Mixtures Of Triacylglycerols Research Articles

Enzymatic synthesis of medium‐chain triacylglycerols by alcoholysis and interesterification of copra oil using a crude papain lipase preparation

AbstractWe have examined the possibility of producing analogs of medium‐chain triglycerides (MCT) from copra oil, i.e. a triacylglycerol mixture with a high content of medium‐chain fatty acid moieties (C6–C10). A two‐step enzymatic process was used in which copra triacylglycerols were first split with papain lipase by alcoholysis with an alkyl alcohol and then subjected to interesterification with the alkyl esters recovered using papain lipase. Effects of temperature, water activity content, substrate ratio, biocatalyst amount, and alcohol chain length were also investigated. On the one hand, the sn‐3 stereoselectivity of the lipase in the alcoholysis of copra oil with butanol has permitted a direct enrichment of caproic, caprylic and capric moieties in the synthesized butyl esters. Thus, in the batch reactor, the reaction led to about 31% conversion of the oil after 24 h, and the content of C6–C10 acids in the synthesized esters increased from about 16% in the starting oil to almost 42%. A similar enzymatic alcoholysis in a packed‐bed column bioreactor gave 31% conversion of the oil after 120 min of reactor residence time. The reaction was also very selective because the C6–C10 fatty acyl groups represented about half of the newly formed butyl esters, whereas they accounted for only 16% of total fatty acids in the starting oil. On the other hand, the transesterification of the alkyl esters recovered (highly enriched in C6–C10 fatty acyl groups) with native copra oil directly led to an increase in the content of MCT in the oil, from 18 mol‐% at the beginning of the reaction to 61 mol‐% of MCT after a time period of 72 h in the batch reactor.

Variations in the composition of acyl lipids and triacylglycerol molecular species of pumpkin seeds (Cucurbita spp.) following microwave treatment

AbstractWhole pumpkin seeds (Cucurbita spp.) of two cultivars were exposed to microwaves for 6, 12, 20 or 30 min at a frequency of 2450 MHz. The kernels were separated from the whole seeds, and were investigated not only for the different acyl lipids and their fatty acid compositions, but also for the molecular species of triacylglycerols (TAGs). A modified argentation TLC procedure, developed to optimize the separation of the complex mixture of total TAGs, provided 11 different groups of TAGs, based on both the degree of unsaturation and the chain‐length of fatty acid groups. With a few exceptions, dioleopalmitin (5.8–18.8 wt‐%), dipalmitolinolein (8.1–8.8 wt‐%), triolein (6.3–20.5 wt‐%), palmitoleolinolein (15.0–16.1 wt‐%), dioleolinolein (16.7–23.0 wt‐%), dilinoleopalmitin (4.6–15.4 wt‐%) and dilinoleolein (6.7–19.4 wt‐%) were the main TAG components. When pumpkin seeds were microwaved for 20 min or more, significant differences (p <0.05) occurred in the acyl lipids as well as their fatty acid distributions with a few exceptions. Therefore, microwave roasting caused a significant decrease (p <0.05), not only in TAGs molecular species containing more than 4 double bonds, but also in the amounts of diene species present in triacylglycerols. These results contribute to the study of the functional properties of pumpkin seed products.

Determination of the fatty acid profile by 1H‐NMR spectroscopy

AbstractThe common unsaturated fatty acids present in many vegetable oils (oleic, linoleic and linolenic acids) can be quantitated by 1H‐nuclear magnetic resonance spectroscopy (1H‐NMR). A key feature is that the signals of the terminal methyl group of linolenic acid are shifted downfield from the corresponding signals in the other fatty acids, permitting their separate integration and quantitation of linolenic acid. Then, using the integration values of the signals of the allylic and bis‐allylic protons, oleic and linoleic acids can be quantitated. The procedure was verified for mixtures of triacylglycerols (vegetable oils) and methyl esters of oleic, linoleic and linolenic acids as well as palmitic and stearic acids. Generally, the NMR (400 MHz) results were in good agreement with gas chromatographic (GC) analyses. As the present 1H‐NMR‐based procedure can be applied to neat vegetable oils, the preparation of derivatives for GC would be unnecessary. The present method is extended to quantitating saturated (palmitic and stearic) acids, although in this case the results deviate more strongly from actual values and GC analyses. Alternatives to the iodine value (allylic position equivalents and bis‐allylic position equivalents) can be derived directly from the integration values of the allylic and bis‐allylic protons.

