The role of nonfat ingredients on confectionery fat crystallization

Confections such as chocolate and biscuit fillings are composed of a continuous fat phase that contains dispersed nonfat ingredients such as sugar and cocoa powder. Research on fat crystallization and rheology in confections often extrapolates crystallization and textural properties from bulk to mixed systems while overlooking the important role of composition or particle interactions. For example, in chocolate processing the fat phase aids dispersed phase lubrication and fluidity whereas the dispersed particles assist in fat crystallization by providing many nucleation sites. In confections with a high dispersed phase volume fraction, fat crystallization may be hindered due to reduced triacyglycerol mobility, confinement, and increased tortuosity. This is further complicated in systems with slow crystallizing fats such as palm oil whose crystallization is exceptionally sensitive to composition and processing. This review breaks down the physical chemistry of fat-based confections and discusses the impact of different nonfat ingredients towards fat crystallization and rheology. The behavior of palm oil is further highlighted as it is becoming increasingly popular as a confectionery ingredient. Lastly, ingredient-ingredient interactions and their role in fat crystallization are described along with force spectroscopy as a novel tool to characterize such phenomena. Force spectroscopy utilizes atomic force microscopy to measure intermolecular forces as a function of distance but remains largely unexplored in the area of food science.     

不同熔点棕榈油脂肪酸组成和SFC测定分析

分析七种不同棕榈油脂肪酸组成及在0℃~25℃(5℃间隔)温度下固体脂肪含量(SFC)及其变化规律。结果表明:随熔点降低,棕榈酸含量有逐渐降低趋势,而油酸和亚油酸含量则逐渐上升;饱和脂肪酸含量逐渐减少,而不饱和脂肪酸含量则逐渐升高;低熔点棕榈油营养价值要比高熔点棕榈油高;在不同温度段,SFC值增加幅度有所不同。该试验为棕榈油进一步深加工研究提供参考数据。     

分提棕榈油性质及其等温结晶过程研究

对比分析熔点为44℃(A)、24℃(B)两种分提棕榈油甘三酯组成、固脂含量、等温结晶特性及等温结晶动力学规律。结果表明：甘三酯的组成对于两者的结晶性能具有很大影响。在等温结晶过程中,样品A能够较快速达到结晶终点。在各等温条件下,A的Avrami指数n与B相差不大,说明两者基于过冷状态下的结晶机理相同。     

Crystallization properties of palm oil by dry fractionation

The crystallization, thermal, physical, chemical and morphological properties of palm oil were investigated using differential scanning calorimetry, polarized microscopy, pulsed nuclear magnetic resonance (NMR) and gas chromatography (GC). The palm oil was fractionated into various stearin and olein (with iodine values (IV)>63) fractions by means of a dry fractionation process. During the cooling sequence, samples were taken at regular intervals from the crystallizer and analyzed for their iodine values, chemical compositions and physical behaviour. The physical properties of olein and stearin fractions, such as cloud point, slip melting point and solid fat content, were dependent on the crystallization temperatures. The iodine values of the olein and stearin fractions increased as the crystallization temperature decreased and both fractions started to cloud at lower temperatures. The palmitic acid content of stearin and olein fractions was also affected by the crystallization temperatures.     

Structured lipids obtained by chemical interesterification of olive oil and palm stearin

Interesterification of palm stearin (PS) with liquid vegetable oils could yield a good solid fat stock that may impart desirable physical properties, because PS is a useful source of vegetable hard fat, providing β′ stable solid fats. Dietary ingestion of olive oil (OO) has been reported to have physiological benefits such as lowering serum cholesterol levels. Fat blends, formulated by binary blends of palm stearin and olive oil in different ratios, were subjected to chemical interesterification with sodium methoxide. The original and interesterified blends were examined for fatty acid and triacylglycerol composition, melting point, solid fat content (SFC) and consistency. Interesterification caused rearrangement of triacylglycerol species, reduction of trisaturated and triunsaturated triacylglycerols content and increase in diunsaturated-monosaturated triacylglycerols of all blends, resulting in lowering of melting point and solid fat content. The incorporation of OO to PS reduced consistency, producing more plastic blends. The mixture and chemical interesterification allowed obtaining fats with various degrees of plasticity, increasing the possibilities for the commercial use of palm stearin and olive oil.     

