A comprehensive study of lipid profiles of round scad (Decapterus maruadsi) based on lipidomic with UPLC-Q-Exactive Orbitrap-MS

Characterization of the differences in lipid profiles and volatile compounds of adipose stem cells adipogenic differentiation and adipocytic transdifferentiation of muscle stem cells from large yellow croakers based on UPLC-MS/MS and GC-IMS

Lipids contribute significantly to the flavor of cell-cultured fish meat as precursor components of flavor compounds. Here, we initially reported the differences in lipid metabolite profiles and volatile compounds between adipogenic differentiation of adipose stem cells (ASCs) and adipocytic transdifferentiation of muscle stem cells (MSCs) from large yellow croakers. A total of 2106 lipid metabolites were identified by UPLC-MS/MS. Compared with the MSCs group, 1263 differentially expressed lipid metabolites were found in the ASCs group, with 1026 up-regulated lipid metabolites and 237 down-regulated ones. The main lipid differences were fatty acyls (FAs) and glycerolipids (GL). GC-IMS identified a total of 47 volatile compounds. Volatile compounds such as ethyl laurate, nonanal, and 2,3-pentanedione were significantly higher in the ASCs group than in the MSCs group. GC-IMS results indicated that the ASCs group was more flavorful. This study provides a theoretical basis for developing cell-cultured fish meat with a familiar flavor.

Storage Stability and Lipidomic Analysis Reveal the Effect of Frozen Storage Temperature on Pacific Saury (Cololabis saira)

OBJECTIVES

This study aimed to assess the effects of storage temperature on the lipidomics profile change in Pacific saury (Cololabis saira).

METHODS

In this paper, C. saira underwent frozen storage at two different temperatures, T1 (-18 °C) and T2 (-25 °C), for a duration of three months. Chemical and lipidomic methods were used to determine the changes in lipids during the storage process.

RESULTS

Results showed that the content of triglyceride and phospholipid decreased significantly (p < 0.05), and free fatty acid increased significantly (p < 0.05), while the content of total cholesterol remained relatively constant across different storage temperatures. Additionally, an increasing trend in AV, POV, and TBARS contents was observed after the freezing process, with lipid oxidation being significantly higher in the -18 °C group compared to the -25 °C group (p < 0.05). A comprehensive analysis identified 4854 lipid molecules in the muscles of C. saira, categorized into 46 lipid subclasses, predominantly including triglycerides (TG), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylglycerol (PG), and diglycerides (DG). Among them, TG was the most abundant lipid, followed by PC. Using orthogonal partial least squares discriminant analysis (OPLS-DA) with a variable importance in projection (VIP) score > 1 and p value < 0.05 as criteria, 338, 271, and 103 highly significantly differentiated lipids were detected in the comparison groups CK vs. T1, CK vs. T2, and T1 vs. T2, respectively. The results indicated that storage at -18 °C had a more pronounced effect than storage at -25 °C. During the freezing process, TG expression was significantly down-regulated, and TG(18:4_14:0_20:5), TG(20:5_13:0_22:6), TG(22:6_14:1_22:6), and TG(18:4_13:0_22:6) were the most predominant individuals. The CK group was initially present in C. saira before storage. Differential lipid molecules in the CK vs. T1 and CK vs. T2 groups were screened using a fold change (FC) > 2 or FC < 0.5. In the CK vs. T2 group, 102 highly significant differential lipid molecules were identified, with 55 being down-regulated across seven subclasses. In contrast, the CK vs. T1 group revealed 254 highly significant differential lipid molecules, with 85 down-regulated across 13 subclasses. The results showed that more PCs and PEs were down-regulated, with a higher differential abundance of PE and PC in the -25 °C group compared to the -18 °C group. The differential metabolites were primarily enriched in 17 metabolic pathways, with glycerophospholipid metabolism being the most prominent, followed by sphingolipid metabolism during the frozen storage.

CONCLUSIONS

Overall, -25 °C storage in production was more favorable for maintaining the lipid stability of C. saira. This work could provide useful information for aquatic product processing and lipidomics.

