Antibacterial Properties of TMA against Escherichia coli and Effect of Temperature and Storage Duration on TMA Content, Lysozyme Activity and Content in Eggs

Metabolomic and proteomic profiling reveals the formation mechanism of volatile flavor in egg whites during fermentation by Streptococcus thermophilus

In this study, the flavor of egg whites was significantly improved by lactic acid fermentation, and the metabolic networks of metabolites, volatile compounds, and enzymes were established using gas chromatography-mass spectrometry, metabolomic, and proteomic. Results indicate that among ten types of common lactic acid bacteria, Streptococcus thermophilus endowed egg white with the most pleasant flavor through increasing aldehydes, ketones, alcohols, esters, terpenoids, and aromatic compounds. Amino acid catabolism was the predominant pathway for generating most aldehydes, alcohols, acids, and esters. The changes in the organic acids and derivatives (mainly amino acids, peptides, and analogues) concentration during fermentation are attributed to the hydrolysis of egg white proteins by proteinases and peptidases, and the regulation of enzymes involved in amino acid biosynthesis and other reactions. This study provides a valuable reference for future investigations focusing on regulating the flavor release of egg whites.

Impact of storage period on hatching egg quality, extra-embryonic structures, embryo morphometry, hatchability, and Rosa 1 chick quality

Storage duration affects the biological value of hatching eggs. The study evaluated the composition and characteristics of hatching eggs from Rosa 1 hens, the morphometric traits of embryos and chicks, and hatching results based on storage time. A total of 1 200 hatching eggs were divided into three groups: NS (control, non-stored), S4 (stored up to day 4), and S7 (stored up to day 7). Storage conditions were 17 °C and approx. 60% relative humidity. Each group's egg quality was measured for 30 eggs. Weight loss during storage was monitored. Lysozyme activity and viscosity were analysed from fresh eggs and incubated eggs on days 7 and 14, using thin and thick albumen or amniotic fluid. Embryo morphometry was measured on days 7, 10, 14, and 18, and posthatching results and the quality of 1-day-old chicks were assessed. Eggs stored for 7 days (S7) had higher (P < 0.05) weight loss compared to the NS group. The proportions of eggshell and yolk increased (P < 0.05) after storage, and the yolk index decreased. Vitelline membrane strength was lower (P < 0.001) in the S4 and S7 groups than in the NS group. The lowest (P < 0.05) pH levels of thin, thick albumen and yolk were observed in the NS group. Lysozyme activity increased (P < 0.001) in the thin albumen of eggs in the NS and S4 groups and the thick albumen from the NS group than in others. On day 7 of incubation, group S7 showed higher (P < 0.05) lysozyme activity in thick albumen, with no activity in amniotic fluid. By day 14, lysozyme activity increased (P < 0.001) in group S7's thick albumen and S4 and S7 groups' amniotic fluid. Viscosity was highest (P < 0.05) in fresh eggs' thin and thick albumen from group S7, but on day 7, thick albumen viscosity was lowest. On day 14, amniotic fluid viscosity was higher (P = 0.009) in group S4 than in NS. Seven-day-old embryos in group S7 had lower (P = 0.004) weight than others. Eye diameter in S7 embryos was also smaller on days 7 and 18. On day 10, NS group embryos had shorter body diagonal lengths. Storage up to 7 days adversely affected hatching efficiency. Storage affected the navel area of 1-day-old chicks, with the highest neck length in male chicks from group S4 and the lowest in females from group S4. It is concluded that egg storage at 17 °C and 60% relative humidity could be limited to 4 days to maintain hatchability and qualitative features.

Microbiome-derived metabolite effects on intestinal barrier integrity and immune cell response to infection

The gut microbiota exerts a significant influence on human health and disease. While compositional changes in the gut microbiota in specific diseases can easily be determined, we lack a detailed mechanistic understanding of how these changes exert effects at the cellular level. However, the putative local and systemic effects on human physiology that are attributed to the gut microbiota are clearly being mediated through molecular communication. Here, we determined the effects of gut microbiome-derived metabolites l-tryptophan, butyrate, trimethylamine (TMA), 3-methyl-4-(trimethylammonio)butanoate (3,4-TMAB), 4-(trimethylammonio)pentanoate (4-TMAP), ursodeoxycholic acid (UDCA), glycocholic acid (GCA) and benzoate on the first line of defence in the gut. Using in vitro models of intestinal barrier integrity and studying the interaction of macrophages with pathogenic and non-pathogenic bacteria, we could ascertain the influence of these metabolites at the cellular level at physiologically relevant concentrations. Nearly all metabolites exerted positive effects on barrier function, but butyrate prevented a reduction in transepithelial resistance in the presence of the pathogen Escherichia coli, despite inducing increased apoptosis and exerting increased cytotoxicity. Induction of IL-8 was unaffected by all metabolites, but GCA stimulated increased intra-macrophage growth of E. coli and tumour necrosis-alpha (TNF-α) release. Butyrate, 3,4-TMAB and benzoate all increased TNF-α release independent of bacterial replication. These findings reiterate the complexity of understanding microbiome effects on host physiology and underline that microbiome metabolites are crucial mediators of barrier function and the innate response to infection. Understanding these metabolites at the cellular level will allow us to move towards a better mechanistic understanding of microbiome influence over host physiology, a crucial step in advancing microbiome research.

