Triacylglycerol Molecules Research Articles

Biosynthesis of Triacylglycerol Molecules with a Tailored PUFA Profile in Industrial Microalgae

The composition of polyunsaturated fatty acids (PUFAs) in triacylglycerols (TAGs) is key to health benefits and for oil applications, yet the underlying genetic mechanism remains poorly understood. In this study, by in silico, ex vivo, and in vivo profiling of type-2 diacylglycerol acyltransferases (DGAT2s) in Nannochloropsis oceanica we revealed two novel PUFA-preferring enzymes that discriminate individual PUFA species in TAG assembly, with NoDGAT2J for linoleic acid (LA) and NoDGAT2K for eicosapentaenoic acid (EPA). The LA and EPA composition of TAG molecules is mediated in vivo via the functional partitioning between NoDGAT2J and 2K, both of which are localized in the chloroplast envelope. By modulating transcript abundance of the DGAT2s, an N. oceanica strain bank was created, where proportions of LA and EPA in TAG vary by 18.7-fold (between 0.21% and 3.92% dry weight) and 34.7-fold (between 0.09% and 3.12% dry weight), respectively. These findings lay the foundation for producing designer TAG molecules with tailored health benefits or for biofuel applications in industrial microalgae and higher-plant crops.

Streamer characteristics of dielectric natural ester-based liquids under long gap distances

Natural esters, as the renewable resources, offer excellent physiochemical and dielectric properties such as the fire-resistance, high biodegradability and satisfactory dielectric breakdown performance. Thus, natural esters are selected as the insulation and heat dissipation medium for electrical equipment. However, the electrical performance of natural esters with different structures under the long gap and higher electrical stress needs further evaluations. In this paper, streamer propagation of various natural esters under the long gap and higher electrical stress were observed optically. The influence of voltage polarity, liquid types and gap distances on streamer characteristics of natural esters were analyzed. Results show that the maximum propagation velocity of streamer in natural esters is greater than that in the hydrocarbon liquids. Breakdown voltage of natural esters under negative polarity is much higher than that under positive polarity for the same gap distance. Among all the natural esters concerned, the camellia liquid demonstrates slower streamer velocity and slight greater lightning breakdown voltages for the positive and negative polarity. The lower content of unsaturation triacylglycerol molecules in camellia liquid contributes to the inhibition of ionization and streamers propagation. Results would be valuable reference for the design, manufacture and operation of the electrical equipment filled with natural ester.

In This Issue…

A wide variety of clinical and basic science articles comprise this issue of the Canadian Journal of Diabetes. Some of the topics covered in this issue are included below. Cimo and Dewa present a qualitative study aimed at exploring the perspectives of adults with type 2 diabetes and mental illness. The authors studied the challenges to engaging in self-care behaviours and accessing diabetes education services (pages 372–81). They highlight the importance of addressing these issues in this population, given the increased prevalence of type 2 diabetes among individuals with mental health illnesses and poorer self-care practices and, ultimately, the poorer outcomes observed in this population. The authors conducted focus groups with individuals who self-identified as having type 2 diabetes and major depressive disorders. Transcripts were analyzed and major themes identified. Participants identified a wide range of barriers to care, including physiological, physical and social challenges. The authors suggest that addressing these issues will be necessary to close the gaps in care that currently exist in this population. Combined aerobic and anaerobic exercise improved the oxidative capacity of skeletal muscle and improved insulin sensitivity in a rodent model of type 1 diabetes, according to the authors of this study (pages 404–11). The improvement in the oxidative capacity of muscle in the combined aerobic and anaerobic group was greater than that of the aerobic-only group. This result led the authors to suggest that combined exercise training may result in a synergistic effect on the oxidative capacity of muscle. Contrary to their original hypothesis, combined aerobic and anaerobic exercise did not reduce lipid accumulation in the skeletal muscle; this was seen in the aerobic-only exercise group. The authors hypothesize that although lipid stores were not decreased, the composition of the lipid stores may differ in the combined aerobic and anaerobic exercise group. They suggest that the fat stores in the aerobic- and anaerobic-exercised rodents are potentially composed of energy-rich neutral triacylglycerol molecules in comparison to the insulin-desensitizing diacylglycerol molecules seen in unexercised animals. Thus, the animals undergoing combined aerobic and anaerobic exercise would have access to energy stores without the effect of insulin resistance. The authors suggest that combined exercise may promote positive metabolic adaptation with increased capacity to both store and oxidize lipids, compared with aerobic activity alone. This is an intriguing hypothesis that is yet to be confirmed among those living with type 1 diabetes. Increased awareness of the criteria and contraindications for islet-cell transplantation is needed for people living with type 1 diabetes and health-care providers, according to Ling et al (pages 419–25). In this article, the authors describe the referral patterns and initial eligibility assessment for the largest clinical islet-cell transplant program in Canada. The authors undertook a retrospective chart review (2009 to 2012) to identify the most common factors resulting in an applicant's being deemed eligible or ineligible for islet-cell transplantation. Overall, only 19% of applicants were deemed acceptable for listing for transplant. The majority of applicants were self-referrals, and among the indications for no transplant, severe hypoglycemia and glucose lability were the most common causes of ineligibility. In addition, the use of a suboptimal insulin regimen was the most common exclusion criterion identified. The majority of applicants were from Alberta. Only a small number of applications came from the 2 most populous provinces (Ontario and Quebec), despite neither of these provinces having a transplant program at the time. In addition to increasing awareness of eligibility for islet-cell transplantation, the authors suggest that their findings can be used as benchmarks for future studies and ongoing program evaluation. Conflicts of interest: None.

