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.     

Estimation of solid-liquid ratios in bulk fats and emulsions by pulsed nuclear magnetic resonance

Several pulsed nuclear magnetic resonance (NMR) methods were evaluated to estimate the solid fat content of fats and oil-in-water emulsions. The methods were checked with samples of paraffin oil or triolein containing known quantities of crystalline tristearate. A method based on the signal of solid fat (with use of a correction factor, the “f-factor”) was rejected in this work for general use. Correct results were obtained with methods that used only the signal of the liquid phase. With emulsions, disturbances could arise due to the surfactant present and to possible solubilization of water in the oil phase, presumably by monoglycerides. Without these disturbances, solid fat content in emulsions could be estimated as in bulk fats, after correction of the liquid phase signal for the contribution of protons from the aqueous phase. The signal from fat crystals inside emulsion droplets differed from that of crystals of the same fat in bulk, which may have been due to difference in crystal size but not to difference in crystal modification. Measurements on natural cream showed that disturbances were also possible in this type of emulsion.     

Structural and Mechanical Properties of Fats Quantified by Ultrasonics

Since the velocity of an ultrasonic wave through a material depends on its density, bulk modulus (K), and shear modulus (G), a new approach to determine the shear elastic modulus and the mass fractal dimension (D) in a fat crystal network was developed. An ultrasonic chirp wave containing a range of frequencies and amplitudes, was used to estimate the structural and mechanical properties of palm oil based fats, crystallized under shear at three different temperatures (20, 25, and 30 °C). Considering the fat crystal network as a two-phase system (i.e. liquid and solid fat) the velocity of sound in both phases was obtained separately, assuming that the speed of sound in the oil phase was inversely dependent on the temperature. A constant shear modulus for the solid fraction was obtained experimentally by rheology, which was independent of the sample’s nature. These parameters were used for the determination of sample compressibility and its corresponding shear modulus by ultrasonic velocimetry. In addition fractal dimensions (D) were determined by using the relationship of the shear elastic modulus (G) to the mass fraction of the solid fat (φ) in a weak-link regime. The obtained results are comparable and consistent with previously reported fractal dimension values. This method allows online determination of the shear modulus of fats and could be potentially applied for quality control purposes in manufacturing.     

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.     

Laboratory separation of crystals from plastic fats using detergent solution

An improved laboratory technique for isolating the solid-fat fraction from plastic fats is described. The fat first is dispersed in an aqueous detergent solution; then the oil and solid fat fractions are separated by high speed centrifugation. To facilitate the separation, a 25% ammonia solution is added to adjust the density of the water phase to between those of the oil and the solid-fat phase. After rinsing with cold ethanol, a solid-fat fraction is obtained-contaminated with only ca. 5% oil-which can directly be used for differential thermal and X-ray analyses. The method also can be applied for a quick determination of the solid-fat content according to the dye dilution principle and for obtaining oil-free fat crystals for electron microscopy.     

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.     

超声-冷冻解冻法处理罐底污油

原油沉降罐罐底污油的三相分离是油田生产急待解决的问题之一,通常采用溶剂萃取和热水洗处理时存在安全风险和二次污染。本论文在分析了罐底污油基本特性后,提出了超声-冷冻解冻复合法处理罐底污油的方法,以三相分离后泥相含油量为考核指标先后进行了单因素和正交实验,得到了最佳工艺条件,并讨论了三相分离机理。得出最佳工艺条件为：超声频率28kHz、温度55℃、超声功率300W、超声时间60min、冷冻温度为-5℃,冷冻时间为3h,解冻温度为60℃并静置1h。此工艺实现三相分离的机理大致如下：超声空化作用可以使固体颗粒在油滴表面脱附沉降至底部,再冷冻破乳时冰晶可以刺破油水界面、油滴聚并从而油水分离。研究表明：采用此工艺处理罐底污油时安全风险低,不会带来二次污染,分离后水相含油率低。     

Shear and longitudinal ultrasonic measurements of solid fat dispersions

Dispersions of coating fat in corn oil (2.5–12.5 wt%) were prepared following two different protocols: Type A dispersions had an average crystal size of 30–36 μm, whereas type B dispersions were less than 1 μm. In both dispersions the fat crystals were aggregated into larger structures (up to 80 μm). The longitudinal ultrasonic properties (i.e., velocity, attenuation, and reflectance) were linearly related to the solid fat content, but only attenuation was sensitive to the different microstructures. The velocity and reflectance measurements were modeled using the Urick equation. Shear ultrasonic reflectance and oscillatory viscometry were used to measure the dynamic viscosity of all dispersions. According to both methods, type B samples were always more viscous than type A at a similar solids content. The correlation between the two techniques was good (r ²>0.99), but the numeric agreement was different for both systems.     

