Rapid and sensitive detection of free fatty acids in edible oils based on chemical derivatization coupled with electrospray ionization tandem mass spectrometry

Passive Wireless Porous Biopolymer Sensors for At-Home Monitoring of Oil and Fatty Acid Nutrition

Dietary oils─rich in omega-3, -6, and -9 fatty acids─exhibit critical impacts on health parameters such as cardiovascular function, bodily inflammation, and neurological development. There has emerged a need for low-cost, accessible method to assess dietary oil consumption and its health implications. Existing methods typically require specialized, complex equipment and extensive sample preparation steps, rendering them unsuitable for home use. Addressing this gap, herein, we study passive wireless, biocompatible biosensors that can be used to monitor dietary oils directly from foods either prepared or cooked in oil. This design uses broad-coupled split ring resonators interceded with porous silk fibroin biopolymer (requiring only food-safe materials, such as aluminum foil and biopolymer). These porous biopolymer films absorb oils at rates proportional to their viscosity/fatty acid composition and whose response can be measured wirelessly without any microelectronic components touching food. The engineering and mechanism of such sensors are explored, alongside their ability to measure the oil presence and fatty acid content directly from foods. Its simplicity, portability, and inexpensiveness are ideal for emerging needs in precision nutrition─such sensors may empower individuals to make informed dietary decisions based on direct-from-food measurements.

Mass Spectrometry Based on Chemical Derivatization Has Brought Novel Discoveries to Lipidomics: A Comprehensive Review

Lipids, as one of the most important organic compounds in organisms, are important components of cells and participate in energy storage and signal transduction of living organisms. As a rapidly rising field, lipidomics research involves the identification and quantification of multiple classes of lipid molecules, as well as the structure, function, dynamics, and interactions of lipids in living organisms. Due to its inherent high selectivity and high sensitivity, mass spectrometry (MS) is the "gold standard" analysis technique for small molecules in biological samples. The combination chemical derivatization with MS detection is a unique strategy that could improve MS ionization efficiency, facilitate structure identification and quantitative analysis. Herein, this review discusses derivatization-based MS strategies for lipidomic analysis over the past decade and focuses on all the reported lipid categories, including fatty acids and modified fatty acids, glycerolipids, glycerophospholipids, sterols and saccharolipids. The functional groups of lipids mainly involved in chemical derivatization include the C=C group, carboxyl group, hydroxyl group, amino group, carbonyl group. Furthermore, representative applications of these derivatization-based lipid profiling methods were summarized. Finally, challenges and countermeasures of lipid derivatization are mentioned and highlighted to guide future studies of derivatization-based MS strategy in lipidomics.

Accurate quantification of TAGs to identify adulteration of edible oils by ultra-high performance liquid chromatography-quadrupole-time of flight-tandem mass spectrometry

Edible oils play important roles in biological functions, and triacylglycerols (TAGs) in edible oils are complex mixtures. This makes accurate TAGs quantitation quite difficult that bring economically motivated food adulteration. Herein, we demonstrated a strategy for accurate quantification of TAGs in edible oils, which could be applied in identification of olive oil adulteration. The results showed that the proposed strategy could significantly improve the accuracy of TAG content determination, reduce the relative error of fatty acids (FAs) content determination, and present a wider accurate quantitative range than that of gas chromatography-flame ionization detection. Most important, this strategy coupled with principal component analysis could be used to identify adulteration of high-priced olive oil with cheaper soybean oils, rapeseed oils or camellia oils at a lower concentration of 2%. These findings indicated that the proposed strategy could be regarded as a potential method for edible oils quality and authenticity analysis.