Graphene oxide aggregate-assisted LDI-MS for the direct analysis of triacylglycerol in complex biological samples

Knowledge of blood triacylglycerol (TAG) species is essential to clarify the physiological functions of individual TAG molecules and also to develop potential biomarkers for related diseases. Commonly, lipid samples prepared by organic liquid-liquid extraction contain complex components, thus cannot be directly characterized by mass spectrometry (MS) and often require an additional purification step. Here, we described a laser desorption ionization - mass spectrometry (LDI-MS) method that utilized aggregated graphene oxide (AGO) as both lipid extractant and MS matrix (AGOLDI-MS), to characterize and quantify plasma TAG species without the use of harmful solvent or complex separation step. We first designed and synthesized the AGO material with a multi-layered sheet structure, which could efficiently break up the structure of lipoproteins, and extract plasma TAGs as solid-phase extraction material. Furthermore, in AGOLDI-MS procedure, the AGO could directly act as matrix and selectively produce the MS signals of TAGs without the interferences of phospholipids, which was hardly achieved by using the routine LDI-MS method based on liquid-liquid extraction and small molecular matrix. We confirmed the suitability of AGOLDI-MS as characterization and quantitative tool for TAG species through studying the analysis performances in TAG standards and real plasma samples. To establish potential utility of our method, we characterized 42 human plasmas from healthy and hyperlipemic donators, indicating that the AGOLDI-MS could not only generate comparable quantitative results of total TAGs to current clinical technology, but also monitor the changes of TAG species between different sample groups. This approach could further characterize the compositions of the fatty acid moieties in even low abundant TAGs by the assistance of tandem MS-MS. This concise, specific, and high-throughput approach will facilitate the rapid and precise characterizations of plasma TAGs, and make the MS approach for TAGs more adaptable for clinical uses.

Characterization of Positional Distribution of Fatty Acids and Triacylglycerol Molecular Compositions of Marine Fish Oils Rich in Omega-3 Polyunsaturated Fatty Acids.

The regiospecific characteristics of n-3 polyunsaturated fatty acids (PUFAs) in triacylglycerol (TAG) significantly affect the physicochemical and physiological properties of marine fish oils. In this study, the TAG molecular species composition and positional distributions of fatty acids were investigated in three marine fish species rich in omega-3 PUFAs (anchovy, tuna, and salmon). The regiospecific distribution of the fatty acids was measured with the allylmagnesium bromide (AMB) degradation method. The TAG compositions were analyzed with HPLC and the TAG molecular species were identified with APCI/MS. DHA was preferentially distributed at the sn-2 position of TAG, whereas EPA was evenly distributed along the glycerol backbone. The combinations of FAs, DDO, EOP, EPS, DSS, OOS, and PPS were the predominant TAG molecular species, and OOP, DOS, and DPoPo were the characteristic TAG molecules in the anchovy, salmon, and tuna, respectively. These data can be used to distinguish other marine fish species. The TAG composition categorized by TCN and ECN showed well-structured distributions, with double or triple peaks. These findings should greatly extend the use of marine fish oils in food production and may significantly affect the future development of the fish oil industry.

