Use of egg yolk phospholipids to generate chicken meat odorants

Effect of adding different egg yolk oil on the flavor and physicochemical properties of mayonnaise

This study explored the differences in physicochemical properties and flavor characteristics of mayonnaise prepared by partially replacing vegetable oil with salted hen egg yolk oil (M-HE), salted duck egg yolk oil (M-DE), and fresh egg yolk oil (M-FE). The results showed that the modified egg yolk oil (EYO) mayonnaise exhibited more homogeneous and denser droplets, along with a richer golden color compared to corn oil-based mayonnaise (M-CO). Additionally, the EYO mayonnaise had higher viscosity and smaller particle size. The electronic nose indicated that all four mayonnaise variants displayed significantly different flavor profiles. Gas chromatography-mass spectrometry (GC-MS) analysis revealed no specific flavor compounds in the EYO mayonnaise, whereas M-CO contained nine unique flavor compounds. Partial least squares discriminant analysis (PLS-DA) suggested that 1-octen-3-ol, 2,5-dimethyl-pyrazine, and (E)-2-nonenal were significantly different among the mayonnaise samples, except for acetic acid. This study provides novel insights into the quality evaluation of EYO as an oil phase supplement for mayonnaise production.

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.

Effects of different drying methods on the chemical components and activities of Taihang chrysanthemum (Opisthopappus taihangensis)

Although the health benefits of chrysanthemums have been widely studied, there is a paucity of knowledge regarding Taihang chrysanthemum (Opisthopappus taihangensis). This study compared indoor shade drying, heat drying and freeze drying on the chemical profile and health-related activities of O. taihangensis. UPLC-Q-TOF-MS and other assays were used to evaluate changes in composition and antioxidant, antibacterial and enzyme inhibitory activities. Different drying methods significantly affected compositions and bioactivities of O. taihangensis. Lipids, phenylpropanoids and polyketides were the most abundant. Freeze-drying maintained bioactive compounbds like phenylpropanoids and superior antioxidant activities. Freeze-dried O. taihangensis also displayed robust antibacterial activity against Streptococcus hemolyticus-β and effective inhiition of pancreatic lipase. These results suggest O. taihangensis is a useful source of functional compounds.

Effect of frozen storage duration on temporal dominance of sensations (TDS), chemical investigations and moisture distribution of roasted chicken wings

In order to guide manufacturers or consumers to choose frozen chicken wings (CWS) reasonably for roasting, the changes of sensory quality and physicochemical properties of CWS with different freezing storage time (0-12 months) after roasting were studied. The results showed that juiciness, fat flavor, meat flavor, and saltiness were the most important dominant attributes of roasted CWS, and their dominance rate gradually decreased from the ninth month. Increased (P < 0.05) TBARS value and water loss result in poor juiciness. According to the results of GC-IMS, the decrease of the dominant rate of meaty may be related to the decrease of the contents of 2-ethyl-5-methylpyrazine, benzene and thiazole. In addition, the accumulation of 1-octen-3-ol, n-hexanol, and hexanal caused by long-term freezing (> 9 months) give chicken wings a fishy and metallic taste. Therefore, CWS that have been frozen for more than 9 months are not ideal ingredients for roasting.

Shrimp lipids improve flavor by regulating characteristic aroma compounds in hot air-dried shrimp

Hot air-dried shrimp (HDS) has a strong fishy smell greatly reducing its flavor quality. This study aimed to investigate the regulation of total lipids, phospholipids and triglycerides isolated from shrimp for improving the characteristic volatile flavor of HDS. It was found that three lipids could promote the formation of aroma compounds with pleasant characteristic aromas (e.g., pyrazines). Phospholipids and triglycerides inhibited the formation of trimethylamine, a key component of fishy smell, with phospholipids exhibiting the best inhibitory effect (47.70 ± 2.63 %), greatly improving the flavor quality of HDS. Aldehydes, unsaturated ketones, and furans, primarily derived from the thermal degradation of C18:1, C18:2, and C22:6, were key intermediate compounds promoting the Maillard reaction. Lipids inhibited trimethylamine by prompting the formation of pyrazines. Maillard reaction was the key pathway for lipids to improve the flavor quality of HDS. This study can provide theoretical support for the development of high-quality thermally processed shrimp products.

Multi-omics analysis of chemical composition variation among different muscle types in Hu lamb

BACKGROUND

Consumers' preferences for lamb meat vary greatly depending on the specific cut. Variations in the chemical composition across different muscle types play a crucial role in determining meat quality, particularly with regard to flavor. Therefore, it is essential to study the variations in chemical composition among different muscle types in lamb, as well as the mechanisms behind their formation, aiming to understand the flavor variation across the muscle types.

RESULTS

Flank muscles showed significantly higher intramuscular fat content and muscle fiber diameter compared to triceps brachii and biceps femoris (BF), at the same time as displaying a significantly lower percentage of type I muscle fibers. Forty-three differentially abundant volatile compounds (DAVC) were identified across five muscles, with the majority of DAVCs being more abundant in the BF. In total, 161 differentially abundant lipids were identified across five muscles, with triglycerides (TG), phosphatidylcholines (PC), phosphatidyl ethanolamines (PE) and phosphatidylmethanol (PMeOH) showing a strong correlation with DAVCs. A lipid-gene regulatory network was established, encompassing 664 lipids and 11 107 genes, leading to the identification of pathways and genes that regulate the metabolism of PEs, PMeOH, PCs and TGs.

CONCLUSION

The present study showed the significant variation in flavor compounds among the five edible muscles, as well as the potential reasons for their formation. The results potentially provide a theoretical foundation for improving the meat quality of lamb. © 2024 Society of Chemical Industry.

