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Fatty acid profiles and volatile composition in the yolks of conventional eggs from seven different species (duck, free‐range chicken, silky chicken, quail, pigeon, goose, and chicken) were compared using GC–MS and electronic nose (E‐nose). The results showed that there were significant differences among the fatty acid profiles of the seven avian eggs. Goose eggs contained the highest contents of saturated and monounsaturated fatty acids but the lowest content of polyunsaturated fatty acids (PUFA), and the differences were significant (p<0.05). The PUFA proportion was the highest in the free‐range chicken eggs of all the tested avian eggs. The ω‐3 PUFA content and the ω‐6/ω‐3 ratio were significantly (p<0.05) higher in the yolks of goose and silky chicken. The volatile compositions of egg yolks are esters, alcohols, alkenes, and nitrogenous compounds, and the major compounds that contributed to discrimination of different species of eggs were ethyl acetate, pathalic acid butyl isohexyl ester, O‐methylisourea hydrogen sulfate, 1‐butanol, and N‐isopropylbenzamide. In addition, seven different species of eggs were distinguished from each other through principal component analysis of E‐nose data, suggesting that the E‐nose may be a potential technology for discriminating different species of eggs. Practical applications: The results showed that the major volatile components could be used as chemical markers to distinguish different species of eggs by the chemometric method. The results obtained from the electronic nose analysis agreed well with the GC–MS results, suggesting the potential application of the E‐nose technique in the market quality control and the detection of counterfeit eggs. Twenty‐two fatty acids were detected and significant differences were found in the fatty acid proportions of different poultry eggs. A total of 41 volatiles were identified by GC–MS, and E‐nose can successfully discrimination different species of eggs.

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The aim of this research was to study S-ovalbumin as a reference index for the freshness of commercial shell eggs in terms of equivalent egg age. The S-ovalbumin content, yolk index, albumen pH, and Haugh units were determined at the storage temperature of 25 and 37°C, respectively, using 85 fresh-laid eggs. A correlation analysis showed a high correlation coefficient of S-ovalbumin content to storage time as well as to the 3 frequently used freshness indices (Haugh unit, yolk index, and albumen pH). Furthermore, a prediction model of equivalent egg age at 25°C was established using S-ovalbumin content as an index on the basis of the correlation analysis. This study confirmed the possibility of using S-ovalbumin as a reference index to express commercial shell egg freshness as equivalent egg age.

The efficiency of a novel biomarker (the transcriptional regulator, XRE ) was tested and evaluated in differentiating Bacillus thuringiensis from Bacillus cereus group species in environmental and spiked samples based on PCR and real-time PCR. Totally 120 strains, representing two bacterial groups, B. cereus group and non- Bacillus sp., were used to evaluate the performance of XRE and crystal protein ( cry 2, an existing biomarker). Further, three diverse samples (kimbap, lettuce, and spinach) were inoculated with B. thuringiensis and prominent biomarkers XRE and cry 2 were used as targets. Direct analysis of the detection results for the pure cultures of B. cereus group wild-types, references and type strains revealed an accuracy rate of 97.5% targeting XRE , and 83.3% targeting cry 2. The real-time PCR was constructed with a R 2 -value of 0.993. For the artificially contaminated samples, a concentration of 10 3 CFU/g of B. thuringiensis in spiked food samples could be detected using real-time PCR targeting XRE. A good performance was obtained with XRE in discriminating B. thuringiensis from B. cereus groups, as well as detecting B. thuringiensis in spiked food samples with PCR or real-time PCR. Therefore, this real-time PCR targeting X RE can be used as a dependable and promising tool to identify B. thuringiensis in foods.

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