2‐Acetyl‐1,3‐Diacyl–sn‐Glycerols with Unusual Acyl Composition in Seed Oils of the Genus Polygala

Seed oils containing unusual triacylglycerol (TAG) molecules, where one fatty acid of a TAG is substituted by an acetate group (Ac), are uncommon but of considerable interest as potential low‐viscosity biofuels and lubricants or reduced calorie food ingredients. Although the properties and pathway of biosynthesis of 3‐acetyl‐1,2‐diacyl‐sn‐glycerols (sn‐3‐acTAGs) have been described, little is known about the occurrence of 2‐acetyl‐1,3‐diacyl‐sn‐glycerols (sn‐2‐acTAGs). Prompted by a report of sn‐2‐acTAGs in the seeds of Polygala virgata, a study of the seed oil of seven members of this genus, and two related species is conducted. The presence of sn‐2‐acTAG and lesser amounts of conventional TAG is conclusively demonstrated in Polygala seed oil by Matrix‐Assisted Laser Desorption/Ionization Time‐of‐Flight Mass Spectrometry (MALDI‐TOF MS) and high resolution C13 nuclear magnetic resonance spectroscopy (C13 NMR). Analysis of seed fatty acids reveals a diversity of composition with oils from P. myrtifolia and P. fruticosa dominated by the medium‐chain fatty acid (MCFA) myristic acid (tetradecanoic acid) at an average of 79.8 and 74.1% of total seed fatty acids, respectively. In contrast, MCFAs are absent from oils from P. tenuifolia and P. virgata, with the very‐long‐chain fatty acid (VLCFA) gondoic acid (cis‐11‐eicosenoic acid) being most abundant. Polygala species therefore represent a rich source of sn‐2‐acTAGs and uncommon fatty acids.Practical applications: The seed oils of Polygala species contain a highly unusual combination of sn‐2‐acTAGs and uncommon fatty acids. These plants can serve as a unique genetic resource for the elucidation of the pathways of biosynthesis of these lipids and the identification of genes for the engineering of novel oils in transgenic plants. As Polygala is morphologically diverse genus ranging from annual herbs to small trees, identification of species with suitable seed production and agronomic characteristics may allow the commercial production of novel oils for specific higher value uses.Plant seed oils are generally composed primarily of triacylglycerol (TAG). In this article, the authors examine the seed oils of seven species in the genus Polygala and report the occurrence of an unusual lipid, 2‐acetyl‐1,3‐diacyl–sn‐glycerol (sn‐2 acTAG). These plants also produce unusual fatty acids in their seed oil, with Polygala tenuifolia being enriched in gondoic acid (cis‐11‐eicosenoic acid, 20:1Δ11) and Polygala myrtifolia containing myristic acid (tetradecanoic acid, 14:0). The genus Polygala represents a potential source of novel oil and a resource for the characterization of sn‐2 acTAG biosynthesis.

Digestion fates of different edible oils vary with their composition specificities and interactions with bile salts

The digestion fates of different edible oils are different. The objective of this study was to understand the influences of lipid composition on their digestion fates, and investigate the roles of bile salts (BS) played in emulsified lipid system (whey protein isolate as emulsifier) in the in-vitro small intestine digestion stage. Three typical oils (palm oil (PO), rapeseed oil (RO) and linseed oil (LINO)) were chosen. Results showed that with the BS addition increased from 0.0 to 2.0 mg/mL, the increasing magnitude of the different fatty acid (FA) apparent release rate constants were: PO > RO ≈ LINO. Although the maximum FA release extent changed with BS addition, the order were: PO > RO > LINO. These may probably be attributed to palmitic acids, the most abundant FA in PO, was mostly located on the Sn-1, 3 positions of triacylglycerol (TAG) molecules, which contributed to the pancreatic lipase hydrolysis action. The relatively short chain length and the lower hydrophobicity also favored this process. However, Sn-1, 3 positions of TAGs in RO and LINO were mainly long chain mono- or poly-unsaturated FAs, which restricted the continuous lipid hydrolysis. Furthermore, the lipid composition may also affect the BS behavior on the O/W emulsion droplet surface, thus modulating lipase hydrolysis reaction. These findings can provide some basic understandings of the digestion differences of different oils.

Preparation of Chiral Triacylglycerols, sn-POO and sn-OOP, via Lipase-mediated Acidolysis Reaction.

