Changes of Potent Odorants in Salted Duck Egg Yolk before and after Roasting.

As the second most widely consumed eggs, duck eggs are made into preserved eggs, salted duck eggs, and roasted duck eggs to extend their shelf-life. To investigate the differences in potent odorants (POs) between salted duck egg yolk (SDEY) and roasted duck egg yolk (RDEY), the volatiles in SDEY and RDEY were extracted through solvent extraction coupled with solvent-assisted flavor evaporation and were assayed with gas chromatography-mass spectrometry-olfactometry. A total of 45 volatiles were identified in two samples, 24 odor-active compounds (OACs) were screened, and more OACs were in RDEY. The flavor-dilution (FD) factors of OACs were obtained by aroma extract dilution analysis and ranged from 3 to 6561. Twenty-two OACs with FD factors ≥ 9 were quantitated, and the results indicated the concentrations of OACs in yolk increased greatly after salted duck eggs were roasted. Based on the concentrations and thresholds, odor activity values (OAVs) were determined; 17 odorants with OAVs ≥ 1 were determined as POs. Acetoin was the most PO in SDEY; there were more POs in RDEY, including 2-ethyl-3,6-dimethylpyrazine, acetoin, 2-acetyl-3-methylthiophene, dihydro-4-hydroxy-2(3H)-furanone, etc. The outcomes obtained have reference values for making better use of duck eggs in the food industry.

Phosphoproteomic analysis of duck egg yolk provides novel insights into its characteristics and biofunctions.

BACKGROUND: Although the importance of phosphorylation in the function of proteins is known, investigation of the protein phosphorylation of duck egg yolk (DEY) is still very limited. This study aimed to conduct a detailed phosphoproteomic study of DEY using immobilized metal affinity chromatography and ultra-high liquid chromatography tandem mass spectrometry. RESULTS: A total of 253 phosphorylation sites assigned to 66 phosphoproteins were identified in DEY, of which VTG-1, VTG-2, and fibrinogen alpha chain were found to be the highly phosphorylated proteins in DEY. The biological functions of the identified phosphoproteins were illuminated through gene ontology analysis, which showed that they were mainly involved in binding, catalytic, immune response, and metabolic activity. S-X-E and S-X-S were found to be the most conserved serine motifs of phosphorylation in DEY. The comparison of DEY phosphoproteins with those of chicken egg yolk (CEY) revealed that differences mostly involved molecular functions and biological processes. The comparison also revealed a higher phosphorylation level in DEY proteins. CONCLUSION: The higher phosphorylation level in DEY proteins than that in CEY proteins are supposed to help enhance duck growth performance and biological activities (e.g. antibacterial and antioxidant ability) for better adapting the humid environment the duck lived. © 2021 Society of Chemical Industry.

On-Line Detection Method of Salted Egg Yolks with Impurities Based on Improved YOLOv7 Combined with DeepSORT.

Salted duck egg yolk, a key ingredient in various specialty foods in China, frequently contains broken eggshell fragments embedded in the yolk due to high-speed shell-breaking processes, which pose significant food safety risks. This paper presents an online detection method, YOLOv7-SEY-DeepSORT (salted egg yolk, SEY), designed to integrate an enhanced YOLOv7 with DeepSORT for real-time and accurate identification of salted egg yolks with impurities on production lines. The proposed method utilizes YOLOv7 as the core network, incorporating multiple Coordinate Attention (CA) modules in its Neck section to enhance the extraction of subtle eggshell impurities. To address the impact of imbalanced sample proportions on detection accuracy, the Focal-EIoU loss function is employed, adaptively adjusting bounding box loss values to ensure precise localization of yolks with impurities in images. The backbone network is replaced with the lightweight MobileOne neural network to reduce model parameters and improve real-time detection performance. DeepSORT is used for matching and tracking yolk targets across frames, accommodating rotational variations. Experimental results demonstrate that YOLOv7-SEY-DeepSORT achieves a mean average precision (mAP) of 0.931, reflecting a 0.53% improvement over the original YOLOv7. The method also shows enhanced tracking performance, with Multiple Object Tracking Accuracy (MOTA) and Multiple Object Tracking Precision (MOTP) scores of 87.9% and 73.8%, respectively, representing increases of 17.0% and 9.8% over SORT and 2.9% and 4.7% over Tracktor. Overall, the proposed method balances high detection accuracy with real-time performance, surpassing other mainstream object detection methods in comprehensive performance. Thus, it provides a robust solution for the rapid and accurate detection of defective salted egg yolks and offers a technical foundation and reference for future research on the automated and safe processing of egg products.

