Microbial quality of industrial liquid egg white: assumptions on spoiling issues in egg-based chilled desserts

Phenotypic, genotypic, and resistome of mesophilic spore-forming bacteria isolated from pasteurized liquid whole egg

The production of whole-liquid eggs is of significant economic and nutritional importance. This study aimed to assess the phenotypic and genotypic diversity of mesophilic aerobic spore-forming bacteria (n = 200) isolated from pasteurized whole liquid egg and liquid egg yolk. The majority of the isolates were identified as belonging to the genera Bacillus (86 %), followed by Brevibacillus (10 %) and Lysinibacillus (4 %). For the phenotypic characterization, isolates were subjected to various heat shocks, with the most significant reductions observed at 80 °C/30 min and 90 °C/10 min for isolates recovered from raw materials. On the other hand, the decrease was similar for isolates recovered from raw material and final product at 100 °C/5 min and 110 °C/5 min. Genotypic genes related to heat resistance (cdnL, spoVAD, dacB, clpC, dnaK, and yitF/Tn1546) were examined for genotypic characterization. The dnaK gene showed a positive correlation with the highest thermal condition tested (110 °C/5 min), while 100 °C/5 min had the highest number of positively correlated genes (clpC, cdnL, yitF/Tn1546, and spoVAD). Whole Genome Sequencing of four strains revealed genes related to sporulation, structure formation, initiation and regulation, stress response, and DNA repair in vegetative cells. The findings of this study indicate that these mesophilic aerobic spore-forming bacteria may adopt several strategies to persist through the process and reach the final product. As the inactivation of these microorganisms during egg processing is challenging, preventing raw materials contamination and their establishment in processing premises must be reinforced.

The effect of solution plasma treatment on the microbial safety and quality characteristics of albumen

The aim of this study was to make eggs microbially safe and increase their durability without damaging the functional properties of the albumen and preserving the solubility of its proteins as much as possible by the solution plasma technique. The pH, Brix, density, and viscosity values of samples decreased during treatment (p < .05 except pH). Although the L* and a* values of both the albumen and egg foam decreased, the b*, hue angle, and chroma values of both increased during treatment. The L* and a* values of the albumen decreased by 7.01 and 1.89 units, and the values of the egg foam decreased by 10.93 and 1.03 units, respectively. At the end of the treatment, foaming capacity and foam stability were decreased by 25% and 21.42%, respectively. Foaming capacity values obtained as a result of this treatment were higher and foam stability values were lower compared to the values obtained in pasteurization of eggs by heat treatment. The count of the two pathogenic bacteria inoculated into the albumen decreased during the treatment (p < .05), the count of Salmonella Enteritidis decreased to 0, and the count of Staphylococcus aureus decreased by 1.09 log cfu/g at the end of the treatment. Compared to current heat treatments, solution plasma treatment caused significantly less adverse effects on albumen quality characteristics. In particular, the foaming properties of the albumen were much less affected by this method and remained at higher values compared to the values achieved by other methods. The treatment also produced a microbiologically safer product.

Advances in pulsed electric stimuli as a physical method for treating liquid foods

There is a need for alternative technologies that can deliver safe and nutritious foods at lower costs as compared to conventional processes. Pulsed electric field (PEF) technology has been utilised for a plethora of different applications in the life and physical sciences, such as gene/drug delivery in medicine and extraction of bioactive compounds in food science and technology. PEF technology for treating liquid foods involves engineering principles to develop the equipment, and quantitative biochemistry and microbiology techniques to validate the process. There are numerous challenges to address for its application in liquid foods such as the 5-log pathogen reduction target in food safety, maintaining the food quality, and scale up of this physical approach for industrial integration. Here, we present the engineering principles associated with pulsed electric fields, related inactivation models of microorganisms, electroporation and electropermeabilization theory, to increase the quality and safety of liquid foods; including water, milk, beer, wine, fruit juices, cider, and liquid eggs. Ultimately, we discuss the outlook of the field and emphasise research gaps.