Analysis of regioisomers of short-chain triacylglycerols by normal phase liquid chromatography–electrospray tandem mass spectrometry

The regiospecific distribution of short-chain fatty acids in triacylglycerols (TAGs) influences their physico-chemical, nutritional, and organoleptic properties. This study demonstrates the applicability of normal phase HPLC with positive electrospray ionization mass spectrometry for the identification and structural analysis of regioisomers of short-chain triacylglycerols in nine interesterified mixtures of monoacid triacylglycerols. The finding that only one type of triacylglycerol adduct ion was formed without fragmentation or with minimal fragmentation was critical for liquid chromatography electrospray mass spectrometric quantification and identification of molecular species of TAGs. In the product ion electrospray tandem mass spectrometry, the 4–11 times lower abundance of the ion formed by cleavage of fatty acid from the secondary position relative to that formed by cleavage from the primary positions provided solid basis for differentiation between regioisomers of mono- and dibutyrates. Although the respective differences were lower, mono- and dicaproate regioisomers could be differentiated despite their incomplete separation. The tandem mass spectra of the short-chain triacylglycerols containing three different acyl groups revealed that the regioisomer having the shortest acyl chain in the secondary position, eluted in the first peak. The mixture of the other two regioisomers, where the shortest acyl chain was located in the primary positions, eluted in the second peak. In one instance only did the tandem mass spectra allow to differentiate between the reverse isomers eluting in the second peak. An effective chromatographic resolution of butyrate triacylglycerols and the linear relationship between the molar and area ratios of analyte and standard, enabled the mass spectrometric quantification of their regioisomers.

Detection of Adulteration in Olive Oils Using Triacylglycerols Compositions by High Temperature Gas Chromatography

Department of Chemistry, Seoul Women's University, Seoul 139-774, KoreaReceived January 3, 2003Key Words : Vegetable oils, Triacylglycerol, High temperature gas chromatography, AdulterationEdible vegetable oils are a valuable component of a fullymature seed due to their relatively high caloric value, and aremainly the mixtures of triacylglycerols (TG), with differentconcentration levels.

Synthesis and analysis of symmetrical and nonsymmetrical disaturated/monounsaturated triacylglycerols.

Symmetrical disaturated triacylglycerols of the structure SUS, where S is stearic acid (18:0) and U is an unsaturated fatty acid, either oleic (O; 9cis-18:1), linoleic (L; 9cis,12cis-18:2), or linolenic (Ln; 9cis,12cis,15cis-18:3), are important components providing functionality to interesterified fat blends and structurally modified oils. Nonsymmetrical triacylglycerols of the structure SSU can significantly change melting point and solid fat content profiles. To characterize the physical properties of pure and symmetrical and nonsymmetrical triacylglycerol mixtures, the same reaction sequence has been used to prepare multigram quantities of triacylglycerols SUS and SSU. Tristearin was converted to a mixture of mono-, di-, and triacylglycerols, and the 1,3- and 1,2-diacylglycerol fraction was isolated by silica column chromatography. The 1,3-diacylglycerols were removed by crystallization from acetone and esterified with the appropriate fatty acid to form the symmetrical triacylglycerols with >99% SUS structure. The more difficult to obtain 1,2-diacylglycerols were prepared by esterification of the enriched 1,2-diacylglycerol fraction (80-86% 1,2-diacylglycerols) remaining after removal of much of the 1,3-isomer by crystallization, but silver resin or silver nitrate impregnated silica gel chromatography was required to isolate the nonsymmetrical triacylglycerols. SSL and SSLn were prepared in purities of >98% by this procedure, but not SSO. Silver ion HPLC was found to be as accurate as, and more rapid than, lipolysis/gas chromatography for the determination of the isomeric purities of the synthesized triacylglycerols.