Volatile and non-volatile compound analysis of ginkgo chicken soup during cooking using a combi oven

This study employed a range of analytical techniques to evaluate the changes in both volatile and non-volatile compounds during different cooking times (30, 60, 90, 120, and 150 min) of ginkgo chicken soup prepared using a multifunctional combi oven, and comparedthese results with those obtained from the traditional ceramic pot method.The techniques included electronic nose (e-nose), electronic tongue (e-tongue), gas chromatography-ion mobility spectrometry (GC-IMS), high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), and automated amino acid analysis. A total of 64 volatile compounds, primarily aldehydes, ketones, esters, and alcohols, were detected, with 23 key aroma components identified. Principal component analysis (PCA) demonstrated similar aroma and taste profiles between the two cooking methods. Additionally, 22 amino acids, 6 nucleotides enhancing umami, and 18 fatty acids were categorized into saturated, monounsaturated, and polyunsaturated groups. Pearson correlation revealed significant relationships among key amino acids, 5'-nucleotides, and volatile compounds, providing insights into industrial-scale applications of multifunctional ovens in ginkgo chicken soup production.

Exploring the contribution of phosphatidylcholine and triglyceride on the formation of beef aroma-active compounds with thermal oxidation system

Thermal oxidation of phospholipids and triglycerides is a major source of beef aroma compounds. In this study, phosphatidylcholine (PC) and triglyceride (TG) were isolated and purified from beef and added to defatted beef and raw beef. The composition of aroma compounds generated by thermal oxidation in three model systems were compared by flavoromics. The main aroma compounds produced by the thermal oxidation of PC were decanal, (E)-2-nonenal, (E)-2-undecenal, and (E,E)-2,4-decadienal, while the main aroma compounds produced by the thermal oxidation of TG were nonanal, (E)-2-undecenal, and decanal. Nonanal remains the main aroma compound produced by PC and TG in defatted beef. Octanal and nonanal were the major aroma compounds generated by thermal oxidation of raw beef samples spiked with PC and TG. Raw beef with added PC and TG had higher levels of sulfides and heterocycles after thermal oxidation compared to defatted beef with added lipids. The comparison of the aroma profiles in three thermo-oxidative models indicated that PC contributed more than TG to the key odor-active compounds in cooked beef. Additionally, the thermo-oxidative degradation of PC facilitated the formation of Maillard reaction products. However, the beef matrix may inhibit the formation of decanal and (E,E)-2,4-decadienal.

Comparative characterization of flavor precursors and volatiles in Chongming white goat of different ages by UPLC-MS/MS and GC-MS

Age has a significant impact on goat meat flavor. However, reporting the effects of age on free amino acid (FAAs), lipid profiles and aromas of goat meat is limited. Here, the FAAs, lipid profiles and aromas in the Chongming white goat with 12 months and 24 months were investigated in this study. A total 1164 lipids were identified using lipidomics, including 31 subclasses. Multivariate statistical analysis showed that 201 lipids had significant changes, FFA, TG and DG increased with goat age. Furthermore, the pathway analysis indicated that glycerophospholipid metabolism and glycerolipid metabolism were the key pathways that relate to lipid profile changes during goat growth. Thirty-five volatile compounds were identified, among them, 14 aromas with odor activity value greater than 1 were considered as potential characteristic aroma compounds of Chongming white goat meat. These findings reveal the FAAs, lipids, and aromas profiles in Chongming white goat meat are affected by age, which provides a basis for improving goat meat flavor.

The revelation of characteristic volatile compounds in egg powder and analysis of their adsorption rules based on HS-GC-IMS technology

The study constructed fingerprints and analyzed adsorption rules of volatile compounds (VOCs) in egg powder (EP) under different production processes, including egg white powder (EWP), egg yolk powder (EYP) and whole egg powder (WEP) by HS-GC-IMS. The 29 VOCs identified were primarily ketones and aldehydes. Characteristic VOCs responsible for flavor differences were clarified by difference comparison, clustering and PCA analysis. Additionally, variations in lipid and protein were the primary causes of the VOCs differences in EP through microscopy imaging, infrared and fluorescence spectroscopy. EWP's stretched structure favored fishy-smelling VOCs adsorption but limited total aldehyde binding due to strong hydrophobic interaction. EYP's higher β-sheet ratio and fewer hydrogen bond sites weakened its alcohol VOCs binding capacity. The abundance of ketone VOCs in EP was linked to their low steric hindrance. Therefore, this study elucidated the flavor differences reasons among EWP, EYP and WEP, laying foundation for EP applications in food industry.

Multi-omics combined approach to analyze the mechanism of flavor evolution in sturgeon caviar (Acipenser gueldenstaedtii) during refrigeration storage

Multi-omics techniques were combined with microstructure, molecular sensory science and non-volatile matrices for the first time to investigate variations in organic macromolecules and flavor in caviar during preservation. After 4-6 weeks of storage, the peroxide value was 35.38 mg/g and the accumulation of thiobarbiturates was significant with caviar membranes exhibiting a decrease in elasticity and an increase in viscosity. Sixteen key volatile compounds were detected by GC-MS, while the volatile compounds that contributed to the differences in caviar flavor at different storage times were mainly tetradecane, (E)-2-hexenal, and heptanal. The pathways associated with flavor release during storage were mainly abundant in the linolenic acid metabolism, alanine metabolism, and glycerophospholipid metabolism pathways. The correlation of 11 differential proteins and 24 differential lipids with odorants was further explored, such as arginine, proline, alanine, PE (20:4/22:6), PE (16:1/18:2), and PE (20:5/18:2). Overall, Aspartate, glutamate, oleic acid, linoleic acid, and phospholipids enriched in C22:6 and C18:2 chains are potential metabolic markers. This study provides a basis from a multi-omics perspective for the investigation of the relationship between quality deterioration and precursor metabolism in caviar storage process.