It is well known that lipases are useful tools for preparing various structured triacylglycerols (TAGs). However, the lipase-mediated preparation of chiral TAGs has never been reported. This study aimed to prepare chiral TAGs (viz., 1-palmitoyl-2,3-dioleoyl-sn-glycerol (sn-POO) or 1,2-dioleoyl-3-palmitoyl-sn-glycerol (sn-OOP)) via lipase mediated acidolysis, using triolein (TO) and palmitic acid (P) as substrates. Three commercially available lipases (viz., Lipozyme RM-IM®, Lipozyme TL-IM®, and Lipase OF®) were used. Lipozyme RM-IM® resulted in an increase 1P-2O (sn-POO + sn-OOP + 1,3-dioleoyl-2-palmitoyl-sn-glycerol) content with reaction time, which plateaued at 2~24 h (max. yield 47.1% at 4 h). The highest sn-POO/sn-OOP ratio of ca. 9 was obtained at 0.25 h, and the rate got close to 1 with reaction time (sn-POO/sn-OOP = 1.3 at 24 h). Lipozyme TL-IM® resulted in a lower 1P-2O synthesis rate than Lipozyme RM-IM®, where its highest sn-POO/sn-OOP ratio of ca. 2 was obtained at 0.25 h and did not vary much further with reaction time. In the case of Lipase OF®, its reaction rate for 1P-2O synthesis was lower than that of the other two lipases, and the highest sn-POO/sn-OOP ratio of ca. 1.4 was obtained at 0.5 h, reaching closer to 1 with a longer reaction time. Reaction solvents (viz., hexane, acetone, and benzene) also affected the 1P-2O preparation, where the highest 1P-2O content was obtained with the solvent-free system. Furthermore, the solvent-free system showed a higher reaction rate for 1P-2O synthesis than did the hexane system, with no effect on chiral specificity of the lipase for the TAG molecules. These results suggested that among three types of commercial lipase, Lipozyme RM-IM® is the most useful for the preparation of chiral TAGs by acidolysis reaction.

Effects of Plant Oil Interesterified Triacylglycerols on Lipemia and Human Health.

The position of the fatty acids (sn-1, sn-2 and sn-3) (stereospecific numbering (sn)) in triacylglycerol (TAG) molecules produces a characteristic stereospecificity that defines the physical properties of the fats and influences their absorption, metabolism and uptake into tissues. Fat interesterification is a process that implies a positional distribution of fatty acids (FAs) within the TAG molecules, generating new TAG species, without affecting the FA cis-trans natural balance. The interesterified (IE) fats, frequently used in the food industry comprise fats that are rich in long-chain saturated FAs, such as palmitic acid (16:0) and stearic acid (18:0). Within the interesterified fats, a critical role is played by FA occupying the sn-2 position; in fact, the presence of an unsaturated FA in this specific position influences early metabolic processing and postprandial clearance that in turn could induce atherogenesis and thrombogenesis events. Here, we provide an overview on the role of TAG structures and interesterified palmitic and stearic acid-rich fats on fasting and postprandial lipemia, focusing our attention on their physical properties and their effects on human health.

Catalyzed Interesterification of Mixed Short & Medium Chain Fatty Acid Triacylglycerols as a Potential Dietary Food Lipid Source: Synthesis and Characterization

Interesterifcation reactions, more commonly called ester-exchange, are a process by which the arrangement of fatty acids in the triacylglycerol molecule is changed. Ester-exchange reactions lead to a random distribution of fatty acids resulting in a triacylglycerol composition that is predictable from the overall fatty acid composition of the starting reaction mixture. In this report, we synthesized various triacylglycerols containing different ratios of saturated short chain fatty acids (SCFA) such as: acetic, propionic and butyric, with a saturated medium chain fatty acid (MCFA) of octanoic acid. The interesterification of these triacylglycerols was prepared by the NaOCH3 catalyzed interesterification of model reactions performed with different molar ratios of Triacetin, Tripropionin, Tributyrin and Trioctanoin. The reaction products were characterized by Gas Chromatography (GC) and Proton NMR. We found that the difference in fatty acid size and the reduced steric demands of the S/MCFA did not give rise to positional specificity and we found no observable deviations from the random interesterification chemistry model. The potential of having different short and medium fatty acids triacylglycerol on one molecule for direct ingestion and metabolism can be of significant importance to maintaining gut health.

