Milk fat fractionation today: A review

Although anhydrous milk fat (AMF) has excellent properties, its variable physicochemical properties and its lack of functionality restrict its uses in the food industry. A technology involving dry fractionation of AMF has been developed, and its attributes include selectivity, reliability and general application. Combining two simple and reliable technologies,i.e., multi-step fractionation and blending, it is possible to overcome functionality problems and the seasonal variations of AMF. Lecture presented at the joint meeting of the International Society for Fat Research and the American Oil Chemists’ Society in Toronto, May 10, 1992.     

Isopropanol fractionation of butter oil and characteristics of fractions

Fractionation of butter oil from isopropanol and characterization of the chemical composition and the melting properties of the fractions obtained have been investigated. Butter oil was fractionated from isopropanol (1∶4 wt/vol) at 15 to 30°C. The yields of stearins and oleins were dependent on the temperature employed during fractionation. Thus, 24.8 to 48.9% of stearins and 51.5 to 75.2% of oleins could be obtained as the crystallization temperature varied from 15 to 30°C. The stearin fractions displayed a distinct variation in the fatty acid compositions. The palmitic acid content of the stearin fractions varied from 39.1 to 44.0%, and that of stearic from 15.1 to 16.8%, respectively. The olein fractions contained 43.2% stearic acid, and 2.4 to 2.8% palmitoleic acid (C16∶1). The solid fat content values of the stearin fractions obtained were 62–67, 39–50, and 21–25 at 10, 20, and 30°C, respectively. From the results, it is evident that anhydrous milk fat can be fractionated at relatively high temperatures from isopropanol to produce stearin and olein fractions of specific composition and properties.     

Crystallization of butter oil and separation by filter-centrifugation

Fractionation by crystallization of melted butter oil can produce fractions that are physically and chemically different. However, many variables affect the formation, growth and separation of the crystalline fat from the entrained oil. The objective of this study was to produce crystalline fractions that contained a minimal volume of entrained oil through optimization of the crystallization and separation conditions. Crystallization was initiated at 33.5°C upon slow cooling from 60°C with stirring (10 rpm). Oil was cooled to 18.5°C and separated by centrifugation, followed by filter-centrifugation. Fractions were analyzed for melting point, solid fat by differential scanning calorimetry, and fatty acid profiles. A split-plot design was used for statistical analyses of data, and the experiment was performed three times. Fractionation caused significant changes in melting profiles of the fractions when compared with the unfractionated butter oil. Melting points of the unfractionated butter oil, liquid and crystalline fractions were 41.6, 25, and 48°C, respectively. The oil content of the crystalline fraction at 18.5°C ranged from 28 to 35%. A 17% increase in C8:0-C10:0, an 11% decrease in C12:0-C16:0, a 32% decrease in C18:0, and a 41% increase in C18:1, C18:2, and C18:3 acids were observed in the liquid fraction when compared with the crystalline fraction.     

Heat treatment of cream: A model of the butter texture response in relation with triglyceride composition

The effects of thermal treatments on butter texture are known and have been used since 1935 on an industrial scale, but without fundamental knowledge. Butter composition influences firmness, as observed through seasonal and regional variations. Experiments were carried out at 15°C by using a cone penetrometer and an industrial testing machine. A significant correlation between heat treatment efficiency and some prevalent triglycerides and fatty acids on butter firmness was outlined. Three fatty acids (myristic, oleic, palmitic) and four major groups of triglycerides mainly affected the firmness, sometimes leading to an inversion of the thermal effect, according to individual sample composition. A crystallographic and thermodynamic model based on triglycerides properties was developed.     

Thermal behavior of butterfat fractions and mixtures of tripalmitin and butterfat

The melting and crystallization behavior of blends of tripalmitin and butterfat were compared with that of butterfat fractions, which were prepared by dry fractionation and by solvent extraction. There were marked similarities in the behavior of the blends, the dry fractions and some solvent fractions. This similarity was not shared with the behavior of the hardest solvent fractions. The functionality or hard butterfat fractions seemed to derive from an enrichment in long-chain saturated triglycerides. Improved functionality could therefore be achieved equally well by blending or by fractionation. Blends of tripalmitin and butterfat could be used as model butterfat fractions, or as an alternative to butterfat fractions in some applications.     

Filtration in hydrophobic media: 1. Evidence of molecular selection by crossflow filtration of butter oil

The oils and fats industry needs well-identified fractions with well-defined physical properties for its final formulated products. In view of future applications, a triglyceride partition phenomenon of butter oil on a hydrophobic membrane is investigated by crossflow filtration. Triglycerides are separated into four groups according to their molecular weight and unsaturation index, leading to behavior that can be interpreted in terms of consistent stereochemical parameters.     

