Crystallization kinetics of fully hydrogenated palm oil in sunflower oil mixtures

The crystallization kinetics of mixtures of fully hydrogenated palm oil (HP) in sunflower oil (SF) was studied. The thermal properties and phase behavior of this model system were characterized by means of differential scanning calorimetry and X-ray diffraction. From the melting enthalpy and clear point of HP, it was possible to calculate the supersaturation at a given temperature for every composition of the model system. Supersaturation of the model system for the β′ but not for the α polymorph yielded the β′ polymorph, while supersaturation for the α polymorph yielded a mixture of mainly β and some β′ polymorphs. The crystallization kinetics of HP/SF mixtures were determined by pulsed wide-line proton nuclear magnetic resonance for various initial supersaturations in the β′ polymorph. The determined curves were modeled by a modified classical nucleation model and an empirical crystal growth function, which are both functions of supersaturation. Heterogeneous nucleation rates in the β′ polymorph yielded a surface Gibbs energy for heterogeneous nucleus formation of 3.8 mJ·m⁻². About 80% of the triglyceride was assumed to be in a suitable conformation for incorporation in a nucleus. Induction times for isothermal crystallization in the β′ polymorph yielded a surface free energy for heterogeneous nucleus formation of 3.4 to 3.9 mJ·⁻².     

Crystallization characteristics of hydrogenated canola oil as affected by addition of palm oil

Addition of palm oil at levels of 5, 10 and 15% to selectively and nonselectively hydrogenated canola oil increased the time of isothermal crystallization at 20°C and delayed the appearance of the isothermal crystallization peak as determined by DSC. The degree of supercooling was also increased. Addition of palm oil to canola oil before selective or nonselective hydrogenation decreased the time of the appearance of the isothermal crystallization peak. Rates of crystallization were determined in selectively hydrogenated canola palm oil mixtures which followed first order kinetics.     

Crystallization of fully hydrogenated and interesterified fat and vegetable oil

Owing to public concern regarding the adverse health effects of trans fatty acids, an alternative technology to trans fats has recently become an important issue. The interesterification of fully hydrogenated vegetable oil and liquid oil blends is one of the most versatile options. This paper reports a physical analysis of high-melting fat (HMF) prepared through the interesterification of fully hydrogenated soybean oil and regular soybean oil, and through fractionation. The thermal and structural properties of the HMF blended with salad oil at a mass ratio of 4:1 (called the HMF blend, hereafter), which was prepared as a model fat blend for margarine, were assessed using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and polarized light microscopy (POM). To observe the polymorphic transformation, all samples were aged after crystallization, and the development of granular crystals during the aging process was observed. We found that the granular crystals are made of SOS/SSO, POS/PSO, and (SOS+POS)/(SSO+PSO) molecular compounds, all of which easily transform into β form with a double-chain-length structure.     

Crystallization behavior of hydrogenated sunflowerseed oil: Kinetics and polymorphism

Kinetics of crystallization of hydrogenated sunflowerseed oil was studied by means of an optical method. Two different aspects were examined: the effects of preheating of the molten liquid on induction time of isothermal crystallization and the effects of cooling rate on the crystallization behavior. Induction time for crystallization was markedly dependent on the crystallization temperature and the cooling rate selected. Morphology, polymorphism and chemical composition of the crystals were examined. At all crystallization temperatures, β′-form was found for the first occurring crystals. Long spacings were also similar in all cases and corresponded to a double chainlength arrangement. The chemical composition of the crystals showed no differences at either cooling rate. However, the melting behavior was different. At a slow cooling rate, fractionation occurred, and differential scanning calorimetry diagrams had a broad second endotherm with three peaks, none of which were completely resolved. The polymorphic transformation rate from β′ to β was slower when induction times were longer.     

