystallization rates, and lower solid fat contents. This delay was comparable in the samples crystallized with EsOF and EsOS for the PO samples but EsOF was more efficient at delaying crystallization in the Mix sample. EsOF generated a less organized crystalline network in both samples (lower enthalpy values) while EsOS generated a more organized crystalline network (high enthalpy values) when used in the Mix sample. The addition of EsO also affected the crystal microstructure in some cases. While a slight increase in crystal size was observed for some PO samples crystallized with EsOF, no change or a decrease in crystal size was observed for the samples crystallized with EsOS. A slight decrease in crystal size was observed for Mix samples crystallized with EsOF while no effect was observed for these samples crystallized with EsOS. Results from this study show that these essential oils can be used as natural additives to modify the crystallization of fats for food applications and therefore widen their functional properties.     

Physicochemical Properties of Interesterified Blends of Fully Hydrogenated Crambe abyssinica Oil and Soybean Oil

The chemical interesterification of blends of soybean (SO) and fully hydrogenated crambe oil (FHCO) in the ratios of 80:20, 75:25, 70:30, 65:35, and 60:40 (w/w), respectively, was investigated. FHCO is a source of behenic acid. The blends and the interesterified fats were analyzed for fatty acid and triacylglycerol composition, regiospecific distribution, slip melting point, solid profile, and consistency. The regiospecific analysis of the TAG indicated random insertion of saturated fatty acids at sn-2 of the glycerol of the interesterified blends with more significant alterations at sn-2 than at sn-1 and sn-3. The gradual addition of FHCO increased the solid fat content and the slip melting point. The chemical interesterification formed new TAG facilitating the miscibility between SO and FHCO. The 70:30 interesterified blend was suitable for general use, 60:40 for use as a base stock. At 35 °C, the 65:35 interesterified blend showed suitable plasticity for use in products with fat contents below 80 %. FHCO, rich in behenic acid, is not associated with increased total cholesterol and LDL cholesterol, and it can be used as a low trans fat. FHCO is not associated with increased total cholesterol and LDL cholesterol, and it can be used as a low trans fat alternative.     

Changes in triacylglycerol molecular species and thermal properties of blended and interesterified mixtures of coconut oil or palm oil with rice bran oil or sesame oil

Blended oils were prepared by mixing appropriate amounts of coconut oil (CNO) or palm oil (PO) with rice bran oil (RBO) or sesame oil (SESO) to get approximately equal proportions of saturated/monounsaturated/polyunsaturated fatty acids in the oil. These blended oils were subjected to interesterification reactions using lipase to randomize the fatty acid distribution on the glycerol molecule. The fatty acid compositions of the modified oils were evaluated by gas chromatography while changes in triacylglycerol molecular species were followed by HPLC. The triacylglycerol molecular species of the blended oils reflected those present in the parent oil. Interesterification of the blended oils resulted in the exchange of fatty acids within and between the triacylglycerol molecules, resulting in alterations in the existing triacylglycerol molecules. Emergence of new triacylglycerol molecular species following interesterification was also observed. The thermal profiles of the native, blended and interesterified oils were determined by differential scanning calorimetry. Thermal behaviour, melting and crystallization properties of the modified oils showed significant changes reflecting the changes in the triacylglycerol molecules present in the oil. Therefore, interesterification of oils introduces significant changes in the physical properties of oils, even though the overall fatty acid composition of blended and interesterified oils remains the same.     

Preparation of Human Milk Fat Substitutes from Lard by Lipase‐Catalyzed Interesterification Based on Triacylglycerol profiles

Human milk fat substitutes (HMFSs) with triacylglycerol profiles highly similar to those of human milk fat (HMF) were prepared from lard by physical blending followed by enzymatic interesterification. Based on the fatty acid profiles of HMF, different vegetable and single‐cell oils were selected and added to the lard. Blend ratios were calculated based on established physical blending models. The blended oils were then enzymatically interesterified using a 1,3‐regiospecific lipase, Lipozyme RM IM (RML from Rhizomucor miehei immobilized on Duolite ES562; Novozymes A/S, Bagsværd, Denmark), to approximate HMF triacylglycerol (TAG) profiles, particularly with respect to the distribution of palmitic acid in the sn?2 position. The optimized blending ratios were determined to be: lard:sunflower oil:canola oil:palm kernel oil:palm oil:algal oil:microbial oil = 1.00:0.10:0.50:0.13:0.12:0.02:0.02. The optimized reaction conditions were determined to be: enzyme load of 11 wt%, temperature of 60 °C, water content of 3.5 wt%, and reaction time of 3 hours. The resulting product was evaluated for total and sn?2 fatty acids, polyunsaturated fatty acids, and TAG composition. A high degree of similarity was obtained, indicating the great potential of the product as a fat alternative for use in infant formulas.     

