Non-destructive characterization of egg odor and fertilization status by SPME/GC-MS coupled with electronic nose.

BACKGROUND: Early and non-destructive identification of fertile (F) eggs is a difficult task in the process of breeding laying hens. The odors emitted from unfertilized (UF), infertile (IF), and fertile (F) eggs were characterized by solid-phase microextraction / gas chromatograph-mass spectrometry (SPME/GC-MS) and electronic nose (E-nose) to determine their differences by principal component, partial least squares, and canonical discriminant analyses. RESULTS: A total of 14 volatiles were identified in unhatched shell white Leghorn eggs, such as nonanal, decanal, 6-methyl-5-hepten-2-one, and 6,10-dimethyl-5,9-undecadien-2-one. Cedrene and decanal contributed greatly to the classification of UF and fertilized (Fd)/IF eggs; cedrene, decanal, 1-octanol and hexanal contributed greatly to the distinction between UF and IF eggs; heptanal might be the potential marker to determine F/IF eggs. P40/1, P10/2, P10/1, TA/2, T40/2 and T30/1, P30/1, P40/2, PA/2, T40/2 mostly contributed to the distinction between UF and Fd eggs and between F and IF eggs, respectively. Canonical discriminant analysis presented superior differentiating efficiency for almost all groups, and the odor differences between UF and Fd eggs were significantly larger than the differences between F and IF eggs. CONCLUSION: Solid-phase microextraction / gas chromatograph-mass spectrometer combined with E-nose may have the potential to non-destructively distinguish UF, F, and IF eggs, which will provide a new perspective to understand the differences among them. © 2018 Society of Chemical Industry.

A new insight into the key matrix components for aftertaste in Ampelopsis grossedentata (vine tea) infusion: From the intensity and duration of taste profiles using non-targeted metabolomics and molecular simulation.

The aftertaste with a prolonged duration in ampelopsis grossedentata infusion (AGTI) is easily perceived, however, its formation mechanism is unclear. Therefore, aftertaste-A and richness were confirmed as the characteristic aftertaste of AGTI through sensory evaluation and electronic tongue. Moreover, 5-KETE, theobromine, etc., metabolites were identified as the differential components between AGTI and green tea infusion. Among them, p-coumaroyl quinic acid, xanthine etc., and proline, dihydromyricetin, etc., components contributed more to the formation of aftertaste-A and richness, respectively. Further, the bonding between characteristic metabolites for aftertaste in AGTI with their receptors were shown to be more stable using molecular docking, compared to metabolites related to typical taste profiles. The aftertaste in AGTI was more easily perceived by saltiness components or in NaCl system by molecular simulation. This study offers novel insight into the interaction mechanism of aftertaste in tea infusion and will contribute to further study on aftertaste for other foods.

Study on the mechanism of improving the quality of salted egg yolks by ultrasonic synergistic NaCl dry-curing.

The dry separate curing of duck egg yolks was carried out by ultrasonic synergize NaCl (sodium chloride) and NaCl alone. The mechanism of the amelioration of salted egg yolk quality by ultrasonic synergistic NaCl dry-curing was studied. The quality variations of the salted egg yolks were analyzed for the same curing time and NaCl content achieved by ultrasonic synergistic NaCl curing and NaCl curing alone. The results showed that under the same salting time, the NaCl content, oil exudation and chewiness of U48-SEY (ultrasonic for 48 h-salted egg yolk) were higher than those in SEY (salted egg yolk). At the same NaCl content, the oil exudation and chewiness of U44-SEY (ultrasonic for 44 h-salted egg yolk) were still significantly increased. Compared to SEY, the soluble protein content and H0 of U44-SEY and U48-SEY were augmented. Scanning electron microscopy (SEM) indicated that the polyhedral particles in the salted egg yolks prepared by ultrasonic synergistic NaCl dry-curing were closely aligned and evenly distributed, and the salted egg yolks were sandier. Structural analysis revealed that the secondary and tertiary structures of egg yolk protein were changed although the ultrasonic synergistic NaCl dry-curing did not cause the fragmentation or aggregation of the peptide chain structure. The above results suggested that ultrasonic not only perfected the quality of salted egg yolk by promoting NaCl penetration, but also modified the structures of egg yolk protein by the action of ultrasonic itself, which prominently improved the quality of salted egg yolks.

