TAG composition of ewe's milk fat. Detection of foreign fats

The TAG composition of 45 samples of ewe's milk, collected throughout the year from five Spanish breeds, was analyzed according to their carbon number by using short capillary column GC. The TAG content had a bimodal distribution with maxima at C₃₈ (12.8%) and C₅₂ (8.4%). The TAG composition did not vary significantly with respect to the time of year of sampling but was affected by the breed. Multiple regression equations based on TAG content are proposed to detect foreign fats in ewe's milk fat. Analysis of known mixtures of lard, palm oil, and cow's milk fat with ewe's milk fat have experimentally confirmed the accuracy of the equations.     

Calculation of the solid fat content of vegetable fats using the Hildebrand equation

Vegetable fats are complex multi-component mixtures of triglycerides. Here, the solidification behavior of a few vegetable fats is calculated using the Hildebrand equation. This calculation assumes, in the liquid phase, ideal mixing of the different components, in combination with literature data about the temperatures and enthalpies of fusion of the individual triglycerides. It further assumes a decomposition of the triglyceride blend into binary blends dissolved in an inert solvent. The solid fat content is calculated as function of the temperature, for only all α and only β and only β ' crystal modifications. The minor triglyceride components are explicitly included in the calculation. The calculated solid fat contents for cocoa butter, palm oil, inter-esterified palm oil and palm kernel olein oil are compared to pNMR data, reported in the literature. The standard deviations between calculated and experimental solid fat content lie between 4% and 14%. Temperature ranges are found, in which specific crystal modifications match to the pNMR data for the solid fat content. These temperature ranges are found to be consistent with literature data obtained using x-ray diffraction. As a by-product, the calculation presented here, enables the construction of scenarios that describe which triglyceride solidifies in which temperature interval.     

Plastic fats and margarines through fractionation,blending and interesterification of milk fat

Milk fat stearins and oleins were blended with high‐ and low‐melting natural fats to produce plastic fats, vanaspati substitute and confectionery fats. Margarines of improved nutritional value were also formulated. Fractionation was carried out using acetone, hexane, and isopropyl alcohol. The yield (wt‐%) of high‐melting stearin (HMS) from acetone and IPA was 13.0 ± 0.2 to 13.3 ± 0.1 after crystallization for 24 h at 20 °C. The melting point of the products was 49.0 ± 0.5 to 49.8 ± 0.6 °C. However, in hexane the yield of HMS was 12.2 ± 0.2% at 10 °C. The olein fractions were further fractionated at 10 °C from acetone and IPA, and at 0 °C from hexane, to obtain superoleins and low‐melting stearins (LMS). HMS fractions were blended with rice bran oil and cottonseed oil at the ratio 70 : 30 (wt/wt), and the superoleins were blended with sal fat and palm stearin at the ratios 40 : 60, 30 : 70 and 20 : 80 (wt/wt). The blends were interesterified (product melting point: 22.7 ± 0.04 to 39.3 ± 0.10 °C) chemically and enzymatically to prepare margarine. The penetration values (in 0.1 mm) of these margarines were noted to be 112 ± 1.52 to 145 ± 0.00.     

Validation of a gas‐chromatographic method for the determination of milk fat contents in mixed fats by butyric acid analysis

Gas‐chromatographic analysis of butyric acid (C4) in mixed spreadable fats can be used to calculate the milk fat proportion, either by additional analysis of the underlying pure milk fat (component sample) or by using a mean C4 content instead. After comparison of several analytical variants and subsequent development of an improved draft standard for quantitation of milk fat in mixed fats, this draft was checked for accuracy in three EU‐wide ring tests performed with 26 participating laboratories. Due to the natural variation of the butyric acid content in European milk fats, deviations from the actual milk fat content may amount up to ± 10% in addition to analytical errors when calculating with a mean C4 content instead of the C4 content of a component sample. Though the reproducibility could be improved by application of correction factors derived from a reference fat, only the calculation based on the additional analysis of a component sample of the pure milk fat led to an acceptable accuracy concerning the trueness of the results in combination with good repeatability (r) and reproducibility (R). Finally, several further improvements of the draft standard led to a precision of r = 4.3% and R = 6.0% relative to the mean of two milk fat contents determined. Thus, the tested procedure proved its suitability for a control method of the declared milk fat content in mixed fat spreads.     

