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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: H1 LUBRICANT TRANSFER FROM A HYDRAULIC PISTON FILLER INTO A SEMI-SOLID FOOD SYSTEM
Creator: Chao, Pin-Chun
Date: 2020
Description: The machinery used to prepare, and process food products need grease and oil for the lubrication of machine parts. H1 (food-grade) lubricants...
Show moreThe machinery used to prepare, and process food products need grease and oil for the lubrication of machine parts. H1 (food-grade) lubricants commonly used in the food industry are regulated as indirect additives by the FDA because they may become components of food through transfer due to incidental contact between lubricants and foods. The maximum level of H1 lubricants currently permitted in foods is 10 ppm, which was derived from FDA data gathered over 50 years ago. Although modern equipment has been designed to minimize the transfer of lubricants during processing and packaging, incidental food contact can still occur resulting from leaks in lubrication systems or over-lubrication. However, there is a lack of data for the FDA to evaluate and determine whether safety issues in the aspect of chemical contamination should be addressed concerning the use of food-grade lubricants in the production of foods. This research was conducted to determine the transfer of an H1 lubricant (Petrol-Gel) into a semi-solid model food from a hydraulic piston filler during conventional operating conditions at 25°C and 50°C. Xanthan gum solutions with concentrations of 2.3% at 25°C and 1.9% at 50°C were used to simulate the viscosity of ketchup at 50°C (970 cP). Petrol-Gel H1 lubricant with a viscosity grade of 70 cSt at 40°C was selected and the aluminum (Al) in the lubricant was targeted as a tracer metal. Analytical methods to quantify Al in both Petrol-Gel and xanthan gum solutions were successfully developed and validated by using inductively coupled plasma – mass spectrometry (ICP-MS) combined with microwave-assisted acid digestion technique. The concentration of Al in the Petrol-Gel was determined to be 3103 ± 26 μg/g. A total of 1.35 g of Petrol-Gel was applied to four ring gaskets in the filler, and 50 g samples of xanthan gum solution were collected into a 100-mL polypropylene tube (DigiTube) with low leachable metals during 500 filling cycles (the full capacity of the piston filler hopper).Results showed that the concentrations of Petrol-Gel transferred into 2.3% xanthan gum solution at 25°C ranged from 1.6 to 63.5 μg/g. A total of 64.47 mg of the applied Petrol-Gel (1.35 g) was transferred into 25 liters of the solution. The average concentration of Petrol-Gel in 2.3% xanthan gum solution was calculated to be 2.84 μg/g, which was lower than the current regulatory limit of 10 ppm. In general, the transfer of Petrol-Gel during the first 100 filling cycles was higher at 50°C than at 25°C. The concentration of Petrol-Gel transferred into 1.9% xanthan gum solution at 50°C for the first 100 filling cycles ranged from 1.6 to 35.06 μg/g and was 6.37 μg/g on average. This research will help FDA to calculate more realistic limits of the H1 lubricants permissible in foods at modern food processing conditions as well as estimate consumer dietary exposure to these indirect food additives.
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Title: IMAGE-ANALYSIS WITH FIJI PROGRAM ON PERIPHERAL BLOOD MONOCULAR CELLS AFTER CONSUMPTION OF HIGH-FAT, HIGH CARBOHYDRATE MEAL WITH OR WITHOUT ADDITION OF SPICES – A SINGLE-CENTER RANDOMIZED, BLINDED, PLACEBO-CONTROLLED, 4-ARM, 24HR ACUTE CROSSOVER STUDY
Creator: Tsai, Meng Fu
Date: 2020
Description: Chronic low-grade inflammation plays a significant role in developing various chronic diseases, such as cardiovascular disease and type II...