Effects of Fat Content and Solid Fat Content on Caramel Texture Attributes

Fat plays an important role in caramel quality attributes, yet there is very little published work on how fat type and level influence caramel characteristics. Fat content was increased from 0 to 20 % to determine the effects of total fat content on caramel texture attributes such as cold flow, hardness, stickiness and tensile strength. Solid fat content (SFC) was also varied, from 3 to 90 %, by using commercially‐available fats with varied SFC at 22 °C. Cold flow decreased significantly with increased fat content, with greater effect for fats with higher SFC. Changes in caramel hardness with fat content were dependent on SFC. Hardness generally decreased with increasing fat content for the fats with low SFC, with the 3 % SFC fat softening the most. Hardness increased slightly with fat content for the hardest fat (90 % SFC). Stickiness generally decreased with increasing fat content although the effect was significantly higher with higher SFC fats. These results document that both fat content and SFC significantly influence caramel texture attributes.     

Shear and Rapeseed Oil Addition Affect the Crystal Polymorphic Behavior of Milk Fat

The effect of shear on the crystallization kinetics of anhydrous milk fat (AMF) and blends with 20 and 30 % w/w added rapeseed oil (RO) was studied. Pulse ¹H NMR was used to follow the α to β′ polymorphic transition. The NMR method was confirmed and supported by SAXS/WAXS experiments. Samples were crystallized at 5 °C and shear of 0, 74 or 444 s^?1 was applied during early crystallization, in the NMR tube. High shear rates decreased the amount of α polymorph formed and accelerated the polymorphic transition; however, shear did not affect the final solid fat content (SFC). The α to β′ transition occurred faster in the presence of RO allowing more room for the conformational changes to occur. Final SFC decreased with increasing RO content. Shear applied in 20 and 30 % blends caused the destruction of β′‐related 3L structure leaving only 2L packing. In AMF and statically crystallized samples, both 3L and 2L packing existed. Shear did not affect the amount of β crystals formed. The study shows that both shear and RO affect the polymorphic behavior of milk fat, and that ¹H NMR is able to detect polymorphic transition in blends with up to 30 % w/w RO.     

m-PE-LLD／PE-LD共混物结晶结构的研究

采用DSC、WAXD和SAXS相结合的方法研究了共混物的相分离、结晶度、片晶厚度等结晶结构参数。研究结果表明，在m-PE-LLD／PE-LD共混物中，当PE-LD含量较大时无论是熔融曲线还是降温曲线都只出现一个峰，说明两者存在共结晶，有很好的相容性。当PE-LD含量减小时，共混物出现相分离，升、降温曲线均出现双峰，但两峰值呈现靠近趋势，预示m-PE-LLD／PE-LD共混物中仍存在少量共结晶。WAXD数据显示，PE-LD添加到m-PE-LLD中，没有改变茂金属聚乙烯固有的晶体结构，共混物仍然保持了聚乙烯的正交晶系结构。并随着PE-LD在m-PE-LLD中添加比例的增加，共混物正交晶系增强的同时晶粒尺寸变小。     

Effect of Interesterification of Palmitic Acid-rich Triacylglycerol on Postprandial Lipid and Factor VII Response