Comparison of crystallization properties of a palm stearin/canola oil blend and lard in bulk and emulsified form

Physical properties of lard and a palm stearin/canola oil (PSCO) blend were characterized with respect to their nucleation and crystallization properties in both bulk and emulsified form over a range of temperatures. Emulsification resulted in a significant decrease (P<0.05) in solid fat content (SFC) in both systems. A decrease in droplet size and increase in the monodispersity of the lard emulsion resulted in a significant decrease (P<0.05) in SFC. Within each fat system there was no detectable modification of the polymorphic form due to emulsification although the onset times of both phase and polymorphic transitions were delayed by emulsification. The free energies of nucleation (ΔG_3D) and diffusion (ΔG_diff) were established for lard and PSCO in order to compare the nucleation behaviour of the bulk fats.     

Influence of SFC, microstructure and polymorphism on texture (hardness) of binary blends of fats involved in the preparation of industrial shortenings

Several binary blends of vegetable oils commonly used in industrial shortenings (i.e., palm oil (PO), hydrogenated palm oil (HPO), soybean oil (SO), hydrogenated soybean oil (HSO), low-erucic acid rapeseed oil (LERO), hydrogenated low-erucic acid rapeseed oil (HLERO)) were studied for their physical properties such as solid fat content (SFC) by nuclear magnetic resonance (NMR) and textural properties (hardness). Microstructure was also observed by microscopy in order to explain the variability in hardness for samples having the same SFC values. The blends studied by microscopy were the following: HSO, HPO and HLERO diluted in LERO. For these three blends which had the same SFC, the level of network structure was different. HSO diluted in LERO had more crystals, closer to each other and overlapped. This can explain that HSO has a higher hardness than HPO or HLERO, for a same SFC value, when diluted in LERO. Polymorphism was also observed by powder X-ray diffraction. The variability in hardness for samples having the same SFC is due to various crystal types and/or network structures that are formed upon crystallization of hard fats. This work demonstrates that for binary blends of studied oils, changes in the hardness are controlled mostly by the SFC, polymorphism and also by the material’s microstructure.     

Physico-chemical properties of various palm-based diacylglycerol oils in comparison with their corresponding palm-based oils

Palm-based diacylglycerol (P-DAG) oils were produced through enzymatic glycerolysis of palm kernel oil (PKO), palm oil (PO), palm olein (POL), palm mid fraction (PMF) and palm stearin (PS). High purity DAG (83–90%, w/w) was obtained and compared to palm-based oils (P-oil) had significantly (P < 0.05) different fatty acid composition (FAC), iodine value (IV) and slip melting point (SMP). Solid fat content (SFC) profiles of P-DAG oils as compared to P-oils had less steep curves with lower SFC at low temperature range (5–10 °C) and the higher complete melting temperatures. Also, P-DAG oils in contrast with P-oils showed endothermic as well as exothermic peaks with higher transition temperatures and significantly (P < 0.05) higher crystallisation onsets, heats of fusion, and heats of crystallisation. Crystal forms for P-DAG oils were mostly in the β form.     

Interactions of milk fat and milk fat fractions with confectionery fats

The objectives of this study were to provide a better understanding of the effects of triacylglycerol (TAG) and non-TAG components (minor lipids) of milk fat on phase and crystallization behavior of binary mixtures of palm kernel oil (PKO) and the physical properties of corresponding compound coatings. Binary mixtures of a fractionated PKO with the different milk fats were examined for melting profiles, crystallization kinetics, and crystalline microstructures, and polymorphic changes during storage. Compound coatings were made with equivalent binary fat mixtures and measured for hardness and bloom formation. Milk fat and milk fat fractions affected crystallization rates of fractionated PKO, depending on the melting point of the fat. High-melting components resulted in more rapid crystallization, whereas the original milk fat and low-melting components inhibited crystallization. The crystal structure (e.g., number, size, shape) of the PKO crystals was influenced significantly by the addition of milk fat fractions and was influenced by the presence or absence of the minor lipids in milk fat. Milk fat and milk fat fractions had a softening effect on fractionated PKO, which was apparent in the binary mixtures as well as the compound coatings. In general, as the solid fat content (at 25 degrees C) of the binary mixtures increased, the hardness of the respective coatings increased. This also was related to an increased rate of bloom formation during storage.     

Interaction of packaging materials and vegetable oils: oil stability

The effects of different plastic films (polyethyleneterephthalate, polyvinylchloride, polypropylene and polystyrene) on the stability of olive, sunflower and palm oils were studied at 24 and 37°C during 60 days of storage. The changes in peroxide value (PV) and thiobarbituric acid value (TBA) were significantly higher (p≤0.05) in the plastic bottles than in glass. Our study indicates that the plastic permeability has played a major role in oil stability. However, both butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) were found to leach out from plastics films into vegetable oils during storage. The rate of oxidation was not reduced by antioxidant migration from plastic films to oils. Natural antioxidant (vitamin E) retarded the oxidation rate, and this was dependent on its concentration in oils examined. The results showed that the ranking of stability of oil samples is PVC≥PET>PP≥PS. Further, the stability was dependent on the type of oil. Palm oil exibited high stability properties while the highest oxidation rate was observed in sunflower oil. In addition, increasing storage temperature accelerated the oxidation and limited the stability of vegetable oils.     

