Tracking phospholipid profiling of muscle from Ctennopharyngodon idellus during storage by shotgun lipidomics

Shotgun-Based Mass Spectrometry Analysis of Phospholipid and Triacylglycerol Molecular Species and Eicosanoids in Salmon Muscle Tissue on Feeding Microbial Oil

The continuous growth of aquaculture places a growing demand on alternative sources of fish oil (FO). Certain microorganisms provide a sustainable replacement for FO due to their content of EPA and DHA, which are essential for fish health. Appreciable evidence shows that changes in feeding sources may alter the nutritional components of salmon; however, the influence of diets on lipid species remains unclear. In this study, the identification and semi-quantification of lipid molecular species in salmon muscle during feeding with a microbial oil (MO) were carried out by focusing on triacylglycerol (TAG) and diacyl-phospholipid using shotgun-based mass spectrometry analysis. DHA in the MO diet was efficiently incorporated into phospholipid structures on feeding, followed by accumulation in salmon muscle. The MO diet elevated the level of certain EPA-containing TAGs, such as TAG C52:5 (16:0_16:0_20:5) and TAG C54:6 (16:0_18:1_20:5), indicating that the MO diet may be an excellent source for enhancement of the abundance of ω3 lipids. Further, prostaglandins (PGs) PGE2 and PGF3α were identified and quantified for the first time in salmonid tissue.

Shotgun lipidomics reveals the changes in phospholipids of brown rice during accelerated aging

Brown rice exhibits higher nutritional value and attracts more and more attentions; however, the change in phospholipid molecular species in brown rice during aging is poorly understood. In this study, shotgun lipidomics was employed to investigate the changes in phospholipid molecular species in four brown rice varieties (two japonica rice and two indica rice) during accelerated aging. A total of 64 phospholipid molecular species were identified, and most of them were rich in polyunsaturated fatty acids. For japonica rice, phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylglycerol (PG) gradually decreased during accelerated aging. However, the content of PC, PE, and PG in indica rice showed no difference during accelerated aging. Significantly different phospholipid molecular species from four brown rice were screened during accelerated aging. Based on these significantly different phospholipids, the metabolic pathways including glycerophospholipid metabolism and linoleic acid metabolism during accelerated aging were depicted. The findings from this study could be helpful in explaining the impact of accelerated aging on phospholipids of brown rice, and offer an understanding on relationships between phospholipids degradation and brown rice deterioration.

Nutritional lipidomics for the characterization of lipids in food

Lipids represent one out of three major macronutrient classes in the human diet. It is estimated to account for about 15-20% of the total dietary intake. Triacylglycerides comprise the majority of them, estimated 90-95%. Other lipid classes include free fatty acids, phospholipids, cholesterol, and plant sterols as minor components. Various methods are used for the characterization of nutritional lipids, however, lipidomics approaches become increasingly attractive for this purpose due to their wide coverage, comprehensiveness and holistic view on composition. In this chapter, analytical methodologies and workflows utilized for lipidomics profiling of food samples are outlined with focus on mass spectrometry-based assays. The chapter describes common lipid extraction protocols, the distinct instrumental mass-spectrometry based analytical platforms for data acquisition, chromatographic and ion-mobility spectrometry methods for lipid separation, briefly mentions alternative methods such as gas chromatography for fatty acid profiling and mass spectrometry imaging. Critical issues of important steps of lipidomics workflows such as structural annotation and identification, quantification and quality assurance are discussed as well. Applications reported over the period of the last 5years are summarized covering the discovery of new lipids in foodstuff, differential profiling approaches for comparing samples from different origin, species, varieties, cultivars and breeds, and for food processing quality control. Lipidomics as a powerful tool for personalized nutrition and nutritional intervention studies is briefly discussed as well. It is expected that this field is significantly growing in the near future and this chapter gives a short insight into the power of nutritional lipidomics approaches.

