Physical and textural evaluation of some shortenings and margarines

Solid fat content of shortening and margarine was estimated by pulsed NMR. These values were compared with those of the melted fats using different cooling methods. Solid fat content of shortenings measured at 10 and 20 C followed the same trend as those measured on the melted fat tempered at 30 C. Solid fat content of margarines followed the same trend as those measured on the nontempered fats. Softening points of the products were similar to the dropping points of the fats, as were the temperatures of the DSC major melting peaks. Compression tests of cylindrical samples provided more information about textural characteristics of the products than one penetration tests.     

Melting behavior of blends of milk fat with hydrogenated coconut and cottonseed oils

The melting behavior of milk fat, hydrogenated coconut and cottonseed oils, and blends of these oils was examined by nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). Solid fat profiles showed that the solid fat contents (SFC) of all blends were close to the weighted averages of the oil components at temperatures below 15°C. However, from 15 to 25°C, blends of milk fat with hydrogenated coconut oils exhibited SFC lower than those of the weighted averages of the oil components by up to 10% less solid fat. Also from 25 to 35°C, in blends of milk fat with hydrogenated cottonseed oils, the SFC were lower than the weighted averages of the original fats. DSC measurements gave higher SFC values than those by NMR. DSC analysis showed that the temperatures of crystallization peaks were lower than those of melting peaks for milk fat, hydrogenated coconut oil, and their blends, indicating that there was considerable hysteresis between the melting and cooling curves. The absence of strong eutectic effects in these blends suggested that blends of milk fat with these hydrogenated vegetable oils had compatible polymorphs in their solid phases. This allowed prediction of melting behavior of milk-fat blends with the above oils by simple arithmetic when the SFC of the individual oils and their interaction effects were considered.     

Vegetable fat hydrogenation in supercritical-fluid solvents: Melting behavior analysis by DSC and NMR

The melting behavior of six fat samples hydrogenated on Pd catalysts (uniform 2% Pd/C and eggshell 0.5% Pd/Al₂O₃) in supercritical dimethylether (DME) or propane as reaction solvents was investigated. Hydrogenation was carried out at 484 K, with pressures between 20 and 28 MPa and a molar hydrogen content ranging from 4 to 9%, and using a continuous internal-recycle reactor. The melting and crystallization behavior of the hydrogenated products was characterized by differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR), which allowed the determination of solid fat content (SFC). DSC values were generally higher than NMR values. Melting behavior is one of the most important characteristics of edible fats and margarines as it has an impact on their organoleptic properties. These are strongly affected by supercritical-fluid (SCF) processing, so readjustment is necessary. The results obtained show that supercritical hydrogenation on the eggshell 0.5% Pd/Al₂O₃ catalyst in supercritical DME leads to an improved melting profile of the hydrogenated products compared with uniform 2% Pd/C catalyst in propane. In addition, supercritical conditions have a greater influence on melting behavior than conventional hydrogenation.     

Optical Determination of Solid Fat Content in Fats and Oils: Effects of Wavelength on Estimated Accuracy

The melting profile of solid fat content (SFC) is a parameter of primary importance for the food industry since it affects many important product characteristics such as stability, physical appearance, spreadability, and sensation in the mouth. Reference techniques to measure SFC in fats and oils include pulsed nuclear magnetic resonance (pNMR) and differential scanning calorimetry (DSC), which are reliable and accurate, but require expensive instrumentation and trained personnel. Herein, the accuracy of a recently proposed optical technique to measure SFC is investigated in terms of peak wavelength of incident radiation. A sensor system featuring an array of seven LEDs with peak wavelength in the visible and NIR range is built, and the results compared with data from DSC. All the wavelengths investigated have high accuracy in SFC estimation, especially at 590 (yellow) and 880 nm (NIR). Practical applications : Quick and easy determination of solid fat content in fats and oils by a simple experimental setup. The technique is based on optical attenuation measurements during a thermal cycle. The technique can be implemented in a measurement instrument for in-situ analysis of solid fat content.     

Evaluation of the differential scanning calorimetric method for fat solids

Denison et al. (1) recently reported a method for measuring the per cent solids in fats using the Differential Scanning Calorimeter (DSC). The present work evaluates that method using the Perkin Elmer DSC-1, compares it with nuclear magnetic resonance (NMR) and dilatation methods, and extends it to hard butters. Although the method gave excellent interlaboratory agreement with soft fats, extension to hard fats led to greater experimental variance than SFI. The DSC method provides greater speed (one hour elapsed time) and additional information (thermal “fingerprint” of the fat). Thus, the DSC determination of fat solids overall compares favorably with the NMR method, as well as the SFI dilatation method. The DSC method is readily adaptable to quality control use. Presented at the AOCS Meeting, New Orleans, May, 1967. Now Mrs. K. Saunders.     

