Detection of lard and randomized lard as adulterants in refined-bleached-deodorized palm oil by differential scanning calorimetry

A study was conducted to assess the use of differential scanning calorimetry (DSC) for detecting the presence of lard/randomized lard as adulterants in refined-bleached-deodorized (RBD) palm oil. Lard extracted from the adipose tissues of pig was chemically interesterified using sodium methoxide as catalyst. DSC thermal profiles of both genuine lard and randomized lard were compared with those of other common animal fats such as beef tallow, mutton tallow, and chicken fat. Lard and randomized lard were then blended with RBD palm oil in two series, in proportions ranging from 0.2 to 20%, and DSC analyses were obtained. The DSC cooling profiles of adulterated RBD palm oil samples showed an adulteration peak corresponding to lard/randomized lard in the low-temperature region. This peak was confirmed as an indicator of the presence of lard in RBD palm oil since similar experiments carried out using other common animal fats such as mutton tallow, beef tallow, and chicken fat showed that the lard adulteration peak could be distinctly identified. Using this method, a detection limit of 1% lard/randomized lard was reached (P<0.0001).     

Effect of randomization on oxidative stability of vegetable oils at two different temperatures

Five vegetable oils were each randomized by chemical means (with the use of a sodium potassium alloy) and by enzymatic means (using a nonspecific lipase). The success of the randomization procedure was confirmed via positional analysis. The oxidative stabilities of the native and chemically randomized oils were determined at storage temperatures of 28°C and 55°C using absorbance at 234 nm as indicative of conjugated diene content. No difference between curves occurred in oils stored at 55°C, however, at the lower temperature all chemically randomized oils had significantly steeper slopes (P<0.05), suggesting a lower stability. When both enzymatically and chemically randomized oils were compared to native oils at 28°C, no significant difference occurred between slopes of native and enzymatically randomized oils, however, the end content of conjugated dienes was significantly higher for chemically randomized canola, corn and soybean oils (P<0.05). No difference was seen between the slopes of the three different oils from either linseed or sunflower. Since both of these oils exhibited higher oxidation rates, it is possible that observation of differences between the stability of native and chemically randomized oild is dependent upon the rate of the reaction.     

FTIR spectroscopic determination of soap in refined vegetable oils

A new analytical method was developed for the determination of soap in palm and groundnut oils by FTIR spectroscopy. Soap from 0 to 80 mg/kg oil was produced in situ in the oils by adding sodium hydroxide. The FTIR spectroscopy was with a sodium chloride transmission cell, and the partial least-squares statistical method was used to calibrate a model for each oil. The accuracy of the method was comparable to that of AOCS Method Cc17-95, with coefficients of determination (R ²) of 0.98 and 0.98 for both palm and groundnut oils. The standard errors of calibration were 1.84 and 1.36 for the two oils, respectively. The calibration models were cross-validated, and the R ² of cross-validation and standard errors of cross validation were computed. The standard deviation of the difference for repeatability of the FTIR method was better than that for the chemical method used for determining soap in palm and groundnut oils. With its speed and ease of data manipulation by computer software, FTIR spectroscopy is a possible alternative to the standard wet chemical methods for rapid (2 min) and accurate routine determination of soap in chemically refined vegetable oils.     

Anomalous high iodine value of squalene and the impact on iodine values of shark liver oils

Squalene has six ethylenic bonds, but the experimental iodine values in two different solvent systems—chloroform and cyclohexane/acetic acid—were 25% higher than the theoretical values. We propose that this results from an additional halogen adding at each of the two terminal ethylenic bonds carrying two methyl groups. In the solvent system of cyclohexane alone, the excess is only 3–4% greater than the theoretical. Mixtures of squalene in seal oil confirmed the additivity of the experimental squalene high iodine value and the seal oil fatty acid iodine value with reasonable accuracy but depended on the skill of the operator in obtaining the titration end point for cyclohexane/acetic acid. This observation has particular relevance for shark liver oils and olive oils.     