A study on ionization potential and electron trap of vegetable insulating oil related to streamer inception and propagation

Vegetable oils, mainly composed of triacylglycerol molecules, have been widely studied as new insulation materials in the recent years. In this work, we study the electronic properties of various triacylglycerol molecules with different degree of unsaturation by density functional theory (DFT). The ionization potential (IP), electron affinity (EA), and electron trap are estimated by theoretical analysis and experiments. The results show that the C atoms of cis CC double bond make the primary contribution to the highest occupied molecular orbital (HOMO) of unsaturated triacylglycerol molecule; the IPs of fully unsaturated triacylglycerol molecules are almost confined to the narrow ranges from 7.30 to 7.45 eV in gas-phase and from 6.77 to 6.84 eV in liquid-phase correspond to LnLnLn and OOO molecules, respectively; the atoms of ester group and neighboring atoms make the primary contribution to the lowest unoccupied molecular orbital (LUMO) of both saturated and unsaturated triacylglycerol molecules; the EAs of triacylglycerol molecules are confined to the narrow ranges from −0.34 to −0.18 eV and the chemical trap is estimated to be 0–0.16 eV; the total trap is 0.32–0.36 eV. The IP distribution character and shallow trap feature maybe the main causes that vegetable oils demonstrate a low resistance against the fast streamers. The work can provide theoretical basis to molecular modification for performance improvement of vegetable insulating oils.

Gene silencing of stearoyl-ACP desaturase enhances the stearic acid content in Chlamydomonas reinhardtii

In this study, stearoyl-ACP desaturase (SAD), the enzyme that converts stearic acid into oleic acid, is silenced by artificial microRNA in the green microalga Chlamydomonas reinhardtii. Two different constructs, which target different positions on the mRNA of stearoyl-ACP desaturase, were tested. The mRNA levels for SAD were reduced after the silencing construct was induced. In one of the strains, the reduction in SAD mRNA resulted in a doubling of the stearic acid content in triacylglycerol molecules, which shows that stearic acid production in microalgae is possible.

Seasonal Variation of Triacylglycerol Profile of Bovine Milk.

Milk contains 3–6% of fat, of which the dominant component is triacylglycerol (TAG). Over 100 TAG groups can be readily detected in any non-enriched milk sample by LC-MS; most TAG groups contain several isomers (TAG molecules with different fatty acid composition), which cannot be fully resolved chromatographically by any single stationary phase. TAG profile of mature milk from 19 cows was surveyed in this study for eight consecutive months using RP-LC-Orbitrap MS. It was found that TAG profile of milk was not constant throughout the milking season and the seasonal pattern varied with TAG groups. The overall unsaturation level of TAG was stable from October 2013 to January 2014, decreased in February/March 2014 and then increased from April and peaked in May 2014. In addition to the seasonal fluctuation in TAG profile, the proportion of different isomeric species within a TAG group also changed substantially across seasons. However, the proportion of different positional isomers within a given TAG group does not seem to vary during the milking season. To our knowledge, this is the first report on the seasonal change of milk lipid at the TAG group and isomer level.

Triacylglycerol regioisomers in human milk resolved with an algorithmic novel electrospray ionization tandem mass spectrometry method

A highly sensitive mass spectrometric (MS) method was developed and validated to analyze ratios of regioisomeric triacylglycerols (TAGs) in fats and oils. UPLC resolution of lithiated TAGs followed by daughter scan MS/MS of positive ions revealed several indicative ions for quantitative analysis. Reference TAGs containing C14–C20 fatty acids (FAs) showed good linear response. Analysis of Finnish and Chinese pooled human milk samples revealed hundreds of regioisomeric TAGs. At least 64mol% of the TAGs were quantified with relative standard deviation <17%. When present in the same TAG molecule together with C18 FAs, palmitic acid was typically in the sn-2 position. When together with FAs 10:0, 12:0, 14:0, 20:1 and 20:2, the sn-2 preference of 16:0 was less clear. Oleic acid occupied typically the sn-1/sn-3 positions but when together with FAs 20:1, 20:2, 18:2, 14:1, 12:0 or 10:0 the positioning of 18:1 did not follow these rules.