Formation and retention of aroma compounds in pigeons roasted by circulating non-fried roast technique by means of UHPLC-HRMS and GC-O-MS

Lipids are key aroma contributors in meat products. However, the role of different lipids in the presence of aroma compounds in roasted pigeons has not been studied. The formation of aroma compounds and lipids during the circulating non-fried roasting of pigeons was investigated. The results presented that 18 aroma compounds, including 5-methy-2,3-diethylpyrazine, were identified as key aroma compounds. A total of 6324 lipids were classed into 47 categories, such as phosphatidylcholine (PC), phosphatidylethanolamine (PE), and triglyceride (TG). Nine lipids, containing PA(P-20:0/22:4(7Z,10Z,13Z,16Z)) and LPC 16:0-SN1, showed promise as potential biomarkers for discriminating differential pigeons using OPLS-DA. PC (13.76%), TG (13.58%), and their products were major lipids, among which TG 16:0 16:0 18:2, LPC 18:2-SN1, and PC 18:1_18:1 played a crucial role in the presence of aroma compounds. Interestingly, the linoleic acid, an important aroma contributor, was predominantly bonded to the sn-2 position of phospholipid and sn-3 position of neutral lipids.

Use of egg yolk phospholipids to improve the thermal-oxidative stability of fatty acids, capsaicinoids and carotenoids in chili oil

Phospholipids can act as antioxidants in food. In this study, egg yolk phospholipids (EPL) and sunflower oil were utilized in making chili oil, and proton nuclear magnetic resonance spectroscopy was employed to quantify the concentrations of fatty acyl groups, carotenoids, capsaicinoids in chili oil according to their specific signals in the spectra. The results showed that the changes in the concentrations of fatty acyl groups in the control samples were greater than those in the EPL-treated samples at the same frying temperature, while the contents of carotenoids and capsaicinoids were significantly lower than those of the EPL-treated samples when fried at 150 °C (p < 0.05). Two-way ANOVA indicated that frying temperature and EPL treatment, as well as their interaction had significant impacts on the thermal-oxidative stability of chili oil (p < 0.05). The results suggest that EPL may act as antioxidants during frying, and EPL can improve the thermal-oxidative stability of chili oil.

Unraveling the formation mechanism of aroma compounds in pork during air frying using UHPLC-HRMS and Orbitrap Exploris GC-MS

Lipids are the key matrix for the presence of odorants in meat products. The formation mechanism of odorants of air-fried (AF) pork at 230 °C was elucidated from the perspectives of lipids and heat transfer using physicochemical analyses and multidimensional statistics. Twenty-nine key aroma compounds were identified, with pyrazines predominantly contributing to the roasty aroma of air-fried roasted pork. Untargeted lipidomics revealed 1184 lipids in pork during roasting, with phosphatidylcholine (PC), phosphatidylethanolamine (PE), and triglyceride (TG) being the major lipids accounting for about 60 % of the total lipids. TG with C18 acyl groups, such as TG 16:1_18:1_18:2 and TG 18:0_18:0_20:3, were particularly significant in forming the aroma of AF pork. The OPLS-DA model identified seven potential biomarkers that differentiate five roasting times, including PC 16:0_18:3 and 2-ethyl-3,5-dimethylpyrazine. Notably, a lower specific heat capacity and water activity accelerated heat transfer, promoting the formation and retention of odorants in AF pork.

Relationship between phospholipid molecules species and volatile compounds in grilled lambs during the heating process

The present study used a comprehensive analysis combining headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) to investigate changes in volatile compounds and phospholipid molecules in grilled lambs. The results revealed 19 key volatile compounds (OAV > 1) involved in the grilling process of lambs. Additionally, UPLC-ESI-MS/MS analysis detected 142 phospholipid molecules in grilled lamb, with phosphatidylcholine exhibiting the highest content (36.62 %), followed by phosphatidyl ethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidyl glycerol, and phosphatidic acid. Through partial least squares analysis, 63 key differential phospholipids were identified. Principal component analysis of the key differential phospholipids and volatile compounds indicated that phosphatidylcholine and phosphatidyl ethanolamine phospholipids are the key substrates in forming volatile compounds in grilled lambs. This information is essential for precisely regulating the flavor profile, enhancing the grilling process, and minimizing the production of harmful compounds in grilled meat products.

Unraveling the Formation Mechanism of Egg's Unique Flavor via Flavoromics and Lipidomics

Egg products after thermal treatment possess a unique flavor and are favored by consumers. In this study, the key aroma-active compounds of egg yolk products and their formation mechanism during thermal treatment were investigated. The volatile aroma compounds in egg yolks were monitored using an electronic nose, gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry-mass spectrometry (GC-O-MS), and the lipid molecular species were explored using ultra-high-performance liquid chromatography- mass spectrometry with a Q-Exactive HF-X Orbitrap (UPLC-Q-Exactive HF-X). A total of 68 volatile compounds were identified. Boiled eggs mainly derived their flavor from hexanal, 2-pentyl-furan, 2-butanone, 3-methyl-butanal and heptane. Meanwhile, fried eggs relied mainly on 14 compounds, the most important of which were 2-ethyl-3-methyl-pyrazine, 3-ethyl-2,5-dimethyl-pyrazine, 2-ethyl-3,5-dimethyl-pyrazine, nonanal and 2,3-diethyl-5-methyl-pyrazine, providing a baked and burnt sugar flavor. A total of 201 lipid molecules, belonging to 21 lipid subclasses, were identified in egg yolks, and 13 oxidized lipids were characterized using a molecular network. Phosphoethanolamines (PEs) containing polyunsaturated fatty acids were the primary flavor precursors contributing to the development of egg yolks' flavor, participating in lipid oxidation reactions and the Maillard reaction and regulating the production of aldehydes and pyrazine compounds. This study provides reference and guidance for the development of egg yolk flavor products.