Effects of Red Vinasse on Physicochemical Qualities of Blue Round Scad (Decapterus maruadsi) During Storage, and Shelf Life Prediction

A fish processed with red vinasse is a type of Fujian cuisine with regional characteristics. In order to monitor the effect of red vinasse on storage quality and shelf life of blue round scad (Decapterus maruadsi) during storage, the changes in fat content, thiobarbituric acid reactive substances (TBARS), composition of polyunsaturated fatty acids (PUFAs), pH value, texture, and sensory quality were studied at different storage temperatures (4 °C, 25 °C, and 37 °C). By analyzing the correlation between changes in sensory qualities and physical and chemical indexes, a first-order kinetic model and the Arrhenius equation were used to build a shelf-life prediction model for blue round scad during storage. The results showed that processing with red vinasse can significantly reduce the malondialdehyde (MDA) production and the decrease in PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (p < 0.05) during storage. Based on partial least squares regression (PLSR), the storage temperature and time have a significant impact on the PUFA composition in blue round scad, which changed less when the samples were stored at 4 °C and 25 °C, and they had better nutritional composition of fatty acids at lower temperatures. Among the PUFAs, DHA (C22:6n-3) and EPA (C20:5n-3) had higher relative contents and significantly decreased during storage (p < 0.05). Additionally, the processing with red vinasse can slow down the increase in total volatile basic nitrogen (TVB-N) value and pH of blue round scad, maintain the appropriate hardness, elasticity, cohesion and chewability, and improve the overall sensory quality of the fish. In addition, according to the results of model prediction based on TBARS value, the storage shelf life of blue round scad with red vinasse added was 55 d, 2.7 d and 28 h at 4 °C, 25 °C and 37 °C, respectively. The accuracy of the forecast model was high, and the relative errors of the measured values and predicted values were less than 10%. Thus, it not only provided a theoretical basis for the processing and application of red vinasse to Chinese traditional food, but also provided innovative ideas for the safe storage and high-value utilization of blue round scad.

A comparative lipid profile of four fish species: From muscle to industrial by-products based on RPLC-Q-TOF-MS/MS

Fish are crucial for the fishing industry and essential nutrient provision, including lipids. This study employed a high-throughput lipidomic approach to evaluate and contrast the lipid profiles of three marine fish species (P. crocea, S. fuscens, and C. saira) and one freshwater species (H. molitrix) across head, muscle, and viscera. Over 1000 molecular lipid species across 17 subclasses were identified. Notably, acylated monogalactosyldiacylglycerol (acMGDG) was detected for the first time in these species, with a high prevalence of saturated fatty acids (44.7 %-87.7 %). Glycerolipids (67.7 - 86.3 %) and PLs (10.7 - 31.8 %) were identified as the dominant lipid classes. Marine fish muscles displayed higher PL content than freshwater species, and P. crocea viscera contained over 30 % PLs of total lipids. In particular, ether phosphatidyl ethanolamine incorporated more DHA than ether phosphatidylcholine. The viscera of four fish species also exhibited a significant abundance of diacylglycerol (DG), indicating their potential as functional lipid sources. Multivariate analysis identified triglyceride (TG) (59:13), DG (16:1/22:5), and MGDG (16:0/18:2) as potential biomarkers for differentiating among fish anatomical parts. This study deepens the understanding of the nutritional values of these fish, providing guidance for consumer dietary choices and paving the way for transforming previously underutilized by-products into resources with high-value potential.

Comprehensive Lipidomic Analysis of Three Edible Microalgae Species Based on RPLC-Q-TOF-MS/MS

Microalgae, integral to marine ecosystems for their rich nutrient content, notably lipids and proteins, were investigated by using reversed-phase liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (RPLC-Q-TOF-MS/MS). This study focused on lipid composition in three commonly used microalgae species (Spirulina platensis, Chlorella vulgaris, and Schizochytrium limacinum) for functional food applications. The analysis unveiled more than 700 lipid molecular species, including glycolipids (GLs), phospholipids (PLs), sphingolipids (SLs), glycerolipids, and betaine lipids (BLs). GLs (19.9-64.8%) and glycerolipids (24.1-70.4%) comprised the primary lipid. Some novel lipid content, such as acylated monogalactosyldiacylglycerols (acMGDG) and acylated digalactosyldiacylglycerols (acDGDG), ranged from 0.62 to 9.68%. The analysis revealed substantial GLs, PLs, and glycerolipid variations across microalgae species. Notably, S. platensis and C. vulgaris displayed a predominance of fatty acid (FA) 18:2 and FA 18:3 in GLs, while S. limacinum exhibited a prevalence of FA 16:0, collectively constituting over 60% of the FAs of GLs. In terms of PLs and glycerolipids, S. platensis and C. vulgaris displayed elevated levels of arachidonic acid (AA) and eicosapentaenoic acid (EPA), whereas S. limacinum exhibited a significant presence of docosahexaenoic acid (DHA). Principal component analysis (PCA) revealed MGDG (16:0/18:1), DG (16:0/22:5), Cer (d18:1/20:0), and LPC (16:1) as promising lipid markers for discriminating between these microalgae samples. This study contributes to a comprehensive understanding of lipid profiles in three microalgae species, emphasizing their distinct biochemical characteristics and potentially informing us of their high-value utilization in the food industry.

