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.

[Study on Non-Destructive Detection Method for Egg Freshness Based on LLE-SVR and Visible/Near-Infrared Spectrum].

The freshness of egg is an important index to reflect the internal quality. In order to achieve non-destructive detection of freshness, micro fiber spectrometer was used to sample 550～950 nm transmittance spectra of eggs which performed quantitative analysis with haugh unit of eggs. Different pretreatment was combined with partial least squares regression(PLS) and support vector regression(SVR) respectively to find that first derivative combined with SVR predicted better than others through comparison, and it was better to model by SVR than by PLS. In order to improve efficiency and decrease adverse effects of useless information for modeling, the linear dimensionality reduction with principal component analysis (PCA) and the nonlinear dimensionality reduction with locally linear embedding(LLE) were used for the data of first derivative respectively. It indicated that LLE was better than PCA after comparison, and the correlation coefficient of calibration and prediction were 92.2%, 91.1%, and the root mean square error were 7.21, 8.80. The root mean square error of cross validation decreased 0.79.The experimental result illustrated that the nonlinear model of LLE combined with SVR improved predictive performance of egg freshness. It is feasible for the detection of visible/near-infrared spectrum of egg freshness to apply this method.

[Quantitative Approach to Melamine Detection in Egg White with Surface-Enhanced Raman Spectroscopy].

Due to the harmfulness of melamine to human, the quantitative detection of melamine in egg is very necessary. In the present study, the surface enhanced Raman spectra technology combined with chemometric analysis method was used to conduct melamine quantitative detection in egg white. Firstly, the melamine egg sample could be got by the method of artificial feeding hens usingdifferent feeding formulation. Then the surface enhanced Raman spectra of egg white was determined using portable Raman spectroscopy (Opto Trace RamTracer-200) and Raman enhancement reagents, and the melamine content within the white eggs was measured with gas chromatography mass spectrometry technology. The software of Raman Analyzer was used for baseline correction of Raman spectra. The correlation coefficient method was used to choose 320 spectral variables from the surface enhanced Raman spectroscopy as input variables to establish partial least squares quantitative calibration model . And the peaks-decomposition method was used to establish peaks-decomposition quantitative calibration model. Both models selected 90 and 44 samples respectively as calibration sets and validation sets during model establishment, and both models achieved good prediction effect. The determination coefficient between predicted values of partial least squares quantitative calibration model and measured values of gas chromatography mass spectrometry was 0.856, and root mean square error of prediction was 1.547. The determination coefficient was 0.947 and RMSEP was 0.893 for the peaks-decomposition quantitative calibration model. This study demonstrated that the method can effectively quantitatively detect melamine in eggs. Testing a sample only takes 15 minutes, which can provide a new way for the melamine egg detection.

[Effect of heat treatment on the allergenicity and microstructure of ovomucoid].

The effect of heat treatment on the allergenicity and microstructure of ovomucoid was studied by enzyme-linked immunosorbent assay (ELISA), CD spectra, ANS fluorescence probe emission spectra and UV absorption spectra. The results showed that the allergenicity of ovomucoid decreased with increasing temperatures and time. CD spectra were used to examine the changes in the secondary structure of the ovomucoid treated by different temperatures. When treated by different temperatures, the mutual transformation between a-helix, b-sheet, b-turn and the random coil was observed, and the disorderliness of the secondary structure was increased with alpha-helix and beta-sheet decreasing, but the random coil increased correspondingly. The ANS fluorescence probe emission spectra analysis demonstrated that heat treatment induced reducing in surface hydrophobicity with the increase in heat temperatures. With the increase in heat temperatures, the amino acid residues with the UV-absorption were exposed gradually, and the UV-absorption maximum value increased. The results indicated that when treated by heating, the changes in the microstructure of ovomucoid can lead to the changes in the allergenicity of ovomucoid.

[Study on the stability of chicken egg yolk immunoglobulin (IgY) modified with mPEG].

The objective of the present paper was to study the effect of monomethoxypolyethlene glycol (mPEG) modification on the stability of chicken IgY and compare the stability of the modification products by Fourier transform infrared spectroscopy (FTIR), CD spectrooscopy and fluorescence spectroscopy. NHS-mPEG was used to modify IgY after mPEG was activated with N-hydroxysuccinimide (NHS). The optimal reaction condition for modification was 1:10 molar rate of IgY to mPEG at pH 7, reaction for 1 h, and the product was obtained with modification rate of 20.56% and activity reservation of 87. 62%. In addition, the thermal and pH stability of IgY and mPEG-IgY was compared by spectroscopic methods. The results showed that the alpha-helix, beta-sheet, beta-turn, and random content of IgY changed from 14.5%, 42.1%, 6.2% and 37.2% to 1.6%, 55.25%, 5.8% and 37.5%, while mPEG changed from 12.9%, 42.7%, 6.3% and 38. 1% to 3.1%, 50.5%, 7.2% and 39.2%, respectively, after incubating for 120 min at 70 degrees C. For the treatment with acid-base, similarly, the structure changes of mPEG-IgY were smaller than IgY. Thus, it is indicated that IgY modified by mPEG had greater stable properties.

[Study of the effect of temperature on the conformation of ovotransferrin by two-dimensional infrared correlation spectroscopy].