Dynamic changes in the water and volatile compounds of chicken breast during the frying process

The influence of frying times (0, 2, 4, 6, 8, and 10 min) on the continuous changes in the water distribution and the concentrations of key volatile compounds in chicken breast during the frying process were studied. The fried chicken samples could be distinguished by PCA of E-nose and PLS-DA of GC-MS. A total of 40 volatile compounds were identified by GC-MS, and 28 compounds were verified to be the key compounds after further screening by OAVs. The T22 was increased first and then decreased, while the M22 and M23 in fried chicken were considerably decreased and increased with increasing frying time, respectively. The content of the water and the total peak area of LF-NMR in fried chicken samples during the frying process significantly decreased, and the water was transferred from high to low degrees of freedom. In addition, water content, T21, T22, M22 and L* value were positively correlated with most alcohols and aldehydes, and were negatively correlated with pyrazines, while a*, b*, M23 and all amino acids were positively correlated with pyrazines and were negatively correlated with most alcohols and aldehydes. The results may guide the production processes of fried chicken and help produce high-quality chicken products.

The effect of lutein on the oxidation of egg yolk phospholipids in a liposome model

Egg yolk phospholipids (PLs) extracted by organic solvent are prone to oxidation, while they are quite stable in egg yolk. This study was to verify the decisive role of lutein (naturally present in egg yolk) on the oxidative stability of PLs by constructing liposome. The liposome samples were heated at 100 °C for 10 min, and then the oxidation products of the liposome samples were analyzed by 1H NMR and GC-MS. The results showed that the concentrations of most of the oxidation products in the PLs-liposomes sample were significantly higher than those in the PLs&lutein-liposomes sample. Therefore, lutein could protect egg yolk PLs from oxidation, thus inhibiting the formation of lipid-derived volatile compounds. As those lipid-derived volatile compounds are the key fatty note odorants, this study has confirmed that the removal of lutein is the determining factor in using egg yolk PLs as an ideal precursor of fatty note odorants.

Characterization of aroma profiles of chinese four most famous traditional red-cooked chickens using GC-MS, GC-IMS, and E-nose

The aroma profile of the four most popular types of red-cooked chickens in China was analyzed using a combination of gas chromatography-mass spectrometry (GC-MS), gas chromatography-ion mobility spectrometry (GC-IMS), and electronic nose (E-nose). Principal component analysis (PCA) demonstrated that the E-nose could successfully distinguish between the four types of red-cooked chickens. Additionally, a fingerprint was created using GC-IMS to examine the variations in volatile organic compounds (VOCs) distribution in the four chicken types. A total number of 84 and 62 VOCs were identified in the four types of red-cooked chickens using GC-MS and GC-IMS, respectively. Odor activity value (OAV) showed that 1-octen-3-ol, heptanal, hexanal, nonanal, octanal, eugenol, dimethyl trisulfide, anethole, anisaldehyde, estragole, and eucalyptol were the key volatile components in all samples. Furthermore, partial least squares-discriminant analysis (PLS-DA) demonstrated that (E, E)-2,4-decadienal, dimethyl trisulfide, octanal, eugenol, hexanal, (E)-2-nonenal, 1-octen-3-ol, butanal, ethyl acetate, ethyl acetate (D), nonanal, and heptanal could be used as markers to distinguish aroma of the four types of red-cooked chickens. Also, it is worth noting that levels of VOCs varied between chicken breast muscle and skin. The obtained results offer theoretical and technological support for flavor identification and control in red-cooked chickens to enhance their quality and encourage consumer consumption, which will be advantageous for the red-cooked chicken production chain.

Weighted gene co-expression network analysis identified hub genes critical to fatty acid composition in Gushi chicken breast muscle

BACKGROUND

The composition and content of fatty acids in the breast muscle are important factors influencing meat quality. In this study, we investigated the fatty acid composition and content in the breast muscle of Gushi chickens at different developmental stages (14 weeks, 22 weeks, and 30 weeks). Additionally, we utilized transcriptomic data from the same tissue and employed WGCNA and module identification methods to identify key genes associated with the fatty acid composition in Gushi chicken breast muscle and elucidate their regulatory networks.

RESULTS

Among them, six modules (blue, brown, green, light yellow, purple, and red modules) showed significant correlations with fatty acid content and metabolic characteristics. Enrichment analysis revealed that these modules were involved in multiple signaling pathways related to fatty acid metabolism, including fatty acid metabolism, PPAR signaling pathway, and fatty acid biosynthesis. Through analysis of key genes, we identified 136 genes significantly associated with fatty acid phenotypic traits. Protein-protein interaction network analysis revealed that nine of these genes were closely related to fatty acid metabolism. Additionally, through correlation analysis of transcriptome data, we identified 51 key ceRNA regulatory networks, including six central genes, 7 miRNAs, and 28 lncRNAs.

CONCLUSION

This study successfully identified key genes closely associated with the fatty acid composition in Gushi chicken breast muscle, as well as their post-transcriptional regulatory networks. These findings provide new insights into the molecular regulatory mechanisms underlying the flavor characteristics of chicken meat and the composition of fatty acids in the breast muscle.