UHPLC-Q-Orbitrap-based untargeted lipidomics reveals the variation of yolk lipids during egg storage

BACKGROUND

Egg yolk is recognized for its excellent nutritional benefit and economic value; however, egg is a perishable food, potentially losing quality if not handled properly between the time from farm production to consumption. Knowledge of the changes of yolk lipid composition under an extreme storage condition close to vitelline membrane breaking, which results in an inedible condition for shelf-eggs, remains incomplete. Considering the complexity of yolk lipids, the architectural features of yolk lipids at high-temperature storage (30°C for 10 days versus fresh) were classified through lipidomics.

RESULTS

This strategy yielded 1508 features within the lipid database coupled with 74 significantly different lipids (P < 0.05, fold change > 1.2 or < 0.83), mainly triglycerides, phospholipids, and sphingolipids. Most of them were decreased after storage; for example, triglycerides were assumed to play a role as a 'buffer' to maintain the system stability during storage by balancing fatty acid saturation, which strongly reduces the egg edible value for humans. Furthermore, phospholipids, especially the highly unsaturated phosphatidylcholine, decreased significantly and were suggested to be the primary cause for the variation in yolk emulsifying properties and flavor.

CONCLUSION

Altogether, these results deriving from oxidation and lipolysis reactions enhance our understanding of lipid transformation and the biochemical mechanisms, at the molecular level, of the deteriorative process of the egg yolk. These findings may lay the foundation for identifying processes, including some modifications of the lipid composition of rations fed to laying hens, aiming to improve the long-term shelf-stability of shell eggs and egg products. © 2022 Society of Chemical Industry.

Analysis of Lipids in Green Coffee by Ultra-Performance Liquid Chromatography–Time-of-Flight Tandem Mass Spectrometry

Lipid components in green coffee were clarified to provide essential data support for green coffee processing. The types, components, and relative contents of lipids in green coffee were first analyzed by ultra-performance liquid chromatography–time-of-flight tandem mass spectrometry (UPLC-TOF-MS/MS). The results showed that the main fatty acids in green coffee were linoleic acid (43.39%), palmitic acid (36.57%), oleic acid (8.22%), and stearic acid (7.37%). Proportionally, the ratio of saturated fatty acids/unsaturated fatty acids/polyunsaturated fatty acids was close to 5.5:1:5.2. A total of 214 lipids were identified, including 15 sterols, 39 sphingosines, 12 free fatty acids, 127 glycerides, and 21 phospholipids. The main components of sterols, sphingosines, free fatty acids, glycerides, and phospholipids were acylhexosyl sitosterol, ceramide esterified omega-hydroxy fatty acid sphingosine, linoleic acid, and triglyceride, respectively. UPLC-TOF-MS/MS furnished high-quality and accurate information on TOF MS and TOF MS/MS spectra, providing a reliable analytical technology platform for analyzing lipid components in green coffee.

Advanced Lipidomics in the Modern Meat Industry: Quality Traceability, Processing Requirement, and Health Concerns

Over the latest decade, lipidomics has been extensively developed to give robust strength to the qualitative and quantitative information of lipid molecules derived from physiological animal tissues and edible muscle foods. The main lipidomics analytical platforms include mass spectrometry (MS) and nuclear magnetic resonance (NMR), where MS-based approaches [e.g., "shotgun lipidomics," ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF-MS)] have been widely used due to their good sensitivity, high availability, and accuracy in identification/quantification of basal lipid profiles in complex biological point of view. However, each method has limitations for lipid-species [e.g., fatty acids, triglycerides (TGs), and phospholipids (PLs)] analysis, and necessitating the extension of effective chemometric-resolved modeling and novel bioinformatic strategies toward molecular insights into alterations in the metabolic pathway. This review summarized the latest research advances regarding the application of advanced lipidomics in muscle origin and meat processing. We concisely highlighted and presented how the biosynthesis and decomposition of muscle-derived lipid molecules can be tailored by intrinsic characteristics during meat production (i.e., muscle type, breed, feeding, and freshness). Meanwhile, the consequences of some crucial hurdle techniques from both thermal/non-thermal perspectives were also discussed, as well as the role of salting/fermentation behaviors in postmortem lipid biotransformation. Finally, we proposed the inter-relationship between potential/putative lipid biomarkers in representative physiological muscles and processed meats, their metabolism accessibility, general nutritional uptake, and potency on human health.