AOCS collaborative study on sensory and volatile compound analyses of vegetable oils

An AOCS collaborative study was conducted to determine the effectiveness of sensory analysis and gas chromatographic analyses of volatile compounds in measuring vegetable oils for levels of oxidation that ranged from none to high. Sixteen laboratories from industry, government, and academia in Canada and the United States participated in the study to evaluate the flavor quality and oxidative stability of aged soybean, corn, sunflower, and canola (low-erucic acid rapeseed) oils. Analytical methods included sensory analyses with both flavor intensity and flavor quality scales and gas-chromatographic volatiles by direct injection, static headspace, and dynamic headspace (purge and trap) techniques. Sensory and volatile compound data were used to rank each of the oils at four levels of oxidation—none, low, moderate, and high. For soybean, canola, and sunflower oils, 85–90% of laboratories correctly ranked the oils by either analysis. For corn oil, only 60% of the laboratories ranked the samples according to the correct levels of oxidation by either analysis. Variance component estimates for flavor scores showed that the variation between sensory panelists within laboratories was lowest for the unaged oils. As storage time increased, the variance also increased, indicating that differences among panelists were greater for more highly oxidized oils. Between-laboratory variance of sensory panel scores was significantly lower than within-laboratory variance.     

Anomalous high iodine value of squalene and the impact on iodine values of shark liver oils

Squalene has six ethylenic bonds, but the experimental iodine values in two different solvent systems—chloroform and cyclohexane/acetic acid—were 25% higher than the theoretical values. We propose that this results from an additional halogen adding at each of the two terminal ethylenic bonds carrying two methyl groups. In the solvent system of cyclohexane alone, the excess is only 3–4% greater than the theoretical. Mixtures of squalene in seal oil confirmed the additivity of the experimental squalene high iodine value and the seal oil fatty acid iodine value with reasonable accuracy but depended on the skill of the operator in obtaining the titration end point for cyclohexane/acetic acid. This observation has particular relevance for shark liver oils and olive oils.     

Estimation of the sharma constant and thermoacoustic properties of vegetable oils

The density and volume of four Indian edible vegetable oils, sunflower, rice bran, groundnut and coconut, and one Indian nonedible oil, castor oil, have been experimentally determined. The values obtained were used to estimate the volume expansivity α, hence the thermoacoustic parameters, such as the Sharma constantS ₀, the isochoric temperature coefficient of internal pressure , the isochoric temperature coefficient of volume expansion , reduced volume , reduced compressibility and the Huggins parameter F. The results obtained show that the Sharma constantS ₀ has the same characteristic value of 1.11±0.01 for the five oils, thus establishing the constancy of the Sharma parameter. All the other parameters are of the expected order of magnitude; however, in all cases there is a uniform deviation at 293°K, which can be attributed to the behavior of density and volume at this temperature.     

Studies on phytosterol oxides. I: Effect of storage on the content in potato chips prepared in different vegetable oils

Potato chips fried in palm oil, sunflower oil, and high-oleic sunflower oil were studied for the content of different phytosterol oxides during 0 to 25 weeks of storage in the dark. Oxidation products of sitosterol (24α-ethyl-5-cholesten-3β-ol) and campesterol (24α-methyl-t-cholesten-3β-ol) were synthesized to help identify the phytosterol oxides. The oxides of phytosterols were analyzed by preparative thin-layer chromatography, solid-phase extraction, capillary column gas chromatography (GC), and GC-mass spectrometry. Epimers of 7-hydroxysitosterol and 7-hydroxycampesterol; 7-ketositosterol and 7-ketocampesterol; epimers of 5,6-epoxy-sitosterol and 5,6-epoxy-campesterol; 24α-ethylcholestane-3β,5,6β-triol (dihydroxysitosterol) and 24α-methylcholestane-3β,5,6β-triol (dihydroxycampesterol) were detected and quantitated in the samples of chips fried in different vegetable oils. Potato chips fried in palm oil had the lowest level of total sterol oxides, ranging from 5 to ca. 9 ppm in the lipids from time 0 to 25 wk of storage. The level of total sterol oxides in chip samples fried in sunflower oil ranged from 46 to 47 ppm, and the lipids in samples fried in high-oleic sunflower oil ranged from 35 to 58 ppm from 0 time to 25 wk of storage. During 25 wk of storage no considerable increase in sterol oxides was observed in the samples of chips fried in palm oil and sunflower oil. The chip samples fried in high-oleic sunflower oil had slightly higher levels of sterol oxides after 10 and 25 weeks of storage. In addition to the levels of individual sterol oxides, a new method for enrichment of phytosterol oxides from the unsaponifiables and full-scan mass spectra of various oxidation products of sitosterol and campesterol are reported in this paper. Part of the results were presented at the 86th Annual Meeting of the AOCS, May 7–11, 1995, San Antonio, TX.     