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.     

Co-crystals of Beeswax and Various Vegetable Waxes with Sterols Studied by X-ray Diffraction and Differential Scanning Calorimetry

In this study, mixtures of purified wax and sterols were melted and subsequently cooled. Using X-ray diffraction of the mixed, solid phase, it was shown that for up to 30–40 wt% sterols no measurable re-crystallisation of sterols occurred, i.e. the sterols became dissolved at a molecular level. Probably a form of amorphous co-crystals of sterols and wax is formed if the molecular ratio does not exceed 1:1. Differential scanning calorimetry (DSC) suggests that a minor amount of pure sterols could already be present at lower sterol levels. This may be because of the higher temperature at which the microstructure is probed when using DSC—melting of the wax might lead to crystallisation of the sterols. For application in foods, the structure as probed by X-rays at ambient temperatures is more relevant. When sunflower wax and rice bran wax are used, prevention of sterol crystallisation is even more pronounced, probably because the melting temperatures of these waxes are closer to the melting temperature of sterol crystals. Replacing the beeswax with a saturated fat (heRP70), sunflower oil, or jojoba wax (a liquid wax) substantially increases the amount of crystalline sterols. The difference between the various waxes and fats was qualitatively the same for X-ray diffraction and DSC. Stanols can be incorporated in the same manner and up to similar concentrations. Another insoluble nutritional compound, ursolic acid, has a greater tendency to crystallise in wax. This is probably because the melting temperature of ursolic acid is much higher than that of wax.     

Pulsed NMR Method for Solid Fat Content Determination in Tempering Fats,Part I: Cocoa Butters and Equivalents

A general pre-treatment and measuring procedure is described for Solid Fat Content (SFC) determination with pulsed NMR on tempering fats (i. e. Cocoa Butters and Cocoa Butter Equivalents). These fats need a careful pre-treatment to reach their stable β-polymorphic form and crystal size. The different steps in the analysis were studied and optimized to give reliable and quick results. Critical steps were found to be how to start the crystallization from the melted fat and the tempering process. The fat sample should be completely melted at 80° C and held at 60° C for 20 min. Commencement of crystallization is carried out at O° C for 90 min and tempering at 26.5° C for 40 hours. Cooling is carried out at O° C for 90 min before the serial measuring procedure with 35 min/bath using 10,20,25,27,5,30,32.5,35,40 and 60° C baths. Only the liquid signal is measured (indirect method) and 1 puls with 6 sec trigger time used. The temperature dependence of the signal is compensated with a liquid soya oil. The standard deviation for the described method was 0.3–1.8% (abs) with the highest deviations at temperatures in the very intensive melting range, showing that the temperature accuracy and stability in these baths is of greatest importance. A method to check the tempering process with SFC determinations at 26.5° C for various tempering times is also proposed.     

Detection of pig and buffalo body fat in cow and buffalo ghees by differential scanning calorimetry

Adding small amounts of pig or buffalo body fat to cow or buffalo ghee results in the appearance of an extra peak located at high temperature in the melting and crystallization curves as determined by the differential scanning calorimetry (DSC) technique. Ghee adulterations with these animal fats at levels down to 5% are clearly seen in the crystallization diagrams. Quantitative measurements can be obtained by this method in the case of adulterations with buffalo body fat. On the other hand, this method does not detect vegetable oils such as coconut oil, and gives similar results for cottonseed-fed buffalo ghee and ghee adulterated with animal body fats.     

Coefficients of dynamic friction and the mechanical melting mechanism for vinylidene chloride copolymers

Previous research and this research indicate that the mechanical melting for poly(vinylidene chloride) copolymers (PVDC) is complex. Mechanical melting is defined as the melting (or devitrification) of a polymer when a significant portion of the thermal energy originates from a mechanical energy dissipative process. PVDC mechanically melted on a moving metal surface at temperatures of the test instrument that were considerably lower than the differential scanning calorimetry (DSC) onset melting temperature. PVDC formulated with low levels of high density polyethylene (HDPE), however, melted at metal temperatures near the DSC onset melting temperature. Two different mechanical melting mechanisms are proposed to explan the data, and the frictional data are discussed with respect to solids conveying in a single-screw, plasticating extruder.     