A Novel Method for Preservation of Labile Lipid Samples at Ambient Temperature with Oxygen Absorber

A novel method for preserving labile lipid samples at ambient temperature was developed with a commercially available oxygen absorber. In order to optimize the preservation conditions, the changes in the fatty acid composition of a triacylglycerol mixture during storage were determined by thermally assisted hydrolysis and methylation gas chromatography in the presence of trimethylsulfonium hydroxide. The polyunsaturated fatty acid (PUFA) components of the sample proved to degrade during preservation at room temperature through autoxidation induced by the trace amount of residual oxygen in a plastic bag for storage even coexisting with the oxygen absorber. On the other hand, once the lipid sample in the plastic bag with the oxygen absorber was subjected to 7 days “pretreatment” in a refrigerator at about 2°C, the PUFA components of the lipid sample in the bag were kept almost completely unchanged during further preservation at room temperature for at least four weeks. The observed results indicated that the residual oxygen in the plastic bag was sufficiently eliminated by the oxygen absorber during the “pretreatment” at about 2°C. Therefore, the labile lipid samples can be preserved at room temperature for a long time without deterioration by using oxygen absorber combined with the appropriate “pretreatment” storage in chilled conditions for a certain period. Moreover, reliable transportation of various biomaterial samples to a distant laboratory is able to be carried out conveniently at ambient temperature by this novel storing method without utilizing any special freezing system.

Analysis of conjugated linoleic acid-enriched triacylglycerol mixtures by isocratic silver-ion high-performance liquid chromatography

Silver-ion HPLC (Ag-HPLC) was applied to the fractionation of a triacylglycerol (TAG) sample enriched (>80%) with conjugated linoleic acid (CLA). After conversion of the TAGs to fatty acid methyl esters using sodium methoxide in methanol, Ag-HPLC (dual-column; isocratic solvent system of 0.1% acetonitrile in hexane; UV detection at 233 nm) was used to determine the CLA isomer distribution (50:50 mixture of 9c,11t- and 10t,12c-18:2). Three or four Ag-HPLC columns connected in series (0.6–1.0% acetonitrile in hexane as solvent; UV detection at 206 nm) were used to analyze the sample in TAG form. Elution times for CLA-enriched TAGs averaged 30 min or less. Isocratic solvent conditions were used to eliminate the solvent equilibration times (often 30 min or more) required between sample injections when solvent programming is used. The ratio of TAGs containing three vs. only two CLA molecules was found to be approximately 3 to 1. Ag-HPLC has thus been shown to be a useful method for rapidly analyzing not only CLA isomers as esters, but also in the TAG form.

Host-recognizing kairomones for parasitic wasp, Anisopteromalus calandrae, from larvae of azuki bean weevil, Callosobruchus chinensis.

Host-recognizing kairomones for the stinging behavior of the parasitic wasp, Anisopteromalus calandrae, were identified on host azuki bean weevil larvae, Callosobruchus chinensis (L.). The kairomones were extracted with acetone from Chinese green beans, from which emerged wasps and host weevils had been removed. The kairomones are a mixture of triacylglycerols and fatty acids, each of which is separately active, and with no observable synergistic effect between them. These compounds are known to be constituents of an oviposition-marking pheromone of host azuki bean weevils. However, they differ from the previously reported saturated hydrocarbons and diacylglycerols of the kairomone that another parasitic wasp, Dinarmus basalis, uses for the host recognition of C. chinensis. Thus, A. calandrae and D. basalis selectively utilize different constituents of the oviposition-marking pheromone of C. chinensis as host-recognizing kairomones.