Differential scanning calorimetric analysis of edible oils: Comparison of thermal properties and chemical composition

The thermal profiles of 17 edible oil samples from different plant origins were examined by differential scanning calorimetry (DSC). Two other confirmatory analytical techniques, namely gas-liquid chromatography (GLC) and high-performance liquid chromatography (HPLC), were used to determine fatty acid (FA) and triacylglycerol (TAG) compositions. The FA and TAG compositions were used to complement the DSC data. Iodine value (IV) analysis was carried out to measure the degree of unsaturation in these oil samples. The DSC melting and crystallization curves of the oil samples are reported. The contrasting DSC thermal curves provide a way of distinguishing among these oil samples. Generally, the oil samples with a high degree of saturation (IV<65) showed DSC melting and crystallization profiles at higher temperature regions than the oil samples with high degree of unsaturation (IV>65). Each thermal curve was used to determine three DSC parameters, namely, onset temperature (T _o ), offset temperature (T _f ) and temperature range (difference between T _o and T _f ). Reproducibility of DSC curves was evaluated based on these parameters. Satisfactory reproducibility was achieved for quantitation of these DSC parameters. The results show that T _o of the crystallization curve and T _f of the melting curve differed significantly (P<0.01) in all oil samples. Our observations strengthen the premise that DSC is an efficient and accurate method for characterizing edible oils.     

Direct measurement of thermal fat crystal properties for milk-fat fractionation

The temperature dependency of the solid-fat content of a fat is important for predicting the consistency of the final product and for process control. Two direct analytical methods for determining the solid-fat content and the melting characteristics of milk-fat fractions have been developed. The fractions are analyzed during crystallization, and the results give reproducible information about the thermal behavior of the fractions and the actual crystal amount in the suspensions. The results are obtained within minutes, and no separation of the fractions before the measurement is necessary. New ways of reducing process time are proposed. It is possible to adapt crystallization time to seasonal variations of the initial milk fat and to the required properties of the final product. Partially crystallized milk fat was directly measured in a calorimeter and a pulsed nuclear magnetic resonance spectrometer. The data showed good correlations and even more accurate results than the conventional methods. The calorimetric method makes it possible to detect polymorphic changes and co-crystallization in the crystals so that the influence of processing parameters, such as energy input, on crystallization behavior can be investigated.     

A novel method for solvent fractionation of two CLA isomers

Conjugated linoleic acid (CLA) is commercially available as a mixture consisting of almost equal amounts of the cis-9,trans-11-CLA (c9, t11) and trans-10, cis-12-CLA (t10, c12) isomers. Separation of the two isomers is highly significant since each exhibits different biochemical properties. Highly efficient separation could be accomplished by crystallization in acetone (solvent) of the two CLA isomers (solutes) in the presence of medium-chain fatty-acid (MCFA) additives. The relative concentration ratios of the two CLA isomers in the solvent-crystallized materials varied depending on which MCFA were added. Addition of lauric and decanoic acids resulted in the crystals predominantly containing t10,c12, whereas octanoic acid yielded those predominantly containing c9,t11. We have confirmed that onetime solvent crystallization using decanoic acid and octanoic acid additives increased the t10,c12 and c9,t11 concentrations, and that repeated solvent crystallization resulted in the ratio of c9,t11 to t10,c12 of at least 4∶96 or 98∶2.     

DSC法对阳离子染料可染共聚酯热性能的研究

利用差示扫描量热法(DSC)对阳离子染料可染共聚酯即高温高压型(CDP)及常压沸染型(ECDP)的熔融和结晶过程进行了研究。结果表明:无定形CDP的玻璃化转变温度(T_g)、冷结晶温度(T_(ch))高于PET,但其熔点(T_m)低于PET,无定形ECDP的T_g与T_m低于PET和CDP,且随第四单体聚乙二醇(PEG)的含量及相对分子质量((?)_n)的增加而降低,其结晶速率随PEG的(?)_n及含量的增加而增加。对于等温结晶的共聚酯,1,3-间苯二甲酸双羟乙酯-5-磺酸钠(SIPE)的引入及PEG含量的增加,共聚酯的熔融焓(△H_m)及T_m下降;当PEG含量相同时,随PEG (?)_n增加,ECDP的△H_m及T_m均增加。     

