Pure Triacylglycerols Research Articles

Enzymatic Preparation, In-Depth Molecular Analysis, and In Vitro Digestion Simulation of Palmitoleic Acid (ω-7)-Enriched Fish Oil Triacylglycerols.

In this study, an enzymatic reaction was developed for synthesizing pure triacylglycerols (TAG) with a high content of palmitoleic acid (POA) using fish byproduct oil. The characteristics of synthesized structural TAGs rich in POA (POA-TAG) were analyzed in detail through ultrahigh-performance liquid chromatography Q Exactive orbitrap mass spectrometry. Optimal conditions were thoroughly investigated and determined for reaction systems, including the use of Lipozyme TL IM and Novozym 435, 15 wt % lipase loading, substrate mass ratio of 1:3, and water content of 2.5 and 0.5 wt %, respectively, resulting in yields of 67.50 and 67.45% for POA-TAG, respectively. Multivariate statistical analysis revealed that TAG 16:1/16:1/20:4, TAG 16:1/16:1/16:1, TAG 16:1/16:1/18:1, and TAG 16:0/16:1/18:1 were the main variables in Lipozyme TL IM and Novozym 435 enzyme-catalyzed products under different water content conditions. Finally, the fate of POA-TAG across the gastrointestinal tract was simulated using an in vitro digestion model. The results showed that the maximum release of free fatty acids and apparent rate constants were 71.44% and 0.0347 s-1, respectively, for POA-TAG lipids, and the physical and structural characteristics during digestion depended on their microenvironments. These findings provide a theoretical basis for studying the rational design of POA-structural lipids and exploring the nutritional and functional benefits of POA products.

The Effects of Dietary Fat Content and Triacylglycerol Structures on the Vitamin A Storage in Mice

ObjectivesVitamin A (VA, retinol) is a fat-soluble micronutrient that plays a variety of physiological functions form development to metabolism in humans and animals. The VA metabolism and storage can be affected by many different factors and high fat diet is one of them. As a major dietary lipid component, elevations of dietary intake of triacylglycerol (TAG) are associated with a variety of metabolic abnormalities. The alternation of TAG structure can change its physicochemical features or physiological impacts. We hypothesis that the structure of TAG fatty acyl position may affect the absorption and metabolism of VA in animal body.MethodsTwenty-seven 6-week-old male C57/BL6J mice at 6 weeks of age were randomly assigned to 3 dietary treatment groups, 1,2-dipalmitoyl-3-oleoylglycerol (PPO, 36% w/w chow diet), 1,3-dipalmitoyl-2-oleoylglycerol (POP, 36% w/w chow diet), and the chow diet control. Mice were fed with assigned diet; their food intake and body weight were measured and record daily. At the end of six-weeks treatment, mice were sacrificed, and liver tissue were collected. Dietary Vitamin A intake for each mouse was calculated based on their food intake and vitamin A content in the chow diet. Vitamin A storage in liver was determined by high performance liquid chromatography.ResultsThe PPO and POP diets have less VA per unit due to the presence of 36% of pure TAG, which diluted the VA content in the basal chew diet. Mice fed the chew diet had significantly higher VA intake after the adjustment of total net food intake, which is associated with higher usage and storage in the chow fed group than the PPO and POP. The mice in the PPO group have significantly higher VA intake, VA storage in the liver and VA usage than those in the POP group. However, the intake/storage ratio between two high fat diet group is not different.ConclusionsThe VA usage and storage amount are associated with its dietary intakes. The feeding of a high-fat diet reduces the usage of VA due to lowered amounts of VA intakes. The TAG structure can impact the VA intakes because of TAG on metabolism in mice fed a high-fat diet.Funding SourcesThe experiment was conducted at the University of Tennessee, PI Guoxun Chen (Nutrition science) and co-PI Toni Wang (Food Science).