Polymorphism of hydrogenated canola oil

The polymorphism of hydrogenated Canola oil was investigated using X-ray diffraction. The effects of hydrogenation conditions (selective: 200 C; 48 kPa hydrogen pressure, and nonselective: 160 C; 303 kPa) and degree of unsaturation on the transformation β′ → β are discussed. A densitometer was used to follow the changes in the relative density of the characteristic short spacings, in an attempt to present a semiquantitative measure of β′ « β transformation during storage. The samples studied were selectively and nonselectively hydrogenated Canola oils of iodine values (IV) 70 and 60, respectively. Among the 4 samples, the selectively hydrogenated sample with IV 70 was the most stable and the nonselectively hydrogenated sample with IV 60 the least stable.     

Solubility of hydrogenated peanut oil in peanut oil

Conclusions Data obtained on the solubility of hydrogenated peanut oil in refined peanut oil and the behavior of the mixtures on cooling indicate that freedom from oil separation on storage is largely determined by the nature as well as the amount of solid crystals present in the oil. The results suggest that the best procedure for prevention of oil separation would involve shockchilling the molten mixture to produce the finely divided metastable crystalline modification followed by tempering at such a temperature as to permit transformation of the crystals into the more desirable higher-melting form without changing the finely divided state necessary for improved palatability. The data imply that under controlled conditions any amount of the high-melting modification of the hard fat incorporated in peanut oil above the solubility temperature in excess of 2% should produce a mixture free from oil separation under average storage conditions. The choice of the actual concentration of the hard fat, above the minimum amount, would depend upon the degree of plasticity desired. Ambient temperature to which the mixture is likely to be subjected will influence to a considerable extent the selection of the hard fat content. The information obtained is of fundamental importance in connection with the problem of oil separation in peanut butter. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

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.     

氢化油中含镍量的测定

对显色剂丁二酮肟与镍在水相中的显色反应进行了研究,优化了显色条件,比较了显色试剂的不同加入顺序,试剂加入顺序应依次为:标准液、丁二酮肟、过硫酸铵、氢氧化钠,用此加入顺序时,标准曲线线性范围较宽(0 1mg·L-1～10mg·L-1),相关系数为0 99974,显色反应快且稳定。比较了测定氢化油中镍的3种预处理方法,确定了以氯仿为溶剂的酸提取最佳预处理方法,用丁二酮肟水相直接分光光度法测定氢化油中镍的相对标准偏差为4 5%,回收率为103 0%。     

Nutritional effects of hydrogenated soya oil

Soybean oil is the leading edible vegetable oil in the world in terms of volume, and considerable amounts are consumed in partially hydrogenated forms. Early recognition that commercial hydrogenation of vegetable fats produces isomeric forms of monoenes and polyunsaturates has prompted much research and speculation on the nutritional properties of hydrogenated fats, including soya oil. Past results of studies with animals and humans will be reviewed and key findings will be summarized and discussed. Particular attention will be devoted to questions recently raised concerning the relationships of health and hydrogenated fats and an attempt will be made to put these matters into factual perspective in light of current knowledge.     

Biological evaluation of hydrogenated rapeseed oil

A 91-day feeding study evaluated soybean oil, rapeseed oil, fully hydrogenated soybean oil, fully hydrogenated rapeseed oil, fully hydrogenated superglycerinated soybean oil and fully hydrogenated superglycerinated rapeseed oil at 7.5% of the diet in rats; a 16-wk feeding study evaluated soybean oil and the three rapeseed oils or fats at 15% of the diet. Each fat was fed to 40 rats as a mixture with soybean oil making up 20% of a semi-synthetic diet. No significant differences in body weight gains or diet-related pathology were seen in the 91-day study although the rats fed liquid rapeseed oil had slightly heavier hearts, kidneys and testes than the others. The rats fed the four fully hydrogenated fats ate more feed and had lower feed efficiencies than those fed oils but no differences were seen among the four hydrogenated fats. In the 16-wk feeding study, no pronounced pathology related to the diet was seen although the rats fed liquid rapeseed oil had a slightly higher incidence of histiocytic infiltration of cardiac muscle than the rats in the other groups. The female rats fed the three rapeseed oil fats gained significantly less weight and the females fed liquid rapeseed oil had enlarged hearts compared to the other groups. The absorbabilities of the six fats were measured in the 91-day study when fed as a mixture with soybean oil and as the sole source of dietary fat in a separate 15-day balance study. The four fully hydrogenated fats were poorly absorbed and the absorption of behenic acid from the two hydrogenated rapeseed oils was found to be 12% and 17% in the balance study and 8-40% in the feeding study. The adverse biological effects of unhydrogenated rapeseed oil containing erucic acid as reported in the literature do not occur with fully hydrogenated rapeseed oil. In addition, the low absorbability of the fully hydrogenated rapeseed oil is an added factor in its biological inertness.     