Mass spectrometry-based lipidomics in food science and nutritional health: A comprehensive review

With the advance in science and technology as well as the improvement of living standards, the function of food is no longer just to meet the needs of survival. Food science and its associated nutritional health issues have been increasingly debated. Lipids, as complex metabolites, play a key role both in food and human health. Taking advantages of mass spectrometry (MS) by combining its high sensitivity and accuracy with extensive selective determination of all lipid classes, MS-based lipidomics has been employed to resolve the conundrum of addressing both qualitative and quantitative aspects of high-abundance and low-abundance lipids in complex food matrices. In this review, we systematically summarize current applications of MS-based lipidomics in food field. First, common MS-based lipidomics procedures are described. Second, the applications of MS-based lipidomics in food science, including lipid composition characterization, adulteration, traceability, and other issues, are discussed. Third, the application of MS-based lipidomics for nutritional health covering the influence of food on health and disease is introduced. Finally, future research trends and challenges are proposed. MS-based lipidomics plays an important role in the field of food science, promoting continuous development of food science and integration of food knowledge with other disciplines. New methods of MS-based lipidomics have been developed to improve accuracy and sensitivity of lipid analysis in food samples. These developments offer the possibility to fully characterize lipids in food samples, identify novel functional lipids, and better understand the role of food in promoting healt.

Electric Soldering Iron Ionization Mass Spectrometry Based Lipidomics for in Situ Monitoring Fish Oil Oxidation Characteristics during Storage

An electric soldering iron ion source (ESII) coupling with rapid evaporative ionization mass spectrometry (REIMS) was developed and used for in situ monitoring the dynamic variation trend in oxidation characteristics of fish oil during storage. The lipidomics profiles of fish oil stored at various days were acquired by ESII-REIMS. The fatty acid and triacylglycerol species were structurally identified, and their abundances were analyzed according to multivariate statistical models mainly including principle component analysis as well as orthogonal partial least-squares analysis. On the shared and unique structure plot, the ions of m/z 255.23, 281.24, 877.72, and 901.72 displayed the most significant variation among the oxidized fish oil samples. Based on receiver operating characteristic curve analysis with an optimal Youden index of 0.91, these markers were further verified. The variation of viscosity and volatiles were also evaluated to further verify the oxidation characteristics of fish oil. The study demonstrated that ESII-REIMS technology used as an advanced detection method could ensure fish oil quality during storage.

Real-Time Monitoring of the Oxidation Characteristics of Antarctic Krill Oil (Euphausia superba) during Storage by Electric Soldering Iron Ionization Mass Spectrometry-Based Lipidomics

Antarctic krill oil (AKO) is susceptible to oxidation due to the high unsaturation degree of bioactive substances. Herein, a lipidomics method for in situ monitoring of the dynamic oxidation characteristics in AKO was explored based on electric soldering iron ion source (ESII) coupling with rapid evaporative ionization mass spectrometry (REIMS). The lipidomics profiles of AKO at different storage periods were successfully acquired. On the basis of principal component analysis and orthogonal partial least-squares analysis, the obtained REIMS data were employed to build a multivariate recognition model. The ions of m/z 707.50, 721.50, 833.49, and 837.54 contributed the most significant effect on the multivariate data model for the authentication of different AKO samples. Besides, the variation of viscosity, astaxanthin, and volatile compounds were also evaluated to corroborate the oxidation characteristics. The results indicated that the ESII-REIMS technology could be applied as an advanced rapid detection method to secure oil and fat quality during storage.