Liquid Chromatographic fractionation of oil-sand and crude oil asphaltenes

Asphaltenes extracted from Alberta oil sands (Athabasca, Cold Lake, and Peace River) and crude oils (Taber South and Fenn-Big Valley) were fractionated by sequential elution solvent chromatography (SESC) involving 10 organic solvents on a silica column. Athabasca asphaltenes and SESC fractions were further studied by elemental analysis, i.r., u.v., and n.m.r. spectroscopy. Incomplete extraction of maltenes from the oil-sand bitumens increased the yields of the first two SESC fractions, the saturates and aromatics, of oil-sand asphaltenes relative to the crude oil asphaltenes. About 55 wt% of the asphaltenes elute in fractions 3–5. Two distinct molecular types are present in the asphaltenes; namely, lower functionality species with lower heteroatom content and the higher functionality species with higher heteroatom content. Compounds eluting in fractions 3–10 are predominantly polynuclear aromatics with alkyl substituants and probably bridged by cycloalkanes. The extent of bridging as well as the location, number and type of heteroatoms determines the fraction in which each compound appears. Complexity of compounds eluting increases with time: earlier fractions are composed of smaller-size polynuclear aromatic centers and contain heteroatoms in predominantly ring locations, whereas later fractions contain a larger proportion of complex species and more functional heteroatom groups.     

Composition and crystallization of milk fat fractions

Milk fat was fractionated by solvent (acetone) fractionation and dry fractionation. Based on their fatty acid and acyl-carbon profiles, the fractions could be divided into three main groups: high-melting triglycerides (HMT), middle-melting triglycerides (MMT), and low-melting triglycerides (LMT). HMT fractions were enriched in long-chain fatty acids, and reduced in short-chain fatty acids and unsaturated fatty acids. The MMT fractions were enriched in long-chain fatty acids, and reduced in unsaturated fatty acids. The LMT fractions were reduced in long-chain fatty acids, and enriched in short-chain fatty acids and unsaturated fatty acids. Crystallization of these fractions was studied by differential scanning calorimetry and X-ray diffraction techniques. In this study, the stable crystal form appeared to be the β′-form for all fractions. At sufficiently low temperature (different for each fraction), the β′-form is preceded by crystallization in the metastable α-form. An important difference between the fractions is the rate of crystallization in the β′-form, which proceeds at a much lower rate for the lower-melting fat fractions than for the higher-melting fat fractions. This may be due to the much lower affinity for crystallization of the lower-melting fractions, due to the less favorable molecular geometry for packing in the β′-crystal lattice.     

A dynamic mechanical and thermal study of various rubber–bitumen blends

Blends of a Nynas 100 penetration‐grade bitumen with a cis‐polybutadiene, a butyl rubber, three polyisobutylenes of different molecular weights, a chlorinated‐polyethylene, polychloroprene in latex form, and a polyurethane rubber (scrap Lycra) were prepared using a Z‐blade masticator mixer at a temperature of about 180°C. The blends contained between 10 and 40 pph (i.e., 9 and 29%) by weight of rubber. They were characterized by fluorescence optical microscopy, differential scanning calorimetry, and dynamic mechanical thermal analysis. The bitumen‐rich phases provided the matrix in most of these systems, polymer‐rich extensive phases being formed with butyl rubber, and low‐ and moderate‐molecular‐weight poly(isobutylenes) when the proportion rose above 30 pph, and for the poly(cis‐butadiene) and chlorinated polyethylene system only when the proportion rose above 40 pph, according to the tan δ plots. Only glass transitions were associated with polymer‐rich phases, and there were some melting transitions from paraffinic wax components ejected from the bitumen‐rich phases. Below room temperature the modulus of blends of polybutadiene, chlorinated polyethylene, and the polyurethane rubber were similar to that of the bitumen; but those of the other polymers were stiffer by a factor of 50, perhaps because of a rearrangement of the asphaltenes. The softer blends, particularly the first two named above, had loss processes (with tan δ > 0.5) ranging over 200°C or more. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 586–601, 2000     

Crystalline fractionation of hydrogenated sunflowerseed oil

Crystalline fractionation of hydrogenated sunflowerseed oil was performed and the chemical composition of the separated fractions at different temperatures was determined. The results show that the triglycerides obtained after a short retention time (less than 16.4 min) were enriched in the low-temperature fractions (lower than 22°C), the triglycerides of long retention time (more than 21.5 min) were concentrated in the higher-temperature fractions (higher than 30°C), and the triglycerides of medium retention time (between 16.4 and 21.5 min) were concentrated in the medium-temperature fractions (22°C to 30°C). The partition ratio of triglycerides with retention times of 8.8, 12.5, 16.5, 21.5 and 29.1 minutes was increased as a function of the fractionation temperature.     

Fatty acid composition, extraction, fractionation, and stabilization of bullfrog (Rana catesbeiana) oil

The oil extracted from the fat-storage organ (fat body) of the bullfrog (Rana catesbeiana) was characterized for its fatty acid composition. The main fatty acids were palmitic (18.1%), stearic (4.1%), myristic (2.7%), oleic (31.7%), and linoleic (12.9%) acids. Long-chain polyunsaturated fatty acids were also present in significant amounts, i.e., eicosapentaenoic (1.5%) and docosahexaenoic (4.7%), and were probably derived from the fish meal content of the diet. A partially fractionated oil was extracted from the homogenized and frozen fat body with an oleic acid content of 43.2%. The natural alkaloid boldine, added at 0.5 mg/g oil level, improved the oxidative stability by a factor ranging from 1.7 to 2.4, as assessed by the Oil Stability Index method between 90 and 110°C. The stabilization effect of boldine was higher than that of naringenin, morin, and quercitin and for the synthetic antioxidant butylated hydroxytoluene at the same concentration level.     