Application of Chromatographic and Spectroscopic-Based Methods for Analysis of Omega-3 (ω-3 FAs) and Omega-6 (ω-6 FAs) Fatty Acids in Marine Natural Products

Omega-3 fatty acids v(ω-3 FAs) such as EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) and omega-6 fatty acids (ω-6 FAs) such as linoleic acid and arachidonic acid are important fatty acids responsible for positive effects on human health. The main sources of ω-3 FAs and ω-6 FAs are marine-based products, especially fish oils. Some food, supplements, and pharmaceutical products would include fish oils as a source of ω-3 FAs and ω-6 FAs; therefore, the quality assurance of these products is highly required. Some analytical methods mainly based on spectroscopic and chromatographic techniques have been reported. Molecular spectroscopy such as Infrared and Raman parallel to chemometrics has been successfully applied for quantitative analysis of individual and total ω-3 FAs and ω-6 FAs. This spectroscopic technique is typically applied as the alternative method to official methods applying chromatographic methods. Due to the capability to provide the separation of ω-3 FAs and ω-6 FAs from other components in the products, gas and liquid chromatography along with sophisticated detectors such as mass spectrometers are ideal analytical methods offering sensitive and specific results that are suitable for routine quality control.

Comparison and enrichment of sn-2 palmitoyl triacylglycerols (OPO/OPL) in fish oil for its potential application as human milk fat substitutes

Triacylglycerols (TAG) are differences in fatty acid distributions between infant formula and human milk. In this study, fish oil (Tilapia, Golden pompano, Tiger grouper, and Basa) showed the potential as the source of human milk fat substitutes by comparing TAG profiles with infant formula and human milk. The total lipids and TAG of fish were concentrated in the by-products of fish (head and viscera) and contained high levels of palmitic acid, oleic acid, and linoleic acid. Compared with infant formula, fish oil was closer to human milk in sn-2 fatty acid distribution, and sn-2 palmitic acid level in fish oil exceeded 52 % of total palmitic acid, Golden pompano head was the highest (64.46 %). Further research showed that the content of sn-2 palmitoyl TAG (OPO and OPL dominated) increased from 157.16 mg/g TAG to 305.18 mg/g TAG by isopropanol enrichment (solid-liquid ratio: 1:4, temperature: -12 °C, time: 4 h).

Changes in the lipid profiles of hairtail (Trichiurus lepturus) muscle during air-drying via liquid chromatography-mass spectrometry analysis

Chemical and liquid chromatography-mass spectrometry (LC/MS)-based lipidomics analyses were performed to explore the alterations in lipid profiles in the hairtail muscle during air-drying. The peroxide value (POV) and carbonyl group value (CGV) in the air-dried hairtail (ADH) significantly increased with air-drying time. Lipidomics results revealed 1,326 lipids, which were grouped into 33 lipid categories, including 422 triglycerides (TGs), 170 phosphatidylcholines (PCs), 110 phosphatidylethanolamines (PEs), among others. In addition, ADH contained 131 and 201 differentially abundant lipids (DALs) at high and low levels, respectively. Among them, DALs, TGs, PCs, LPCs, and LPEs could be used to distinguish between ADH and FH samples. The apparent alterations in ADH and FH samples were attributed to lipid decomposition, side-chain modifications during oxidation, or oxygen- and salt-promoted lipid oxidation. Thus, this study provides a more comprehensive understanding of hairtail lipid profiles before and after air-drying which can be used as a guide for hairtail products.