Comparative lipid profile of four edible shellfishes by UPLC-Triple TOF-MS/MS

An ultra performance liquid chromatography-Triple time of flight mass spectrometry (UPLC-Triple TOF-MS/MS) method were established to characterize the lipid profiles in four shellfish species. More than 600 lipid molecular species belonging to 14 classes were detected. Phospholipids (PLs) were predominant in Chlamys farreri (54.9%) and glycerolipids (GLs) were dominant in Ostrea gigas (51.6%). PLs that contained polyunsaturated fatty acids (PUFAs) such as PC (16:0/20:5), PC (16:0/22:6) and PE (18:0/22:6) were the main molecular species. Especially, the percentage of sphingolipids (SLs) in four shellfishes is considerable (18.8-38.6%), the characterization of their special long-chain base (LCB) structure (mainly d19:3) and N-acyl group (mainly 16:0) was realized. Several SL subclasses with low abundance in four shellfish species, such as ceramide 2-aminoethylphosphonate (CAEP) and deoxy-ceramide (DeoxyCer), were also detected. These active lipids identified by this method have potential value in revealing the nutritional value of shellfishes and serving as biomarkers for distinguishing different shellfishes.

Comparative Lipid Profile Analysis of Four Fish Species by Ultraperformance Liquid Chromatography Coupled with Quadrupole Time-of-Flight Mass Spectrometry

A high-throughput lipid analysis method was established to comprehensively investigate the lipid profiles of three marine (Scomberomorus niphonius, Scophthalmus maximus, and Oncorhynchus keta) and one freshwater (Ctenopharyngodon idellus) fish species using ultraperformance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Over 700 molecular species from 12 major lipid subclasses were identified. Glycerolipids (73.7-85.6%) and phospholipids (PLs, 13.7-25.6%) were dominant components in total lipids. Polyunsaturated fatty acid PLs, such as phosphatidylethanolamine (PE, 16:0-22:6), PE (18:1-22:6), and phosphatidylcholine (16:0-22:6), were the major molecular species in PLs. The lipid composition of three marine fish (mainly C22:5) was significantly different from that in C. idellus (mainly C20:4 and C20:5). A unique long-chain base of sphingolipids was found in fish (mainly d19:3). These bioactive lipids were proposed to be potential biomarkers for distinguishing different fish species and evaluating nutritional values.

Natural phospholipids: Occurrence, biosynthesis, separation, identification, and beneficial health aspects

During the last years, phospholipids (PLs) have attracted great attention because of their crucial roles in providing nutritional values, technological and medical applications. There are considerable proofs that PLs have unique nutritional benefits on human health, such as reducing cholesterol absorption, improving liver functions, and decreasing the risk of cardiovascular diseases. PLs are the main structural lipid components of cell and organelle membranes in all living organisms, and therefore, they occur in all organisms and the derived food products. PLs are distinguished by the presence of a hydrophilic head and a hydrophobic tail, consequently they possess amphiphilic features. Due to their unique characteristics, the extraction, separation, and identification of PLs are critical issues to be concerned. This review is focused on the content of PLs classes in several sources (including milk, vegetable oils, egg yolk, and mitochondria). As well, it highlights PLs biosynthesis, and the methodologies applied for PLs extraction and separation, such as solvent extraction and solid-phase extraction. In addition, the determination and quantification of PLs classes by using thin layer chromatography, high-performance liquid chromatography coupled with different detectors, and nuclear magnetic resonance spectroscopy techniques.

Use of Foodomics for Control of Food Processing and Assessing of Food Safety

Food chain, food safety, and food-processing sectors face new challenges due to globalization of food chain and changes in the modern consumer preferences. In addition, gradually increasing microbial resistance, changes in climate, and human errors in food handling remain a pending barrier for the efficient global food safety management. Consequently, a need for development, validation, and implementation of rapid, sensitive, and accurate methods for assessment of food safety often termed as foodomics methods is required. Even though, the growing role of these high-throughput foodomic methods based on genomic, transcriptomic, proteomic, and metabolomic techniques has yet to be completely acknowledged by the regulatory agencies and bodies. The sensitivity and accuracy of these methods are superior to previously used standard analytical procedures and new methods are suitable to address a number of novel requirements posed by the food production sector and global food market.