Molecular Structure and Electronic Properties of Triolein Molecule under an External Electric Field Related to Streamer Initiation and Propagation

Natural ester has been widely studied as an alternative dielectric liquid to mineral oil in recent years. Unsaturated triacylglycerol molecules are the main components of natural ester; therefore, in this paper, we investigate the molecular structure and electronic properties of the triolein molecule, an oleic-type triacylglycerol molecule, as a representative component of natural ester oils. The effects of external electric fields at the electric field intensity related to streamer initiation and propagation on the bond lengths, dipole moment, total energy, infrared spectra, and orbital energy of the triolein molecule are investigated using density functional theory (DFT). In addition, the excitation energies, transition wavelengths, and oscillator strengths of the first eight excited states of the triolein molecule under external electric fields are calculated by time-dependent DFT. The results show that the bond lengths, dipole moments, total energy, and infrared spectra change obviously under external electric fields. With increasing external electric field intensity, the energy of the highest occupied molecular orbital increases, and the gap between that and the energy of the lowest unoccupied molecular orbital decreases, which make the molecule susceptible to excitation. The calculations contribute to an understanding of the causes behind the degradation of the insulation properties of natural ester oils.

Metabolic engineering of Saccharomyces cerevisiae to produce a reduced viscosity oil from lignocellulose

BackgroundAcetyl-triacylglycerols (acetyl-TAGs) are unusual triacylglycerol (TAG) molecules that contain an sn-3 acetate group. Compared to typical triacylglycerol molecules (here referred to as long chain TAGs; lcTAGs), acetyl-TAGs possess reduced viscosity and improved cold temperature properties, which may allow direct use as a drop-in diesel fuel. Their different chemical and physical properties also make acetyl-TAGs useful for other applications such as lubricants and plasticizers. Acetyl-TAGs can be synthesized by EaDAcT, a diacylglycerol acetyltransferase enzyme originally isolated from Euonymus alatus (Burning Bush). The heterologous expression of EaDAcT in different organisms, including Saccharomyces cerevisiae, resulted in the accumulation of acetyl-TAGs in storage lipids. Microbial conversion of lignocellulose into acetyl-TAGs could allow biorefinery production of versatile molecules for biofuel and bioproducts.ResultsIn order to produce acetyl-TAGs from abundant lignocellulose feedstocks, we expressed EaDAcT in S. cerevisiae previously engineered to utilize xylose as a carbon source. The resulting strains were capable of producing acetyl-TAGs when grown on different media. The highest levels of acetyl-TAG production were observed with growth on synthetic lab media containing glucose or xylose. Importantly, acetyl-TAGs were also synthesized by this strain in ammonia fiber expansion (AFEX)-pretreated corn stover hydrolysate (ACSH) at higher volumetric titers than previously published strains. The deletion of the four endogenous enzymes known to contribute to lcTAG production increased the proportion of acetyl-TAGs in the total storage lipids beyond that in existing strains, which will make purification of these useful lipids easier. Surprisingly, the strains containing the four deletions were still capable of synthesizing lcTAG, suggesting that the particular strain used in this study possesses additional undetermined diacylglycerol acyltransferase activity. Additionally, the carbon source used for growth influenced the accumulation of these residual lcTAGs, with higher levels in strains cultured on xylose containing media.ConclusionOur results demonstrate that S. cerevisiae can be metabolically engineered to produce acetyl-TAGs when grown on different carbon sources, including hydrolysate derived from lignocellulose. Deletion of four endogenous acyltransferases enabled a higher purity of acetyl-TAGs to be achieved, but lcTAGs were still synthesized. Longer incubation times also decreased the levels of acetyl-TAGs produced. Therefore, additional work is needed to further manipulate acetyl-TAG production in this strain of S. cerevisiae, including the identification of other TAG biosynthetic and lipolytic enzymes and a better understanding of the regulation of the synthesis and degradation of storage lipids.

Palm oil and human health. Meeting report of NFI: Nutrition Foundation of Italy symposium

The use of palm oil by the food industry is increasingly criticized, especially in Italy, for its purported negative effects on human health and environment. This paper summarizes the conclusions of a Symposium on this topic, gathered by the Nutrition Foundation of Italy, among experts representing a number of Italian Medical and Nutritional Scientific Societies. Toxicological and environmental issues were not considered.Participants agreed that: no evidence does exist on the specific health effects of palm oil consumption as compared to other saturated fatty acids-rich fats; the stereospecific distribution of saturated fatty acids in the triacylglycerol molecule of palm oil limits their absorption rate and metabolic effects; in agreement with International guidelines, saturated fatty acids intake should be kept <10% of total energy, within a balanced diet; within these limits, no effect of palm oil consumption on human health (and specifically on CVD or cancer risk) can be foreseen.