Multi-omics revealed the formation mechanism of flavor in salted egg yolk induced by the stages of lipid oxidation during salting.

To explore the contribution of different lipid oxidation stages to flavor formation in salted egg yolk, potential pathways of flavor formation were characterized by multi-omics strategy and partial least squares structural equation model (PLS-SEM). 72 lipids, 135 metabolites and 5 volatiles related to lipid oxidation were screened out. The degradation of aldehydes and ketones, and the generation of tryptamine and elaidic acid, etc. were promoted by triglycerides (TG) (10:0 16:0 18:1), triglycerides (TG) (18:0 20:1 22:0), etc. at primary and secondary oxidation stage, respectively. The generation of acetophenone, thianaphthene, etc. through the pathway of 2-phenylacetamide, hexanoylcarnitine, etc. was facilitated by these triglycerides (TG) at primary oxidation stage. Furthermore, amino acid metabolisms, pentose phosphate pathway and linoleic acid metabolism occurred at secondary oxidation stage were key pathways to form distinctive flavor. In conclusion, secondary oxidation stage may be more important for the formation of unique flavor (taste) in salted egg yolk.

Translucency mechanism of heat-induced pigeon egg white gel.

In this study, the properties of pigeon egg white (PEW) and chicken egg white (CEW) thermal gels were compared, with the aim of revealing the mechanisms involved in the high transparency of PEW thermal gels. Results demonstrated that PEW gels exhibited higher transparency than CEW gels. Scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis revealed that PEW gels formed a fine chain gel network structure with an average diameter of thermal aggregates (89.84 ± 7.13 nm). The molecular properties of PEW proteins, such as higher content of ß-sheet structures (32.73 %), reactive groups (free sulfhydryl groups, hydrophobic groups), and absolute zeta potential (-3.563 mV), were found to contribute to the formation of smaller thermal aggregates during thermal denaturation. The microrheology measurements showed that these features allowed PEW proteins to interact less with each other and form smaller thermal aggregates during thermal denaturation, which facilitated the formation of fine chain gel networks and thus improved the transparency of the gels. The present study initially reveals the molecular basis of the high transparency of PEW thermal gels and provides a theoretical reference for the development of new highly transparent protein materials.

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.

Multiomics reveals the formation pathway of volatile compounds in preserved egg yolk (PEY) induced by NaCl: Based on the model of PEY and salted egg yolk (SEY) treated with/without NaCl.

The models of preserved egg yolk (PEY) and salted egg yolk both treated with or without NaCl were performed to explore the effect of NaCl on the characteristic volatile compounds (VOCs) in PEY. 1-hexanol, 2-heptanone, isoamyl acetate, etc., compounds were confirmed as the characteristic VOCs in PEY mainly induced by NaCl and the formation of 1-octanol, 2-pentylfuran, ammonia, etc., characteristic VOCs induced by NaCl may depend on the combined effect of Cu2+ and OH-. Among them, 1-hexanol and 2-heptanone were formed from linoleic acid in PS(18:0_18:2) and oleic acid in PG(22:6_18:1), respectively, through multi-omics and correlation analysis. Meanwhile, 1-octanol may originated from ß-oxidation of oleic acid in PS(18:1); 2-pentylfuran and ammonia maybe derived from the derivative of aspartate and the degradation of l-methionine, respectively. Moreover, this study provides a new insight to parse the influence of NaCl with/without other exogenous factors on the formation of VOCs in food products.

Differential proteomics between unhatched male and female egg yolks reveal the molecular mechanisms of sex-allocation and sex-determination in chicken.

