Synthesis of structured triglycerides from peanut oil with immobilized lipase

Structured triglycerides (ST) that contain medium- and long-chain fatty acids were synthesized by lipase-catalyzed interesterification between tricaprylin and peanut oil. To select appropriate enzymes, we investigated nine commercial lipase preparations for their ability to hydrolyze pure triglycerides as well as natural oils. Three microbial lipases from Rhizomucor miehei (RML), Candida sp. (CSL), and Chromobacterium viscosum (CVL) gave good results, and immobilized preparations were used in the interesterification. RML gave the highest yields of ST (73%, 40°C), although its hydrolytic activity toward triolein was low. As the temperature was raised to 50°C, the yield of ST increased to 79%. After 120 h reaction time, remaining activities were high for CSL (71%), moderate for CVL (48%), and low for RML (20%). Parts of this paper were presented as a poster at the Biochemical Engineering Conference IX, May 1995, Davos, Switzerland.     

Characterization of triacylglycerols in madeira laurel oil by HPLC-atmospheric pressure chemical ionization-MS

Madeira laurel oil was fractionated by liquid extraction combined with TLC, and TAGs were analyzed by HPLC coupled with atmospheric pressure chemical ionization-MS (APCI-MS). Eluted molecular species compositions of the eluted TAG in the complex natural mixture were determined by GC identification of FAME and byLC-atmospheric pressure chemical ionization (APCI)-MS analysis of the lipid. The APCI-MS spectra of most TAG exhibited [M+H]⁺ and [M−RCOO]⁺ ions, which defined the M.W. and the molecular association of fatty acyl residues, respectively. Despite the relatively high degree of saturation, with a saturated/unsaturated ratio of 0.70, no totally saturated TAG nor mixed asymmetric TAG with two saturated FA (SSM or SSU, where S is saturated, M is monounsaturated, and U is unsaturated) were found. This type of molecular structure provides a possible explanation for the relatively low m.p. (12–15°C) and also the high oxidative resistance observed.     

Enzyme-assisted aqueous extraction of peanut oil

Enzyme-assisted aqueous extraction of oil from oilseeds is a relatively recent technique. In the present study, peanut oil was extracted under optimized aqueous extraction conditions using Protizyme^™, which is predominantly a mixture of acid, neutral, and alkaline proteases. The optimal conditions were: enzyme concentration of 2.5% (w/w) in 10 g of peanut seeds, pH 4.0, 40°C, and 18 h incubation with constant shaking at 80 rpm. Centrifuging the mixture at 18,000 × g for 20 min separated the oil with a recovery of 86–92%. The merits of this process over existing solvent extraction and/or mechanical pressing methods are discussed.     

Method for analysis of TAG formed by reaction of fish oil with hydrogenated soybean oil

An HPLC method was developed for analysis of the TAG formed during interesterification of a fish oil rich in DHA residues and of a fully hydrogenated soybean oil. TAG species were separated using a three-phase (acetone/acetonitrile/chloroform) solvent system. Peak identities were assigned on the basis of a multiple linear regression analysis by using factors such as carbon number, number of double bonds, and number of PUFA in the molecule as predictors for TAG retention time. Good agreement between experimental and predicted retention times was observed when the effect of the PUFA was separated in the regression model from that of the monounsaturated FA. In addition, the new method permits one to determine tristearin at concentrations up to 3 mg/mL without encountering the problem of partial retention of this TAG in the column that was observed when chloroform is not incorporated in the mobile phase.     

Retarding autoxidation in raw peanut oil by addition of water

Addition of water at levels of 0.25 to 1.00% (wt/vol) to raw peanut oil inhibited the formation of peroxides in the oil. The free fatty acid content of oils to which water had been added also did not increase appreciably compared to a control oil. To improve the stability of the oil, a moisture content of 0.2%, which is about ten times higher than the Brunauer-Emmett-Teller monomolecular moisture content of the oil, has been suggested.     