植物油供需市场

概述了印度植物油市场状况,从大豆油、菜籽油和棕榈油市场供需方面深入地进行了分析。重点对棕榈油市场进行了剖析,并对其市场供需状况进行了分析和预测。     

Studies on phytosterol oxides. II: Content in some vegetable oils and in French fries prepared in these oils

Hydrogenated rapeseed oil/palm oil blend, sunflower oil and high-oleic sunflower oil, and French fries fried in these oils were assessed for contents of sterol oxidation products. Different oxidation products of phytosterols (7α- and 7β-hydroxy-sito-and campesterol, 7-ketosito- and 7-ketocampesterol, 5α,6α-epoxy-sito- and campesterol, 5β,6β-epoxy-sito-and campesterol, dihydroxysitosterol and dihydroxycampesterol) were identified and quantiated by gas chromatography (GC) and GC-mass spectroscopy. Rapeseed oil/palm oil blend contained 41 ppm total sterol oxides before frying operations. After two days of frying, this level was increased to 60 ppm. Sunflower oil and high-oleic sunflower oil had 40 and 46 ppm sterol oxides, respectively, before frying operations. After two days of frying operations, these levels increased to 57 and 56 ppm, respectively. In addition to campesterol and sitosterol oxidation products, small amounts of 7α- and 7β-hydroxystigmasterol were detected in the oil samples. Total sterol oxides in the lipids of French fries fried at 200°C in rapeseed oil/palm oil blend, sunflower oil, and high-oleic sunflower oil were 32, 37, and 54 ppm, respectively. The levels of total oxidized sterols, calculated per g sample, ranged from 2.4 to 4.0 ppm. In addition to the content of phytosterol oxides, full scan mass spectra of several oxidation products of stigmasterol are reported for the first time. Part of these results were presented at the 86th Annual Meeting of the AOCS, May 7–11, 1995, San Antonio, TX.     

Polymorphic stability of hydrogenated palm oleins in dilutions with unhydrogenated liquid oils

Palm oil was hydrogenated under selective and nonselective conditions. Some of the hydrogenated samples were chosen for their physical characteristics and were diluted with 70% sunflower oil. A commercial hydrogenated palm olein (H-olein) was diluted up to 80% with canola oil. The diluted mixtures were evaluated for their polymorphic β' stability by a temperature-cycling procedure between 4 and 20°C. All of the mixtures were stable in the β' form. The dropping point and solid fat content of the mixtures were compared with those of commercial soft and stick margarines. Soft margarines can be prepared from mixtures of 20% H-olein and 80% unhydrogenated oil, and stick margarines from 40% H-olein and 60% liquid oil. If canola oil is the liquid oil, the saturated content in the soft formulation is 13% and that of a stick formulation 17%.     