Quantitative Analysis and Structural Elucidation of Fatty Acids by Isobaric Multiplex Labeling Reagents for Carbonyl-Containing Compound (SUGAR) Tags and m-CPBA Epoxidation

In this study, a novel analytical method was developed to investigate fatty acids (FAs) for relative quantification, carbon-carbon double-bond localization, and cis-/trans-geometry differentiation by isobaric multiplex labeling reagents for carbonyl-containing compound (SUGAR) tag conjugation and meta-chloroperoxybenzoic acid (m-CPBA) epoxidation. FAs are essential components of cells and have diverse functions in energy storage and as complex lipid constituents. It has been reported that FAs play different roles in various biological processes such as the functional development of the brain. The comprehensive characterization and quantification of FAs are crucial to further elucidate their biological roles. However, it is challenging to perform relative quantification and structural elucidation of FAs using integrated mass spectrometry (MS)-based methods. Recently, our group developed isobaric multiplex SUGAR tags for quantitative glycomics. Besides aldehyde/ketone groups on glycans, hydrazide groups also possess reactivity toward carboxylic acids on FAs. In this study, we extended SUGAR tag labeling with FAs for the quantitative analysis by liquid chromatography (LC)-MS/MS in the positive ion mode and applied this strategy for the comparative analysis of FAs hydrolyzed from oil samples. In addition, to comprehensively elucidate the structures of unsaturated FAs, epoxidation by m-CPBA was performed before SUGAR tag labeling to enable carbon-carbon double-bond localization. Moreover, the cis- and trans-geometries of carbon-carbon double bonds in multiple pairs of monounsaturated FAs could also be differentiated in higher-energy collisional dissociation (HCD)-MS/MS. This study developed a high-throughput comprehensive FA analysis platform, which could be widely applied and utilized in biological and clinical studies.

A Novel and Sensitive Method for the Analysis of Fatty Acid Biosignatures by Capillary Electrophoresis-Mass Spectrometry

Fatty acids are a well-established class of compounds targeted as biosignatures for future missions to look for evidence of life on ocean worlds such as Europa and Enceladus. In order to establish their abiotic or biotic origin, we need to separate and quantify fatty acids to determine their relative abundances within a sample. In this study, we demonstrate the high potential of capillary electrophoresis coupled to mass spectrometry (CE-MS) for the efficient separation and sensitive detection of a wide variety of fatty acids. Three derivatization strategies were evaluated to allow the detection of fatty acids by positive ionization mode MS. Furthermore, CE-MS conditions were optimized to provide maximum separation efficiencies and detection sensitivities for the analysis of saturated and unsaturated fatty acids with even- and odd-numbered carbon chain lengths. Optimum separation and detection were obtained using a background electrolyte of 2 M acetic acid in 45% acetonitrile, after derivatization of the fatty acids with 2-picolylamine or N,N-diethylethylenediamine. The limits of detection for the derivatized fatty acids using the optimized method ranged from 25 to 250 nM. The optimized method was also used for the analysis of fatty acids in cell cultures and natural samples. Two distinctive biosignatures were obtained for the microorganisms Halobacillus halophilus and Pseudoalteromonas haloplanktis. In addition, multiple fatty acids were detected in a natural sample from Mono Lake, California.

Mass spectrometry in food authentication and origin traceability

Food authentication and origin traceability are popular research topics, especially as concerns about food quality continue to increase. Mass spectrometry (MS) plays an indispensable role in food authentication and origin traceability. In this review, the applications of MS in food authentication and origin traceability by analyzing the main components and chemical fingerprints or profiles are summarized. In addition, the characteristic markers for food authentication are also reviewed, and the advantages and disadvantages of MS-based techniques for food authentication, as well as the current trends and challenges, are discussed. The fingerprinting and profiling methods, in combination with multivariate statistical analysis, are more suitable for the authentication of high-value foods, while characteristic marker-based methods are more suitable for adulteration detection. Several new techniques have been introduced to the field, such as proton transfer reaction mass spectrometry, ambient ionization mass spectrometry (AIMS), and ion mobility mass spectrometry, for the determination of food adulteration due to their fast and convenient analysis. As an important trend, the miniaturization of MS offers advantages, such as small and portable instrumentation and fast and nondestructive analysis. Moreover, many applications in food authentication are using AIMS, which can help food authentication in food inspection/field analysis. This review provides a reference and guide for food authentication and traceability based on MS.