Characterization of olive oil classes using a Chemsensor and pattern recognition techniques

Classification is an important component of food quality assurance, as methods to guarantee authenticity of food products are widely demanded by food producers, processors, consumers, and regulatory bodies. The objective of this work was to develop a rapid classification method in order to discriminate virgin olive oil, olive oil, and „orujo” olive oil, the prices of which differ dramatically in the market on a ccount of the high quality level of the former. For these purposes, new ChemSensor equipment that combines a headspace autosampler with a mass-selective detector and Pirouette data evaluation software was used. To take into account the large number of samples analyzed (50 samples repeated 10 times), as well as the wide interval of m/z ratios scanned (41–170), chemometric approaches were necessary. Cluster analysis, principal component analysis, K-nearest neighbors, and soft independent modeling of class analogy (SIMCA) were applied to model the different oil classes. The results indicated good classification and prediction abilities, with SIMCA affording the best results (viz. 97% specificity).     

Stereospecific analysis of TAG from sunflower seed oil

Stereospecific analysis of TAG from a sunflower seed oil of Tunisian origin was performed. The TAG were first fractionated according to chain length and degree of unsaturation by RP-HPLC. The four major diacid- and triacid-TAG fractions were palmitoyldilinoleoyl-glycerol, dioleoyllinoleoylglycerol, oleoyldilinoleoylglycerol, and palmitoyloleoyl-linoleoyl-glycerol, amounting to 7.2, 16.6, 29.5, and 12 mol%, respectively. The TAG of the four fractions were individually submitted to stereospecific analysis, using a Grignard-based partial deacylation, separation of sn-1,2(2,3)-DAG from sn-1,3-DAG by boric acid-impregnated silica gel TLC plates, conversion of the sn-1,2(2,3)-DAG to their 3,5-dinitrophenylurethane (DNPU) derivatives, fractionation of DNPU derivatives by RP-HPLC, resolution of the DNPU-DAG by HPLC on a chiral column, transmethylation of each sn-DNPU-DAG fraction, and analysis of the resulting FAME by GC. The data obtained were used to determine the triacyl-sn-glycerol composition of the main TAG of the oil. Fifteen triacyl-sn-glycerols were identified and quantified, representing, along with the monoacid-TAG, trilinoleoylglycerol and trioleoylglycerol, more than 90% of the total oil TAG. The two major triacyl-sn-glycerols were trilinoleoyl-glycerol and 1-linoleoyl-2-linoleoyl-3-oleoyl-glycerol (18.6 and 18.5% of the total, respectively). Results clearly identified linoleic acid as the major FA at the sn-2 position, whereas oleic and palmitic acids were the major FA at the sn-3 position. The sn-1 position was occupied to nearly the same extent by linoleic and oleic acids, and to a greater extent by palmitic acid, which was practically absent at the sn-2 position.     

Enrichment of phospholipids from neutral lipids in peanut oil by high-performance liquid chromatography

Phospholipids from crude peanut oil were enriched on a 2-cm silica column and subsequently separated from neutral lipids within the chromatographic system without prior concentration. Hexane effectively removed the bulk neutral lipids, leaving the adsorbed phospholipids on the silica precolumn. Individual phospholipids were separated from the remaining neutral lipids and from each other by using two mixed solvents and a gradient program. This method separates the phospholipids in approximately 27 min after the desired enrichment level has been reached. The research reported in this paper was a cooperative effort by the Agricultural Research Service of the United States Department of Agriculture and the North Carolina Agricultural Research Service, Raleigh, NC 27695-7625.     

Antioxidant constituents of peanut oil

The components responsible for increased stability of raw peanut oil at a high relative humidity (RH) of 91% were examined in peanut oil and methyl linoleate systems. Of the constituents, the native gums, which were mostly phospholipids and glycolipids, showed increased antioxidant activity at 91% RH. The isolated components of the gums, namely phospholipids and glycolipids, were prooxidant individually or in combination. Tocopherols did not show increased antioxidant activity at 91% RH.     