Preparation of Highly Pure n‐3 PUFA‐Enriched Triacylglycerols by Two‐Step Enzymatic Reactions Combined with Molecular Distillation

AbstractHighly pure n‐3 polyunsaturated fatty acids (PUFA)‐enriched triacylglycerols (TAG) have attracted considerable attention due to their nutritional benefits and pharmacological effects. In this study, an alternative approach to the conventional method for the synthesis of highly pure n‐3 PUFA‐enriched TAG by using a multi‐step process was reported. First, glyceride mixtures were synthesized through Novozym 435 [Novozymes A/S (Bagsvaerd, Denmark)] catalyzed esterification of n‐3 PUFA‐enriched FA and glycerol. Second, partial glycerides in the resulting glyceride mixtures were hydrolyzed to FA by immobilized partial glycerides‐selective lipase from Malassezia globosa. The purity of TAG reached 99.84% under the optimized conditions: buffer solution of pH 6.0, water content of 100% (w/w, with respect to the oil mass), enzyme loading of 120 U/g (U/w, with respect to oil mass) and reaction temperature of 30 °C. During hydrolysis, the immobilized SMG1‐F278N exhibited good reusability and TAG purity of over 94% was maintained after being used for six cycles. Subsequently, purification of TAG was accomplished by molecular distillation at low temperature (150 °C) and highly pure (99.85%) TAG with 88.73% n‐3 PUFA was obtained. The final glyceride mixtures with low acid, peroxide and anisidine value were promising products for medical and dietetic purposes. Compared with the conventional one‐step synthesis of n‐3 PUFA‐enriched TAG by enzymatic esterification or glycerolysis or the two‐step method by combined transesterification and ethanolysis, this improved process allows for higher purity of n‐3 PUFA‐enriched TAG and significant reduction in reaction time.

Synthesis of Chlorinated and Non‐chlorinated Polyols from Model Cross‐Metathesis Modified Triacylglycerols

AbstractThree pure triacylglycerols (TAG) containing decenoic acid (D), and stearic acid (S), were hydroxylated into chlorinated and non‐chlorinated polyols and studied in detail. D is a fatty moiety that can result from the cross metathesis of small olefins with common vegetable oils such as soybean oil. A fundamental understanding relating chemical composition and derived structure, particularly the number and position of the hydroxyl groups, to physical properties was established allowing us to add some perspective to the growing body of knowledge on industrially relevant polyol and polyurethane systems produced with metathesis‐modified TAG (MTAG). The hydroxyl value, crystallization and melting behaviors, thermal degradation behavior of the polyols were directly related to their peculiar shortened and primary functionality inherited from the parent MTAG. The effect of regiochemistry on the physical properties of the polyols was investigated with the chromatography fractions of the trichlorinated polyol of propane‐1,2,3‐triyl tris(dec‐9‐enoate), giving an unhindered insight into the role of short and terminal functionality of MTAG polyols that will help select the optimal isomer composition for designer polyurethane materials.

A Novel Process for the Synthesis of Highly Pure n-3 Polyunsaturated Fatty Acid (PUFA)-Enriched Triglycerides by Combined Transesterification and Ethanolysis

In this study, a novel two-step enzymatic reaction was developed for the synthesis of highly pure triacylglycerols (TAGs) with a high content of n-3 polyunsaturated fatty acids (PUFAs). Glyceride mixtures were primarily synthesized by Novozym 435-catalyzed transesterification of glycerol and DHA/EPA-rich ethyl esters (EEs), followed by removal of partial glycerides, for the first time, by immobilized mono- and diacylglycerol lipase SMG1-F278N-catalyzed ethanolysis. TAG yield as high as 98.66% was achieved under the optimized conditions, and highly pure (98.75%) n-3 PUFA-enriched TAGs with 88.44% of n-3 PUFA was obtained after molecular distillation at lower temperature (140 °C). In addition, the EEs produced during ethanolysis had a FA composition similar to that of the original EEs, making them feasible for cyclic utilization. This was the first study reporting removal of partial glycerides by ethanolysis. Through ethanolysis, a higher purity product could be easily obtained at a relatively low temperature compared with the conventional high-temperature molecular distillation.

An efficient catalytic three‐step synthesis of enantiopure triacylglycerols

With the developments in high performance chromatography and mass spectrometry, the analysis of complex mixtures of closely related triacylglycerols has come within reach. Currently, however, the availability of chemically pure triacylglycerols is limited, mainly due to the lack of efficient synthetic methods that allow their synthesis. Here, we report an efficient and operationally simple three‐step synthesis of enantiopure triacylglycerols with yields ranging from 79 to 92%, that tolerates a broad range of saturated and unsaturated fatty acids. Furthermore, we developed an automated protocol, which might greatly facilitate the synthesis of triacylglycerol libraries.Practical applications: The analysis of the composition of milk fat and as analytical standards in lipidomics.An efficient three‐step synthesis of enantiopure triacylglycerols with yields ranging from 79 to 92% is reported. This is accompanied by an automated protocol for triacylglycerol synthesis.