Nutritional studies of partially hydrogenated rapeseed oil

In three experiments rats were fed a purified basal diet with 20% by weight of partially hydrogenated rapeseed oil. One sample promoted, greater weight gains that the unhydrogenated oil. Another sample, containing a higher concentration of octadecadienoic acids other than 9,12-linoleic acid, produced the same response as the unhydrogenated material. With other samples of hydrogenated rapeseed oil, possessing less linoleic acid but other octadecadienoic acids, significantly lower weight gains were obtained. The alterations in the C₁₈ fatty acids resulting from hydrogenation of rapeseed oil appeared to be responsible for differing responses in weight gain.     

Removal of copper from hydrogenated soybean oil

Hydrogenation with a copper-chromite catalyst at 170 C, 30 psi, increased the copper content of a refined, bleached soybean oil from 0.02 to as much as 3.8 ppm. Removing residual copper from soybean oil is essential to the successful use of copper catalysts for selective hydrogenation. Various methods were examined to remove this copper, including alkali refining, bleaching, acid washing, citric acid treatment and cation-exchange resin treatment. Properly conducted, each of the methods except alkali refining gives 95% or higher removal of copper introduced during hydrogenation. Ion exchange appears to be the most economical, but addition of about 0.01% citric acid during deodorization may be needed to inactivate traces of unremoved copper. Soybean oil hydrogenated with a copper-chromite catalyst, bleached or treated with an ion-exchange resin and deodorized with 0.01% citric acid added had low AOM peroxide values and acceptable flavor scores after eight days at 60 C which indicate that removal of residual copper from the oil should be adequate for the production of stable oils low in linolenic acid content. Presented at AOCS Meeting, Chicago, October 1967.     

The use of hydrogenated fish oil to extend vegetable oil

During the last four years, national production of fish oil has increased appreciably due to the expansion of the "reduction" industries (fish flour). Nevertheless, this production is almost totally destined to industrial use (lubricants, tannery, etc.). In contrast, some countries like Japan, Canada and Peru have been using oil from different fish species for human consumption. In view of the above, the objectives of the present work were: first, to establish the experimental conditions for obtention of a hydrogenated fish oil and second, the formulation of fish and vegetable oil mixtures for use in the food industry. The methodology followed comprised: 1) characterization of crude fish oil through physical and chemical analysis; 2) adaptation of the vegetable oil refining procedures to fish oil, and 3) development of fish oil with vegetable oils. A hydrogenated fish oil with a melting point of 36 degrees C, iodine index of 80, and lovibond color, yellow 20, red 13, was produced. Based on the results of the sensory test, the possibility of using up to 30% extension of this oil with vegetable oils for frying, and up to 50% extension for baking, without affecting acceptability of product, was established.     

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.     

Crystallization of sunflower oil waxes

Activation free energies of nucleation (ΔG _c ) were calculated using induction times of crystallization measurements. Results showed that ΔG _c decreased exponentially as wax concentration increased at a constant crystallization temperature (T _c ). In contrast, for a constant supersaturation, ΔG _c increased from 12 to 22°C but decreased between 22 and 35°C. Melting behavior of purified waxes and solutions of purified waxes in sunflower oil were studied by DSC after crystallization at fast and slow cooling rates (20 and 1°C/min, respectively). Low supercooling temperatures (T _c >65°C) showed an increase in the onset temperature (T ₀ ) as T _c increased for both fast and slow cooling rates. Broader peaks were obtained for samples crystallized at a slow cooling rate at the same T _c . Regarding the solutions of waxes in sunflower oil, the wax concentration (supersaturation of the system) controlled crystallization as well as T _c . As T _c increased, the enthalpy (ΔH) decreased at a constant wax concentration. When wax concentration decreased, ΔH decreased at a constant T _c . For a low driving force, a small shoulder was obtained in the DSC diagrams owing to some type of fractionation. These results showed that wax crystallization is affected by different experimental parameters, such as T _c and cooling rate, depending on the wax concentration of the sample.     