Detection of animal fats in butter by differential scanning calorimetry: A pilot study

Because of its high price, butter has always been the object of adulteration by addition of less expensive vegetable or animal fats. Although a number of methods have been proposed for the detection of butterfat adulteration, none has found widespread use. For this reason, a study was conduced to assess the use of differential scanning calorimetry (DSC) for detecting the presence of added animal fat, i.e., chicken fat, in butter. The results obtained show that DSC is an efficient method for characterizing pure animal fats as well as their mixtures. Furthermore, the accuracy with which data are obtained, in combination with the sensitivity of DSC to subtle changes in chemical composition of the sample, makes DSC an attractive possibility for development as a quality control procedure.     

Relationship between cooling rate and crystallization behavior of hydrogenated sunflowerseed oil

The relationship between cooling rate and crystallization behavior of hydrogenated sunflowerseed oil and its thermal properties during melting were investigated by differential scanning calorimetry and x-ray diffraction. At crystallization, temperature peaks and area percents of components with higher melting points were found to be greater when cooling rate was slower. When samples were melted, total enthalpies were similar at all rates. According to the chemical composition of the analyzed samples, the components with higher melting points were found in samples with a higher saturated fatty acid content. Changes in the profile of melting curves might be due to differences in triglyceride intersolubility.     

Calibration of thermal field-flow fractionation using broad molecular weight standards

Thermal field-flow fractionation (ThFFF) is a new elution-based separation method for determining molecular weight distributions of polymers. Calibration can be achieved using monodisperse standards of the specific polymer of interest. In order to expand the range of polymer types for which absolute molecular weight data can be obtained using ThFFF a calibration procedure has been developed and tested which uses only broad molecular weight polymer samples. The method requires two polydisperse molecular weight standards of the required polymer whose average molecular weight (normally M?_w) is measured by an independent method (e.g. light scattering). From the average molecular weight data and the ThFFF elution pattern (fractogram) the required calibration constants can be calculated. The method has been tested using the polystyrene-tetrahydrofuran system and gave satisfactory results when checked against a series of monodisperse polystyrene standards. This calibration approach should expand the applicability of ThFFF to include a wide range of polymer types.     

Pilot-scale supercritical carbon dioxide extraction and fractionation of wheat germ oil

There is a need for the development of new processing techniques to facilitate vegetable oil extraction and refining while sustaining the nutritional components naturally present in edible oils and reducing the adverse impact of oil processing on the environment. In this study supercritical carbon dioxide (SC−CO₂) extraction and fractionation techniques were examined as alternative methods to obtain wheat germ oil (WGO) of high quality and purity. It was shown that the SC−CO₂ extraction technique is effective in extraction of WGO. There was no significant difference in the FA composition of SC−CO₂- and hexane-extracted WGO. Both hexane-and SC−CO₂-extracted WGO were rich in α-tocopherol. Moisture content of the SC−CO₂-extracted oil was higher than that of the hexane-extracted oil. Solvent/feed ratio had a significant effect on the SC−CO₂ extraction yields. This study demonstrated that supercritical fluid fractionation was a viable process to remove FFA efficiently from both hexane-and SC−CO₂-extracted WGO while retaining bioactive oil components in the final product.     

Contribution of triglycerides from cocoa butter to the physical properties of milkfat fractions

Milkfat was separated into major chainlength fractions by solid-phase extraction. The effect on thermal behavior and texture of replacing both saturated and monounsaturated long-chain triglycerides from milkfat by long-chain monounsaturated triglycerides with an unsaturated fatty acid in thesn-2 position is reported. Increasing proportions of cocoa butter were added to fractions of short-to medium-chain triglycerides (C₂₂−C₄₄) and medium- to long-chain triglycerides (C₃₆−C₄₈) isolated from milkfat. Thermal behavior and texture of the mixtures were measured. Results indicated that long-chain monounsaturated triglycerides from cocoa butter enhanced co-crystallization and co-operative melting and did not induce polymorphic transitions upon crystallization and melting of the fractions. At 4°C, they acted as texture builder if present in proportions of more than 30%, whereas below this level, they acted as texture softeners. The effect of the long-chain monounsaturated triglycerides on the texture of fractions that melt at low temperature could not be predicted from the proportion of solid fat at that temperature. Presented at the 1995 AOCS Annual Meeting & Expo, San Antonio, Texas, May 1995.