Biodegradation and toxicity of vegetable oils in contaminated aquatic environments: Effect of antioxidants and oil composition

Antioxidants may affect the oxidative rate of vegetable oils determining their fate and impact in contaminated aquatic media. In previous studies, we demonstrated the effectiveness of butylated hydroxytoluene (BHT), one of the most used antioxidants in edible oils, in enhancing the biodegradation of glyceryl trilinoleate, a pure triacylglycerol of cis,cis-9,12-octadecadienoic acid (C18:2 delta), through retarding its oxidative polymerization relatively to the oil with no added antioxidant. In this study, the effect of BHT on the biodegradation and toxicity of purified canola oil, a mixed-acid triacylglycerol with high C18:1 content, was investigated in respirometric microcosms and by use of the Microtox® assay. Investigations were carried out in the absence and presence (200mgkg−1) of the antioxidant, and at an oil loading of 0.31Lm−2 (333galacre−1). Substantial oil mineralization was achieved after 16weeks of incubation (>77%) and was not significantly different (p>0.05) between the two BHT treatments, demonstrating an important role of the oil fatty acid composition in determining the potency of antioxidants and, consequently, the fate of spilled vegetable oils. Furthermore, for both treatments, toxicity was measured at early stages of the experiments and disappeared at a later stage of incubation. The observed transient toxicity was associated with the combined effect of toxic biodegradation intermediates and autoxidation products. These results were supported by the gradual disappearance of BHT in the microcosms initially supplemented with the antioxidant, reaching negligible amounts after only 2weeks of incubation.

Effect of diacylglycerol addition on crystallization properties of pure triacylglycerols

The objective of this study was to investigate the effects of blending triacylglycerols (TAGs) and diacylglycerols (DAGs) on the melting and crystallization properties in a fat system. To this end, differential scanning calorimetry (DSC), X-ray diffraction (XRD) and polarized light microscopy (PLM) methods were used. Different DAGs (diolein—OO, dipalmitin—PP and distearin—SS) were added at 5% to each TAG (triolein—OOO, tripalmitin—PPP and tristearin—SSS). DSC results showed that the addition of DAGs delayed the onset of crystallization of saturated TAGs (PPP and SSS). By contrast, the addition of DAGs to unsaturated TAG (OOO) accelerated the onset of crystallization, with the appearance of an extra crystallization peak upon the addition of SS and PP. PLM results revealed that the addition of OO affected the polymorphic transition of the TAGs studied findings were consistent with DSC melting curves and XRD results.

Enzymatic Synthesis of Extremely Pure Triacylglycerols Enriched in Conjugated Linoleic Acids

This work was objectively targeted to synthesize extremely pure triacylglycerols (TAG) enriched in conjugated linoleic acids (CLAs) for medical and dietetic purposes. Extremely pure CLA-enriched TAG was successfully synthesized by using the multi-step process: TAG was primarily synthesized by lipase-catalyzed esterification of CLA and glycerol and then the lower glycerides [monoacylglycerol (MAG) and diacylglycerol (DAG)] in the esterification mixtures was hydrolyzed to free fatty acids (FFAs) by a mono- and di-acylglycerol lipase (lipase SMG1), finally, the FFAs were further separated from TAG by low temperature (150 °C) molecular distillation. The operation parameters for the lipase SMG1-catalyzed hydrolysis were optimized using response surface methodology based on the central composite rotatable design (CCRD). The operation parameters included water content, pH and reaction temperature and all of these three parameters showed significant effects on the hydrolysis of lower glycerides. The optimal conditions were obtained with a water content of 66.4% (w/w, with respect to oil mass), pH at 5.7 and 1 h of reaction time at 19.6 °C. Under these conditions, the content of lower glycerides in the reaction mixture decreased from 45.2% to 0.3% and the purity of CLA-enriched TAG reached 99.7%. Further purification of TAG was accomplished by molecular distillation and the final CLA-enriched TAG product yielded 99.8% of TAG. These extremely pure CLA-enriched TAG would be used for in vivo studies in animals and humans in order to get specific information concerning CLA metabolism.