中鎖脂肪酸を含むランダムエステル交換した油脂と物理的に混合した油脂のラットに対する栄養効果

Examination was made of the effects of edible oils containing medium-chain fatty acids (MCFA) on the body fat weight and blood lipid concentrations of rats fed a mixture of randomly interesterified rapeseed oil (87%) and medium-chain triacylglycerols (13%) (MLCT), and a physical mixture of rapeseed oil (87%) and medium-chain triacylglycerols (13%) (MIX). Wistar male rats were randomly divided into three groups and fed diets containing 7% rapeseed oil, MLCT and MIX for 6 weeks. Although the body fat weight and blood cholesterol concentration of rats fed MLCT and MIX diets were significantly lower than those of rapeseed oil diet, those of rats fed MLCT and MIX diets were not significantly different. The result suggests that the lowering effects of MCFA in the diet on body fat accumulation and blood cholesterol concentration in rats are similar to those caused by MLCT and MIX. It is of particular interest that the effective suppression of body fat accumulation in rats has been observed in the diet with a relatively small amount of MCFA (0.9% in experimental diet) when it is compared with the amounts of MLCT and MIX in diets.

A new 75% diphenyl, 25% dimethyl-polysiloxane coated on fused silica capillary columns for high temperature gas chromatography

The three 75% phenyl, 25% methyl-polysiloxanes OV-25, PS162, and a new laboratory-made polymer called SOP-75 were coated on fused silica capillary columns and tested in high temperature gas chromatography. The synthesis of SOP-75 as a methoxy-terminated, symmetrically substituted 75% diphenyl, 25% dimethyl-polysiloxane is reported. For better comparison the polymers were characterized by 1H and 29Si nuclear magnetic resonance spectroscopy. The coated fused silica capillary columns were evaluated in respect of their selectivity, inertness, separation efficiency, and bleeding. The three stationary phases exhibited similar selectivity and high inertness up to 400 or 410°C. A minimum allowable operating temperature was established, since the capillaries offered insufficient separation efficiency at low temperatures. SOP-75 offered the best chromatographic properties with superior separation efficiency compared to PS126 and OV-25. A commercially available capillary column with similar polarity was used for comparison, where increased separation efficiency and inertness but also increased bleeding of SOP-75 were found. Improved separation of triacylglycerol mixtures was obtained due to the increased polarity and thermal stability of SOP-75. So far, SOP-75 is the polysiloxane with the highest phenyl content that has been successfully coated onto fused silica capillary columns for high temperature gas chromatography.

Viscosity estimation of triacylglycerols and of some vegetable oils, based on their triacylglycerol composition

AbstractThe experimentally determined kinematic viscosities of simple triacylglycerols [trilaurin, trimyristin (MMM), tripalmitin (PPP), tristearin (SSS), triolein (OOO), and trilinolein (LiLiLi) were correlated to a modified Andrade‐type equation. The constants for the modified equation were derived for each simple triacylglycerol. The method was also used to estimate the viscosity of mixed triacylglycerols [1,2‐dimyristoyl‐3‐palmitoyl (MMP), 1,2‐dioleoyl‐3‐palmitoyl (OOP), 1,2‐dimyristoyl‐3‐oleoyl (MMO), and 1,2‐dipalmitoyl‐3‐oleoyl (PPO)], binary triacylglycerol mixtures (PPO/OOP, PPP/SSS, and OOO/SSS of different portions), and three types of vegetable oils [refined, bleached, and deodorized palm oil; cocoa butter; and canola oil] by applying modified Kay’s rule utilizing the simple triacylglycerol constants derived earlier. In all cases, the estimated values for liquid viscosity were compared with experimental values determined in this work and with previous work from the literature. When applied to vegetable oils, the method requires knowledge of their triacylglycerol composition. Despite its simplicity, the method gives a reasonable estimate. The method may be used to predict the viscosity of different blends of vegetable oils, and the accuracy is expected to increase when more experimental data on simple triacylglycerols become available.