Crystallization Enhancement by a High Behenic Acid Stabilizer in a Palm Oil-Based Model Fat Blend and its Corresponding Fat-Reduced Water-in-Oil Emulsion

A high behenic stabilizer (HBS) at concentrations of 0.3%, 0.6%, and 0.9% w/w was added to the oil phase of a fat-reduced water-in-oil (W/O) emulsion intended for margarine manufacture. The crystallization kinetics, thermal behavior, and microstructure of an oil phase and its 35/65 w/w fat-reduced W/O emulsion were studied. The oil phase was composed of a palm oil-based model fat blend, three emulsifiers, and the HBS. Differential scanning calorimetry results showed that, when 0.9% of stabilizer was added, the crystallization started 2.5 °C higher than when no HBS was added, hence reducing the time needed for crystallization. Polarized light microscopy results showed that the cocrystallization of the high-melting triacylglycerols of the oil phase with the HBS significantly decreased the fat crystal size and increased the number of crystals. The solid fat content also was increased by 2.4%. Interfacial tension experiments corroborated that HBS was located in the oil phase and not at the emulsion interface. This work shows that margarine can be successfully manufactured by adding 0.9% HBS to a 35/65 w/w fat-reduced W/O emulsion without losing functionality, as shown by the presence of the β′ polymorph. This work also suggests that 15% fat could be removed from the system without changing functionality by merely adding up to 0.9% of HBS.     

超声波与解聚剂协同处理含聚油泥

为了有效降低含聚油泥中聚合物的含量,减少聚合物对含聚油泥后续处理的影响,采用超声波、解聚剂以及两者协同的方法对含聚油泥进行处理,研究了超声时间、超声频率、解聚剂加量等参数对解聚和除油效果的影响。实验结果表明,含聚油泥在超声频率20kHz、超声时间5min的处理条件下,离心分离后减量60%左右,除油率75%左右,但超声波对聚合物降解效果不明显,适用于含聚油泥的减量化处理;含聚油泥经过解聚剂处理后,聚合物降解率最高可达96.7%,离心分离后底泥疏松,水相澄清;含聚油泥经过超声波与解聚剂协同处理后,聚合物降解率最高达到97.5%,在超声频率20kHz、超声时间5min、解聚剂量4000mg/kg、热解温度550℃的处理条件下,热解后固渣含油率低于0.3%,满足油泥资源化处理的要求。     

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.     

Influence of Fat and Emulsifier Content on Volatile Release of Butter Aroma Used in Water Phase and Physical Attributes of Model Margarines

Margarines are water‐in‐oil (W/O) emulsion‐type products produced with butter aroma. The aim of this study is to investigate the volatile release of the butter aroma compounds used in the water phase of model margarine and sensory properties influenced by the change of fat and emulsifier. A headspace/solid phase microextraction/gas chromatography/mass spectrometry (HS/SPME/GC/MS) system is used for the identification of the volatile compounds. It is determined that high fat content in model margarine samples results in an increase in the release of both 2,3‐butandione and butanoic acid. On the other hand, an increase in fat content reduces the release of butanoic acid ethyl ester and vanillin. In addition, an increase in the emulsifier content of the model margarines results in a decrease in butanoic acid ethyl ester release. The model margarines with 80% fat content have the highest hardness and storage modulus (G′) values. The perception of butter aroma and taste are more intense in high‐fat margarine samples, while fruity aroma and taste, vanilla aroma, and taste perception are higher in low‐fat margarine samples. However, emulsifier content does not affect the sensory properties of the model margarines. Practical Applications: Decreasing high fat content food intake has become increasingly popular among consumers. Thus, in order to meet consumer demands, manufacturers have begun to reduce the fat content of the foods they produce. However, the flavor properties of a product can change as a consequence of fat content reduction. In order to produce a product in accordance with the properties demanded by the consumer, the change in the flavor of that product should be foreseen depending on the change in fat content. This study aimed to determine the volatile compound release and sensory properties of margarine samples due to fat and emulsifier changes. The findings of this study are a guide for the production of low‐fat products.     