The dynamic changes of flavors and UPLC-Q-Exactive-Orbitrap-MS based lipidomics in mackerel (Scomberomorus niphonius) during dry-cured processing

Dry-cured mackerel is favored by consumers for its suitable salty flavor. Herein, the dynamic changes of volatile compounds and lipids in the mackerel, and the lipidomics based on UPLC-Orbitrap/MS technique during dry-cured processing were investigated. The results showed that endogenous lipases activities in dry-cured mackerel decreased. The dry-cured processing of mackerel had significant effects on its lipid classes and content. The contents of Arachidonic acid (C20:4n6), docosapentaenoic acid (C22:5n3), linoleic acid (LA, C18:2n6), alpha-linolenic acid (C18:3n3), eicosatrienoic acid (C20:3n3) and docosahexaenoic acid (DHA, C22:6n3) increased during dry-cured processing. A total of 38 kinds of volatile compounds were detected in the dry-cured mackerel, 12 of which were derived from fatty acid oxidation. Among 30 lipid metabolites (FC ≥ 2 and VIP > 2), phosphatidylethanolamine (PE, 19:0/22:6) accounted for the highest content, and its difference between three stages was the most obvious. Glycerophospholipid and sphingolipid metabolisms were the most important metabolic pathways involved in dry-cured processing.

UHPLC-Q-Exactive Orbitrap MS/MS-based untargeted lipidomics reveals molecular mechanisms and metabolic pathways of lipid changes during golden pomfret (Trachinotus ovatus) fermentation

Fermented golden pomfret (a popular marine fish product) is prepared via spontaneous fermentation. However, no comprehensive analysis has been reported on its lipid composition and metabolism. Herein, UHPLC-MS/MS-based untargeted lipidomic analysis identified 998 lipids (six classes; 29 subclasses) in fermented golden pomfret, including glycerolipids (47.70%) and glycerophospholipids (32.06%). As fermentation proceeded, triglyceride and diglyceride contents increased and subsequently decreased, while that of poly-unsaturated fatty acid-containing lipids increased (including those with docosahexaenoic acid, eicosapentaenoic acid, and docosapentaenoic acid). Pathway enrichment analysis identified seven lipid-related metabolic pathways, with the glycerophospholipid pathway found to be the most pertinent. Moreover, the decreased abundance of phosphatidylethanolamines and phosphatidylcholines during fermentation results from their high unsaturated fatty acid (FA) content. Indeed, essential FA contents increase following fermentation, due to their occurrence as glycerolipid side chains. Collectively, the results of this study provide a theoretical reference for optimizing the quality of fermented fish products.

Different Thermal Treatment Methods and TGase Addition Affect Gel Quality and Flavour Characteristics of Decapterus maruadsi Surimi Products

Decapterus maruadsi surimi products were prepared using the thermal treatment methods of boiling (BOI), steaming (STE), back-pressure sterilization (BAC), roasting (ROA), microwaving (MIC), and frying (FRI), respectively. The effect of glutamine transaminase (TGase) addition was also investigated. The moisture distribution, water retention, microstructure, color, fracture constant, protein secondary structure, chemical forces, and flavor components of each sample were determined. The differences in gel and favor characteristics between D. maruadsi surimi products caused by thermal treatment methods were analyzed. The results showed that BOI, STE, and FRI had the largest protein secondary structure transitions and formed dense gel structures with high fracture constant. The kinds of flavour components in BOI and STE were completer and more balanced. The high temperature treatment available at BAC and FRI (110 °C and 150 °C) accelerated the chemical reaction involved in flavor formation, which highlighted the flavor profiles dominated by furans or esters. The open thermal treatment environments of ROA, MIC, and FRI gave them a low moisture content and water loss. This allowed the MIC to underheat during the heat treatment, which formed a loose gel structure with a low fracture coefficient. The addition of TGase enhances the gel quality, most noticeably in the ROA. The aldehyde content of the FRI was enhanced in the flavor characteristic. The effect of adding TGase to enhance the quality of the gel is most evident in ROA. It also substantially increased the content of aldehydes in FRI. In conclusion, different heat treatments could change the gel characteristics of surimi products and provide different flavor profiles. The gel quality of BOI and STE was consistently better in all aspects.