Show moreChronic low-grade inflammation plays a significant role in developing various chronic diseases, such as cardiovascular disease and type II diabetes. Western-type diets characterized by high-fat (saturated fat) and high-carbohydrate (HFHC) calories induce oxidative stress leading to inflammation. Polyphenol rich foods, such as berries, tea, and herbs and spices, have antioxidant properties. Spices have been shown to have anti-inflammatory effects in cell and animal studies; however, data are limited in humans. In the present study, we hypothesized that bioactive polyphenolic compounds in herbs and species would reduce diet-induced inflammation in overweight and obese (OW/OB) individuals. In a randomized, single-blinded 4-arm, 24-h, crossover clinical trial, sixteen OW/OB adults consumed an HFHC meal with and without three herbs and spices combinations, including Italian herbs (rosemary, basil, thyme, oregano, and parsley), cinnamon and pumpkin pie spice (cinnamon, ginger, nutmeg, and allspice) on four separate occasions at least three days apart. Markers of inflammation were assessed before and at 2, 4, 5.5, and 7 hours after meal consumption by tracking nuclear translocation of nuclear factor kappa B (NF-κB), a transcription factor in inflammatory signaling, in human peripheral blood monocular cells (PBMCs) and by measuring plasma interleukin-6 (IL-6), a pro-inflammatory cytokine. Nuclear translocation of NF-κB and the proportion of PBMCs activated were estimated through a new method leveraging machine-learning immunofluorescence image analysis. Metabolic markers were also investigated by RX Daytona automated clinical chemistry analyzer. Statistical analysis was conducted using a statistical package for the social sciences (SPSS) (α<0.05, significance). Preliminary results suggested the pumpkin pie spice mixture may improve inflammatory status. Compared to the control meal, the meal with pumpkin spice reduced nuclear translocation of NF-κB and proportion of PBMCs activation, p=0.007, and p=0.005, respectively. The addition of herbs/spices in HFHC meal had no apparent effect on postprandial glucose, insulin, or IL-6 concentrations compared to the control meal. Increased triglyceride concentrations were suggested after consuming the meal with Italian herbs compared to control (p=0.004). Overall, the results of this research suggested the potential of pumpkin pie spice as having anti-inflammatory effects in the context of a typical western-style eating pattern. A major component of this research was to develop a new method for assessing real-time inflammation in the human body. While the method and data are encouraging, upgrading image resolution and programming will be the subject of future research.
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Title: Population Dynamics of Listeria monocytogenes in Nut, Seed and Legume Butters
Creator: Zhang, Xinyuan
Date: 2020
Description: Nut, seed, and legume butters are low water activity foods and do not support the growth of foodborne pathogens. Research has determined that...
Show moreNut, seed, and legume butters are low water activity foods and do not support the growth of foodborne pathogens. Research has determined that some pathogens, such as Listeria monocytogenes, can survive for long periods of time in butters, such as almond butter. However, information on the persistence of L. monocytogenes in butters is lacking. The purpose of this study was to determine the population dynamics of L. monocytogenes in butters stored at 5 and 25°C. Nut (almond, hazelnut, pecan), seed (pumpkin, sesame, sunflower), legume (peanut and soy) and butters containing chocolate (hazelnut and peanut) were inoculated with a 4-strain cocktail of rifampicin-resistant L. monocytogenes at 4 (high inoculation) or 1 log CFU/g (low inoculation). High inoculation butters were mixed by hand for 15 min and 100-g portions were weighed into deli-style containers with lids and stored at 5 or 25°C for 12 mo (370 d). Low inoculation butters were stored in 25- g portions in stomacher bags at 25°C for 6 mo (180 d). During storage, 25 g from the 100- g high inoculation portion or 25 g from the low inoculation samples, in triplicate, were homogenized with 225 mL BPB (or BLEB for FDA BAM enrichments when necessary) and serial dilutions of the homogenate were plated onto BHIA with rifampicin for enumeration of L. monocytogenes. Data were statistically analyzed using Student’s t-test (α=0.05). The average initial population of L. monocytogenes in the butters was 3.58±0.25 log CFU/g for the high inoculation butters; L. monocytogenes was detected through enrichments for all low inoculation butters. After 12 mo storage at 5°C, the population of L. monocytogenes decreased by 1.34, 1.27, 1.72, 2.04 and 0.93 log CFU/g in almond, hazelnut, peanut with chocolate, hazelnut with chocolate and pecan butter, respectively, when inoculated at the higher level. Significantly less population reduction was observed in pumpkin, sesame, soy, peanut and sunflower butters (1.08, 0.61, 0.84, 0.05 and 0.40 log CFU/g, respectively). After 12 mo storage at 25°C, the L. monocytogenes population in all butters, with the exception of sunflower butter, decreased to below the limit of enumeration (1.67 log CFU/g), but the pathogen was still present via enrichment. For low inoculation butters, L. monocytogenes was present as determined by enrichment in all butters in at least one of two trials after 6 mo. The results of this study provide information on the survival of L. monocytogenes in different butter types when stored at different temperatures.