Simultaneous determination of ascorbyl palmitate and nine phenolic antioxidants in vegetable oils and edible fats by HPLC

This study describes an HPLC method for the simultaneous determination of ascorbyl palmitate (AP) and synthetic phenolic antioxidants (SPA) in vegetable oils and edible fats in a single run. To achieve this, citric acid was used in combination with isoascorbic acid for stabilization of AP in standard and sample solutions and for deactivation of oxidizing agents in the HPLC system. SPA and AP were directly extracted from samples with methanol containing 1 mg/mL each of citric acid and isoascorbic acid. HPLC analytical and guard columns were pretreated with 90% methanol/acetonitrile 1∶1 (vol/vol), containing 4 mg/mL each of citric acid and isoascorbic acid, and 10% water at pH 3, for 30 min. Under these conditions, AP was stable for about 7 h at room temperature. The relative SD of repeatability for AP (0.5–3.6%) was comparable to that for SPA (0.3–2.8%). Average recovery from spiked samples was 100% for AP, 98–103% for SPA, and 85% for BHT (up to 90% using double extraction with methanol).     

Determination of mixtures in vegetable oils and milk fat by analysis of sterol fraction by gas chromatography

A rapid gas-chromatographic (GC) procedure was developed for the analysis of the total sterol fraction of vegetable oils, milk fat or mixtures, to detect possible admixtures of sunflower with olive oil and the addition of vegetable oils to milk fat. The method, which employs alkali-catalyzed transesterification with KOH/methanol, was compared with saponification procedures with and without transformation of sterols into silyl derivatives prior to analysis. Repeatability of the method was assessed, and the coefficient of variation was 6.0 and 8.0% for β-sitosterol in olive and sunflower oils, respectively. Recovery of β-sitosterol ranged from 92.6 to 95.8 for both oils. The GC method assayed in this work requires little analysis time and eliminates the need for saponification, extraction, and derivatization steps. It offers good repeatability and recovery and is thus well suited to routine use.     

The determination of heat capacities of milk fat by differential thermal analysis

A differential thermal analysis calorimeter was used in determining the heat capacities of milk fat. The heat capacities of milk fat at −43 and 70 C were .423 cal/g/C (average value) and .521 cal/g/C (average value) respectively.     

An investigation of the basic conditions for tocopherol determination in vegetable oils and fats by differential pulse polarography

The polarographic behavior of α-, γ-, and δ-tocopherols was studied according to the proposed official IUPAC method for tocopherol determination in vegetable oils and fats. Each of the tocopherols had a different polarographic response; however, the tocotrienols had the same half-wave potentials and probably also the same polarographic response as the corresponding tocopherols. Additives previously investigated plus several others were examined for possible interference. The results by polarography and a new high performance liquid chromatography (HPLC) method were compared. The analysis by t-test at 99% significance level showed no differences for the determinations of α-tocopherol, but the results for three of the γ-tocopherol results were less consistent under the same conditions. The results for the determination of δ-tocopherol were below the detection limit for polarography and could not be statistically evaluated. The polarographic method investigated was found to be uncomplicated and therefore suitable for routine work. However, when using the method, one has to take into account possible interference by additives and the limitations due to the lack of separation of β- from γ-tocopherol and/or the interference of tocotrienols with the corresponding tocopherol peaks. From this aspect the HPLC method gives better resolution.     

Triglyceride structure of milk fats

The enantiomeric nature of the triglycerides of bovine milk fat was reinvestigated by determining the stereospecific distribution of fatty acids in rearranged butterfat, following partial hydrolysis with pancreatic lipase, and in certain molecular distillates of native butterfat, following Grignard degradation. The results with rearranged butterfat confirmed the validity of pancreatic lipase hydrolysis as a means of generating representative diglycerides from milk fat triglycerides. The Grignard degradation and lipolysis gave identical distributions for fatty acids when included as part of the assay system in the stereospecific analysis. Characteristically, butyric acid and the other short chain acids occupied the 3 position in the native butterfat, while in the rearranged oil they were distributed more or less randomly. Gas chromatographic analysis of the short chain glycerides on polyester columns allowed an effective resolution of butyryl, caproyl and caprylyl glycerides of identical numbers of total acyl carbons and double bonds. The method was especially well suited for resolution of the 2,3-diglycerides, which were recovered either as the more polar fraction from thin layer chromatography of the X-1,2-diacylglycerols, or by acetolysis of the residual phenolphosphatides resulting from phospholipase A digestion. It was shown that butyric acid in the 3 position was preferentially paired with myristic, palmitic and oleic acid in the 2 position, and palmitic and oleic acid in the 1 position, which was also characteristic of the other short chain acids. One of eight papers presented in the symposium “Milk Lipids,” AOCS Meeting, Ottawa, September 1972.     