The conformation changes of Apo-Ovotransferrin and Holo-Ovotransferrin were studied with the heat treatment 25-95 degrees C by using Fourier transform infrared spectroscopy (FTIR) and two-dimensional correlation spectroscopy analyzer. The results of one-dimensional infrared spectroscopy showed that with the increase in temperature, the peak at 3 300 cm(-1) of Apo-Ovo-transferrin shifted more than that of Holo-Ovotransferrin. The peak at 3 300 cm(-1) derived from stretching vibrations of N-H and O-H indicates that iron-binding enhanced the role of hydrogen bonds and resistance to heat. The changing order of the secondary structure of ovotransferrin was determined by analyzing two-dimensional infrared spectra,witch is beta-sheet>amide II >-CH2 - bending vibration. In addition, it was found that the cross-peaks at 1 652 and 1 688 cm(-1) are different in synchronous and asynchronous counter maps by comparing Apo-Ovotransferrin with Holo-Ovotransferrin. It was suggested that the temperature made less impact on the alpha-helix in Holo-Ovotransferrin than on that in Apo-Ovotransferrin, however, the beta-turn in Holo-Ovotransferrin was more sensitive to temperature.

[The detection of hatching eggs prior to incubation by the near infrared spectrum].

The detection of the infertile eggs and fertile eggs by the near infrared diffuse reflectance spectra was proposed. Models based on different band regions range, different principal component numbers and the different spectral pre-processing methods were compared and the optimal calibration model was established. The results show that qualitative forecasting model of hatching eggs is established by Mahalanobis Distance, which is with band regions range being 4 119.20-9 881.46 cm(-1), principal component number being 19 and spectral pre-processing method being SNV + first derivative + Norris differential filter. The precision rate of calibration set is 92.5% and that of validation set is 91.67%. The study provides a new way for nondestructive testing of the fertile eggs and infertile eggs prior to incubation.

[Investigation of interaction between riboflavin and riboflavin binding protein by fluorescence spectroscopy].

The interaction between riboflavin and egg white riboflavin binding protein (RBP) was investigated using fluorescence spectroscopy. The binding mode, binding constants, thermodynamic parameters between riboflavin and RBP and energy transfer were studied. The experimental results showed that riboflavin has the ability to quench the intrinsic fluorescence of RBP because of a complex formed, and the quenching mechanism is static quenching. The binding constants were 5.35 x 10(8), 1.54 x 10(8), 0.56 x 10(8) L x mol(-1) at 298, 308 and 318 K, respectively. The thermodynamic parameters were calculated, which suggested hydrogen bonds and Van der Waals played a major role in the interaction. The distance and efficiency of energy transfer between riboflavin and RBP were 0.70 nm and 0.39, respectively, based on the theory of Forster nonradiative energy transfer. Furthermore, the synchronous fluorescence spectroscopy was utilized to investigate the conformational transformation.

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.

[Effect of S-configuration transformation on the microstructure of ovalbumin].

The effect of S-configuration transformation on the microstructure of ovalbumin was studied by CD spectra, XRD spectra, ANS fluorescence probe emission spectra and UV absorption spectra. CD spectra was used to examine the changes in the secondary structure of the ovalbumin during S-ovalbumin information process. When the induction time was prolonged, the mutual transformation between alpha-helix, beta-sheet, beta-turn and the random coil was observed, and the orderliness of the secondary structure was increased with alpha-helix decreasing slightly and beta-sheet increasing correspondingly. XRD spectra analysis showed that the crystal structure content of the ovalbumin increased with prolonging the induction time and the largest data was observed at 72 h, indicating that the orderliness of the secondary structure was increased. The results were similar to CD spectra analysis. The ANS fluorescence probe emission spectra analysis demonstrated that S-configuration transformation induced an increase in surface hydrophobicity with prolonging the induction time, and the largest data was also observed at 72 h. In addition, UV absorption spectra analysis indicated that S-configuration transformation resulted in a decrease in the UV-absorption maximum value with prolonging the induction time, indicating that the aromatic amino acid was buried in the molecular interior. The results indicated that the changes in the microstructure of ovalbumin were relevant to S-configuration transformation.

[A facile colloid aqueous method for synthesis of water soluble ZnSe quantum dots with high fluorescence and stability characterization].

Highly fluorescent and stable ZnSe quantum dots were synthesized by a facile colloid aqueous phase route. It overcame the defects such as instability and low quantum yields of the quantum dots synthesized by early aqueous phase route. Optimum conditions were found. L-glutathione was used as the stabilizer, the molar ratio of L-glutathione, Se2- and Zn2+ is 5 : 1 : 5, the reaction media is pH 10.5, and the proper temperature is between 90 and 100 degrees C. Quantum yields (QYs) could reach to 50.1% without post irradiation in prime synthetical conditions. And the fluorescence intensity of ZnSe QDs almost didn't change after 3 months. Its water-soluble property is also excellent. The properties of ZnSe QDs were characterized by means of ultraviolet visible spectra, fluorescence spectra, and transmission electron microscopy. The synthesized ZnSe QDs emit blue-purple fluorescence (370 nm) when excited at 300 nm. And the excellent photochemical characteristics of the ZnSe QDs will be advantageous in the application in optothermal device manufacture and chemistry biology domain.

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.

[Second derivative FTIR spectroscopic study of Bacillus cereus].

Some particular cell components of intact Bacillus cereus could be detected and identified by Fourier transform infrared spectroscopy (FTIR). FTIR were collected directly, then the FTIR spectra of the samples were converted into second derivative spectra. Typical marker bands were used to identify these bacterial cell components such as capsules, endospores or storage materials. Capsules were detected in cell by a strong amide band near 1654 cm(-1) typical for alpha-helical structures and by strong carboxylate stretching vibrations (approximately 1601 cm(-1) and approximately 1403 cm(-1), respectively). The formation of endospores was discovered using marker bands for dipicolinic acid (located at approximately 1617 cm(-1), approximately 1372 cm(-1) and approximately 1569 cm(-1)). Spectra of this strain showed expression of poly-beta-hydroxybutyric acid granules, capsules and endospores simultaneously. These bacterial cell components can be identified by second derivative FTIR spectroscopy which can distinguish the overlap spectrum. And that offered some referenced information for molecular biology and cellular biology.