Hydrophilic interaction chromatography based solid-phase extraction and MALDI TOF mass spectrometry for revealing the influence of Pseudomonas fluorescens on phospholipids in salmon fillet

Salmon is a popular food but it is easily susceptible to spoilage by contamination with microorganisms. In this study, a method using hydrophilic interaction chromatography (HILIC)-based solid-phase extraction (SPE) and matrix-assisted laser desorption and ionization time-of-flight/time-of-flight mass spectrometry was developed and applied to reveal the effect of Pseudomonas fluorescens on salmon fillet during the shelf-life period by measuring the changes in the levels of phosphatidylcholine and phosphatidylethanolamine. Fresh samples were inoculated with P. fluorescens (10(6) cfu g(-1)) for 30 s, and lipids were extracted at 0, 24, 48, and 72 h. A homemade SPE cartridge packed with HILIC sorbent (silica derivatized with 1,2-dihydroxypropane) was used for matrix cleanup prior to analysis by mass spectrometry. In total, 30 phospholipids and 16 lysophospholipids were detected and elucidated. The results revealed that the content of phospholipids decreased significantly, whereas that of lysophospholipids increased initially, followed by a gradual reduction as the cold storage time increased. The contamination by P. fluorescens negatively affected the quality of fresh salmon without obvious physical changes, but it posed a potential threat to human health. This study suggests that the well-established method could be used for detecting phospholipids in salmon fillet and perhaps other foods as well.

A lipidomic platform establishment for structural identification of skin ceramides with non-hydroxyacyl chains

The stratum corneum (SC) is the outermost layer of skin that functions as a barrier and protects against environmental influences and transepidermal water loss. Its unique morphology consists of keratin-enriched corneocytes embedded in a distinctive mixture of lipids containing mainly ceramides, free fatty acids, and cholesterol. Ceramides are sphingolipids consisting of sphingoid bases, which are linked to fatty acids by an amide bond. Typical sphingoid bases in the skin are composed of dihydrosphingosine (dS), sphingosine (S), phytosphingosine (P), and 6-hydroxysphingosine (H), and the fatty acid acyl chains are composed of non-hydroxy fatty acid (N), α-hydroxy fatty acid (A), ω-hydroxy fatty acid (O), and esterified ω-hydroxy fatty acid (E). The 16 ceramide classes include several combinations of sphingoid bases and fatty acid acyl chains. Among them, N-type ceramides are the most abundant in the SC. Mass spectrometry (MS)/MS analysis of N-type ceramides using chip-based direct infusion nanoelectrospray-ion trap mass spectrometry generated the characteristic fragmentation pattern of both acyl and sphingoid units, which could be applied to structural identification of ceramides. Based on the MS/MS fragmentation patterns of N-type ceramides, comprehensive fragmentation schemes were proposed. In addition, mass fragmentation patterns, which are specific to the sphingoid backbone of N-type ceramides, were found in higher m/z regions of tandem mass spectra. These characteristic and general fragmentation patterns were used to identify N-type ceramides in human SC. Based on established MS/MS fragmentation patterns of N-type ceramides, 52 ceramides (including different classes of NS, NdS, NP, and NH) were identified in human SC. The MS/MS fragmentation patterns of N-type ceramides were characterized by interpreting their product ion scan mass spectra. This information may be used to identify N-type ceramides in the SC of human, rat, and mouse skin.

Lipidomic fingerprint of almonds (Prunus dulcis L. cv Nonpareil) using TiO₂ nanoparticle based matrix solid-phase dispersion and MALDI-TOF/MS and its potential in geographical origin verification

A matrix solid-phase dispersion (MSPD) procedure with titanium dioxide (TiO2) nanoparticles (NP) as sorbent was developed for the selective extraction of phospholipids from almond samples, and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF/MS) was employed for analysis. A remarkable increase in the signals of phospholipid accompanied by a decrease in those of triacylglycerols and diacylglycerols was observed in the relevant mass spectra. The proposed method was applied to five batches of almonds originating from four geographical areas, whereas principal component analysis (PCA) was utilized to normalize the relative amounts of the identified phospholipid species. The results indicated that the lipidomic fingerprint of almonds was successfully established by the negative ion mode spectrum, and the ratio of m/z 833.6 to 835.6 as well as m/z 821.6 could be introduced as potential markers for the differentiation of the tested almonds with different geographical origins. The whole method is of great promise for selective separation of phospholipids from nonphospholipids, especially the glycerides, and superior in fast screening and characterization of phospholipids in almond samples.

