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(1 - 3 of 3)
- Title
- Efficacy of Organic Acid Treatments for the Reduction of Listeria Monocytogenes on Hard Boiled Eggs
- Creator
- Khouja, Bashayer
- Date
- 2022
- Description
-
Ready-to-eat hard-boiled eggs (HBEs) are a popular and convenient choice for consumers and food servicers. Recentrecalls of hard-boiled eggs...
Show moreReady-to-eat hard-boiled eggs (HBEs) are a popular and convenient choice for consumers and food servicers. Recentrecalls of hard-boiled eggs have highlighted the susceptibility of contamination with Listeria monocytogenes. HBEs are generally treated with antibacterials to ensure the safety and quality of the product. While citric acid is often used, research has determined it is not effective in some situations; therefore, the assessment of additional organic acids is necessary. This study examined the efficacy of acetic, lactic, and malic acid on the reduction of L. monocytogenes on HBEs after a 24- hour treatment trials and 28 days storage trials. Fresh eggs were cooked in boiling water, peeled, and stored at 4°C for 24h before use. For treatment trials, HBEs were dip- inoculated with a 4-strain cocktail of rifampicin resistant L. monocytogenes, resulting in 8 log CFU/egg. Following air drying, hard-boiled eggs were treated at 5 or 25°C with 2% acetic, lactic, or malic acid. L monocytogenes populations were enumerated in intervals up to 24h by homogenization of HBEs with BLEB and cultivation on BHIrif. For pre- treatment storage trials, HBEs were first dip- inoculated with a rifampicin- resistant 4- strain L. monocytogenes cocktail for 20 min, resulting in 1 log CFU/egg, air dried for 10 min, followed by treatment with 2% acetic, lactic, or malic acid for 24 h at either 5 or 25°C. For post- treatment inoculation trials, HBEs were first soaked in 2% acetic, lactic, or malic acid for 24 h at either 5 or 25°C, air dried for 10 min, spot-inoculated at 1 log CFU/egg, and then dried for 20 min. All HBEs were individually stored in bags at 5°C for up to 28 days. The presence of L. monocytogenes was determined at intervals during storage by enrichment with BLEB on BHIrif and Brilliance Listeria Agar. Triplicate eggs were assessed for each timepoint, and three independent trials were conducted. Data were analyzed by Student’s T-test, ANOVA, and Fisher’s exact test, p≤0.05. The initial inoculation level of L. monocytogenes on HBEs was 8.27±0.37 log CFU/egg. After 24 h treatment, all L. monocytogenes populations were significantly reduced on HBEs. At 5°C, populations were reduced by 3.15±0.70, 3.46±0.02, and 4.78±0.23 log CFU/egg. Compared to 5°C, a significantly higher population reduction occurred with acetic and lactic acid when treatment occurred at 25°C. The inactivation of L. monocytogenes on HBEs for the storage trials was associated with the order of the contamination: pre-or post-the acid treatment. Prior storage, L. monocytogenes was detected on 100% of the HBEs. Malic acid pre-treatment was significantly effective in eliminating L. monocytogenes on HBEs at 5 and 25°C, while acetic acid was effective only at 5°C. All acids did not eliminate L. monocytogenes in the case of post-treatment contamination at any tested temperature. The results of this study aid in understanding the efficacy of organic acid treatments against L. monocytogenes on HBEs. Results are useful in the development of preventive controls and guidelines to ensure the safety of HBEs.
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- Title
- Examination of Listeria monocytogenes survival in refrigerated chopped hard-boiled eggs and deli salads containing this ingredient
- Creator
- Marathe, Aishwarya Nagesh
- Date
- 2024
- Description
-
Peeled hard-boiled eggs (HBEs) are widely favored by both consumers and food services due to their convenience. These HBEs are often chopped...
Show morePeeled hard-boiled eggs (HBEs) are widely favored by both consumers and food services due to their convenience. These HBEs are often chopped and incorporated into various dishes such as deli salads. However, recent recalls of hard-boiled eggs have brought attention to the risk of contamination with Listeria monocytogenes. Prepared HBEs are typically subjected to antibacterial treatment to maintain product safety and quality. Citric acid is a common antibacterial used in the food industry to treat the HBEs. Previous research has determined that 2% citric acid treatment is effective against L. monocytogenes on whole HBEs. This study examined the efficacy of citric acid on the reduction of L. monocytogenes on chopped HBEs and in deli salads containing chopped HBEs. HBEs were treated with 2% citric acid or water (untreated) by submersion for 24 h at 5°C. HBEs were dried for 10 min, inoculated with a 4-strain cocktail of rifampicin-resistant L. monocytogenes, at 1 (low-level inoculation) or 4 log CFU/HBE (high level-inoculation), and allowed to dry for 10 min. Low-level inoculated HBEs were chopped and stored at 5, 10, or 15°C for 28 d. High-level inoculated HBEs were chopped and stored at 5, 10, and 25°C for 14 d. Low-level inoculated HBEs were also chopped and incorporated into potato, tuna, chicken, or macaroni salad at a 1:6 ratio (HBE to other ingredients), or into egg salad at a 7:1 ratio. Salads were stored at 5, 10, or 15°C for 28 d. The presence of L. monocytogenes was determined at intervals during storage by enrichment with BLEB and/or enumerated on BHIArif throughout storage. Triplicate samples were assessed for each time point, and three independent trials were conducted. Data was analyzed by Student’s T-test, ANOVA, and Fisher’s exact