Oxidative stabilities of enzymatically interesterified goose fat and rapeseed oil blend by rancimat and PDSC

Goose fat (GF) and rapeseed oil (RSO) 2:3 m m−1 blend was enzymatically interesterified at 60 °C with and without microwaves assistance. As the catalyst, a commercial preparation of the immobilized lipase from Rhizomucor miehei (Lipozyme RM IM) containing 2 % of water was used, and the catalyst load was 8 % in each case. The starting mixture and the interesterified products were separated by column chromatography into pure triacylglycerols fraction (TAG) and a non-triacylglycerol fraction, which contained free fatty acids (FFA), mono- and diacylglycerols (MAG and DAG). The oxidative stabilities of fats studied and TAG derived from them were assessed by Rancimat at 100 °C and by pressure differential scanning calorimetry (PDSC) under oxygen at 110–140 °C. Interesterification reduced the oxidative stability of GF and RSO blend. The main factors influenced on the oxidative stabilities of fats studied were concentrations of tocopherols and the presence of FFA, MAG and DAG. The structures of TAGs were of minor importance. From the resulting PDSC exotherms, their times to reach the onset (τ on) and peak maximum (τ max) were measured and used for calculations of parameters of the Arrhenius type kinetics for thermaloxidative decomposition of fats studied.

Enzymatic Interesterification of a Lard and Rapeseed Oil Equal-Weight Blend

A mixture of lard and rapeseed oil (1:1, wt/wt) was interesterified using immobilized lipases from Rhizomucor miehei (Lipozyme RM IM) and Candida antarctica (Novozym 435) as catalysts. Enzymatic interesterifications were carried out at 60°C for 8 h with Lipozyme RM IM or at 80°C for 4 h with Novozym 435. The biocatalyst doses were kept constant (8 wt-%). The starting blend was quantitatively separated by column chromatography into pure triacylglycerol fraction (98.5%), and a nontriacylglycerol fraction containing free fatty acids (0.3%) and of mono- and diacylglycerols (1.2%). It was found that after interesterification the contents of free fatty acids and of mono- and diacylglycerols increased to 3.5% and 6.3% or to 1.5% and 4.5% when Lipozyme RM IM and Novozym 435 were used, respectively.The slip melting temperatures and solid fat contents of the triacylglycerol fractions separated from interesterified samples were lower compared with the nonesterified blend. The sn-2 and sn-1,3 distribution of fatty acids in the triacylglycerol fractions before and after interesterification were determined. The compositions of fatty acids at sn-2 were near statistical (33.3%) when Novozym 435 was used. When Lipozyme RM IM was used, the fatty acid compositions at the sn-2 position remained practically unchanged, compared with the starting blend. The changes in molecular structures of fat components due to interesterification have greatly influenced on the melting profiles of products as illustrated by the DSC melting scans. The interesterified fats and isolated triacylglycerols had reduced oxidative stabilities, as assessed by Dynamic DSC and Isothermal PDSC measurements. The Arrhenius kinetic parameters for fats oxidation based on DSC and PDSC measurements were calculated.

Properties and Oxidative Stabilities of Enzymatically Interesterified Chicken Fat and Sunflower Oil Blend

Chicken fat and sunflower oil 2:3 m/m blend was enzymatically interesterified at 60°C with and without microwaves assistance. As the catalyst a commercial preparation of the immobilized lipase from Rhizomucor miehei (Lipozyme RM IM) containing 2% of water was used, and the catalyst load was 8% in each case. The starting mixture and the interesterified products were separated by column chromatography into pure triacylglycerols fraction (TAG) and a non-triacylglycerol fraction, which contained free fatty acids (FFA), mono- and diacylglycerols (MAG and DAG). The oxidative stabilities (OS) of fats studied and TAG derived from them were assessed by Rancimat at 100°C and by Pressure Differential Scanning Calorimetry (PDSC) under oxygen at 110-140°C. Interesterification reduced the OS of chicken fat and sunflower oil blend. The main factors influenced on the OS of fats studied were concentrations of tocopherols and presence of FFA, MAG- and DAG. The structures of TAGs were of minor importance. From the resulting PDSC exotherms their times to reach the onset (τon) and peak maximum (τmax) were measured and used for calculations of parameters of the Arrhenius type kinetics for thermaloxidative decomposition of fats studied.