Rapid MS method for analysis of cocoa butter TAG

Ammonia negative ion CI-MS was applied to analyze the M.W. distribution and regioisomeric structure of TAG in cocoa butter and in cocoa butter equivalents. The M.W. distribution results obtained for a reference cocoa butter were consistent with corresponding results obtained in an intercomparison study by chromatographic methods. Minor but statistically significant differences were observed when proportions of the three major M.W. species (52∶1, 54∶1, and 50∶1; acyl carbon number/number of double bonds) in a mixture of nine cocoa butters and in mixtures containing 10 or 20% (w/w) of specific cocoa butter equivalents were compared. Tandem MS was used to determine the regioisomeric structure of the three major TAG M.W. species in cocoa butter and in cocoa butter equivalents. The regioisomeric structure in cocoa butter and in all the equivalents analyzed were nearly identical, oleic acid being located primarily in the sn-2 position. These results cannot be exploited in detecting added foreign fats in this case. However, the present study shows that useful TAG composition data, which may be used to detect foreign fats in cocoa butter by applying chemometric data evaluation, can be obtained by MS in a significantly shorter time compared to chromatographic methods.     

LCMS-MS法检测小麦粉中12种农药的残留

[目的]建立吡蚜酮、氧乐果、敌百虫、啶虫脒、乐果、甲磺隆、氯磺隆、多效唑、嘧菌环胺、烯唑醇、喹硫磷、甲氨基阿维菌素苯甲酸盐12种农药在小麦中的液相色谱-三重串联质谱同时检测和确证方法.[方法]小麦样品经粉碎后,0.1％(体积分数)冰醋酸-乙腈提取,NH2氨基柱填料和石墨化炭黑固相分散净化,含0.1％甲酸的乙腈水混合液定容过微孔滤膜后用液相色谱串联四级杆质谱联用仪LC-MS-MS检测和确证.[结果]方法在10～1000μg/L范围内保持良好的线性关系,相关系数大于0.99.12种农药在10、50、100 tg/kg添加水平的回收率和相对标准偏差的数据表明:12种农药的回收率均为72％～107％,RSD为1.5％～13.3％,回收率和相对标准偏差达到相应标准的要求.[结论]该方法快速、灵敏、适用广泛、操作简便及污染小,适用于小麦籽粒中农药残留的定性定量分析.     

Mass spectrometric characterization ofVernonia galamensis oil

Vernonia galamensis seed oil is a natural source of epoxidized triacylglycerols, which consist of 52% trivernolin and a mixture of other triacylglycerols. Epoxidized oils are used for industrial applications, such as coatings and plastic formulations. To determine the major molecular species present in Vernonia oil, desorption chemical ionization/mass spectrometry and mass spectrometry/mass spectrometry were used to determine its glyceride composition. Seven triacylglycerols predominated: divernoloylarachidonate, trivernolin, divernoloylstearate, divernoloyloleate, divernoloyllinoleate, dilinolenoyl vernolate and divernoloylpalmitate.     

Study on the aluminium chloride-modification for heavy fraction of light diesel oil using tandem mass spectrometry

Tandem mass spectrometry was used to follow the low temperature catalytic modification of the diesel oil heavy fraction in the presence of aluminium chloride. The molecular distribution from chemical ionization mass spectroscopy (c.i.m.s.) of raw feedstock ranges from 150 to 250, with an average molecular weight of 219 (v.p.o.). That of the finally modified pitch ranges from 200 to 800, mainly concentrated between 200 and 500 with v.p.o. molecular weight of 452. The m.s.-m.s. fragmentation analysis of three dominant, characteristic protonated parent ions m/z 207, 373, 385, showed ethyl phenanthrenes (-anthracenes), dimers from phenanthrene (anthracene) and C₁-phenanthrene with substantial naphthenic groups, dimers from C₁-phenanthrenes and copolymers from hexahydropyrene with phenanthrene, chrysene with C₂-naphthalene, etc., respectively, to be the main structural types of these parent mass numbers. This modified pitch material, with a characteristic low degree of condensation and extensive naphthenic structures proved to be suitable for transformation into mesophase pitch with high fluidity and a large domain-type anisotropic texture.     