Effect of blending and emulsification on thermal behavior, solid fat content, and microstructure properties of palm oil-based margarine fats

The ability of palm oil (PO) to crystallize as beta prime polymorph has made it an attractive option for the production of margarine fat (MF). Palm stearin (PS) expresses similar crystallization behavior and is considered one of the best substitutes of hydrogenated oils due to its capability to impart the required level of plasticity and body to the finished product. Normally, PS is blended with PO to reduce the melting point at body temperature (37 °C). Lipid phase, formulated by PO and PS in different ratios were subjected to an emulsification process and the following analyses were done: triacylglycerols, solid fat content (SFC), and thermal behavior. In addition, the microstructure properties, including size and number of crystals, were determined for experimental MFs (EMFs) and commercial MFs (CMFs). Results showed that blending and emulsification at PS levels over 40 wt% significantly changed the physicochemical and microstructure properties of EMF as compared to CMF, resulting in a desirable dipalmitoyl-oleoyl-glycerol content of less than 36.1%. SFC at 37 °C, crystal size, crystal number, crystallization, and melting enthalpies (ΔH) were 15%, 5.37 μm, 1425 crystal/μm(2), 17.25 J/g, and 57.69J/g, respectively. All data reported indicate that the formation of granular crystals in MFs was dominated by high-melting triacylglycerol namely dipalmitoyl-oleoyl-glycerol, while the small dose of monoacylglycerol that is used as emulsifier slowed crystallization rate. Practical Application: Most of the past studies were focused on thermal behavior of edible oils and some blends of oils and fats. The crystallization of oils and fats are well documented but there is scarce information concerning some mechanism related to crystallization and emulsification. Therefore, this study will help to gather information on the behavior of emulsifier on crystallization regime; also the dominating TAG responsible for primary granular crystal formations, as well as to determine the best level of stearin to impart the required microstructure properties and body to the finished products.     

On the fractional crystallization of palm olein: Solid solutions and eutectic solidification

In this contribution, the nature of particular crystal growth behavior observed in industrial dry fractionation of palm olein is further elucidated. Refined palm olein was prepared with three different concentrations of tripalmitoyl-glycerol (0.6%, 0.8% and 1%) and crystallized under stirring at 13, 15 and 17 °C to study the effect of internal seeding with tripalmitoyl-glycerol (PPP) on bulk crystallization properties. Notably at 15 °C, the increase in the solid fat content of the crystal suspension as function of time was heavily promoted by higher PPP-contents. The resulting crystals displayed a broad melting peak between 28 and 40 °C in DSC-measurements, which suggested the presence of a solid solution in a metastable form, mainly consisting of PPP and dipalmitoyl-oleoylglycerol (POP). SAXS-measurements supported this thesis by revealing long spacings with varying length, while short spacings obtained in WAXD consistently indicated the orthorhombic subcell of a β′-polymorph. The data suggest that the internal seeding effect of PPP in palm olein, as applied in industrial crystallization, in fact relies on substantial miscibility with POP, rather than on a heterogeneous nucleation effect resulting in two separate crystalline phases. The miscibility of PPP and POP then would result in a facilitated alignment of POP-molecules in the direction of the methyl end (or lamellar) plane and higher growth rates. Secondly, a peculiar change in crystal morphology could be consistently linked with the occurrence of a sharp melting peak at 24 °C in DSC, as well as with a substantial increase of the viscosity of the crystal suspension. This morphological shift concurred with an increased incorporation of palmitoyl-oleoyl-stearoylglycerol in the lattice, possibly giving rise to eutectic crystallization in lamellar crystal structures instead of the commonly observed dendritic crystals. The clarification of both phenomena provides a valuable, profound insight in the crystal growth step in the processing of edible oils.     

Tropical oils: nutritional and scientific issues.