Dynamic changes in the water distribution and key aroma compounds of roasted chicken during roasting

The effects of roasting times (0, 2, 4, 6, 8, 10, 12, and 14 min) on the dynamic changes of the water distribution and key aroma compounds in roasted chicken during the electric roasting process were studied. In total, 36 volatile compounds were further determined by GC-MS and 11 compounds, including 1-octen-3-ol, 1-heptanol, hexanal, decanal, (E)-2-octenal, acetic acid hexyl ester, nonanal, 2-pentylfuran, heptanal, (E, E)-2,4-decadienal and octanal, were confirmed as key aroma compounds. The relaxation time of T22 and T23 was increased first and then decreased, while the M22 and M23 in roasted chicken were decreased and increased with increasing roasting time, respectively. The fluidity of the water in the chicken during the roasting process was decreased, and the water with a high degree of freedom migrated to the water with a low degree of freedom. In addition, the L*, a*, b*, M23 and all amino acids were positively correlated with all the key aroma compounds, while T22, M22 and moisture content were negatively correlated with all the key aroma compounds.

Comparative characterization of flavor precursors and volatiles of Taihe black-boned silky fowl and Hy-line Brown yolks using multiomics and GC-O-MS-based volatilomics

Eggs are nutritious and highly valued by consumers. However, egg flavor varies greatly among different hen breeds. The present study used gas chromatography-olfactometry-mass spectrometry-based volatilomics to identify and compare volatile compounds in Taihe black-boned silky fowl (TS) and Hy-line Brown (HL) egg yolks. In addition, the relationships between the levels of different metabolites and lipids and flavor-associated differences were investigated using multiomics. Twenty-eight odorants in total were identified; among them, the levels of 3-methyl-butanal, 1-octen-3-ol, 2-pentylfuran, and (E, E)-2,4-decadienal differed significantly (P < 0.05) between TS and HL egg yolks. The difference in flavor compounds results in TS egg yolks having a stronger overall odor and flavor and a higher acceptance level than HL egg yolks. Metabolomic analysis revealed that 112 metabolites in the egg yolks were significantly different between the two breeds. Furthermore, these different metabolites in the egg yolks of both breeds were significantly enriched in phenylalanine, tyrosine, and tryptophan biosynthesis pathways and phenylalanine metabolism, alanine, aspartate, and glutamate metabolism pathways (P < 0.05), as identified by both metabolite set enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analyses. Lipidomic analysis revealed significant differences in the lipid subclasses, lipid molecules, and fatty acid profiles between the egg yolks from the two breeds. As a result, 48 lipid molecules had variable influence in projection values > 1 based on the partial least squares regression model, which may play a role in the differences in aroma characteristics between the two breeds through oxidative degradation of fatty acids. Our study revealed the metabolite, lipid, and volatility profiles of TS and HL egg yolks and may provide an important basis for improving egg flavor to satisfy various consumer preferences.

Lipid oxidation and flavor changes in saturated and unsaturated fat fractions from chicken fat during a thermal process

Chicken fat, due to its rich fatty acids (FAs), is more prone to lipid oxidation and the production of volatile compounds. The aim of the present study was to investigate the oxidative characteristics and flavor changes of saturated (SFF) and unsaturated fat fractions (USFF) from chicken fat induced by heating (140 °C at 70 rpm min-1 for 1 h and 2 h: SFF1, USFF1, SFF2 and USFF2). The FAs and volatile compounds were analyzed by gas chromatography-mass spectrometry (GC-MS) and two-dimensional gas chromatography time of flight mass spectrometry (GC × GC-ToFMS), respectively. The results showed that higher contents of unsaturated fatty acids (UFAs) were found in USFF compared to that in SFF, whereas USFF showed lower levels of saturated fatty acids (SFAs). With the extension of heating time, the SFA/UFA ratio in USFF and SFF significantly increased (p < 0.05), and more aldehydes, alcohols, ketones, and lactones were formed. Moreover, the odor activity values of 23 important compounds in USFF1-2 were significantly higher (p < 0.05) than those in SFF1-2. As revealed by principal component analysis (PCA) and cluster analysis (CA), it was obviously observed that all samples were divided into four clusters (USFF-SFF, USFF1-SFF1, USFF2, and SFF2). According to correlation analysis between FAs and volatile compounds, C18:2 ω6, C18:3 ω6 and C18:3 ω3 were significantly associated with dodecanal, (Z)-3-hexenal, (E)-2-decenal, 2-undecenal, (E)-2-dodecenal, (E,E)-2,4-nonadienal, (E,E)-2,4-decadienal, 2-decanone, γ-octalactone and γ-nonalactone. Our data elucidated that fat fractions from chicken fat with varying degrees of saturation could impart different flavor characteristics during a thermal process.

LC/MS- and GC/MS-based metabolomic profiling to determine changes in flavor quality and bioactive components of Phlebopus portentosus under low-temperature storage

Introduction

Low temperature is the most common method used to maintain the freshness of Phlebopus portentosus during long-distance transportation. However, there is no information regarding the nutritional changes that occur in P. portentosus preserved postharvest in low temperature.

Methods

In this study, the changes in flavor quality and bioactive components in fruiting bodies stored at 4 °C for different storage periods were determined through LC/MS and GC/MS analyses. Sampling was performed at 0, 3, 5, 7, and 13 days storage.

Results and Discussion

Based on the results, the metabolites present in caps and stipes were different at the same period and significantly different after 7 days of storage. A total of 583 and 500 different metabolites were detected in caps and stipes, respectively, and were mainly lipids and lipid-like molecules, organic acids and derivatives, organic oxygen compounds and others. Except for prenol lipids and nucleotides, the expression levels of most metabolites increased with longer storage time. In addition, geosmin was identified as the major contributor to earthy-musty odors, and the level of geosmin was increased when the storage time was short.

Conclusion

The variations in these metabolites might cause changes in flavor quality and bioactive components in P. portentosus. Variations in these metabolites were thoroughly analyzed, and the results revealed how storage processes affect the postharvest quality of P. portentosus for the first time.