Discrimination of Free-Range and Caged Eggs by Chemometrics Analysis of the Elemental Profiles of Eggshell

As one of the foods commonly eaten all over the world, eggs have attracted more and more attention for their quality and price. A method based on elemental profiles and chemometrics to discriminate between free-range and caged eggs was established. Free-range (n1 = 127) and caged (n2 = 122) eggs were collected from different producing areas in China. The content of 16 elements (Zn, Pb, Cd, Co, Ni, Fe, Mn, Cr, Mg, Cu, Se, Ca, Al, Sr, Na, and K) in the eggshell was determined using a inductively coupled plasma atomic emission spectrometer (ICP-AES). Outlier diagnosis is performed by robust Stahel-Donoho estimation (SDE) and the Kennard and Stone (K-S) algorithm for training and test set partitioning. Partial least squares discriminant analysis (PLS-DA) and least squares support vector machine (LS-SVM) were used for classification of the two types of eggs. As a result, Cd, Mn, Mg, Se, and K make an important contribution to the classification of free-range and caged eggs. By combining column-wise and row-wise rescaling of the elemental data, the sensitivity, specificity, and accuracy were 91.9%, 91.1%, and 92.7% for PLS-DA, while the results of LS-SVM were 95.3%, 95.6%, and 95.1%, respectively. The result indicates that chemometrics analysis of the elemental profiles of eggshells could provide a useful and effective method to discriminate between free-range and caged eggs.

FMO3 deficiency of duck leads to decreased lipid deposition and increased antibacterial activity

Background

Most duck eggs possess a fishy odor, indicating that ducks generally exhibit impaired trimethylamine (TMA) metabolism. TMA accumulation is responsible for this unpleasant odor, and TMA metabolism plays an essential role in trimethylaminuria (TMAU), also known as fish odor syndrome. In this study, we focused on the unusual TMA metabolism mechanism in ducks, and further explored the unclear reasons leading to the debilitating TMA metabolism.

Methods

To achieve this, transcriptome, proteome, and metagenome analyses were first integrated based on the constructed duck populations with high and low TMA metabolism abilities. Additionally, further experiments were conducted to validate the hypothesis regarding the limited flavin-containing monooxygenase 3 (FMO3) metabolism ability of ducks.

Results

The study demonstrated that liver FMO3 and cecal microbes, including Akkermansia and Mucispirillum, participated in TMA metabolism in ducks. The limited oxidation ability of FMO3 explains the weakening of TMA metabolism in ducks. Nevertheless, it decreases lipid deposition and increases antibacterial activity, contributing to its survival and reproduction during the evolutionary adaptation process.

Conclusions

This study demonstrated the function of FMO3 and intestinal microbes in regulating TMA metabolism and illustrated the biological significance of FMO3 impairment in ducks.

Thermal Processing of Liquid Egg Yolks Modulates Physio-Chemical Properties of Mayonnaise

In this study, the effect of various heating temperatures (61−70 °C) and times (1−10 min) on physical and chemical properties of liquid egg yolk (LEY) and mayonnaise were investigated. Initially, we found that the increase of LEY protein denaturation was highly correlated with the increase of temperature and time, without causing either protein degradation or aggregation. In addition, the viscosity and particle size of LEY were significantly increased with greater heating temperature and time. Furthermore, the emulsification stability of mayonnaise prepared from thermally processed LEY were significantly better than that of the unheated control group, in particular, the emulsion stability of mayonnaise was higher at a temperature ranging from 62 °C to 68 °C, whereas the emulsion stability decreased above 69 °C. A rheological analysis showed that mayonnaise prepared from thermally processed LEY has higher shear stress when compared with the control group. Indeed, a sharp increase in the shear stress was observed when LEY was heated above 67 °C. Results from storage behavior analysis suggest that mayonnaise prepared from thermally processed LEY failed to affect the chemical qualities of mayonnaise, as evidenced by the fact that acid values and TBA values were not statistically significant with the unheated control group. Microscopic observation indicates that the number of complete oil droplets were significantly reduced at higher heating (70 °C/5 and 10 min) conditions. Finally, the sensory evaluation results suggest that mayonnaise prepared from thermally processed LEY does not influence the appearance, aroma, taste, greasy feeling, and overall acceptance of mayonnaise, as indicated by there being no significant differences between the experimental group and the control group (p > 0.05). We conclude from our study that a combination of heating conditions over 67 °C/5 min can allow the mayonnaise to retain better quality in terms of stability.