A High-Resolution NMR Approach Combined to MALDI-TOF-MS to Estimate the Positional Distribution of Acyl-Linked Unsaturated Fatty Acids in Triacylglycerols

Triacylglycerols (TAGs) are the most abundant constituents of vegetable oils and adipose tissues. TAG analysis is even, nowadays, challenging because the presence of three (often different) fatty acyl residues leads to many different, regioisomeric species. While the overall fatty acyl composition of TAG can be determined by gas chromatography/mass spectrometry (GC/MS), all positional information is completely lost by this approach. Therefore, GC/MS is often replaced or combined with LC/MS that provides information (by MS/MS) which fatty acyl residues are present in a given TAG and sometimes also about the location at the glycerol backbone. Since TAGs are normally available in huge amounts, the comparably low sensitivity of NMR is not a major issue. We show that high-resolution 13C NMR spectroscopy is an excellent method to determine the overall fatty acyl composition and the positions of the related (unsaturated) fatty acyl residues in a given TAG molecule. These data will be compared with MALDI-TOF MS data of the same vegetable oil samples. Although the 13C NMR method is particularly applicable to unsaturated TAG, this approach can be regarded as a significant methodological progress in this field.

Quantification of Triacylglycerol Molecular Species in Edible Fats and Oils by Gas Chromatography-Flame Ionization Detector Using Correction Factors.

In the present study, the resolution parameters and correction factors (CFs) of triacylglycerol (TAG) standards were estimated by gas chromatography-flame ionization detector (GC-FID) to achieve the precise quantification of the TAG composition in edible fats and oils. Forty seven TAG standards comprising capric acid, lauric acid, myristic acid, pentadecanoic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, and/or linolenic acid were analyzed, and the CFs of these TAGs were obtained against tripentadecanoyl glycerol as the internal standard. The capillary column was Ultra ALLOY+-65 (30 m × 0.25 mm i.d., 0.10 μm thickness) and the column temperature was programmed to rise from 250°C to 360°C at 4°C/min and then hold for 25 min. The limit of detection (LOD) and limit of quantification (LOQ) values of the TAG standards were > 0.10 mg and > 0.32 mg per 100 mg fat and oil, respectively, except for LnLnLn, and the LOD and LOQ values of LnLnLn were 0.55 mg and 1.84 mg per 100 mg fat and oil, respectively. The CFs of TAG standards decreased with increasing total acyl carbon number and degree of desaturation of TAG molecules. Also, there were no remarkable differences in the CFs between TAG positional isomers such as 1-palmitoyl-2-oleoyl-3-stearoyl-rac-glycerol, 1-stearoyl-2-palmitoyl-3-oleoyl-rac-glycerol, and 1-palmitoyl-2-stearoyl-3-oleoyl-rac-glycerol, which cannot be separated by GC-FID. Furthermore, this method was able to predict the CFs of heterogeneous (AAB- and ABC-type) TAGs from the CFs of homogenous (AAA-, BBB-, and CCC-type) TAGs. In addition, the TAG composition in cocoa butter, palm oil, and canola oil was determined using CFs, and the results were found to be in good agreement with those reported in the literature. Therefore, the GC-FID method using CFs can be successfully used for the quantification of TAG molecular species in natural fats and oils.

Effect of the distribution of saturated fatty acids in the melting and crystallization profiles of high-oleic high-stearic oils

The composition and distribution of fatty acids in triacylglycerol (TAG) molecules are commonly considered as factors that determine the physical properties of a given oil or fat. The distribution of any fatty acid in fats and oils can be described through the α coefficient of asymmetry, which can be calculated from the TAG composition and fatty acid composition of the sn-2 position of the TAGs determined through lipase hydrolysis. High-oleic high-stearic oils and fats are considered stable and healthy, and they are good substitutes for hydrogenated vegetable oils and palm fractions in many food products, such as spreads and confectionery. Here, different high-oleic high-stearic acid oils were formulated which contained different distributions of saturated fatty acids in their TAGs, while maintaining a similar fatty acid composition. The aim of this work was to discuss the possibility of using the α coefficient to predict the physical properties of fats in function of their chemical composition and their melting and crystallization behavior as examined by differential scanning calorimetry.