不同植物油脂在近临界水中水解反应动力学的比较

系统地测定了压力10 MPa、温度170℃～240℃范围内橄榄油、花生油、大豆油、红花油等植物油脂在近临界水中无催化水解反应动力学数据。实验结果表明,近临界水中油脂水解反应是一个典型的自催化反应,采用二级自催化反应动力学模型对动力学数据进行了拟合,得到了橄榄油、花生油、大豆油、红花油等四种植物油脂的水解反应活化能分别为41.8 kJ/mol、37.3 kJ/mol、37.7 kJ/mol、31.2 kJ/mol。油脂水解活化能与其碘价密切相关,随着油脂碘价的增加,水解活化能逐渐降低。     

Characterization of stored regular and low-linolenic canola oils at different levels of consumer acceptance

A ten-member trained sensory panel evaluated regular (RCO) and low-linolenic (LLCO) canola oils that had been stored at 60°C to four levels of consumer acceptance identified in a prior study. These levels were 70, 60, 50, and 40% acceptance for RCO and 80, 70, 60, and 50% acceptance LLCO. Painty odor intensity increased as consumer acceptance decreased. This same trend was found for chemical measurements of peroxide values, total volatiles, total carbonyls, unsaturated carbonyls, and dienals. These chemical indices were significantly correlated with each other, suggesting that they can be used to monitor related changes in oil quality with respect to lipid oxidation. Values for 19 individual volatiles at each consumer acceptance level were also reported. The data collected in this study provide chemical and sensory characterization of stored RCO and LLCO at distinct levels of consumer acceptance. Presented in part at the 84th Annual Meeting of the American Oil Chemists’ Society, Atlanta, Georgia, May 8–12, 1994.     

Lubrication properties of trimethylolpropane esters based on palm oil and palm kernel oils

Due to the global drive towards biodegradable products, trimethylolpropane [2‐ethyl‐2‐(hydroxymethyl)‐1, 3‐propanediol] (TMP) esters based on palm and palm kernel oils were synthesized, their lubrication properties evaluated, and their potential as base stock for biodegradable lubricants assessed. Two types of TMP esters were considered: palm kernel (PKOTE) and palm oil (PPOTE) TMP esters, derived from palm oil and palm kernel methyl esters, respectively. Lubrication properties such as viscosity, viscosity index (VI) and pour point (PP) were determined according to methods of the American Society for Testing and Materials. Wear and friction properties were evaluated using a four‐ball test machine, while oxidative stability was studied with the Penn State Micro‐oxidation thin‐film test. High VI ranges between 170 to 200 were recorded for these base stocks. PP were relatively high, between 4 to —1 °C, but were improved to at least —33 °C in high oleic palm oil TMP esters. The effects of chemical structure and impurities on wear properties and oxidative stability were also studied. The presence of methyl esters was found to improve wear, but hydroxyl groups in mono‐ and diesters had negative effects at high concentrations. Differences in chemical structures of PKOTE and PPOTE were shown to affect friction and wear results. Both base fluids exhibit oxidative stability comparable to other high oleic base fluids.     

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.     

An integrated process of catalytic hydrolysis and membrane separation for fatty acids production from lard oil

An integrated process of catalytic hydrolysis and membrane separation was developed for fatty acids (FAs) production from lard oil. Both sulphonated cation exchange resin (SCER) and 0.98 g/g H₂SO₄ as catalysts were used to produce fatty acids (FAs) from lard oil by three‐step hydrolysis, respectively. Simultaneously, polyethersulphone (PES) ultrafiltration membrane was employed to separate glycerol and water from the products. The hydrophilicity and morphology of the pristine and used PES membranes were characterized by contact angle measurement and field‐emission scanning electronic microscopy, respectively. The final optimal yields of FAs obtained by SCER and H₂SO₄ catalysis at 100 °C and atmospheric pressure were 85.6 % at 16.0 h of operation and 94.5 % at 18.0 h of operation, respectively. Furthermore, the yield of FAs obtained from an integrated process of SCER‐catalyzed hydrolysis and membrane separation achieved up to 99.9 % at 10.0 h, 90 °C, and operating pressure of 100 kPa.