Some physical properties of castor oil esters and hydrogenated castor oil esters

Esters of castor oil and hydrogenated castor oil were prepared with C₆, C₁₂, C₁₆, C₁₈ fatty acids, using tetra‐n‐butyl titanate as a catalyst and n‐butyl benzene as a water entrainer. Physical properties such as melting point, refractive index, viscosity, and specific gravity of these esters were measured. Slip melting points of the esters were very low in both cases. These esters did not crystallize even at low temperature. The highest slip melting point obtained was 21 °C with stearoyl hydrogenated castor oil ester and lowest slip melting point obtained was —6 °C with hexanoyl castor oil ester.     

Flavor evaluation of copper-nickel hydrogenated soybean oil and blends with unhydrogenated oil

Journal of the American Oil Chemists' Society - Soybean oils hydrogenated to zero linolenate in the pilot plant with a mixed copper-nickel catalyst and a straight copper chromite catalyst were...     

Polymorphic behavior of high-melting glycerides from hydrogenated canola oil

Canola oil was hydrogenated with a commercial nickel catalyst at 175°C and 15 psi hydrogen pressure. Samples were taken during the reaction starting at 15 min and thereafter at ten-minute intervals. The reaction was stopped after two hours. The high-melting glycerides (HMG) were obtained by fractional crystallization at 15°C with acetone as solvent. The HMG were analyzed for fatty acid and triglyceride composition by gas liquid chromatography andtrans was determined by infrared spectroscopy. In the first 45 min of hydrogenation of canola oil, the 18:0 fatty acid increased at a low rate while thetrans fatty acid content increased at a much faster rate. The 16:0 and 18:0 content of the HMG was highest andtrans content the lowest during the period in which the triglyceride composition was the most diverse. The 54-carbon triglyceride content of the HMG increased from 64% to 78% during the two hours of hydrogenation. The short spacings for the HMG showed the presence ofβ crystals as well as several intermediate forms. The number of short-spacings increased with hydrogenation time. The differential scanning calorimetry (DSC) melting profile of the HMG showed one broad peak between 20 and 30°C and two peaks around 60°C and above. Crystallization temperatures of the HMG were in the range of 40–45°C. Presented at the 81st American Oil Chemists' Society Annual Meeting, April, 1990, Baltimore, Maryland.     

Polymorphic stability of hydrogenated canola oil as affected by addition of palm oil

Palm oil was added to canola oil before and after hydrogenation and the effect of this addition on the polymorphic stability of the hydrogenated oils was investigated. Palm oil was added to canola oil at two levels to produce hydrogenated canola and palm oil blends containing 5 and 10% palm oil. The levels of palm oil added to hydrogenated canola oil were 5, 10 and 15%. Samples were subjected to temperature cycling between 5 and 20°C as well as storage at 5°C up to 56 days. X-ray diffraction and polarized light microscopy were used to follow the changes of polymorphic form and crystal growth, respectively, during cycling and storage. Theβ-crystal contents of the oils were quantified based on the relative density of the characteristic short spacings using a Soft Laser Scanning Densitometer. The delaying effect of palm oil on phase transition was observed using Differential Scanning Calorimetry. Palm oil showed no effect on the polymorphic stability of the temperature cycled selectively hydrogenated oil, however, it delayed the transition rate at a constant temperature of 5°C. Addition of palm oil at the 10% level before hydrogenation and the level after hydrogenation proved to be effective in delaying polymorphic instability of nonselectively hydrogenated canola oil. Theβ′ stabilization effect of palm oil on the polymorphic stability of hydrogenated canola oil is most likely due to a decrease of fatty acid chain length uniformity.