Emulsifying properties of phospholipids in the reconstitution of cream using butter oil

Phospholipids (PL) extracted from bovine milk and soybeans were tested for their emulsifying properties in reconstituted cream using butter oil. Bovine milk PL dispersed in the oil phase were found to stabilize the cream, whereas soybean PL were found to solidify the cream. Differential scanning calorimetry was carried out on the two creams, revealing that the addition of soybean PL to the butter oil retarded the onset of crystallization during cooling, which consequently led to a lower solid fat content within the fat globules. It was suggested that the difference in the crystallization behavior of butter oil due to the addition of different PL led to the different emulsion stabilities of the reconstituted creams.     

Effect of oil unsaturation and wax composition on stability,properties and food applicability of oleogels

Oleogelation is emerging as one of the most exigent oil structuring technique. The main objective of this study was to formulate and characterize rice bran/sunflower wax-based oleogels using eight refined food grade oils such as sunflower oil, mustard oil, soybean oil, sesame oil, groundnut oil, rice bran oil, palm oil, and coconut oil. Stability and properties of these oleogels with respect to oil unsaturation and wax composition were explored. Sunflower wax exhibited excellent gelation ability even at 1%–1.5% (w/v) concentration compared to rice bran wax (8%–10% w/v). As the oleogelator concentration increased, peak melting temperature also increased with increase in strength of oleogels as per rheological studies. X-ray diffraction and morphological studies revealed that oleogel microstructure has major influence of wax composition only. Sunflower wax oleogels unveiled rapid crystal formation with maximum oil binding capacity of 99.46% in highly unsaturated sunflower oil with maximum polyunsaturated fatty acid content. Further, the applicability of this wax based oleogels as solid fat substitute in marketed butter products was also scrutinized. The lowest value of solid fat content (SFC) in oleogel was 0.20% at 25°C, resembling closely with the marketed butter products. With increase in oil unsaturation, oleogels displayed remarkable reduction in SFC. Depending upon prerequisite, oleogel properties can be modulated by tuning wax type and oil unsaturation. In conclusion, this wax-based oleogel can be used as solid fat substitute in food products with extensive applications in other fields too.     

Hydrogenation of vegetable oils using mixtures of supercritical carbon dioxide and hydrogen

Hydrogenation of vegetable oils under supercritical conditions can involve a homogeneous one-phase system, or alternatively two supercritical components in the presence of a condensed phase consisting of oil and a solid catalyst. The former operation is usually conducted in flow reactors while the latter mode is more amenable to stirred, batch-reactor technology. Although many advantages have been cited for the one-phase hydrogenation of oils or oleochemicals using supercritical carbon dioxide or propane, its ultimate productivity is limited by the oil solubility in the supercritical fluid phase as well as unconventional conditions that affect the hydrogenation. In this study, a dead-end reactor has been utilized in conjunction with a head-space consisting of either a binary fluid phase consisting of varying amounts of carbon dioxide mixed with hydrogen or neat hydrogen for comparison purposes. Reaction pressures up to 2000 psi and temperatures in the range of 120–140°C have been utilized with a conventional nickel catalyst to hydrogenate soybean oil. Depending on the chosen reaction conditions, a wide variety of end products can be produced having different iodine values, percentage trans fatty acid content, and dropping points or solid fat indices. Although addition of carbon dioxide to the fluid phase containing hydrogen retards the overall reaction rate in most of the studied cases, the majority of products have low trans fatty acid content, consistent with a nonselective mode of hydrogenation.     

Physical properties of interesterified fat blends

Fat blends, formulated by mixing fully hydrogenated soybean oil with nine different commonly used vegetable oils in a ratio of 1:1 (w/w), were subjected to interesterification (also commonly referred to as rearrangement or randomization) with sodium methoxide catalyst. Fatty acid composition and triacylglycerol molecular species of each fat blend and the interesterified product were determined and correlated with the following physical properties: melting, crystallization characteristics and solid fat content. The differences in the endothermic and exothermic peak temperatures, total heat of fusion and crystallization (β and β′ crystalline content) and solid fat content among the fat blends clearly showed the effect of the composition of each oil on the physical properties. Oils that contained a considerable amount of palmitic acid had a favorable influence on the crystallization and polymorphic form of interesterified fat blends.     