Integration of LC-MS-Based and GC-MS-Based Metabolic Profiling to Reveal the Effects of Domestication and Boiling on the Composition of Duck Egg Yolks.

Egg yolks contain abundant lipids, proteins, and minerals that provide not only essential nutrients for embryonic development but also cheap sources of nutrients for consumers worldwide. Previous composition analyses of egg yolks primarily focused on nutrients such as lipids and minerals. However, few studies have reported the effects of domestication and heating on yolk composition and characteristics. The objective of this study was to investigate the impact of domestication and boiling on the metabolite contents of egg yolks via untargeted metabolomics using GC-MS and LC-MS. In this study, eggs were collected from Fenghua teals, captive mallards, and Shaoxing ducks. Twelve duck eggs (half raw and half cooked) were randomly selected from each variety, and the egg yolks were separated for metabolic profiling. The analysis identified 1205 compounds in the egg yolks. Domestication generated more differential metabolites than boiling, which indicated that the changes in the metabolome of duck egg yolk caused by domestication were greater than those caused by boiling. In a comparative analysis of domestic and mallard ducks, 48 overlapping differential metabolites were discovered. Among them, nine metabolites were upregulated in domesticated ducks, including monoolein, emodin, daidzein, genistein, and glycitein, which may be involved in lipid metabolism; some of them may also act as phytoestrogens (flavonoids). Another 39 metabolites, including imethylethanolamine, harmalan, mannitol, nornicotine, linoleic acid, diphenylamine, proline betaine, alloxanthin, and resolvin d1, were downregulated by domestication and were linked to immunity, anti-inflammatory, antibacterial, and antioxidant properties. Furthermore, four overlapping differential metabolites that included amino acids and dipeptides were discovered in paired comparisons of the raw and boiled samples. Our findings provided new insights into the molecular response of duck domestication and supported the use of metabolomics to examine the impact of boiling on the composition of egg yolks.

N-glycoproteomic analysis of duck egg yolk proteins: Implications for biofunctions and evolution.

Egg yolk contains multifunctional glycoproteins, which modulate embryogenesis and indicate species-specific adaptation. Here, we conducted an N-glycoproteomic study of duck egg yolk (DEY) and identified 359 N-glycosites corresponding to 113 glycoproteins. The comparison of DEY N-glycoproteins with those of chicken egg yolk (CEY) revealed a higher N-glycosylation level in DEY proteins, suggesting a biological adaption to meet the requirements for embryo development by modulating protein structure and binding ability, including immune response and ligand transport. This variation may be correlated to the strong resistance to the influenza virus disease of duck. A large set of corresponding glycoproteins between DEY and CEY were detected with similar molecular functions, which suggested a relatively lower evolution speed of avian egg yolk proteins than that of egg white proteins.

Extracts of red yolk from duck eggs inhibit metastasis of human mammary carcinoma (4T1) cells in mice

The aim of the present study was to investigate the in vivo anti-metastatic activity of the red pigments of red yolk eggs laid by the ducks dieting on Potamogeton cripus L on the mammary carcinoma (4T1). The pigments were extracted with petroleum ether and acetone (2:1, v/v). BALB/c mice were divided into three groups (n=6), fed with the extracts at 150 mg/kg body weight (BW)/day (DEYE-H) or at 50 mg/kg BW/day (DEYE-L) and identical buffer without the extract (control group). The extracts were administered for 34 days. The treatment significantly inhibited the growth of orthotopical 4T1 tumour (DEYE-H vs control, 1:2; DEYE-L vs control, 2:3) and reduced the metastasis of tumour in the lungs (DEYE-H vs control, 4:7; DEYE-L vs control, 5:7), without statistical difference of body weight among the three groups.