There is a huge demand to identify the sex of unhatched fertilized eggs for laying industry and to understand the differences between male and female eggs as early as possible. Then the molecular mechanisms of sex determination and sex allocation in chicken were revealed. Therefore, TMT proteomic was applied to characterize the variation of molecular matrix between unhatched male and female egg yolks. A total of 411 proteins were identified and 35 differentially expressed proteins (DEPs), including 375332005, 015809562, 763550308 (upregulated, UPs) and 1337178851, 89000557, 89000581 (downregulated, DPs), etc. were confirmed between them. Gene ontology analyses showed that DEPs were mainly involved in response to stimulus, distributed in the extracellular region and participated in binding; KEGG analyses showed that few DPs were participated in cell growth and death, transport and catabolism, signaling molecules, interaction and were enriched in ubiquitin mediated proteolysis, endocytosis, ferroptosis, etc. metabolic pathways. Moreover, most of the DEPs and related metabolic pathways were associated with sex hormones. More importantly, this study supports maternal sex-allocation theory and extends our understanding of the molecular mechanism of sex determination and differentiation in avian. Which also provides a powerful evidence for ovo sexing of unhatched fertilized domestic chicken eggs by nondestructive approach and will be of great significance to eggs processing and production.

Effects of ultrasound-assisted glycosylation on the interface and foaming characteristics of ovotransferrin.

Ovotransferrin (OVT) is one of the major functional proteins in egg white protein. Most of the industry only paid attention the biological activity of OVT in iron supplement, antibacterial and other aspects, few reports were carried out on its processing characteristics such as foaming, interfacial behavior such as emulsification and foaming, which was an important processing functional attribute affecting its application scenario. In this study, the effects of ultrasound-assisted glycosylation on the interface and foaming characteristics of OVT were investigated. The results showed that proper ultrasonic treatment had a significant effect on the structure and physicochemical properties of OVT glycosylation products. When ultrasonic treatment lasted for 20 min, the grafting degree of OVT was 20.98%, the particle size decreased and the absolute value of potential increased. The foaming ability of OVT increased first and then decreased after ultrasonic-assisted glycosylation treatment. The foaming ability of OVT increased from 43.54% to 96.73% and the foaming stability increased from 68.92% to 89.19% after ultrasonic-assisted glycosylation treatment for 20 min. The experimental study effectively discovered the effect of ultrasound-assisted glycosylation on the foaming property of OVT, and would provide important technical references for expanding its application in food, biology, medicine and other fields.

Nondestructive characterization gender of chicken eggs by odor using SPME/GC-MS coupled with chemometrics.

It's a difficult task for researchers to identify the gender of chicken eggs by nondestructive approach in the early of incubation, which not only could reduce the cost of incubation, but also could improve the welfare of chicks. Therefore, SPME/GC-MS has been applied to investigate its potential as a nondestructive tool for characterizing the differences of odor between male and female chicken eggs during early of incubation and even before hatch. The results showed that more volatiles were found in female White leghorn eggs during early of incubation and 6,10-dimethyl-5,9-undecadien-2-one, 6-methyl-5-hepten-2-one, nonanal, decanal, octanal, 2-nonen-1-ol, etc. were important for the distinction of male and female White leghorn eggs during E1-E9 of incubation. 2-ethyl-1-hexanol; octanal, nonanal, 2,2,4-trimethyl-3-carboxyisopropyl pentanoic acid isobutyl ester; 2-nonen-1-ol, cyclopropanecarboxamide, heptadecane were correlated with gender of unhatched White leghorn, Hy-line brown and Jing fen eggs, respectively. Moreover, sex-related volatiles have been strongly influenced by incubation process and egg breed, and to be related to steroid hormone biosynthesis. What's more, this study enables us to develop a new visual for ovo sexing of chicken eggs and advances our understanding of the biological significance behind volatiles emitted from chicken eggs.

Potential correlation between volatiles and microbiome of Xiang xi sausages from four different regions.

Volatiles and microbiome from different Xiang xi sausages (HBD, HBN, HHY and HDK) were performed by Chromatography-Ion Mobility Spectrometry and Illumina MiSeq platform (16 S rRNA and ITS sequencing). Results indicated that ethanol, ethyl acetate, ethyl-propanoate, pinene, limonene, cineole, etc. were the key (main) volatiles; whereas staphylococcus, lactobacillus, solanum-torvum, brochothrix and debaryomyces, candida were the dominant bacteria and fungi, respectively. The variation and relationship between microbiome and volatiles were disclosed by multivariate and spearman's correlation analysis. Volatiles of HDK is similar to HBN and HBD compared to HHY, while microbiome community of HHY is similar to HBN and HDK compared to HBD. Solanum-torvum, pseudomonas (bacteria) and debaryomyces (fungi) contributed positively to the development of major volatiles in Xiangxi sausages. Meanwhile, 'carbohydrate metabolism', 'amino acid metabolism' (microbia) and glycolysis/gluconeogenesis (volatiles) were commented in KEGG database. This study provides a deep insight into the relation between volatiles and microbiome (bacteria and fungi) of Xiangxi sausages.