Composition and thermal properties of Rhea oil and its fractions

The rhea (Rhea americana) is a large running bird of the ratite family, native to South America. Oil extracted from rhea fat tissue is used in cosmetic manufacture. Here, the thermal behaviour and the fatty acid and triacylglycerol composition of Uruguayan rhea oil are studied. The results are compared with those obtained from two commercial samples of emu oil. The fatty acid profiles of emu and rhea oils are similar. Small variations are reflected in the non‐identical thermal behaviour of the oils. The solid content of both oils is fairly similar at room temperature. Thus, emu oil and rhea oil may replace one another in certain formulations, without resulting in important changes in physicochemical behaviour. The semisolid rhea oil was fractionated in two successive stages: an olein was obtained at 15 °C, which was refractionated at 10 °C. The thermogram of the olein obtained by cooling at 15 °C does not have the peak found at 34 °C in the thermogram of the original oil and is a softer product than the original oil. A further stage of fractionation of this olein produced a new liquid phase of slightly different thermal behaviour from that of the original olein. This product has a solid fat index around 7% at 15 °C and has melted completely at 20 °C. This second olein has more appropriate physical characteristics than those of the olein obtained from the first fractionation when used in liquid cosmetic formulations.     

Beschleunigung der gelenkten Umesterung mittels periodischer,variabler Temperaturführung

Acceleration of the Directed Interesterification of Oils by Periodic Variation of the Reaction Temperature By means of directed interesterification the solid phase content in an oil can be increased without affecting the physiologically important linoleic acid. However, the directed interesterification of highly unsaturated oils proceeds very slowly. Calculations with a mathematical model demonstrate that the directed interesterification can be accelerated considerably, by periodically decreasing the reaction temperature for a short period. This procedure applied on laboratory scale to the directed interesterification of e. g. sunflowerseed oil and lard accelerated the reaction by approximately a factor of 3. Further it appeared to be possible to prepare a margarine of which the fat phase had been composed entirely of directed inter-esterified sunflowerseed oil.     

Relationship between slip melting point and pulsed NMR data of palm kernel oil

A quantitative relationship between slip melting point (SMP) of palm kernel oil and pulsed nuclear magnetic resonance (NMR) data was established. Regression analysis on the SMP and solid fat content (SFC) data by NMR afforded the following relationship: SMP (°C) = 0.03278 X (SFC 10) + 0.1458 X (SFC 20) + 19.1738 where SFC 10 was the solid fat content (%) at 10°C and SFC 20 was the solid fat content (%) at 20°C. The coefficient of multiple correlation was 0.87871. The equation was tested with 12 samples of crude and refined palm kernel oil. SMPs as determined indirectly by NMR correlated well with the conventional open capillary tube results (r = 0.99998). The maximum difference observed was 0.3°C. The correlation can be applied usefully for quality control.     

Rheology of Cream-like Emulsions Prepared with Soybean Milk and Low Trans Vegetable Fat

The objective of this work was to study the effect of fat globule size and fat content on the rheological behavior of oil-in-water emulsions prepared with soybean milk, sunflower oil and low trans vegetable fat (LTF). Emulsions were prepared with 40 % w/w lipid phase (containing different proportions of LTF) and three different homogenization methods were used in order to obtain different globule sizes. Emulsions were subjected to controlled magnetic shaking until an increase in thickness. Partial coalescence was observed in all systems containing solid fat, which gave a rheopectic behavior and an increase in the viscoelastic parameters of the emulsions. Smaller particle sizes required higher shaking times to produce an increase in thickness, even though this did not lead to different final values of the viscoelastic parameters. The highest partial coalescence degree was observed at 50 % LTF in lipid phase, but the highest final viscoelastic parameters after shaking were observed at 100 % LTF in the lipid phase. The rheological behavior of these emulsions indicates that they could be a potential vegetable substitute for traditional dairy creams.