Microbial Profile and Safety of Chicken Eggs from a Poultry Farm and Small-Scale Vendors in Hawassa, Southern Ethiopia

A freshly laid hen’s egg is devoid of microorganism, but soon after oviposition, it is contaminated by various spoilage and pathogenic microorganisms. The aim of this study was to assess the microbial profile and safety of chicken eggs in Hawassa City. A total of 60 egg samples were collected from Hawassa University Poultry Farm (HUPF) and small-scale vendors in Hawassa. The samples were analyzed for aerobic mesophilic bacterial count (AMBC), Staphylococcal count (SC), Enterobacteriaceae count (EC), total coliform count (TCC), fecal coliform count (FCC), and yeast and mold count (YMC). Moreover, the dominant mesophilic aerobic bacterial genera and common bacterial pathogens were identified by phenotypic methods. Accordingly, the mean aerobic mesophilic bacterial load of the shell surface rinsate of the egg samples ranged from 1.22 log10 CFU/ml to 9.7 log10 CFU/ml, while that of the internal contents ranged from 1.52 log CFU/ml to 9.36 log CFU/ml. The microbial load values of the egg contents were beyond the international recommended acceptable limits and suggested incipient spoilage. The mesophilic aerobic bacterial genera of the shell and internal contents of the egg samples were similarly dominated by Pseudomonas, Micrococcus, and Staphylococcus. The incidence of E. coli in shell rinsate and egg content was 10% (6 of 60) and 1.67% (1 of 60), respectively. Salmonellae were detected in shell rinsate of six egg samples (10%) and in the contents of eight samples (13.33%), all from small-scale vendors. These findings call for vigilant exercise of good agricultural and hygienic practices by primary producers and retailers.

Reducing microbial contamination risk and improving physical properties of plant-based mayonnaise produced using chickpea aquafaba

Aquafaba is obtained by soaking different types of legumes, and utilised in the production of several plant-based foods due to its functional properties. The present work aimed to evaluate the effects of aquafaba produced by soaking chickpeas at different durations, on the safety, physicochemical properties, and consumer acceptability of plant-based mayonnaise. The chickpea aquafaba was prepared by soaking chickpea at different durations of 12, 18, and 24 h, and later boiled for 35 min at 120°C. The results demonstrated significantly (p < 0.05) higher TSS (5.89 ± 0.00), viscosity (7.23 ± 0.06), and peptide content (0.463 ± 0.001) in chickpea aquafaba soaked for 24 h. The mayonnaise prepared with 24 h chickpea aquafaba showed improved firmness (129.47 ± 9.64 g) and consistency (860.26 ± 26.52 g/s). The bacterial load was observed to decrease in 24 h chickpea aquafaba mayonnaise (3.857 ± 0.948 log CFU/g), and increased by one-fold in 12 h chickpea aquafaba mayonnaise (4.672 ± 0.588 log CFU/g) after 35 days at 28 ± 2°C. The consumer acceptability evaluation showed no significant difference (p > 0.05) among all the tested attributes with the 24 h aquafaba mayonnaise received the highest score for taste (6.80 ± 1.38). The aquafaba produced from chickpeas soaked for 24 h and boiled for 35 min has high potential for applications in plant-based mayonnaise production to enhance safety and improve physicochemical and consumer acceptability.

Changes in microbial, physiochemical, and functional properties of pasteurized liquid whole egg during refrigerated storage

BACKGROUND

Liquid eggs have the advantages of high hygiene security, easy use, and convenient transportation, but their shelf life is only limited to 2~3 weeks. The microbial, physiochemical, and functional properties of pasteurized LWE were investigated in this study to evaluate the quality of pasteurized liquid whole egg (LWE) during refrigerated storage.