Physicochemical, structural and adhesion properties of walnut protein isolate-xanthan gum composite adhesives using walnut protein modified by ethanol.

Low-sugar and high-protein adhesives have broad market application prospects, while natural plant proteins have confronted technical bottlenecks due to their poor adhesion. In this study, the effects of ethanol with different concentrations (0-80%) on the adhesion properties of walnut protein isolate-xanthan gum (WNPI-XG) composite adhesives were investigated. Results showed the bonding strength of WNPI-XG treated with 40% ethanol reached 12.55 MPa, the denaturation temperature and the surface hydrophobicity increased to 87.91 and 185.07 respectively, displaying the best rheological and texture properties. It also indicated appropriate concentration of ethanol (40%) didn't change the molecular weight of WNPI-XG, but greatly strengthened the fluorescence intensity, leading changes in contents of reactive sulfhydryl groups, electrostatic forces, hydrophobic interactions, hydrogen bonds and disulfide bonds. Furthermore, the treatment also facilitated a conformation conversion of the secondary structures from ß-sheet to α-helix, promoting the full unfolding of protein molecules. The microstructure analysis showed after 40% ethanol treatment, the WNPI structure was uniform, the surface of WNPI-XG adhesive was flat and smooth, combined more closely with water molecules. By analyzing the influence of ethanol treatment on adhesion of WNPI-XG, the research laid a theoretical foundation for protein modification, providing good technical references for its development and utilization.

Study on the emulsification and oxidative stability of ovalbumin-pectin-pumpkin seed oil emulsions using ovalbumin solution prepared by ultrasound.

Pumpkin seed oil (PSO), which is a valuable compound with high nutritional value used for the prevention of various chronic diseases, is prone to oxidation. In this work, small and uniform (su) ovalbumin (OVA) and pectin (PEC) were used to stabilize PSO in the form of an emulsion. The results showed that suOVA-PEC-PSO emulsion with a droplet size of 9.82 ± 0.05 µm was successfully self-assembled from PSO, PEC, and suOVA solution (with a droplet size of 230.13 ± 14.10 nm) treated with 300 W ultrasound, owing to the formation of a more stable interfacial film on the surface of droplets. The interfacial, rheological, emulsifying, and antioxidant properties of the suOVA-PES-PSO emulsions were excellent, owing to the synergistic effects between PEC and suOVA solution. Moreover, the physical stability of the suOVA-PEC-PSO emulsions to salt stress, a freeze-thaw cycle, and heat treatment was also increased and the oxidation of linolenic acid was notably delayed. These results have extended the food-related applications of OVA and PSO, and provide a promising foundation for further exploration of the self-assembly of composite emulsions by small and uniform proteins.

Improvement of quality and flavor of salted egg yolks by ultrasonic assisted cooking.

Physicochemical, texture indexes, microstructure and volatiles were used to characterize the changes in quality, structure and flavor of cooked salted egg yolks (SEYs) with or without ultrasonic treatment. Experimental results indicated that ultrasonic significantly increased cooking (water) loss, oil exudation, lipids oxidation (TBARS), accelerated the doneness of cooked SEYs and then promoted the generation of volatiles. These results were further confirmed by the improvement of thermal stability, the changes in color, secondary structure of proteins, water distribution and mobility. Meanwhile, more "fragments" and "cracks" were observed in scanning electron microscope (SEM) and the decrease in gumminess and chewiness were detected using texture profile analysis (TPA), inducing that the migration of lipids and collapse of gel network were intensified. Moreover, ultrasonic treatment decreased the content of sodium chloride in SEYs. Therefore, it was concluded that the doneness, quality and flavor of cooked SEYs were improved by ultrasonic treatment, which could be used as an effective and alternative method for the production of SEYs with good flavor, sandy and oily texture.

SPME-GC-MS & metal oxide E-Nose 18 sensors to validate the possible interactions between bio-active terpenes and egg yolk volatiles.