Optical activity of lactones from animal and vegetable fats

The isolation of optically active lactones from animal and vegetable fats is described. As the optical activity of lactones isolated from butterfat is ascribed to their biological origin, special attention was paid to the optical purity of the lactones. Lactone mixtures from butterfat, goat milk fat and coconut oil were found to be dextrorotatory, those from babassu oil levorotatory. The total lactone mixtures of two out of three samples of palm-kernel oil were slightly dextro-, whereas that of the third one was levorotatory. After isolation of the individual lactones from the mixtures, levo- and dextrorotatory lactones were demonstrated side by side in palm-kernel oil and in coconut oil. The δ-lactones of palmkernel oil were levo-, the γ-isomers dextrorotatory. In coconut oil only the δ-C₁₂ lactone was levorotatory, whereas the other components of the δ-series were dextrorotatory. The specific rotation [a] _d of the chemically pure lactones was considerably lower than that of model lactones, this being an indication of their optical impurity. As it was evident from model experiments that no racemization of the lactones occurred during isolation, it follows that both optical antipodes are formed in the fats in unequal amounts, via different pathways.     

Determination of sorbitan tristearate in vegetable oils and fats

A new method for analysis of Sorbitan Tristearate (STS) in vegetable oils and fats has been developed. The method is based on isolation and hydrolysis of STS compounds in a silica cartridge. The polyalcohols are eluted from the silica cartridge and the final separation and quantitation are done by high-performance liquid chromatography and refractive index detection. Linearity, precision, and recovery satisfy general demands on quantitative methods. The detection limit and the quantitation limit are well below the concentrations normally used to attain functional effects of STS in vegetable oils and fats.     

Determination of the glyceride structure of fats; analysis of 14 animal and vegetable fats

The glyceride compositions of seven animals and seven vegetable fats have been determined by GLC analysis of the oxidized esterified glycerides as described in an earlier paper in this series. The compositions determined are compared with those calculated from lipase hydrolysis data according to the method of VanderWal. Good agreement was found between the calculated and determined compositions for the majority of the 14 fats. The exceptions were human fat and the more satu-rated vegetable fats, palm oil and cocoa butter, where some discrepancies occurred. Issued as NRC No. 8052. National Research Council of Canada Postdoctorate Fellow.     

Measurement of the consistency of plastic vegetable fats

Summary 1. An improved micropenetrometer is described, by means of which it is possible to measure the consistency of fats with a high degree of precision. 2. The intelligent use of a micropenetration method requires some consideration of the theory of plasticity in fats. This theory is briefly discussed. 3. The influence of various factors on the consistency of solidified fats has been investigated, and as a result of this investigation a standard technique for making micropenetration tests is proposed. 4. Micropenetration data are recorded on cottonseed, peanut, and soybean oils hydrogenated to different degrees, on cottonseed oil blended with various proportions of highly hydrogenated oil, and on various commercial samples of shortening and margarine. 5. A quick micropenetration method, applicable as a control in the hydrogenation of fat products, is described.     

Trans-geometrical and positional isomers of linoleic acid including conjugated linoleic acid (CLA) in German milk and vegetable fats

A representative number of different milk fats based on a wide range of feeding and lactation conditions as well as 123 German margarines, shortenings, cooking and dietetic fats were analyzed for a variety of trans-C18:2 isomers (exhibiting at least one trans double bond) by means of gas chromatography on a 100m Sil 88 capillary column. In milk fats contents of trans Δ9,trans Δ12,cis Δ9,trans Δ13 (+ trans Δ8,cis Δ12),trans Δ8,cis Δ13,cis Δ9,trans Δ12,trans Δ9,cis Δ12 and trans Δ11,cis Δ15 amounted to 0.09%, 0.11%, 0.11%, 0.10%, 0.07% and 0.33% on average and the content of total trans-C18:2 isomers (without cis Δ9, trans Δ11) was 0.99% in the mean. The content of conjugated linoleic acid cis Δ9,trans Δ11 amounted to 0.81% on average in 238 milk fats. In margarine among others the isomers trans Δ9,trans Δ12,cis Δ9,trans Δ13 (+ trans Δ8,cis Δ12), cis Δ9,trans Δ12 and trans Δ9,cis Δ12 were determined and quantified to 0.03%, 0.04%, 0.29% and 0.23% on average. The mean total content of trans-C18:2 isomers in margarines was 0.61%. Moreover, for all trans-C18:2 isomers the frequency distributions as well as the correlation coefficients towards the trans-C18:1 isomers trans Δ6 to trans Δ16 were derived.     