Lipidomic analysis of non-esterified furan fatty acids and fatty acid compositions in dietary shellfish and salmon by UHPLC/LTQ-Orbitrap-MS

Lipids such as furan fatty acids (F-acids) are the valuable minor bioactive components of food such as fatty fish and plants. They are reported to have positive health benefits, including antioxidant and anti-inflammatory activities. Despite their importance, limited studies are focusing on F-acid determination in dietary seafood. This study aimed to identify and profile non-esterified F-acids and free fatty acids in total lipid extract of seafood such as shellfish and salmon. The lipidomic analysis using liquid chromatography-linear trap quadrupole-orbitrap mass spectrometry led to identifying seven types of free F-acids in shellfish (n = 5) and salmon (n = 4). The identified F-acids were confirmed by their high-resolution masses and acquired mass spectra. The relative concentrations of F-acids in shellfish range from 0.01 to 10.93 mg/100 g of the fillet, and in salmon, 0.01 to 14.21 mg/100 g of the fillet. The results revealed the highest abundance of F-acids in Sakhalin surf clam, Japanese scallop, and a fatty salmon trout. Besides, relative levels of saturated, monounsaturated, and polyunsaturated fatty acids (PUFAs) in these seafoods were compared with each other, suggesting basket clams and salmon trout to have significantly higher levels of PUFAs. The dietary seafoods enriched with F-acids and PUFAs may have possible health benefits. Hence, the applied technique could be a promising tool for rapid detection and analysis of non-esterified fatty acids in food.

Characterization of lipid profiling in three parts (muscle, head and viscera) of tilapia (Oreochromis niloticus) using lipidomics with UPLC-ESI-Q-TOF-MS

A lipidomic evaluation was performed on the tilapia muscle, head and viscera, including studying the composition, distribution and stereospecific characteristics of fatty acids and lipid species. The head and viscera lipids were significantly richer than the muscle lipids. Triacylglycerols were the predominant fraction (over 80% of total lipid in the muscle and head). Additionally, polyunsaturated fatty acids had higher percentages in phospholipids (30.35-52.05% of total fatty acids) than in triacylglycerols (18.11-25.15%). The C52:2 and C52:3 were the most abundant triacylglycerols, which indicates the potential application in infant food. Moreover, 622, 530 and 513 lipids were identified using ultraperformance liquid chromatography-quadrupole time-of-flight-mass spectrometry in the muscle, head and viscera, respectively. The three tilapia parts were distinguished using multivariate analysis. Five fatty acids and 33 lipid species were considered as the potential biomarkers. This comprehensive analysis will help to evaluate the lipid nutritional values and facilitate exploitation in tilapia consumption and processing.

Reliability of LipidSearch software identification and its application to assess the effect of dry salting on the long-chain free fatty acid profile of tilapia muscles

Dry salting has important effects on food lipids. In this work, the reliability of LipidSearch software identification and its application to assess the effect of dry salting on the long-chain free fatty acid profile of tilapia muscles were studied by ultra-high-performance liquid chromatography-Q-Extractive Orbitrap mass spectrometry and LipidSearch software. Compared with the standard reference identification method, the LipidSearch software identification method was suggested to be a reliable identification method for long-chain free fatty acid identification. During the dry salting process, tilapia muscles with low muscle-to-salt mass ratios of 3-8 might have stable and similar free fatty acid profile changes, and the free fatty acid amounts decreased and then increased with time. This work could provide useful information to evaluate the development and application of LipidSearch software as well as a way to analyze the effect of dry salting on the free fatty acids change of aquatic products.

Structure determination of conjugated linoleic and linolenic acids

Conjugated linoleic and linolenic acids (CLA and CLnA) can be found in dairy, ruminant meat and oilseeds, these types of unsaturated fatty acids consist of various positional and geometrical isomers, and have demonstrated health-promoting potential for human beings. Extensive reviews have reported the physiological effects of CLA, CLnA, while little is known regarding their isomer-specific effects. However, the isomers are difficult to identify, owing to (i) the similar retention time in common chromatographic methods; and (ii) the isomers are highly sensitive to high temperature, pH changes, and oxidation. The uncertainties in molecular structure have hindered investigations on the physiological effects of CLA and CLnA. Therefore, this review presents a summary of the currently available technologies for the structural determination of CLA and CLnA, including the presence confirmation, double bond position determination, and the potential stereo-isomer determination. Special focus has been projected to the novel techniques for structure determination of CLA and CLnA. Some possible future directions are also proposed.