test, p≤0.05. For low-level inoculated chopped HBEs, the L. monocytogenes population was significantly higher in untreated chopped HBEs (1.86±0.33 log CFU/g) as compared to treated chopped HBEs (1.47±0.27 log CFU/g) on day 14 at 15°C. On both untreated and treated chopped HBEs, there was no significant difference in the population of L. monocytogenes up to 7 d. However, from 14 d, there was a significant increase in the growth of L. monocytogenes (1.86±0.33 to 2.18±0.35 log CFU/g on untreated chopped HBEs and 1.47±0.27 to 1.94±0.47 log CFU/g for treated, respectively). For high-level inoculated HBEs, a higher L. monocytogenes growth rate was observed on untreated chopped HBEs as compared to treated chopped HBEs at 10 and 25°C. It was observed that treated chopped HBEs at 5°C took the longest to reach 1 log CFU/g increase in the L. monocytogenes population (50 d) whereas, untreated chopped HBEs at 25°C took the shortest (0.22 d). Untreated chopped HBEs showed a significantly higher population of L. monocytogenes as compared to treated chopped HBEs on 14 d at all storage temperatures. In deli salads containing chopped HBEs, potato salad showed the highest growth of L. monocytogenes after 14 d, followed by macaroni, egg, chicken, and tuna salad. The population of L. monocytogenes was the lowest in tuna salad. L. monocytogenes was present throughout the storage period at all storage temperatures. It was observed that 2% citric acid is more efficient in controlling the growth of L. monocytogenes in chopped HBEs as compared to when those HBEs are incorporated into deli salads. The findings contribute to the formulation of preventive measures and standards aimed at guaranteeing the safety of HBEs.
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- Title
- Examination of Listeria monocytogenes survival in refrigerated chopped hard-boiled eggs and deli salads containing this ingredient
- Creator
- Marathe, Aishwarya Nagesh
- Date
- 2024
- Description
-
Peeled hard-boiled eggs (HBEs) are widely favored by both consumers and food services due to their convenience. These HBEs are often chopped...
Show morePeeled hard-boiled eggs (HBEs) are widely favored by both consumers and food services due to their convenience. These HBEs are often chopped and incorporated into various dishes such as deli salads. However, recent recalls of hard-boiled eggs have brought attention to the risk of contamination with Listeria monocytogenes. Prepared HBEs are typically subjected to antibacterial treatment to maintain product safety and quality. Citric acid is a common antibacterial used in the food industry to treat the HBEs. Previous research has determined that 2% citric acid treatment is effective against L. monocytogenes on whole HBEs. This study examined the efficacy of citric acid on the reduction of L. monocytogenes on chopped HBEs and in deli salads containing chopped HBEs. HBEs were treated with 2% citric acid or water (untreated) by submersion for 24 h at 5°C. HBEs were dried for 10 min, inoculated with a 4-strain cocktail of rifampicin-resistant L. monocytogenes, at 1 (low-level inoculation) or 4 log CFU/HBE (high level-inoculation), and allowed to dry for 10 min. Low-level inoculated HBEs were chopped and stored at 5, 10, or 15°C for 28 d. High-level inoculated HBEs were chopped and stored at 5, 10, and 25°C for 14 d. Low-level inoculated HBEs were also chopped and incorporated into potato, tuna, chicken, or macaroni salad at a 1:6 ratio (HBE to other ingredients), or into egg salad at a 7:1 ratio. Salads were stored at 5, 10, or 15°C for 28 d. The presence of L. monocytogenes was determined at intervals during storage by enrichment with BLEB and/or enumerated on BHIArif throughout storage. Triplicate samples were assessed for each time point, and three independent trials were conducted. Data was analyzed by Student’s T-test, ANOVA, and Fisher’s exact test, p≤0.05. For low-level inoculated chopped HBEs, the L. monocytogenes population was significantly higher in untreated chopped HBEs (1.86±0.33 log CFU/g) as compared to treated chopped HBEs (1.47±0.27 log CFU/g) on day 14 at 15°C. On both untreated and treated chopped HBEs, there was no significant difference in the population of L. monocytogenes up to 7 d. However, from 14 d, there was a significant increase in the growth of L. monocytogenes (1.86±0.33 to 2.18±0.35 log CFU/g on untreated chopped HBEs and 1.47±0.27 to 1.94±0.47 log CFU/g for treated, respectively). For high-level inoculated HBEs, a higher L. monocytogenes growth rate was observed on untreated chopped HBEs as compared to treated chopped HBEs at 10 and 25°C. It was observed that treated chopped HBEs at 5°C took the longest to reach 1 log CFU/g increase in the L. monocytogenes population (50 d) whereas, untreated chopped HBEs at 25°C took the shortest (0.22 d). Untreated chopped HBEs showed a significantly higher population of L. monocytogenes as compared to treated chopped HBEs on 14 d at all storage temperatures. In deli salads containing chopped HBEs, potato salad showed the highest growth of L. monocytogenes after 14 d, followed by macaroni, egg, chicken, and tuna salad. The population of L. monocytogenes was the lowest in tuna salad. L. monocytogenes was present throughout the storage period at all storage temperatures. It was observed that 2% citric acid is more efficient in controlling the growth of L. monocytogenes in chopped HBEs as compared to when those HBEs are incorporated into deli salads. The findings contribute to the formulation of preventive measures and standards aimed at guaranteeing the safety of HBEs.
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