Lípidos estructurados obtenidos por interesterificación de las mezclas binarias y ternarias de las grasas de palma, semilla de palma y triglicéridos de cadena media

Structured lipids are modified triacylglycerols to alter the fatty acid composition and/or their distribution into the glycerol molecules, by using enzymatic or chemical methods. Some of them can be classified as functional foods or nutraceuticals because they are directly associated to the prevention and treatment of many diseases. The objectives of this paper were to obtain and to characterize structured lipids by chemical interesterification of binary and ternary mixtures of vegetable fats (palm and palm kernel) and medium chain triacylglycerols (Trigliceril CM). Ten samples consisting of three individual samples, three binary mixtures, and four ternary mixtures were studied. The fatty acid composition, solid fat content and consistency at the temperatures from 10oC to 35oC were analysed. A mathematical model of multiple regression of the special cubic type was applied, and from the significant coefficients triangular diagrams were confectioned, which indicate curves of levels. The results showed that the interactions between the three components were not significant. The solid fat content depended on the palm and palm kernel fats, and on the binary interactions between them. The negative coefficients for the interactions showed an antagonic effect, which is characteristic of eutectic interactions between fats.

Software (MSPECTRA) for automatic interpretation of triacylglycerol molecular mass distribution spectra and collision induced dissociation product ion spectra obtained by ammonia negative ion chemical ionization mass spectrometry.

Rapid analysis of molecular mass distributions of triacylglycerol (TAG) mixtures and regioisomeric structures of selected molecular mass species is possible using ammonia negative ion chemical ionization mass spectrometry utilizing sample introduction by direct exposure probe. However, interpretation of spectra and calculation of results is time consuming, thus lengthening the total analysis time. To facilitate result calculation a software package (MSPECTRA 1.3) was developed and applied to automatic processing of triacylglycerol molecular mass distribution spectra and collision induced dissociation (CID) product ion spectra. The program is capable of identifying triacylglycerol molecular mass species possessing different ACN:DB (acyl carbon number:number of double bonds) ratios on the basis of m/z values of [M - H](-) ions. In addition to such identification the program also corrects spectra for abundances of naturally occurring (13)C isotopes and calculates relative proportions of triacylglycerol molecular species in the analyzed samples. If several replicate spectra are processed simultaneously the program automatically calculates an average and standard deviation of relative proportions of molecular species. In the case of CID spectra the program identifies fatty acid fragment ions [RCO(2)](-) and the corresponding [M - H - RCO(2)H - 100](-) ions, and calculates the relative proportions of ions in both groups. These proportions are then used automatically to calculate the fatty acid combinations comprising the parent triacylglycerol molecule and the regiospecific positions of fatty acids. Processing of several replicate product ion spectra simultaneously produces averaged proportions of regioisomers comprising the parent triacylglycerol molecular species and the standard deviation of the analysis. The performance of the program was tested by analyzing triacylglycerol samples of human milk, human milk substitutes, human chylomicron and cocoa butter, and by comparing results obtained by automated processing of the data with manually calculated results.

Roasting influences on molecular species of triacylglycerols in sunflower seeds ( Helianthus annuus L.)

Sunflower seeds ( Helianthus annuus L.) were exposed to microwaves for 6, 12, 20 or 30 min at a frequency of 2450 MHz. The nucleoluses were separated from the seeds roasted in a domestic microwave oven. Molecular species and fatty acid distributions of triacylglycerols (TAGs) isolated from the total lipids in the nucleoluses were analysed by a combination of argentation thin-layer chromatography (TLC) and gas–liquid chromatography. A modified argentation TLC procedure, developed to optimise the separation of the complex mixture of total TAGs, provided 14 different groups of TAGs, based on both the degree of unsaturation and the total chain-length of fatty acid groups. Dilinoleolein (25–26.2%), trilinolein (14.4–17.7%), dilinoleostearin (15.1–15.8%), dioleolinolein (12.2–12.4%) and triolein (10.5–11.3%) were the main components during microwave roasting. Roasting for 20 min caused a significant decrease ( P<0.05) not only in molecular species containing more than four double bonds, but also in the amount of diene species present in TAGs.