Formation mechanisms of Monochloropropanediol (MCPD) fatty acid diesters in refined palm (Elaeis guineensis) oil and related fractions

Monochloropropanediol (MCPD) fatty acid esters are process contaminants generated during the deodorisation of edible oils. In particular, MCPD diesters are found in higher abundance in refined palm oil than other edible oils. In the present study, a series of model reactions mimicking palm oil deodorisation has been conducted with pure acylglycerols in the presence or absence of either organic or inorganic chlorine-containing compounds. Results showed that the bulk of MCPD diesters are formed above 200°C through the reaction of organochlorines with triacylglycerols (TAG). Additional experiments confirmed that this reaction can be initiated during palm oil deodorisation by hydrogen chloride (HCl) gas evolved through the thermal degradation of organochlorines present in the oil. Therein, the majority of the ultimately produced MCPD diesters are the result of HCl reacting with TAG, via protonation, followed by the elimination of a fatty acid residue. Two possible MCPD diester formation mechanisms are highlighted, both of which involve acyloxonium ion reactive intermediates. Investigations with pure TAG regio-isomers showed that MCPD ester formation is regioselective and the sn-1(3) position of the glycerol backbone is favoured.

Enzymatic production of human milk fat substitutes containing palmitic and docosahexaenoic acids at sn-2 position and oleic acid at sn-1,3 positions

This paper studies the synthesis of structured triacylglycerols (STAGs) rich in palmitic and docosahexaenoic acids (PA and DHA) at sn-2 position and oleic acid (OA) at sn-1,3 positions by a four step process. First, triacylglycerols (TAGs) were obtained with 63–66 mol PA/100 mol total fatty acids and 10 mol DHA/100 mol by acidolysis of tuna oil and commercial PA, catalyzed by the non-positionally specific lipase Novozym 435. Then these TAGs were purified neutralizing the free fatty acids (FFAs) by KOH hydroethanolic solutions and extracting TAGs with hexane; these TAGs were completely recovered as pure TAGs (without FFAs). The third step involved the displacement of fatty acids located at sn-1,3 positions by acidolysis of PA and DHA enriched TAGs with OA rich FFAs, catalyzed by the sn-1,3 specific lipase DF from Rhizopus oryzae, immobilized on Accurel MP-1000; TAGs with 67 mol OA/100 mol at sn-1,3 positions and 52.1 and 15.4 mol PA and DHA, respectively, per 100 mol at sn-2 position were obtained. Both acidolysis reactions were carried out in stirred tank reactors (STRs) with lipase both dispersed in the reaction medium and contained in a cartridge filter attached to the stirrer rod. Finally STAGs were purified and obtained with yields of over 80 mol STAGs/100 mol STAGs in the reaction product (no FFAs were detected).

High Performance Liquid Chromatography–Size Exclusion Chromatography for Rapid Analysis of Total Polar Compounds in Used Frying Oils

AbstractAnalysis of used frying oil samples by high performance liquid chromatography–size exclusion chromatography (HPLC–SEC or HPSEC) was compared to AOCS Official Method Cd 20‐91 (silica gel column chromatography) for the purpose of developing a rapid analysis of total polar compounds (TPC). In a direct comparison of the two analytical methods using four different sets of used frying oils (21 total oil samples) ranging from fresh to discard quality (4.3 to 35.4% TPC by column chromatography), the weight percent total polar compounds (%TPC) determined by HPLC–SEC averaged 0.71% higher than the values by silica gel column chromatography. Reproducibility of the HPLC–SEC method of sr = 0.30 and RSDr% = 1.22 compares to the variability of sr = 0.29 and RSDr = 1.3 for samples of approximately the same %TPC, reported in AOCS Method Cd 20‐91. Because the rapid method does not separate pure (non‐polar) triacylglycerol (TAG) and polar, oxidized TAG (OX‐TAG), a high concentration of OX‐TAG will quantitatively affect the results. This places practical limits on the types of studies to which the method may be applied if a separate analysis for the OX‐TAG is not performed. Advantages of the HPLC–SEC method include the following. It uses about 75% less solvent than standard column chromatography methods for determination of %TPC. This HPLC–SEC method is very similar to AOCS Official Method Cd 22‐91, and thus, also separates and quantifies polymerized triacylglycerols. The HPLC–SEC method determines both TAG polymer concentration and %TPC of used frying oils in about 1 h.