Utilizing AgNPt-SALDI to Classify Edible Oils by Multivariate Statistics of Triacylglycerol Profile

Edible oils are valuable sources of nutrients, and their classification is necessary to ensure high quality, which is essential to food safety. This study reports the establishment of a rapid and straightforward SALDI-TOF MS platform used to detect triacylglycerol (TAG) in various edible oils. Silver nanoplates (AgNPts) were used to optimize the SALDI samples for high sensitivity and reproducibility of TAG signals. TAG fingerprints were combined with multivariate statistics to identify the critical features of edible oil discrimination. Eleven various edible oils were discriminated using principal component analysis (PCA). The results suggested the creation of a robust platform that can examine food adulteration and food fraud, potentially ensuring high-quality foods and agricultural products.

Serumal Lipidomics Reveals the Anti-inflammatory Effect of Flax Lignans and Sinapic Acid in High-Fat-Diet-Fed Mice

Flax lignans (SDG) and sinapic acid (SA) both have the function of antioxidation and anti-inflammation. However, previous studies have focused mainly on biochemical measurements, gene expression analysis, and clinical assessments. There are limited studies that systematically reveal the underlying mechanism of the anti-inflammation effect of SDG or SA from the lipidomic point of view. Herein, the integrated lipidomic profiling platform was used for the analysis of free fatty acids (FFAs), phospholipids (PLs), triacylglycerols (TAGs), and oxylipins in high-fat (HF)-diet-fed mice after SDG or SA administration. Dietary supplementation of SDG or SA downregulated the levels of total TAGs and FFAs in the ApoE^-/- mice model. Furthermore, 28 potential lipids were screened out and considered as key evaluation factors to understand the anti-inflammation function and mechanism of SDG and SA. The results indicated that the anti-inflammatory effect of SDG and SA was principally exerted via regulation of lipid homeostasis.

Pseudotargeted Lipidomics Strategy Enabling Comprehensive Profiling and Precise Lipid Structural Elucidation of Polyunsaturated Lipid-Rich Echium Oil

Echium oil has great nutritional value as a result of its high content of α-linolenic acid (ALA, 18:3ω-3) and stearidonic acid (SDA, 18:4ω-3). However, the comprehensive lipid profiling and exact structural characterization of bioactive polyunsaturated lipids in echium oil have not yet been obtained. In this study, we developed a novel pseudotargeted lipidomics strategy for comprehensive profiling and lipid structural elucidation of polyunsaturated lipid-rich echium oil. Our approach integrated untargeted lipidomics analysis with a targeted lipidomics strategy based on Paternò-Büchi (PB)-tandem mass spectrometry (MS/MS) using 2-acetylpyridine (2-AP) as the reaction reagent, allowing for high-coverage lipid profiling and simultaneous determination of C═C locations in triacylglycerols (TGs), diacylglycerols (DGs), free fatty acids (FFAs), and sterol esters (SEs) in echium oil. A total of 209 lipid species were profiled, among which 162 unsaturated lipids were identified with C═C location assignment and 42 groups of ω-3 and ω-6 C═C location isomers were discovered. In addition, relative isomer ratios of certain groups of lipid C═C location isomers were revealed. This pseudotargeted lipidomics strategy described in this study is expected to provide new insight into structural characterization of distinctive bioactive lipids in food.

Methods of Lipidomic Analysis: Extraction, Derivatization, Separation, and Identification of Lipids

Lipidomics refers to the large-scale study of pathways and networks of cellular lipids in biological systems. A lipidomic analysis often involves the identification and quantification of the thousands of cellular lipid molecular species within a complex biological sample and therefore requires a well optimized method for lipid profiling. In this chapter, the methods for lipidomic analysis, including sample collection and preparation, lipid derivatization and separation, mass spectrometric identification of lipids, data processing and interpretation, and quality control, are overviewed.