Two-dimensional ³¹P,¹H NMR spectroscopic profiling of phospholipids in cheese and fish

Phospholipids (PLs) comprise an important lipid class in food because of their technological use as emulsifiers and their nutritional value. This study used one-dimensional (31)P NMR and two-dimensional (2D) (31)P,(1)H COSY NMR spectroscopy for the determination of the PL composition of cheese and fish after liquid-liquid enrichment. This extraction step enabled the identification of 10 PLs in cheese and 9 PLs in fish by 2D (31)P,(1)H NMR. Variations in the (31)P shifts indicated differences in the fatty acids attached to the individual PLs. The total PL content in cheese fat and fish oil ranged from 0.3 to 0.4% and from 5 to 12%, respectively. Phosphatidylcholine was the most prominent PL in both matrices (up to 65%). Minor PLs (limit of detection = 4 nmol, i.e. 500 μL of an 8 μM solution) were identified in forms of phosphatidic acid, lysophosphatidic acid, and phosphatidylglycerol. Specific cross couplings and (1)H fine structures in the 2D (31)P,(1)H NMR spectra proved to be valuable for the assignment and verification of known and uncommon PLs in the samples.

Analysis of phospholipids in infant formulas using high performance liquid chromatography-tandem mass spectrometry

Phospholipids have been used widely in the food industry as emulsifiers, but it is their biological and nutritional function that has been the focus over recent years. The recognition of the importance of phospholipids and sphingomyelin for infant development has led to an increase in the number of infant formulas claiming to contain these complex lipid components. Therefore, the ability to measure these lipids in infant formulas and dairy-derived complex lipid ingredients for fortification purposes is important. A high-performance liquid chromatography-tandem mass spectrometry method that quantifies phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and sphingomyelin found in infant formulas and dairy-derived complex lipid ingredients is described. The method uses external standards of similar fatty acid profile for calibration. The recovery of phospholipids ranged from 92% to 102% with a method repeatability coefficient of variation of 6-10%. In addition to the specificity and selectivity of the method, details of the molecular species in the individual phospholipid classes are available using this method.

Shotgun lipidomics strategy for fast analysis of phospholipids in fisheries waste and its potential in species differentiation

An efficient shotgun lipidomics strategy was established and optimized for fast phospholipid profiling of viscera from three fish species: Lateolabrax japonicas, Ctenopharyngodon idellus, and Carassius auratus. This strategy relies on direct infusion of total lipid extracts into a tandem mass spectrometer without additional separation of the individual molecular species. Four classes of phospholipids, including phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), and phosphatidylserine (PS), were analyzed, and at least 81 molecular species of phospholipids were identified, including 34 species of PC, 24 species of PE, 12 species of PS, and 11 species of PI, in both positive- and negative-ion electrospray ionization mode. The results show that fish viscera, which are traditionally discarded as fisheries wastes, are nutritional in phospholipids with total contents of the four detected phospholipid classes ranging from 1.52 to 3.29 mg/g in the three tested fish species. Regardless of the tested fish species, PC and PE are the dominant phospholipid classes, followed by PI and PS. Furthermore, principal component analysis (PCA) was applied to normalize the relative amounts of the identified phospholipid species. The results demonstrate that PS 18:0/22:6, PI 18:0/20:4, and PI 18:0/20:5 were the main contributors of cumulative value and could be used as an indicator for fish species differentiation. This shotgun lipidomics method was >10 times faster than traditional methods, because no chromatographic separation was needed. The successful application of this strategy paves the way for full utilization of traditionally discarded fisheries wastes and provides an alternative means for fish species differentiation.