Individually and in combination with other oils, the tropical oils impart into manufactured foods functional properties that appeal to consumers. The use of and/or labeling in the ingredient lists give the impression that these oils are used extensively in commercially processed foods. The estimated daily intake of tropical oils by adult males is slightly more than one fourth of a tablespoon (3.8 g), 75% of which consists of saturated fatty acids. Dietary fats containing saturated fatty acids at the beta-position tend to raise plasma total and LDL-cholesterol, which, of course, contribute to atherosclerosis and coronary heart disease. Health professionals express concern that consumers who choose foods containing tropical oils unknowingly increase their intake of saturated fatty acids. The saturated fatty acid-rich tropical oils, coconut oil, hydrogenated coconut oil, and palm kernel oil, raise cholesterol levels; studies demonstrating this effect are often confounded by a developing essential fatty acid deficiency. Palm oil, an essential fatty acid-sufficient tropical oil, raises plasma cholesterol only when an excess of cholesterol is presented in the diet. The failure of palm oil to elevate blood cholesterol as predicted by the regression equations developed by Keys et al. and Hegsted et al. might be due to the dominant alpha-position location of its constituent saturated fatty acids. If so, the substitution of interesterified artificial fats for palm oil in food formulations, a recommendation of some health professionals, has the potential of raising cholesterol levels. A second rationale addresses prospective roles minor constituents of palm oil might play in health maintenance. This rationale is founded on the following observations. Dietary palm oil does not raise plasma cholesterol. Single fat studies suggests that oils richer in polyunsaturated fatty acid content tend to decrease thrombus formation. Anomalously, palm oil differs from other of the more saturated fats in tending to decrease thrombus formation. Finally, in studies comparing palm oil with other fats and oils, experimental carcinogenesis is enhanced both by vegetable oils richer in linoleic acid content and by more highly saturated animal fats. The carotenoid constituents of red palm oil are potent dietary anticarcinogens. A second group of antioxidants, the tocotrienols, are present in both palm olein and red palm oil. These vitamin E-active constituents are potent suppressors of cholesterol biosynthesis; emerging data point to their anticarcinogenic and antithrombotic activities. This review does not support claims that foods containing palm oil have no place in a prudent diet.     

FUNCTIONALITY OF PALM OIL IN FOODS

The functional properties of commercial solid fats such as shortening and margarine are closely related to their fatty acid and triacylglycerol compositions. Plastic fats produced from hydrogenated seed oils may suffer from undesirable crystal structure changes during handling and storage. It has been demonstrated that this problem increases with increasing chain length uniformity of the component fatty acids. This is also evidenced by the carbon number composition of the high melting triacylglycerols of the plastic fats. Triacylglycerols with carbon numbers 48 and 54 promote β crystallization, those with carbon numbers 50 and 52 promote β' crystallization. Since palm oil and its products contain high levels of C50 and C52 triacylglycerols they are useful for improving the functional properties of plastic fats.     

Effects of variation in the palm stearin: Palm olein ratio on the crystallisation of a low-trans shortening

Changes in the rheological properties during crystallisation and in the crystal size and morphology of blends containing rapeseed oil with varying percentages of palm stearin (POs) and palm olein (POf) have been studied. The crystals formed from all three blends were studied by confocal laser scanning microscopy, light microscopy and environmental scanning electron microscopy, which revealed the development of clusters of 3–5 individual elementary “spherulites” in the early stages of crystallisation. The saturated triacylglycerol content of the solid crystals separated at the onset of crystallisation was much greater than that in the total fat. Fat blends with a higher content of palm stearin had a more rapid nucleation rate when observed by light microscopy, and this caused an earlier change in the rheological properties of the fat during crystallisation. Using a low torque amplitude (0.005 Pa, which was within the linear viscoelastic region of all samples studied) and a frequency of 1 Hz, the viscoelastic properties of melted fat during cooling were studied. All samples, prior to crystallisation, showed weak viscoelastic liquid behaviour (G″, loss modulus >G′, storage modulus). After crystallisation, a more “solid like” behaviour was observed (G′ similar to or greater than G″). The blend having the highest concentration of POs was found to have the earliest onset of crystallisation (27% w/w POs; 12 mins, 22% w/w POs; 13.5 mins, 17% w/w POs, 15 mins, respectively). However, there were no significant differences in the time to the point when G′ became greater than G′ among the three blends.     