Determination of molecular species of oil triacylglycerols by reversed-phase and chiral-phase high-performance liquid chromatography

A method is described for the determination of molecular species of oil triacylglycerols. The method is based on the analytical separation of the enantiomericsn-1,2-andsn-2,3-diacylglycerols, derived from triacylglycerols, by high-performance liquid-chromatography (HPLC) on a chiral column containing N-(R)-1-(α-naphthyl)ethylaminocarbonyl-(S)-valinecarbonyl-(S)-valine as stationary phase. Model triacyl-glycerol molecules comprising three known fatty acids were isolated from peanut oil and cottonseed oil by a combination of argentation-TLC and reversed-phase HPLC and submitted to partial chemical deacylation. The derivedsn-1,2(2,3)-diacylglycerols were analyzed and fractionated as 3,5-dinitrophenyl urethane derivatives by reversed-phase HPLC according to chainlength and unsaturation. From thesn-1,2(2,3)-diacylglycerol composition and the diacylglycerolsn-1,2-andsn-2,3-enantiomer composition, the individual molecular species of four peanut oil triacylglycerols and one cottonseed oil triacylglycerol were identified and quantitated. The method can be applied to triacylglycerols of any other oil or fat.     

LC-electrospray ionization and LC-FABMS study of flavonoid glycosides extracted from peanut meal

HPLC, HPLC-electrospray ionization (LC-ESI), and LC-FABMS were used to characterize flavonoid glycosides in the methanol extract from peanut meal. Five isoflavones, diadzin, glycitin, genistin, daidzein, and genistein, were separated by HPLC and characterized by comparison with known standards using ESI-MS. The flavonoid methylquercetin (rhamnetin) was present in the methanol extract from peanuts and identified by ESI-MS. Four other flavonoids, two quercetin diglycosides, one quercetin monoglucoside, and isorhamnetin glucoside, were found to be present in the methanol extract based on their reversed-phase elution pattern, mass ions, and fragment ions using flow-FABMS.     

Fractionation of the triacylglycerols of lipase-modified butter oil

Triacylglycerols (TGs) of lipase-modified butter oil were separated into saturated, monoene, diene and triene fractions on ap-propylbenzene sulfonic acid solid-phase extraction column loaded with silver ions. Fatty acid analysis of the fractions showed that the amounts of saturated TGs (98.4 mol%) and monoene TGs (26.0 mol%) in the saturated and monoene fractions, respectively, were close to the theoretical amounts of TGs in pure fractions. The column method provides a useful alternative to AgNO₃-thin-layer chromatography as a means of separating the TGs of butterfat and producing relatively pure TG fractions for further analysis by gas chromatography (GC) or GC-mass spectrometry.     

液相色谱和液质联用技术在水产品安全检测中的应用

介绍了近年来高效液相色谱和色质联用技术在水产品安全检测中的应用进展。本文介绍了高效液相色谱和液质联用技术(LC-MS)的特点,及其在水产品中渔药、抗生素及赤潮藻毒素类有毒有害物质残留分析中的应用。     

Fast quantitative analysis of soybean oil in olive oil by high-temperature capillary gas chromatography

Analysis of glycerides has always been of great interest, especially to the food industry. Several methods have been developed, and attempts to improve analytical conditions are prevalent. Among these methods, high-temperature capillary gas chromatography has received particular consideration because it rapidly provides a glyceride profile. In this paper, we discuss a method to identify and quantitate mixtures of olive and soybean oils with the intention of verifying the latter as an adulterant of olive oils. The contamination of olive oil with soybean oil was detected by the presence of the triglyceride trilinolein, which does not exist in pure olive oil, although it is abundant in soybean oil. A calibration curve was constructed with several levels of contamination, and the lowest amount of detectable soybean oil was determined to be 4%.     

Assessment of olive oil adulteration by reversed-phase high-performance liquid chromatography/amperometric detection of tocopherols and tocotrienols

A method involving reversed-phase high-performance liquid chromatography with amperometric detection has been developed for the analysis of tocopherols and tocotrienols in vegetable oils. The sample preparation avoids saponification. Recoveries of α-tocotrienol and γ-tocotrienol in extra virgin olive oil were 97.0 and 102.0%, respectively. No tocotrienols were detected in olive, hazelnut, sunflower, and soybean oils, whether virgin or refined. However, relatively high levels of tocotrienols were found in palm and grapeseed oils. This method could detect small quantities (1–2%) of palm and grapeseed oils in olive oil or in any tocotrienol-free vegetable oil and might, therefore, help assess authenticity of vegetable oils.