     

Densities of vegetable oils and fatty acids

Complete data for density as a function of temperature have been measured for a number of vegetable oils (crambe, rapeseed, corn, soybean, milkweed, coconut, lesquerella), as well as eight fatty acids in the range C₉ to C₂₂ at temperatures from above their melting points to 110°C (230°F). The specific gravity and density measurements were performed according to American Society for Testing and Materials (ASTM) standard test methods D 368, D 891 and D 1298 for hydrometers and a modified ASTM D 369 and D 891 for pycnometers. Correlation constants, based on the experimental data, are presented for calculating the density of fatty acids and vegetable oils in the range of temperature from 24°C (75°F) or the melting point of the substance, to 110°C (230°F). The constants are valuable for designing or evaluating such chemical process equipment as heat exchangers, reactors, process piping and storage tanks. Estimated density of fatty acids by a modified Rackett equation is also presented.     

The study of natural epoxy oils and epoxidized vegetable oils by13C nuclear magnetic resonance spectroscopy

The¹³C nuclear magnetic resonance spectra ofVernonia galamensis seed oil and of epoxidized palm super olein, soybean oil and linseed oil have been recorded and interpreted. The chemical shifts of the major signals are assigned and semi-quantitative results are derived. The spectroscopic procedure provides a useful method of analyzing oils that contain epoxy acids. The epoxide function differs from a double bond in its influence on the chemical shifts of nearby carbon atoms.     

Effect of vacuum frying on the oxidative stability of oils

The purpose of this study was to evaluate frying oil quality with different assessment methods during vacuum frying of carrot slices. In six consecutive days, palm oil, lard, and soybean oil were fried under vacuum at 105°C for 20 min each hour in an 8-h shift. Peroxide value, acid value, carbonyl value, total polar components, dielectric constant (Food Oil Sensor reading), viscosity, and fatty acid composition were used to evaluate the quality of these oils. Results showed that palm oil and lard possess greater thermal stability than soybean oil. The decrease in C_18:2/C_16:0 ratio was greater for soybean oil than the other two oils. Of the assessment methods used, peroxide value, carbonyl value, total polar components, and dielectric constant all showed good correlation with frying time and between each other. Viscosity was suitable to assess vacuum-fried lard and soybean oil, but not palm oil. The measurement of dielectric constant, on the other hand, appeared to be unsuitable to assess vacuum-fried soybean oil.     

The influence of chemical interesterification on the physicochemical properties of complex fat systems. 2. Morphology and polymorphism

Palm oil-soybean oil (POSBO) blends and lard-canola oil (LCO) blends were chemically interesterified with sodium methoxide. Changes in crystal morphology using polarized light microscopy and crystal polymorphic behavior using X-ray diffraction spectroscopy (XRD) were studied. Spherulitic crystalline particles, measuring 10–20 μm, were detected in palm oil (PO). These spherulitic particles were characterized by a dense core surrounded by a lower-density halo region. PO fat-crystal morphology was not greatly altered on addition of soybean oil (SBO), except for a gradual reduction in spherulite size as the amount of SBO in the blends was increased. Chemical interesterification (IE) did not alter PO or POSBO blend fat-crystal morphology significantly. Irregular particles and spherulites of different sizes and shapes were observed in lard, from small crystals to irregular, angular crystal aggregates. Changes in lard fat-crystal morphology due to the addition of canola oil (CO) were concentration-dependent. In general, spherulite diameter decreased with increasing CO addition. IE dramatically altered lard fat-crystal morphology—IE induced the formation of more symmetrical spherulitic crystalline particles, and the halo-to-core ratio was increased significantly. XRD spectroscopic analysis of POSBO blends revealed small changes in the long spacings of PO fat crystals with either blending or IE; all values were close to 45 ?. Short spacings of fat crystals in noninteresterified (NIE) POSBO blends suggested the predominance of β′ polymorphs. IE led to an increase in the proportion of the β polymorph in PO and POSBO blends. Long spacings of NIE lard fat crystals suggested the presence of a bilayer structure in their unit cells (45 ?). Dilution with ≥10% canola oil led to the appearance of a second reflection at 35 ?. β′ polymorphs were predominantly detected in NIE lard and NIE LCO blends. The β polymorph became more evident with increasing addition of CO. Fat crystals in IE lard and IE LCO blends displayed a single long-spacing reflection at 40 ?. IE of lard and LCO blends induced the formation of β polymorphs.