Effects of ionizing radiation on some vegetable fats

The volatile compounds produced by irradiation, under vacuum at 6 megarads, in five vegetable fats were analyzed qualitatively and quantitatively by gas chromatography and mass spectrometry. A series of compounds,n-alkanes, 1-alkenes, internally unsaturated alkenes, alkadienes, alkatrienes, alkanals and methyl and ethyl esters of fatty acids, were identified in each of the fats studied. A wide variation occurs in the amounts of the volatiles produced from each fat. The major radiolytic products were few in number and were found to depend largely on the fatty acid composition of the fat. These compounds were essentially the hydrocarbons containing one or two carbon atoms less than the component fatty acids. This relationship was found consistent if radiolytic products of fats with different fatty acid compositions are compared or if the fatty acid composition of the same fat is altered by hydrogenation. The results correlate well with those of earlier studies on simple triglycerides.     

Investigations on physical refining of animal fats and vegetable oils

Alcohols, polyethyleneglycols, supercritical fluids, and some of their mixtures have been investigated as to their usefulness to purify animal fats and vegetable oils by extraction. The main impurities are free fatty acids. Phase equilibrium was measured as function of temperature and pressure. As primary substances abattoir fat and palm oil were used. Carbon dioxide, dimethylether, and mixtures thereof, likewise methanol and ethanol were tested as extractants for free fatty acids by counter-current extraction in a pilot plant including a high-pressure column and by cross-flow extraction on laboratory scale. With experiments and process simulations including the recovery of the extractants the deacidification of animal fats and vegetable oils was found to be possible. Polyethyleneglycols extract carotenes together with free fatty acids. With the physical refining methods investigated, the formation of waste materials was avoided.     

Determination of ultratrace metals in hydrogenated vegetable oils and fats

Ultratrace levels of nickel, chromium, copper and iron occurring in hydrogenated vegetable oil products were estimated by dispersion of the samples in 4 methyl-2-pentanone and atomic absorption analysis by the graphite furnace technique. The principal goals in establishing the analytical methods were improved sensitivity to metals at low levels and applicability to limited amounts of products. Using reproducibility and linearity of response as criteria, optimum oil concentration in solvent and instrument parameters were established. For a series of commercial products, the method of standard addi-tions was adopted to correct for matrix differences between the products and salad oil-based standards. The range for the metals was determined in five cooking oils: Ni, 29–207 ppb; Cr, 1–5 ppb; Cu, 13–37 ppb; and Fe, 138–301 ppb; in recovered oils from five margarines: Ni, 34–70 ppb; Cr, 2–12 ppb; Cu, 26–58 ppb; and Fe, 239–540 ppb; and in five solid shortenings: Ni, 592–2772 ppb; Cr, 8–35 ppb; Cu, 26–108 ppb.     

Melting and solidification characteristics of confectionery fats: Anhydrous milk fat,cocoa butter and palm kernel stearin blends

Differential scanning calorimetry measurements of crystallization and melting characteristics of commercial samples of anhydrous milk fat (AMF), cocoa butter (CB) and hydrogenated palm kernel stearin (PKS) in ternary blends were studied. Results showed that stabilization at 26°C (either for 40 h or 7 d) did not greatly affect the melting thermogram trace of PKS. However, the effect of stabilization became prominent as CB was added into the system. Deviation of measured enthalpy from the corresponding values, calculated for thermodynamically ideal blends, showed clear interaction between all three fats. At 20°C, the strongest deviation occurred at about the AMF/CB/PKS (1∶1∶1) blend, whereas at 30°C the deviation moved toward the CB/MF (1∶1) blend. The presence of 25% AMF in PKS had little effect on its solidification capability, but solidification was adversely affected with inclusion of CB.