Pulsed NMR Method for Solid Fat Content Determination in Tempering Fats Part II: Cocoa Butters and Equivalents in Blends with Milk Fat

Earlier, in part I of this paper, a method for Solid Fat Content (SFC) determination with pulsed NMR has been described for cocoa butters and cocoa butter equivalents. The present work (part II) is a continuation with these fats together with 10 to 30% milk fat. These fat blends need a modified pretreatment before NMR analysis. Crystallisation of the melted fat should be done at 0° C for 150 min and subsequent tempering performed at 19.0° C for 40 h. No other deviations from the earlier reported method have been carried out. Also SFC determination for chocolate has been described and used as a tool for the development of a proper NMR method, giving SFC on a pure fat blend more or less equal to SFC in corresponding milk chocolate. Different pretreatments (i.e. tempering temperatures) have given very different SFC results. A crystallographic understanding of these were achieved using X-ray, microscope and thermal analysis techniques. The chosen tempering temperature 19.0° C gave a single solid solution, which is essential in chocolate if the right properties of the fat are to be reached. Differences in SFC on pure fat blends by different tempering temperatures could, in the same way, be found in milk chocolates stored at corresponding temperatures. Storage temperature can, to a certain degree, be chosen in order to optimize and control the SFC (i.e. properties) in a chocolate product. The choice of initial temperature especially will strongly influence the SFC in chocolate and the crystal lattice remains virtually unaffected by changes in storage temperature.     

Phase behavior of model lipid systems: Solubility of high-melting fats in low-melting fats

The solubility behavior of three high-melting fats (tripalmitin sample, PPP-S; cocoa butter-stearin, CB-S; and palm oil-stearin, PO-S) in five low-melting fats (tricaprylin, CCC; canola oil; sunflower oil; lard-olein, LD-O; and palm oil-olein, PO-O) was studied. To create the solubility curve, the high-melting fat was first equilibrated in the low-melting model lipid system between 25 and 62.5°C for 1 wk. The amount of high-melting fat dissolved in the low-melting model lipid system was then determined by analyzing TAG compositions in the liquid phase using GC. The low-melting CCC formed partial solid solutions with each of the high-melting fats as a result of its very short chain length. PPP-S formed an ideal solution in all of the low-melting fats except CCC. The mixtures of CB-S/LD-O, CB-S/PO-O, and PO-S/LD-O deviated from ideality, illustrating closer interactions between TAG from CB-S and PO-S and those from LD-O or PO-O. The melting temperature and heat of fusion of the high-melting fats calculated from the Hildebrand equation was very close to those determined by DSC.     

Wide-line NMR for product and process control in fat industries1

A modified method is described for the determination of the content of solid phase in fats at various temperatures using a Varian PA-7 wide Une NMR instrument with temperature accessory. To avoid variations in instrument sensitivity a liquid soybean oil was used as reference. There was no need for corrections depending on the IV of the fat or the temperature. The optimal instrument settings were determined and the importance of a standardized temperature conditioning of the sample was confirmed. With the observance of proper conditions a standard deviation of 0.7% solid phase was obtained. Using this method a large number of samples can be examined with only a reasonable amount of work, but there is an increased demand for faster and more exact temperature conditioning of the samples, better stability and easier handling to fit more routine conditions. With these improvements the NMR method does offer some advantages for product control over solid fat index. However, for the time being the NMR method cannot be used for process control of hydrogenation because the need to condition the sample does not permit the determination of the result in less than 1 hr. On the other hand, a direct measurement of fat content of pressmeal gave a standard deviation (1.3% fat) too large for satisfactory production control. One of 10 papers to be published from the Symposium “Wide Line Nuclear Magnetic Resonance” presented at the AOCS Meeting, Minneapolis, October 1969.     

Measurement of solids in triglycerides using nuclear magnetic resonance spectroscopy

A rapid and accurate method using nuclear magnetic resonance (NMR) spectroscopy is presented for determining the percentage of solids in fats and shortenings conditioned at selected temperatures or as received in the laboratory. This method provides more reliable information on the solids content of fatty materials than the empirical dilatometric solid fat index, and is applicable in the range of 50–100% solids which is beyond the limit of the official solid fat index method. The relationship between instrument response and actual solids present was determined on known mixtures of liquid and solid triglycerides. NMR and solid fat index (SFI) measurements were made on a series of commercial margarine oils of varying composition and consistency. Comparisons are presented giving the precision of the two techniques and the relationship between percentage of solids by the NMR technique and the solids fat index.     

Differential scanning calorimetry of water buffalo and cow milk fat in mozzarella cheese

The thermal profiles of the fat in mozzarella cheeses made from cow milk (CM) and water buffalo milk (WBM) were obtained by differential scanning calorimetry (DSC). The DSC curves of mozzarella cheese made from WBM were distinguishable from those of CM. The curves resembled those of the corresponding milk fats and could be divided into low-, medium-, and high-temperature melting regions. The valley in the curve between the low- and medium-temperature melting regions was at 10.8°C in WBM cheese and below 10°C in CM cheese. In the WBM cheese, the area of the low-melting region was larger than the area of the medium-temperature melting region, but the two areas were equal in the CM cheeses. Mixtures of the two cheeses exhibited temperature and area values between those of the pure cheeses. Milk-fat mixtures showed similar behavior. The contrasting DSC melting profiles provide a way of distinguishing between the two mozzarella cheese types and for detecting mixtures of the two fats in mozzarella cheese.     