Production of triacylglycerols rich in palmitic acid at sn-2 position by lipase-catalyzed acidolysis

This paper studies the synthesis of triacylglycerols (TAGs) rich in palmitic acid (PA) at sn-2 position from palm stearin (PS), a vegetable oil highly rich in PA (60%, but only 12.8% of this is located at sn-2 position). These PA rich TAGs were obtained by lipase-catalyzed acidolysis of this oil with free fatty acids (FFAs) highly rich in PA, such as commercial PA (98% PA) and a FFA extract obtained by saponification of PS (60% PA). PA has a melting point of 63 °C and during the acidolysis reaction the substrates, highly rich in this acid, must remain liquid; therefore high temperatures or solvents must be used. An important objective of this work was to operate without solvent and at the lowest possible temperature. In this acidolysis reaction four factors were firstly studied: type of lipase, temperature, solvent amount and the intensity of treatment (IOT = lipase amount × reaction time/PS amount). The influence of these variables was studied in a stirred tank reactor (STR). The lipases tested were Novozym 435 from Candida antarctica (immobilized on a macroporous acrylic resin), and lipases QLC (immobilized on diatomaceous earth), and QLM (non-immobilized), both from Alcaligenes sp., and the one selected was lipase QLC. According to the manufacturer the optimum temperature for this lipase is 65–70 °C, which allows it to operate without solvent. The best results with lipase QLC (TAGs with 80% PA, both total and at sn-2 position) were obtained with commercial PA, at 65 °C, a 3:1 FFA/PS molar ratio (1:1, w/w), without solvent and an IOT = 7 g lipase × h/g PS (for example 2.5 g PS, 2.5 g commercial PA, 0.75 g lipase and 24 h). These results were the basis for establishing the operational conditions to obtain PA rich TAGs with the lipase immobilized in a packed bed reactor (PBR), operating by recirculation of the reaction mixture through the lipase bed. In this system TAGs with 75% PA were obtained at an IOT = 8 g lipase × h/g PS. This result and the apparent kinetic constants obtained in both reactors show that the reaction rate is lower in the PBR than in the STR. Subsequently, PA enriched TAGs were separated from FFAs by two procedures: the first one at room temperature and in presence of hexane and the second one at 65 °C and without hexane. Using the first procedure, 95% of TAGs in the acidolysis reaction mixture were recovered with a purity of 99%. Using the second one, 98% pure TAGs were obtained with a recovery yield of 80%. Therefore, these highly rich PA TAGs can be obtained by acidolysis of PS and PA rich FFAs in solvent-free media, and then these TAGs also can be purified to 98% in absence of hexane, using only a hydroethanolic KOH solution.

Determining nutritional labeling data for fats and oils by 1H NMR

AbstractThe nutrition labeling compositional data (NLCD) required for fat‐containing food products consists of the percentages of saturated, cis‐monounsaturated, and cis‐polyunsaturated fat as well as trans content. The capability of 1H NMR spectroscopy to determine the NLCD components in oils that do not contain significant levels of trans isomers has already been established in the literature, but not its capability to differentiate between cis‐ and trans‐unsaturation. In the present study, the determination of all four NLCD components in fats and oils has been demonstrated for the first time. A preliminary analysis of the intensity‐normalized 1H NMR spectra of defined mixtures of pure triacylglycerols (TAG) by partial least squares (PLS) regression revealed that the (mono)allylic proton resonances of cis and trans bonds were sufficiently well separated to allow for accurate quantitation of trans content by simple peak integration. This chemometric approach also served to facilitate the identification of optimal integration limits for these cis‐ and trans‐allylic resonances. Fixed integration limits were also set for the other resonances employed in the determination of the four NLCD components, and a standardized spectral preprocessing procedure was established. The 1H NMR NLCD data obtained for the TAG mixtures by this methodology was a good match to the actual values, calculated from the known molar composition of these gravimetrically prepared mixtures. A procedure for the conversion of the NMR mol% NLCD to units of wt%, previously developed for 13C NMR, was adapted for 1H NMR and shown to be effective in compensating for the overestimation of wt% saturates and underestimation of wt% unsaturates by 1H NMR if this conversion is not made. The 1H NMR methodology for NLCD determination was validated by analyzing AOCS Laboratory Proficiency Program GC samples as well as samples taken from a hydrogenator over time and analyzed for trans content by GC and IR spectroscopy. Comparison of the 1H NMR mol% and wt% NLCD obtained for these validation samples with the data obtained from the reference methods indicated that 1H NMR can deliver high‐quality, accurate NLCD, much like 13C NMR, but in a much shorter time frame. Thus, 1H NMR provides a more rapid and cost‐effective means of obtaining NLCD than 13C NMR and can replace GC as a primary reference method for the calibration of simpler and automatable instrumental methods such as Fourier transform infrared (FTIR) spectroscopy.