RESULTS

The tested shelf life of the pasteurized LWE was 16 days when stored at 4 °C. During refrigerated storage, Pseudomonas gradually became the dominant bacterium in LWE following lactic acid bacteria, although the initial number of Pseudomonas after pasteurization was relatively limited (< 10 CFU mL^-1 ). A total of 23 strains, including six Pseudomonas strains, were obtained. The pH of pasteurized LWE decreased with the growth of microorganisms, while the content of total volatile basic nitrogen (TVB-N) increased curvilinearly. The average particle size increased almost continuously until the sample reached its shelf life. The functional properties of pasteurized LWE were also reduced after a week of refrigerated storage at 4 °C when the microorganisms in pasteurized LWE entered an exponential growth period and the TVB-N content of pasteurized LWE reached its first peak.

CONCLUSION

During refrigerated storage, Pseudomonas was the dominant bacterium in LWE next to lactic acid bacteria. After a week of refrigerated storage at 4 °C, the particle size of LWE increased, while the functional properties of LWE reduced. This study provides a basis for extending the shelf life of liquid egg products in future research. © 2020 Society of Chemical Industry.

Inactivation of Escherichia coli K-12 in Liquid Egg White By a Flow-through Pulsed Uv Light Treatment System

ABSTRACT

Unpasteurized liquid egg can be contaminated with pathogenic microorganisms and may cause foodborne outbreaks. Thus, it is essential to decontaminate the liquid egg to ensure food safety. Pulsed UV light is one of the emerging technologies for food decontamination in recent years. This static treatment system has been studied previously in our laboratory. However, continuous processing using a flow-through treatment system needs to be evaluated for potential commercial applications. Therefore, in this study, a flow-through treatment system of pulsed UV light was evaluated and optimized for inactivation of Escherichia coli K12NSR for liquid egg white decontamination. Treatment factors including flow rate (40 to 80 mL/min), number of passes (one to three passes), and distance from the sample to the pulsed UV light strobe (5 to 13 cm) were optimized using response surface methodology. This methodology suggested three passes with 40 mL/min flow rate and a 5-cm distance as the optimum conditions. The model was then validated for the maximum reduction of E. coli K12NSR, which was measured as 1.57 log CFU/mL at the optimal conditions. The energy doses of the pulsed UV light and temperature changes of the liquid egg white during the treatment were measured. Furthermore, several quality parameters were assessed at the optimum treatment conditions to determine the impact of the flow-through pulsed UV processing on the quality of liquid egg white. The results showed significant differences in pH, lipid oxidation, turbidity, and color between control and pulsed UV light-treated samples (P < 0.05). However, there was no significant difference in foaming ability or foam stability between pulsed UV light-treated samples and the control. Overall, this study demonstrated the potential of flow-through pulsed UV light to decontaminate liquid egg white, but further research is needed for optimal enhancement.

HIGHLIGHTS

Bacterial diversity on stainless steel surfaces of egg processing companies and potential of selected isolates to spoil liquid whole egg products

AIMS

To assess the bacterial diversity in the French egg processing industry and to explore the adhesion and spoilage potential of selected bacteria.

METHODS AND RESULTS

Sterile stainless steel chips were suspended for 2 months inside the pipelines of seven egg processing companies, before and after the pasteurizer, at warm and cold seasons. After exposure, the bacterial diversity was assessed by 16S rDNA sequencing. The 231 collected isolates were mainly facultative anaerobic Gram positive bacteria, such as Streptococcus, Staphylococcus, Bacillus and Kocuria. Sixty-five representative isolates were further characterized in vitro regarding the potential for adhesion and egg product spoilage. A high diversity was observed from one genus to another. Kocuria and Rothia isolates showed significantly higher adhesion than the isolates of the other genera. Only the isolates belonging to the genera Bacillus and Lysinibacillus, associated with high enzymatic activities on a solid egg-based medium, were able to induce spoilage of liquid whole egg.

CONCLUSIONS

Bacteria collected on stainless steel surfaces placed in egg processing industries could be associated to liquid egg product spoilage.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides new insights on the bacterial contamination in egg processing companies and represents a first step for the effective control of undesirable bacteria in liquid egg products.