Evaluation of shortenings based on various palm oil products

Several formulations based on blends of hydrogenated palm oil (MP 41·5°C) and palm stearin (IV 44) with other liquid oils, on direct blends of palm stearin with other liquid oils, and on 100% inter-esterified palm olein, were used as feedstocks in shortening production. The shortenings were stored at 20°C over a period of one month. Physicochemical characteristics, creaming properties and baking performance of the shortenings were evaluated and compared with the best shortening on the market. Slip melting point of the shortenings ranged from 41·5 to 46·4°C. Palm-cottonseed oil shortenings had higher solid fat contents at all temperatures than palm-soya bean or palm-low erucic acid rapeseed oil shortenings. The shortenings were rich in C₅₀, C₅₂and C₅₄ glycerides. Creaming power after 12 min of beating ranged from 1·55 to 1·77 cm³ g^?1. Palm stearin-cottonseed (3:2) oil shortening showed the best creaming performance. The specific volume of cakes ranged, for the experimental shortening, from 90% to 101% from the control, with low erucic acid-palm blends showing the best performance. In applications for both aerated cream and cakes, inter-esterified palm olein was excellent.     

猪油基和棕榈油基起酥油的晶型结构研究

应用X-射线衍射法分别研究了在不同结晶条件下制作的猪油基起酥油和棕榈油基起酥油的晶型结构,以便决定能否用廉价的棕榈油取代猪油生产起酥油并丰富有关固体脂肪的晶型结构研究资料。结果表明,猪油和猪油基起酥油的晶型在任何结晶条件下均表现为β型;而棕榈油基起酥油的晶型主要受熟化温度的影响,当熟化温度为15~20℃时表现为β型、当熟化温度25~28℃时表现为β’型。说明棕榈油比猪油更适合成为制作起酥油所需要的固相基料油。     

Pan-frying of French fries in three different edible oils enriched with olive leaf extract: Oxidative stability and fate of microconstituents

Sunflower oil, olive oil, and refined palm oil were enriched with an extract - rich in polyphenols - obtained from olive tree (Olea europaea) leaves at levels of 120 and 240 mg total polyphenols per kg oil. Potatoes were pan-fried in both the enriched and the non-supplemented oils under domestic frying conditions. Total polyphenols were estimated by Folin-Ciocalteu and antioxidant capacity was assessed by the DPPH radical scavenging assay. Tocopherols' content was determined by HPLC analysis, phytosterols and squalene by GC, and oxidative stability by Rancimat. Supplemented frying oils had higher total polyphenols and tocopherols' content, oxidative stability, and antioxidant capacity, while phytosterols and squalene content were not affected by the supplementation. French fries prepared in supplemented oils had higher total polyphenols, tocopherols, phytosterols, and squalene content and exhibited higher antioxidant capacity than those fried in non-supplemented oils. By consuming French fries pan-fried in enriched oils, up to 1.4-, 2.2-, and 1.5-fold increase of tocopherols, phytosterols, and squalene intake could be achieved as compared to those prepared in the non-supplemented oils.     

Properties of high-oleic palm oils derived by fractional crystallization

ABSTRACT:  High-oleic palm oil (HOPO) with an oleic acid content of 59.0% and an iodine value (IV) of 78.2 was crystallized in a 200-kg De Smet crystallizer with a predetermined cooling program and appropriate agitation. The slurry was then fractionated by means of dry fractionation at 4, 8, 10, 12, and 15 °C. The oil and the fractionated products were subjected to physical and chemical analyses, including fatty acid composition, triacylglycerol and diacylglycerol composition, solid fat content, cloud point, slip melting point, and cold stability test. Fractionation at 15 °C resulted in the highest olein yield but with minimal oleic acid content. Due to the enhanced unsaturation of the oil, fractionation at relatively lower crystallization temperature showed a considerable effect on fatty acid composition as well as triacylglycerol and diacylglycerol composition of liquid fractions compared to higher crystallization temperature. The olein and stearin fractionated at 4 °C had the best cold stability at 0 °C and sharper melting profile, respectively.     

Comparison of nutrient composition in kernel of tenera and clonal materials of oil palm (Elaeis guineensis Jacq.)

Nutritive information about oil palm kernel is scarce, especially on the composition of sugars and water-soluble vitamins. This study aims to evaluate both tenera and clonal materials for their proximate composition, fatty acid profile, amino acid composition, sugar, mineral and water-soluble vitamin contents. The tenera material had a higher moisture, fat and fibre content as compared to the clonal material, whereas protein, carbohydrate and ash content were higher in the clonal material. The major fatty acid constituents in palm kernel oil were lauric acid, myristic acid and oleic acid. The palm kernel proteins were deficient in lysine and tryptophan but rich in glutamic acid, arginine and aspartic acid. Sucrose was the most abundant sugar in palm kernel. The mineral analysis of the samples showed high levels of potassium, phosphorus, magnesium, calcium and manganese, while niacin was the water-soluble vitamin present at the highest concentrations in palm kernel.