This study was focused on the differences between three concentrations of four safe bio-active volatile terpenes and natural compounds (trans-cinnamaldehyde, thymol, menthol, and vanillin) on the egg yolk volatile components. In which, Headspace Solid phase Micro Extraction (HS-SPME) followed by GC/MS were used for volatiles analysis, and electronic nose (E-Nose) with 18 sensors was used for the aroma pattern. In the results, a total of 111 different volatile compounds were identified by using GC/MS. Some ketones, amines, nitro and organic acid compounds such as hexanone were significantly reduced after using these compounds. On the other hand, first principal components (PC1) of trans-cinnamaldehyde (0.1%) was decreased significantly (p < .05) to -4.8 ±â€¯0.8, compared to the control with 4.3 ±â€¯2.1. And, it increased benzaldehyde and nonanal peaks area significantly to 46.56 ±â€¯14.46 and 9.22 ±â€¯4.81 MPA. In menthol (0.1%), the content of d-limonene was decreased to 4.65 ±â€¯0.49 MPA, compared to the control with 14.16 ±â€¯4.95 MPA. On the other hand, by E-Nose, vanillin (0.1%) PC1 was decreased significantly to -4.48 ±â€¯0.43. Moreover, thymol (0.1%) decreased hydrocarbon sensation to 0.448 ±â€¯0.005. And, vanillin (0.1%) decreased hydrogen sulfide and ketones sensation to 0.169 ±â€¯0.01 and 0.344 ±â€¯0.01, respectively. In conclusion, this study is providing novel information to understand the effects of bio-active molecules on the biological fatty media volatility. Also, it explains how terpenes can protect egg yolk media from the unacceptable odor formation which results from the degradation of its lipids and proteins.

Sex differences in serum steroid hormone levels during embryonic development in hen eggs.

This experiment was conducted to explore the differences of serum steroid hormones with age and sex in hen eggs during incubation periods for identification of males and females. The concentrations of estrone (E1), estradiol (E2), estriol (E3), testosterone (T), androstenedione (A4), and dihydrotestosterone (DHT) in serum were measured by enzyme-linked immunosorbent assays in chicken embryos on 8, 10, 12, 14, and 16 D, respectively. During the development of chicken embryo, egg weight loss was closely related to age but no sex. However, it was found that both age and sex significantly affected hormones and had obviously more effect on androgens levels. Besides E2 and T, other steroids such as E1, A4, and DHT were also significantly correlated with sex (P < 0.05). Notably, the level of T and the ratio of T to E2 were significantly higher in males than females (P < 0.05). The ratio of E1 to E2 displayed different trends in different sexes, which increased in males but decreased in females. The distribution proportions of androgens and estrogens kept stable level during the late hatching periods of 12 to 16 D. The sex differences of steroids were more obvious at the late hatching stage through PCA. These suggested that the serum hormones differences in male and female embryos played a vital role in sexual differentiation. These findings not only provided the theoretical basis for sex determination of fertilized eggs in egg-laying hen strains, but also contributed to develop a non-invasive way to sex determination of fertilized eggs to meet the modern commercial application.

Characterization and classification of volatiles from different breeds of eggs by SPME-GC-MS and chemometrics.

Volatiles of shell eggs were identified by SPME-GC-MS to characterize and discriminate white Leghorn (W), Hy-line brown (H) and Jing fen (J) hatching eggs with comparison, principal components (PC), partial least squares (PLS), random forest classification (RFC) and canonical discriminant (CD) analyses. DVB/CAR/PDMS fiber and extraction 60 min were suited to analyze the volatiles emitted from eggs. A total of 17 or 18 volatile compounds were identified in raw shell hatching eggs, namely, nonanal, decanal and 6-methly-5-hepten-2-one were the main volatile components with contributions that over 70%. The composition and/or profile of volatile compounds from W and H eggs were much more similar than J eggs. Hexanal, decanal, 6-methly-5-hepten-2-one, heptanal, etc. have greatly contributed to the distinction of W, H and J eggs in sparse (S)-PLS and orthogonal (O)-PLS models. The accuracy of RFC and CD model were 100%, 100% (initial) and 83.3% (cross-validation), respectively. Heptanal, 6-methly-5-hepten-2-one, octanal, etc. were contributed positively to the classification of W, H, J eggs in RFC, especially for heptanal.