The process of interesterification results in changes in triacylglycerol (TAG) structure and is used to increase the melting point of dietary fats. The acute health effects of this process on palmitic acid-rich fats are uncertain with regard to postprandial lipemia, insulin and factor VII activated (FVIIa) concentrations. Two randomized crossover trials in healthy male subjects compared the effects of meals containing 50 g fat [interesterified palm oil (IPO) versus native palm oil (NPO); n = 20, and IPO versus high-oleic sunflower oil (HOS); n = 18], on postprandial changes in lipids, glucose, insulin, chylomicron composition and FVIIa. Compared with NPO, IPO decreased postprandial TAG and insulin concentrations. Both NPO and IPO increased FVIIa concentrations postprandially; mean increases at 6 h were 21 and 19%, respectively. Compared with HOS, IPO decreased postprandial TAG (47% lower incremental area under the curve) and reduced the postprandial increase in FVIIa concentration by 64% at 6 h; no significant differences in hepatic and total lipase activities or insulin concentrations were noted. All three test meals increased postprandial leukocyte counts (average 26% at 6 h). The fatty acid composition of the chylomicron TAG was similar to the test fats following all test meals. It is concluded that interesterification of palm oil does not result in adverse changes in postprandial lipids, insulin or FVIIa compared to high oleate and native palm oils. George J. Miller: Deceased August 2006.     

Characterization and Oxidative Stability of Human Milk Fat Substitutes Enzymatically Produced from Palm Stearin

Production of human milk fat substitutes (HMFSs) from three types of palm stearin with palmitic acid (PA) of 91.3, 70.3 and 62.6 %, respectively, was scaled up to a kilogram scale. The physiochemical properties of these products including fatty acid profiles, triacylglycerol compositions, tocopherol contents, oxidative stability and melting and crystallization profiles were compared with those of HMFSs from lard, butterfat and tripalmitin and fats from infant formulas. Based on their chemical compositions, HMFSs from palm stearin with PA contents of 70.3 and 62.6 % produced by enzymatic acidolysis were found to have the highest degree of similarity to human milk fat, which indicated that these HMFSs were the most suitable for use in infant formulas. However, HMFSs from palm stearin with PA content of 91.3 % had the highest tocopherol contents. By investigation of the primary and secondary oxidation products during accelerated oxidation, the oxidative stability of HMFSs was found to be positively correlated to the contents of tocopherols, and the volatile oxidation compounds with the highest relative contents in HMFSs were aldehydes analyzed by solid-phase microextraction-GC–MS. All HMFSs had final melting points lower than body temperature.     

Changing the SFC Profile of Lauric Fat Blends Based on Melting Group Triacylglycerol Formulation

Lauric fat blends could be prepared from formulation of different melting triacylglycerol (TAG) group to obtain various desired SFC profiles as required by different fat rich products such as margarine and shortening. At the interval temperature from 0 to 20 °C, an increase ratio of body and heated (BH) melting TAG group in the fat blends imposed higher SFC values with steeper SFC slopes. Meanwhile, at the interval temperature from 20 to 40 °C, an increase ratio of heated (H) melting TAG group resulted higher SFC values with comparable SFC slopes. The use of Palm Stearin (PS) or Fully Hydrogenated Rapeseed Oil (FHRO) as the hard fat gave comparable SFC profiles but the fat blends with FHRO melted completely (SFC 0 %) at higher temperature (60 °C) while those of PS did not. In addition, the crystallization and melting behaviors of lauric fat blends as measured by DSC were influenced by different ratio of TAG distribution formulated at H15 (varied BH) and BH50 (varied H). Fat blends with PS also showed different crystal morphology compared to those with FHRO as measured by PLM.     

Influence of Different Factors on the Particle Size Distribution and Solid Fat Content of Water-in-Oil Emulsions

The influence of the variation of different parameters on the particle size distribution and solid fat content (SFC) of water‐in‐oil emulsions was studied. The use of solid fat instead of liquid oil, higher polyglycerol polyricinoleate (PGPR) concentration, or higher homogenization energy led to smaller mean particle sizes. The decrease of the emulsifier/water ratio turned the particle size distribution of the emulsions from bimodal to trimodal. The increase of PGPR concentration increased the SFC of the fat in the absence of water, but it did not produce the same effect in the emulsion. This result suggested that the presence of dispersed aqueous phase prevented the modifying action of the emulsifier on the crystallization of the continuous lipid phase. The experimentation indicated that the adsorption of the surfactant at the interface would reduce its availability to affect crystallization in bulk fat, as the SFC in lipid phase decreased with increasing interfacial area.