Roasting influences on molecular species of triacylglycerols in sesame seeds (Sesamum indicum)

Sesame seeds were roasted at different temperatures (180–220 °C) using a domestic electric oven. Molecular species and fatty acid distributions of triacylglycerols (TAGs) isolated from total lipids in the sesame seeds were analysed by a combination of argentation thin-layer chromatography (TLC) and gas–liquid chromatography. A modified argentation TLC procedure, developed to optimise the separation of the complex mixture of total TAGs, provided 11 different groups of TAGs, based on both the degree of unsaturation and the total length of fatty acid groups. Fatty acid methyl ester analysis was performed to determine the composition of each zone. Eleven molecular species of TAGs were still detected in the sesame seeds following roasting treatment. Dilinoleolein (33.7–35.8%), palmitoleolinolein (20.3–22.8%), dioleolinolein (15.0–15.4%) and trilinolein (8.8–10.7%) were the main components during roasting. However, roasting for 10 min at 220 °C caused a significant decrease (P < 0.05) not only in molecular species containing more than four double bonds, but also in the amount of diene and triene species present in TAGs (with a few exceptions). These results suggest that no significant changes in molecular species or fatty acid distribution of TAGs would occur within 25 min of roasting at 180 °C, ensuring that a good-quality product would be attained. © 2000 Society of Chemical Industry

Lipase activity and fatty acid typoselectivities of plant extracts in hydrolysis and interesterification

AbstractLipase fatty acid typoselectivities of Euphorbia characias latex and commercially available crude preparation of bromelain were determined in the hydrolysis of homogeneous triacylglycerols (TAG) and natural TAG mixtures. Their activities were compared to a commercially available crude preparation of papain. Under optimal lipolysis conditions at pH 8.0 and 10 min of incubation time, maximal activities were observed at 45, 55, and 50°C, respectively, for E. characias latex, crude bromelain, and crude papain. Commercially available crude preparations of bromelain exhibited very poor hydrolysis activity. Latex from E. characias, which contained 340 mg of dried material per milliliter of fresh latex, exhibited a high lipase activity and a short‐chain fatty acid preference in the hydrolysis of homogeneous TAG. For all substrates, it showed a better activity than crude papain. Lipase fatty acid typoselectivities of crude bromelain and crude papain also were studied in interesterification reactions of tributyrin with a series of homogeneous TAG. Experiments showed that crude bromelain [water activity (Aw)∶ 0.21] had no activity in interesterification. Regarding reactions with crude papain (Aw∶ 0.55), yields of newly formed TAG decreased with increasing chain length of TAG, except for the reaction with trimargarin. For interesterification of tributyrin with unsaturated TAG, triolein reacted faster than polyunsaturated TAG. During these interesterification reactions, the proportion of new TAG with two butyroyl residues was higher than new TAG with only one butyroyl residue. This phenomenon was more pronounced for reactions with long‐chain TAG.

Roasting influences on molecular species of triacylglycerols in sesame seeds (Sesamum indicum)