A comprehensive study of raw and roasted macadamia nuts: Lipid profile, physicochemical, nutritional, and sensory properties

Macadamia nuts have high nutritional value and positive health attributes. Changes to the composition and availability of these compounds during roasting contribute to product quality. In this study, changes to the chemical composition of lipids (fatty acids, triglycerides, and free fatty acids) and other phytochemicals were analyzed, and a sensory evaluation was carried out of two major varieties of macadamia nuts planted in China, after roasting. Only small changes in fatty acid (FA) content and a slight decrease in total triglycerides (TAGs) were observed after roasting. The free fatty acid (FFA) content and the peroxide value were increased by roasting. The total available polyphenol content increased by 25.6% and the oxidative stability index of kernels increased by 21.6%. The sensory scores for taste and aroma were doubled by roasting. Overall, the sensory, nutritional quality, and oxidative stability of roasted macadamia nuts were greatly improved, compared with raw nuts.

A rapid and highly sensitive UPLC-ESI-MS/MS method for the analysis of the fatty acid profile of edible vegetable oils

The analysis of the fatty acid profile of triglycerides has long played a central role in the evaluation and classification of edible vegetable oils. However, the range of analytical procedures available to evaluate these profiles remains limited and are typically based on transesterification of the triglyceride fatty acid residues to methyl esters, followed by capillary gas-liquid chromatography (GC) coupled with flame ionization or mass spectrometry detection. Although robust and long-proven, these analytical methods tend to entail long chromatographic runs and are relatively insensitive. In order to expand the range of available techniques for the analysis of the fatty acid profile of triglycerides in vegetable oils, we report herein a novel method based upon a rapid and straightforward transesterification of the triglycerides with dimethylaminoethanol under alkaline conditions, followed by a "dilute-and-shoot" analysis by ultra-performance liquid chromatography coupled with electrospray tandem mass spectrometry. The chromatographic analysis is accomplished in 1.5 min, affording a high throughput of samples compared to techniques based upon GC approaches. The method performance was assessed intra- and inter-day with 10 representative saturated and unsaturated fatty acids ranging from C₈ to C₁₈ and afforded fatty acid profile accuracies of 93-108% and imprecisions of only 0.3-2.0%. The limit of quantification of the method, estimated as the minimum amount of derivatized oil sample capable of affording less than 20% accuracy and precision error was determined to be approximately 0.5 pg on-column, making this new method potentially valuable for fields where high sensitivity, precision, and accuracy may be required, such as in toxicology studies, forensics, archeology, or art analysis.

Rapid and Sensitive Detection of Aflatoxin B1, B2, G1 and G2 in Vegetable Oils Using Bare Fe3O4 as Magnetic Sorbents Coupled with High-Performance Liquid Chromatography with Fluorescence Detection

This paper reports a simple, sensitive and reliable method for the simultaneous detection of aflatoxin B1, B2, G1 and G2 in vegetable oils. Aflatoxins were extracted by magnetic solid phase extraction followed by high-performance liquid chromatography, then postcolumn photochemical derivatization and finally detected by fluorescence detector. Vegetable oil samples were first diluted with hexane and then commercial bare Fe3O4 nanoparticles were directly employed as sorbents to extract aflatoxins from complex vegetable oil samples, which significantly simplified the procedure of sample preparation and largely improved the sample analysis throughput. The effects of various parameters such as the amount of sorbent, loading, washing and eluting conditions were carefully optimized to improve the extraction efficiencies of aflatoxins. Under the optimal conditions, the limits of detection of four aflatoxins ranged from 0.01 μg/kg to 0.16 μg/kg, and squared regression coefficients (R2) >0.9990 were obtained within the linear range of 0.1-20 μg/kg (except for aflatoxin G2 with 0.5-20 μg/kg). Furthermore, the recoveries spiked at four concentration levels in a blank vegetable oil sample were from 82.6 to 106.2%, with inter- and intraday relative standard deviations <9.8%, indicating good accuracy and precision of the proposed method.

Lipid profiling in serum from apolipoprotein E-knock out mice fed with different diets and its application to the study of the regulatory effect on lipid metabolism

A lipidome profiling platform was established that could evaluate the cardiovascular health products from lipid changes, their metabolism regulation and intervention mechanism in chronic disease, such as atherosclerosis.