Study on the formation pathways of characteristic volatiles in preserved egg yolk caused by lipid species during pickling

The formation of volatiles in high-fat foods is strongly influenced by the composition and structure of lipids. The relationship between key variable lipid species and characteristic volatiles were performed by lipidomics and flavoromics to resolve the pathways of volatiles in preserved egg yolk (PEY) during pickling. The results showed that the formation of nonanal and benzaldehyde at early stage possibly derived from oleic acid sited at Sn-1 in TG(18:1_18:2_20:4), Sn-2 in PE(22:6_18:1), and linoleic acid bonded at Sn-2 in TG(18:1_18:2_20:4), respectively. 1-octen-3-ol may be formed from linoleic acid located at Sn-2 in TG(18:1_18:2_20:4) and arachidonic acid sited at Sn-3 in TG(18:1_18:2_20:4). Indole was formed through TGs(16:0_16:1_20:1;16:1_18:1_22:1;23:0_18:1_18:1) at the later stage, and acetophenone through TGs(14:0_20:0_20:4;14:0_15:0_18:1; 16:0_16:0_22:6), PCs(24:0_18:1;O-18:1_18:2), PEs(P-18:1_20:4;P-18:1_22:6) and SPH(d18:0) during whole process of pickling. Our study provides a deep and precise insight for the formation pathways of characteristic volatiles in PEY through lipids degradation during pickling at the molecular level.

Egg yolk phospholipids as an ideal precursor of fatty note odorants for chicken meat and fried foods: A review

Egg yolk phospholipids (PLs) have been demonstrated to generate large quantities of lipid-derived odorants, especially the fatty note odorants. Recently, egg yolk PLs have been successfully used in chicken meat and fried foods to improve aroma. This review comprehensively summarizes the properties of egg yolk PLs as precursors of fatty note odorants, including their classes, extraction, identification, oxidation, decomposition and odorant formation, applications, considerations and future prospects in the food industry. Most likely, phosphatidylcholine (PC) is the most abundant class in egg yolk PLs, and PC is more efficient than phosphatidylethanolamine in generating fatty note odorants; moreover, the predominant polyunsaturated fatty acid is linoleic acid, and its corresponding predominant hydroperoxide is 9-hydroperoxy-10,12-octadecadienoic acid during autoxidation, which is the precursor of 2,4-decadienals and 2,4-nonadienals, the key fatty note odorants. Therefore, egg yolk PLs could be an ideal precursor of fatty note odorants for chicken meat and fried foods.

Effect of Feeding Olive Pomace Acid Oil on Dark Chicken Meat Lipid Composition, Oxidative Stability, Color, and Sensory Acceptance

This study evaluated the effect of using olive pomace acid oil (OPAO) instead of crude palm oil (PO) or refined olive pomace oil (ROPO) on lipid composition, lipid oxidation, and quality of chicken meat. Broiler chickens were fed diets with 6% of PO, ROPO, or OPAO, and deboned legs with skin were sampled. Fresh and refrigerated (commercial conditions; 7 days) chicken meat samples were assessed for fatty acid (FA) composition, tocopherol (T) and tocotrienol (T3) content, lipid oxidative stability, 2-thiobarbituric acid (TBA) values, volatile compounds, color, and sensory acceptance. Using ROPO and OPAO led to meat richer in monounsaturated FAs and OPAO to lower α-T levels compared to PO. Oxidative stability, TBA values, volatile compounds, and overall acceptance of meat were not affected by diet. Refrigeration increased TBA values and some volatile compounds' concentrations, but it did not decrease redness or consumers' overall acceptance. Therefore, the OPAO used was an adequate fat source for chicken diets at 6%, as it produced dark meat lower in saturated FAs than PO without affecting lipid oxidation or overall acceptance. According to this, upcycling OPAO as an energy source in chicken diets would be possible, which can contribute to the sustainability of the food chain.

Effects of egg powder on the structure of highland barley dough and the quality of highland barley bread

The influences of egg white (EW), egg yolk (EY) and whole egg (WE) on the structure of highland barley dough and the quality of highland barley bread were explored. The results showed that egg powder reduced G' and G" of highland barley dough, which led to the softer texture of dough and endowed bread with a larger specific volume. EW increased the percentage of β-sheet of highland barley dough, EY and WE promoted the transformation from random coil to β-sheet and α-helix. Meanwhile, more disulfide bonds were formed from free sulfhydryl groups in the doughs with EY and WE. These properties of highland barley dough could help highland barley bread develop a preferable appearance and textural feature. It is worth noting that highland barley bread containing EY has more flavorful substances and a better crumb structure, which were similar to that of whole wheat bread. The highland barley bread with EY received a high score according to the sensory evaluation in consumer acceptance.

Characterization of meat quality traits, fatty acids and volatile compounds in Hu and Tan sheep

Sheep breed has a major influence on characteristics of meat quality and intramuscular fat (IMF), however, studies into the relationship between sheep breed and meat quality traits rarely consider the large variation in IMF within breed. In this study, groups of 176 Hu and 76 Tan male sheep were established, weaned at 56 days old, with similar weights, and representative samples were selected based on the distribution of IMF in each population, to investigate variations in meat quality, IMF and volatile compound profiles between breeds. Significant differences were observed in drip loss, shear force, cooking loss, and color coordinates between Hu and Tan sheep (p < 0.01). The IMF content and the predominate unsaturated fatty acids, oleic and cis, cis-linoleic acids, were similar. Eighteen out of 53 volatile compounds were identified as important odor contributors. Of these 18 odor-active volatile compounds, no significant concentration differences were detected between breeds. In another 35 volatile compounds, γ-nonalactone was lower in Tan sheep relative to Hu sheep (p < 0.05). In summary, Tan sheep exhibited lower drip loss, higher shear force values, and redder color, had less saturated fatty acids, and contained less γ-nonalactone against Hu sheep. These findings improve understanding of aroma differences between Hu and Tan sheep meat. Graphical Abstract.