Solid−Liquid Equilibrium of Saturated Fatty Acids + Triacylglycerols

Phase diagrams of tricaprylin (1,3-di(octanoyloxy)propan-2-yl octanoate) + myristic acid (tetradecanoic acid), commercial triolein + palmitic acid (hexadecanoic acid), and trilinolenin (propane-1,2,3-triyl tris[(9Z,12Z,15Z)-octadeca-9,12,15-trienoate]) + stearic acid (octadecanoic acid) were obtained by differential scanning calorimetry (DSC). The occurrence of an eutectic point very close to the pure triacylglycerol can be assumed in all of the three investigated systems. The liquid phase was modeled using Margules two-suffix, Margules three-suffix, nonrandom two-liquid (NRTL), and universal quasichemical functional group activity coefficient (UNIFAC) Dortmund models. The best modeling results were obtained using the NRTL model. The UNIFAC Dortmund model describes the multicomponent system containing commercial triolein + palmitic acid well.

Volatile oxidation compounds in a conjugated linoleic acid-rich oil

In this study, volatile oxidation compounds formed in a commercial conjugated linoleic acid (CLA)-rich oil were quantified and results compared to those found in safflower oil (rich in linoleic acid, LA). Intact oil samples and pure triacylglycerols obtained following elimination of tocopherols and minor compounds were oxidised at 60 °C, and volatile oxidation compounds were analysed by solid phase microextraction-gas chromatography with flame ionisation detector and mass spectrometer. Results showed that while, as expected, hexanal was the major volatile oxidation compound found in oil and triacylglycerols rich in LA, both hexanal and heptanal equally were the most abundant compounds in oil and triacylglycerols rich in CLA. Besides, samples rich in CLA also showed significantly high quantities of trans-2-octenal and trans-2-nonenal and the latter, along with heptanal, were absent in samples rich in LA. Results for CLA samples were not easy to interpret since major volatiles found are not expected from theoretically stable hydroperoxides formed in CLA and could in part derive from dioxetanes coming from 1,2-cycloadditions of CLA with oxygen. Overall, results obtained support evidence that oxidation mechanisms of CLA may differ than those of LA. Also, it was concluded that heptanal determination could serve as a useful marker of oxidation progress in CLA-rich oils.

Docosahexaenoic Acid is More Stable to Oxidation when Located at the sn‐2 Position of Triacylglycerol Compared to sn‐1(3)

AbstractRegio‐isomeric effects on the oxidative stability of triacylglycerols (TAG) containing docosahexaenoic acid (DHA) were investigated using two pairs of regio‐isomerically pure TAG, namely 1,3‐dihexadecanoyl‐2‐(4,7,10,13,16,19‐docosahexaenoyl)glycerol (PDP)/1,2‐dihexadecanoyl‐3‐(4,7,10,13,16,19‐docosahexaenoyl)glycerol (PPD) and 1,3‐dioctadecenoyl‐2‐(4,7,10,13,16,19‐docosahexaenoyl)glycerol (ODO)/1,2‐dioctadecenoyl‐3‐(4,7,10,13,16,19‐docosahexaenoyl)glycerol (OOD) where P, O, and D represent palmitic acid, oleic acid, and DHA respectively. Each pair of regio‐isomers was subjected to accelerated auto‐oxidation (at 40 or 50 °C inside a dark oven). In each case, the TAG oxidized more slowly when DHA was located at the sn‐2 position (PDP and ODO) compared to the sn‐1(3) position (PPD and OOD), as evidenced by slower development of peroxide value, slower depletion of DHA, and slower generation of secondary oxidation products propanal and trans, trans‐2,4‐heptadienal. The positional effect on auto‐oxidation was more pronounced when DHA occurred in combination with oleic acid than with palmitic acid.