Fully automated determination of solid fat content by pulsed NMR

Pulsed NMR has been developed into a quick, accurate fully automated method for the determination of the solid fat content in partially crystallized fats. Accepting a standard deviation of 0.3% solids, the percentage of solids is displayed on a digital voltmeter or printed out 6 sec after placing the sample into the sample holder. To allow for the dead time of the receiver, a correction factor has been introduced giving rise to only small errors (<1%) in the solid fat content. Due to the short measuring time, no temperature control of the sample holder is needed between 10–45 C. Pulsed NMR values can be converted into dilatations and vice versa.     

Comparison of ultrasonic and pulsed NMR techniques for determination of solid fat content

In this work an ultrasonic velocity technique was compared to direct pulsed NMR (pNMR) spectroscopy for the determination of the solid fat content (SFC) of anhydrous milk fat (AMF), cocoa butter (CB), and blends of AMF and CB with canola oil (CO) in the range 100 to 70% (w/w). In situ measurements of ultrasonic velocity were carried out during cooling (50–5°C) and heating (5–50°C) of the fat samples, and SFC values were calculated. The SFC were also determined simultaneously by pNMR. Peak melting temperatures determined by DSC were used as an indicator of the polymorphic state of the different fats and fat blends. Estimates of SFC obtained using pNMR and ultrasonic velocimetry did not agree. Our results suggested that ultrasonic velocity was highly dependent on the polymorphic state of the solid fat. Ultrasonic velocity in fat that contained crystals in a more stable polymorphic form was consistently higher than in fat that contained crystals in a less stable polymorphic modification. A high attenuation of the signal was observed in milkfat and CB at lower temperatures, particularly after sitting for 24 h. This high attenuation could be a product of scattering by crystallites or by microscopic air pockets formed upon solidification of the material, or it could be due to high ultrasonic absorption associated with phase transitions. This research highlights some of the problems associated with applying ultrasonics to the determination of SFC.     

Accelerated Fat Bloom in Chocolate Model Systems: Solid Fat Content and Temperature Fluctuation Frequency

Chocolate model systems were designed with high‐melting fat (cocoa butter stearin, CB‐S) mixed with low‐melting fats (sunflower oil, canola oil, cottonseed oil, peanut oil) to give 45, 55, and 65 % solid fat content (SFC). Defatted cocoa powder provided a 50 % particulate level in the model chocolates. The effects of SFC, low‐melting fat type and storage temperature fluctuation frequency on bloom whiteness were investigated. Both SFC and storage condition had significant influences on bloom whiteness (p < 0.0001), although the type of low‐melting fat did not (p = 0.1223). Increasing the SFC significantly reduced bloom formation, as did more rapid temperature fluctuations.     

Blending of hydrogenated low-erucic acid rapeseed oil,low-erucic acid rapeseed oil,and hydrogenated palm oil or palm oil in the preparation of shortenings

Two ternary systems of fats were studied. In the first system, low-erucic acid rapeseed oil (LERO), hydrogenated lowerucic acid rapeseed oil (HLERO), and palm oil (PO) were blended. In the second system, hydrogenated palm oil (HPO) was used instead of PO and was blended with LERO and HLERO. The blends were then studied for their physical properties such as solid fat content (SFC), melting curves by DSC, and polymorphism (X-ray). HPO showed the highest melting enthalpy after 48 h at 15°C (141±1 J/g), followed by HLERO (131±2 J/g), PO (110±2 J/g), and LERO (65±4 J/g). Binary phase behavior diagrams were constructed from the DSC and X-ray results. Iso-line diagrams of partial-melting enthalpies were constructed from the DSC results, and binary and ternary isosolid diagrams were constructed from the NMR results. The isosolid diagrams demonstrated formation of a eutectic along the binary blend of PO/HLERO. However, no eutectic effect was observed along the binary lines of HPO/HLERO, PO/LERO, HPO/LERO, or HLERO/LERO. The same results were found with the iso-line diagrams of partial-melting enthalpies. As expected, addition of PO or HPO increased polymorphic stability in the β′ form of the HLERO/LERO mixture.     

Relations between pulsed NMR,wide-line NMR,and dilatometry

Hitherto, solid fat contents often have been expressed as dilatations. Since the development of pulsed NMR into a quick and accurate method for the determination of the solid fat content, while wide-line NMR still is being used, accurate equations are needed to enable conversion from dilatations to NMR values and vice versa. The inaccuracies arising when NMR values are converted into dilatations are almost equal for the various NMR methods. The direct pulse method in which one mean solid fat factor f is used is the most attractive method to replace dilatometry. For further reduction of the standard deviation when converting NMR values into dilations and vice versa, it will be necessary to split up the fats into groups with similar compositions.