The occurrence of Cronobacter spp. was investigated in table eggs and egg-based desserts obtained from retail stores. Cronobacter was isolated from 57 out of 180 (31.7%) (95% Confidence Interval [CI]: 26–43%) examined samples of eggs and egg-based desserts. The prevalence of Cronobacter spp. was significantly higher in farm eggs (67%) (P < 0.05) than in Balady eggs (23%), cream cake (27%) and small-scale ice cream (27%). Cronobacter (C.) sakazakii and C. muytjensii were the predominant isolates obtained in the present study. All C. sakazakii isolates were molecularly confirmed with higher incidence in small-scale ice cream (62.5%).

Tallaga cheese is the most popular type of white soft cheese in Egypt. Cronobacter sakazakii is an opportunistic foodborne pathogen that poses a threat to the health of almost every age group, with a particular emphasis on neonates and infants. Essential oils (EOs), such as olive oil and thyme oil, exhibit a broad-spectrum antibacterial effect. However, few studies have investigated the antibacterial activity of these EOs and their formulated nanoemulsions (NEs)—olive oil nano-emulsions (ONE) and thyme oil nano-emulsions (TNE)—on C. sakazakii in cheese to date. The purpose of this study was to investigate the inhibitory effects of these EOs and their NEs on the development of C. sakazakii during the processing and storage of Tallaga cheese. Additionally, the organoleptic properties of the resulting cheese were evaluated. Herein, ONE and TNE were prepared and characterized using a zetasizer and transmission electron microscopy (TEM). Furthermore, the minimum inhibitory concentrations (MICs) of EOs and NEs were determined using well diffusion assay. Fresh buffalo's milk for the elaboration of Tallaga cheese was inoculated with C. sakazakii at a concentration of 6 logCFU/mL, along with the addition of MICs of either EOs or NEs. The obtained results showed that the MICs were 15mg/mL (v/v) for either olive oil, thyme oil, ONE and TNE with diameter inhibition zones of 10.3±0.5, 13.3±1.7, 12.3±0.5, and 16±0.8mm, respectively. In addition, NEs exhibited high antibacterial activities against C. sakazakii in comparison to pure EOs. Particularly, the strongest antibacterial effect toward C. sakazakii was reported with TNE during manufacturing and storage of Tallaga cheese. Overall, these results suggest that thyme and its NEs have the potential toprevent bacterial contamination by C. sakazakii in the dairy industry.

The current study aimed to evaluate the antibacterial efficacy of black seed oil (BSO) and its nanoemulsion (BSO-NE) against two foodborne pathogens, Listeria monocytogenes and Salmonella Typhimurium, during the processing and storage of yoghurt. Additionally, the sensory properties of the resulting yoghurt were assessed. Firstly, BSO-NE was prepared and characterized using zeta-sizer and Transmission electron microscopy (TEM). Then, the antibacterial activity and minimum inhibitory concentration (MIC) were determined via a resazurin-based microtiter dilution assay. Fresh buffalo’s milk was inoculated with L. monocytogenes and Salmonella Typhimurium (1×10⁵ CFU/ml) with the addition of either BSO or BSO-NE. The inoculated milk was then used for yoghurt making. The organoleptic properties and bacterial load of the obtained yoghurt were evaluated during storage in comparison to a control group. This study elucidated that BSO can be successfully produced in a nanoemulsion form, exhibiting acceptable particle size, stability, and morphology. The results demonstrated a strong antibacterial activity of BSO-NE (3.125 mg/mL) against both L. monocytogenes and Salmonella Typhimurium compared to the control and pure oil groups. Notably, complete eradication of L. monocytogenes and Salmonella Typhimurium was observed in yoghurt formulated with BSO-NE on the 8th day of storage. Interestingly, the antibacterial effect of BSO and BSO-NE on Salmonella Typhimurium was approximately similar throughout the experiment. Moreover, the results indicated that the addition of BSO-NE to yoghurt enhanced its organoleptic properties. Overall, these findings suggest that yoghurt can be fortified with BSO-NE to prevent bacterial contamination by L. monocytogenes and Salmonella Typhimurium in the dairy industry

Greater resistance to environmental aggressors, including resistance to antibiotics and other disinfectants is a characteristic of the Pseudomonas spp. Consequently, one of the current study's goals was to isolate Pseudomonas spp. from 165 cheese samples (55 each of Tallaga, Bramily, and Ras cheese) were collected from various dairy markets and shops in Assiut city, Egypt. The isolates were identified and tested for 16S rRNA, showing positive results. According to the collected data, Pseudomonas spp. was found in 42.42% of the samples that were investigated, while Pseudomonas aeruginosa was found in 10.9% of the samples. Then, the effects of essential oils (EOs) of pumpkin (P) and onion (EO) on the viability of Pseudomonas aeruginosa were investigated, the minimum inhibitory concentration (MIC) of the prepared onion EO (OEO) and pumpkin EO (PEO) was detected. Tallaga cheese samples were produced utilizing the MIC of the two prepared Eos separately. The agar well diffusion method was used to assess the influence of EOs, and the results showed that the MIC for PEO and OEO was 0.39%. In conclusion, after Tallaga cheese manufacturing, the OEO proved to be the most effective againstPseudomonas aeruginosa. with a count of 5 log10 at 0 h and <1 after the first week.

Throughout the years, consumer demand for healthy, proper food has increased significantly. To cater the consumer demands, present trends in the food manufacturing are shifting to natural, high-quality products with decreasing processed additives changing them with plant-based substitutes. In the current study, the antibacterial activity of thyme essential oil and thyme oil-nanoemulsion (NE) was detected against E. coli O157, S. Typhimurium, S. aureus and L. monocytogenes in manufactured yoghurt. The antibacterial activities of TEO and TNE were evaluated using disc diffusion and resazurin microdilution methods. The droplets size of the TNE was 135.7±23.04 nm also, showed a greater reduction in MIC and a greater increase in zone of inhibition (ZOI) against E. coli O157 (0.04%; 36 mm), S. Typhimurium (0.01%; 41.5 mm), S. aureus (0.08%; 45 mm), and L. monocytogenes (0.01%; 31 mm). A scanning electron microscope was applied to perceive the morphological changes in the selected bacterial cells. Damage in bacterial cells following the addition of the nanoemulsion was observed. Yoghurt inoculated with the tested bacteria was supplemented with TEO and TNE at different concentrations (0.5%, 1.0%, and 2.0%) to enhance its quality. The supplementation of yoghurt with TEO nanoemulsion could represent a promising natural preservative for enhancing the microbiological safety and maintaining the sensory properties in the youghurt