Sesame seeds were roasted at different temperatures (180–220 °C) using a domestic electric oven. Molecular species and fatty acid distributions of triacylglycerols (TAGs) isolated from total lipids in the sesame seeds were analysed by a combination of argentation thin-layer chromatography (TLC) and gas–liquid chromatography. A modified argentation TLC procedure, developed to optimise the separation of the complex mixture of total TAGs, provided 11 different groups of TAGs, based on both the degree of unsaturation and the total length of fatty acid groups. Fatty acid methyl ester analysis was performed to determine the composition of each zone. Eleven molecular species of TAGs were still detected in the sesame seeds following roasting treatment. Dilinoleolein (33.7–35.8%), palmitoleolinolein (20.3–22.8%), dioleolinolein (15.0–15.4%) and trilinolein (8.8–10.7%) were the main components during roasting. However, roasting for 10 min at 220 °C caused a significant decrease (P < 0.05) not only in molecular species containing more than four double bonds, but also in the amount of diene and triene species present in TAGs (with a few exceptions). These results suggest that no significant changes in molecular species or fatty acid distribution of TAGs would occur within 25 min of roasting at 180 °C, ensuring that a good-quality product would be attained. © 2000 Society of Chemical Industry

Quantitative determination of triacylglycerol profile of structured lipid by capillary supercritical fluid chromatography and high‐temperature gas chromatography

AbstractTwo analytical methods have been developed for the qualitative and quantitative analyses of triacylglycerol profile of structured lipid (SL)‐containing medium‐chain and long‐chain fatty acids. Supercritical fluid chromatography (SFC) was used in the first method. The SL was dissolved in chloroform/methanol, 95:5 (vol/vol), and analyzed directly using a super‐critical fluid chromatograph equipped with temperature and density programming capabilities. No derivatization was required for sample preparation. An SB‐methyl‐100 capillary column (10 m, 100 µ i.d., 0.25 µ film thickness) was used for the separation of the triacylglycerol species and a flame‐ionization detector (FID) was used for the detection. Supercritical fluid carbon dioxide was used as the mobile phase. In the second method, the SL was hydrogenated to complete saturation prior to analysis using gas chromatography at high temperatures of up to 375°C. A DB‐5HT capillary column (30 m × 0.32 mm i.d., 0.1 µ film thickness) was used for the separation. FID was used for the detection and helium gas was used as mobile phase. The triacylglycerol species were separated and identified based on their equivalent carbon number (ECN), the total carbon number of the acyl side chains. A calibration curve was constructed using a triacylglycerol mixture containing known amounts of monoacyltriacylglycerol standard materials ranging from ECN 18 (trihexanoin) to ECN 66 (tridocosanoin). The novel triacylglycerol species, ECN 32–43, created by the interesterification of medium‐chain triacylglycerol (MCT) and long‐chain triacylglycerol (LCT) were separated and identified based on their retention times. These triacylglycerols, ECN 32–43, were absent in the physical mixture of MCT and LCT. The unique triacylglycerol specieis, ECN 32‐43, were therefore selected as the fingerprinting region for the qualitative identification of the SL. Quantitation of the novel triacylglycerol species in the SL was achieved by using the integrated peak area of the new species. Both methods were employed successfully to distinguish the physical mixture from the corresponding interesterified SL. Results generated by the two methods were compared and found to be in good agreement.

Microwave roasting and molecular species of triacylglycerols in soybean embryonic axes

AbstractEmbryonic axes were separated from soybeans roasted in a microwave oven. Molecular species and fatty acid distributions of triacylglycerols (TAG) isolated from total lipids in the embryonic axis were analyzed by a combination of argentation thin‐layer chromatography (TLC) and gas‐liquid chromatography. A modified argentation‐TLC procedure, developed to optimize the separation of the complex mixture of total TAG, provided 15 different groups of TAG, based on both the degree of unsaturation and the total length of fatty acid groups. Fatty acid methyl ester analysis was performed to determine the composition of each band. Fifteen molecular species of TAG were still found in the embryonic axes following roasting treatment. Microwave roasting for 6 min did not change the molecular species of the embryonic axis TAG (with a few exceptions), nor cause a loss of unsaturated fatty acids. However, microwave roasting for 12 min caused a significant decrease (P&lt;0.05) not only in molecular species containing more than four double bonds but also in the amount of diene and triene species present in TAG. These results suggest that no significant changes in molecular species or fatty acid distribution of TAG would occur within 6 min of microwave roasting, ensuring that a good quality product would be attained.