Effect of oxidation and in vitro intestinal hydrolysis on phospholipid toxicity towards HT29 cell line serving as a model of human intestinal epithelium

Oxidation of food-derived phospholipids (PLs) can influence nutrient digestion and induce oxidative stress in gastrointestinal epithelium. In this study, hen egg yolk PL fraction was used to evaluate the effect of lipoxygenase (LOX)-induced PL oxidation on the rate of PL hydrolysis catalyzed by pancreatic phospholipase A₂ (PLA₂) in the presence of bile salts (BSs). Then, PL/BS solutions containing native or oxidized PLs were used in in vitro intestinal digestion to assess the effect of PL oxidation and hydrolysis on the toxicity towards HT29 cell line. Based on the obtained results, we suggest that hexanal and (E)-2-nonenal, formed by the decomposition of PL hydroperoxides, inhibited PLA₂ activity. The cell exposure to simulated intestinal fluid (SIF) containing BSs decreased HT29 cell viability and significantly damaged cellular DNA. However, the genotoxic effect was reversed in the presence of all tested PL samples, while the protective effect against the BS-induced cytotoxicity was observed for native non-hydrolyzed PLs, but was not clearly visible for other samples. This can result from an overlap of other toxic effects such as lipotoxicity or disturbance of cellular redox homeostasis. Taking into account the data obtained, it was proposed that the PLA₂ activity decline in the presence of PL oxidation products may be a kind of protective mechanism against rapid release of oxidized FAs characterized by high cytotoxic effect towards intestinal epithelium cells.

Integrating transcriptome and metabolome to identify key genes regulating important muscular flavour precursors in sheep

Flavour precursors are the basis of meat flavour, and their metabolism is regulated by a variety of enzymes. Thus, it is of great significance to identify the key genes related to meat flavour precursors. In this study, the difference in flavour precursors and transcriptome between Hu sheep and Dorper with different intramuscular fat (IMF) content were investigated using widely targeted metabolomics and RNA-sequencing technologies. Then, the key genes regulating the metabolism of vital precursors were explored by integrating transcriptome and metabolome. Consequently, 594 metabolites were detected in sheep longissimus dorsi, and 76 differentially abundant metabolites (DAMs) were identified between Hu sheep and Dorper. No DAMs were observed between distinct IMF content groups within each breed. A total of 10 lysophospholipids (LPs), including four lysophospholipid ethanolamines and six lysophospholipid cholines, were identified as the main differential precursors between Hu sheep and Dorper. Furthermore, the weighted gene coexpression network analysis uncovered three differentially coexpression modules that were significantly associated with the content of differential LPs in Dorper. From the three modules, GLB1, PLD3, LPCAT2, DGKE, ACOT7, and CH25H genes were identified as key genes regulating the metabolism of LPs. This work provides an insight into understanding the difference in flavour between different sheep breeds, as well as a basis for further exploring the regulatory mechanism of key genes on LPs.

Ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry based untargeted metabolomics to reveal the characteristics of Dictyophora rubrovolvata from different drying methods

Dictyophora rubrovolvata is a highly valuable and economically important edible fungus whose nutrition and flavor components may vary based on drying methods. Herein, an untargeted ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) metabolomics method combined with multivariate analysis was first performed to characterize the metabolomics profiles of D. rubrovolvata upon different drying treatments, viz., coal burning drying (CD), electrothermal hot air drying (ED), and freeze drying (FD). The results indicated that 69 differential metabolites were identified, vastly involving lipids, amino acids, nucleotides, organic acids, carbohydrates, and their derivatives, of which 13 compounds were confirmed as biomarkers in response to diverse drying treatments. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis illustrated that differential metabolites were significantly assigned to 59, 55, and 60 pathways of CD vs. ED, CD vs. FD, and FD vs. ED groups, respectively, with 9 of the top 20 KEGG pathways shared. Specifically, most of lipids, such as fatty acyls, glycerophospholipids and sphingolipids, achieved the highest levels in D. rubrovolvata after the CD treatment. ED method substantially enhanced the contents of sterol lipids, nucleotides, organic acids and carbohydrates, while the levels of amino acids, prenol lipids and glycerolipids were elevated dramatically against the FD treatment. Collectively, this study shed light on metabolomic profiles and proposed biomarkers of D. rubrovolvata subjected to multiple drying techniques, which may contribute to quality control and drying efficiency in edible fungi production.

Integrative analyses of widely targeted metabolomic profiling and derivatization-based LC-MS/MS reveals metabolic changes of Zingiberis Rhizoma and its processed products

Zingiberis Rhizoma (ZR) has nutritional value and application potentiality, while Zingiberis Rhizoma Praeparatum (ZRP) and Carbonised Ginger (CG) are two main processed products of ZR based on different methods. Here, we performed a widely targeted metabolomics method with Sequential Windowed Acquisition of all Theoretical fragment ions (SWATH) mode to analyze differential metabolites in ZR, ZRP and CG. Additionally, the chemical derivatization was applied to characterize different submetabolomes and improve the separation effect and MS response of metabolites. In total, 369 metabolites were identified and divided into 14 categories, 104 of which were differential metabolites. Our results suggest that carbohydrates, nucleotides, organic acids, vitamins, lipids, indoles, alkaloids, and terpenes contributed to a downward trend after processing, but the maximum content of flavanones, phenylpropanes and polyphenols appeared in ZRP, and that of alcohols appeared in CG. These findings serve as promising perspectives for developing functional food in ZR, ZRP and CG.

Changes in lipids and aroma compounds in intramuscular fat from Hu sheep

Intramuscular fat (IMF) content is associated with lamb flavor and largely varies between individuals of the same breed. However, studies investigating the effects of IMF variations on lipid profiles and aroma compounds are limited. Here, we performed lipidomic and volatilomic profiling of high-IMF and low-IMF Hu lambs. Triglycerides and diglycerides in the high-IMF group were significantly higher than those in the low-IMF group (p < 0.05). Seventy-nine of 842 lipids identified were significantly different between the groups under positive and negative ion modes (variable importance in projection > 1, p < 0.05). Volatilomic analyses revealed that the aroma profiles also differed between the groups. Fifteen aroma compounds, mainly originating from lipid oxidation, could be responsible for this difference. Thus, our findings provide a comprehensive understanding of the increases in IMF content that drive consumers' satisfaction and also provide a basis for underpinning breeding value for IMF.

Effect of beef tallow, phospholipid and microwave combined ultrasonic pretreatment on Maillard reaction of bovine bone enzymatic hydrolysate

The effects of beef tallow, phospholipid, microwave, and ultrasonic pretreatment (MUP) on the Maillard reaction process, the sensory characteristics of Maillard reaction products (MRPs), and the composition and content of volatile compounds were studied. Maillard reaction of the sample was more intense after MUP, but more hydrophobic amino acids were generated, resulting in relatively high sourness in MRPs. Beef tallow encapsulation has no significant effect on the sensory characteristics of MRPs. The content of volatile compounds in MRPs added with phospholipids increased significantly, and the content of sulfur compounds (especially furan and furanthiol) increased most significantly. Hexanal, Nonanal, 2-Hexylfuran, 2-Hexylthiophene, and 1-Octanol were positively correlated with the value of umami and saltiness of MRPs. The addition of phospholipids after MUP and beef tallow encapsulation helps to increase the saltiness and umami of MRPs, reduce astringency, and produce more sulfur and other flavor compounds.

Use of egg yolk to imitate meat aroma

Egg yolk contains abundant meat precursors, but its odor is quite different from meat aroma. In this study, the lipids in egg yolk were partly removed by acetone or totally removed by chloroform/methanol, and lutein was removed simultaneously by the solvents. Then, the samples were heated, and the volatiles and aroma profiles were analyzed. The results showed that chicken meat aroma and meat aroma were imitated successfully through the removal of neutral lipids and lutein (acetone-treated) and total lipids and lutein (chloroform/methanol-treated) egg yolk samples, respectively. Finally, additional lutein and tert-butylhydroquinone were employed for validating the inhibiting effects of lutein on lipid oxidation and Maillard reaction, and the results demonstrated that it was lutein rather than lipids or their degradation products that determined the flavor formation. These findings push forward the mechanisms for the formation of meat flavor and provide insights for future manufacturing of meat aroma.

The Role of Coffee Silver Skin against Oxidative Phenomena in Newly Formulated Chicken Meat Burgers after Cooking

Coffee Silver Skin (CSS) is the unique by-product discarded after the roasting of coffee beans. This research aimed to evaluate the effect of two levels of CSS (1.5% and 3%) added as a natural ingredient in new formulations of chicken meat burgers. This is one of the first studies proposing a "formulation approach" to control the emergence of off flavours after meat cooking. Physical, chemical, and sensory analyses were carried out, within the CSS content and the evolution of volatile organic compounds in different samples. Newly formulated chicken burgers could limit food waste, while also becoming a source of fibres, minerals, and bioactive molecules. CSS limited weight losses (after cooking process) to 10.50% (1.5% addition) and 11.05% (3% addition), significantly lower (p < 0.01) than the control (23.85%). In cooked burgers, the occurrence of hexanal was reduced from 55.1% (CTRL T₀) to 11.7% (CSS T₀ 1.5%) to 0 (CSS T₀ 3%). As for the limitation of off-flavours, CSS also showed good activity, contrasting with the emergence of octanal, alcohols and other markers of lipid oxidation. From the sensory test carried out, the volatile profile of CSS does not seem to impair the flavour of burgers, though at higher percentages hydrocarbons and pyrazines are traceable. The thiobarbituric acid reactive substances (TBARS assay confirmed the protective effect of CSS against oxidation.

Comparative characterization of lipids and volatile compounds of Beijing Heiliu and Laiwu Chinese black pork as markers

Chinese black pork is preferred by consumers due to its unique organoleptic characteristics, which are closely related to lipids and volatiles. The primary aim of this study was to reveal key lipids and volatiles for the differentiation of Duroc × (Landrace × Yorkshire) (DLY), and Beijing Heiliu and Laiwu black (BHLB) pork. Here, lipid and volatile profiles were comprehensively characterized and compared using untargeted lipidomic and volatilomic analysis. The BHLB pork showed higher intramuscular fat content (p < 0.05). The content of total monounsaturated fatty acids, along with C16:1, C17:1, C18:1, and C20:1, was higher in BHLB pork compared with DLY pork (p < 0.05). Lipidomic analysis showed that DLY and BHLB pork significantly differed in lipids at the class and molecular levels. The BHLB pork had significantly more triglyceride and less lysophosphatidylcholine compared with DLY pork (p < 0.05). In positive and negative modes, 34 and 21 potential lipid markers, respectively, were selected for the discrimination of DLY and BHLB pork. In addition, volatilomic analysis showed that DLY and BHLB pork were well distinguished, and 13 volatiles were considered as potential discriminatory markers. Our findings provide a comprehensive lipidomic and volatilomic profiles characteristic of BHLB pork and will hopefully provide an important basis for the effective identification of Chinese black pork.