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Title: Development of a Model To Investigate Inflammation Using Peripheral Blood Mononucleated Cells
Creator: Geevarghese Alex, Peter
Date: 2023
Description: Our modern culture in our society is facing one of the biggest risks in health which is high-calorie diet-related postprandial inflammation....
Show moreOur modern culture in our society is facing one of the biggest risks in health which is high-calorie diet-related postprandial inflammation. Chronic diseases may be caused if the energy-dense food is the choice meaning if it is uncontrolled, clinical studies have demonstrated this with the body's post-meal inflammatory response. We aimed to find the causes of postprandial inflammation in response to various dietary treatments and provide a model to demonstrate. We aimed to make use of in vivo and in vitro techniques and statistics to create a model. The created model would help us to design specific treatments to minimize inflammation with response to dietary. In addition to figuring out vital dietary additives, the model additionally facilitates the layout of individualized interventions to reduce inflammation, thereby improving long-time period health outcomes. We aim to understand the clinical observations of diet-induced postprandial inflammation on the molecular level. We desire to make contributions to reduce the impact of chronic inflammatory disorders that is associated with postprandial inflammation.
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Title: Development of validation guidelines for high pressure processing to inactivate pressure resistant and matrix-adapted Escherichia coli O157:H7, Salmonella spp. and Listeria monocytogenes in treated juices
Creator: Rolfe, Catherine
Date: 2020
Description: The fruit and vegetable juice industry has shown a growing trend in minimally processed juices. A frequent technology used in the functional...
Show moreThe fruit and vegetable juice industry has shown a growing trend in minimally processed juices. A frequent technology used in the functional juice division is cold pressure, which refers to the application of high pressure processing (HPP) at low temperatures for a mild treatment to inactivate foodborne pathogens instead of thermal pasteurization. HPP juice manufacturers are required to demonstrate a 5-log reduction of the pertinent microorganism to comply with FDA Juice HACCP. The effectiveness of HPP on pathogen inactivation is determinant on processing parameters, juice composition, packaging application, as well as the bacterial strains included for validation studies. Unlike thermal pasteurization, there is currently no consensus on validation study approaches for bacterial strain selection or preparation and no agreement on which HPP process parameters contribute to overall process efficacy.The purpose of this study was to develop validation guidelines for HPP inactivation and post-HPP recovery of pressure resistant and matrix-adapted Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes in juice systems. Ten strains of each microorganism were prepared in three growth conditions (neutral, cold-adapted, or acid-adapted) and assessed for barotolerance or sensitivity. Pressure resistant and sensitive strains from each were used to evaluate HPP inactivation with increasing pressure levels (200 – 600 MPa) in two juice matrices (apple and orange). A 75-day shelf-life analysis was conducted on HPP-treated juices inoculated with acid-adapted resistant strains for each pathogen and examined for inactivation and recovery. Individual strains of E. coli O157:H7, Salmonella spp., and L. monocytogenes demonstrated significant (p <0.05) differences in reduction levels in response to pressure treatment in high acid environments. E. coli O157:H7 was the most barotolerant of the three microorganism in multiple matrices. Bacterial screening resulted in identification of pressure resistant strains E. coli O157:H7 TW14359, Salmonella Cubana, and L. monocytogenes MAD328, and pressure sensitive strains E. coli O15:H7 SEA13B88, S. Anatum, and L. monocytogenes CDC. HPP inactivation in juice matrices (apple and orange) confirmed acid adaptation as the most advantageous of the growth conditions. Shelf-life analyses reached the required 5-log reduction in HPP-treated juices immediately following pressure treatment, after 24 h in cold storage, and after 4 days of cold storage for L. monocytogenes MAD328, S. Cubana, and E. coli O157:H7 TW14359, respectively. Recovery of L. monocytogenes in orange juice was observed with prolonged cold storage time. These results suggest the preferred inoculum preparation for HPP validation studies is the use of acid-adapted, pressure resistant strains. At 586 – 600 MPa, critical inactivation (5-log reduction) was achieved during post-HPP cold storage, suggesting sufficient HPP lethality is reached at elevated pressure levels with a subsequent cold holding duration.
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Title: GROWTH KINETICS OF SALMONELLA ENTERICA DURING REHYDRATION OF DEHYDRATED PLANT FOODS AND SUBSEQUENT STORAGE
Creator: Ren, Yuying
Date: 2020
Description: Dehydrated plant foods have low water activities and do not support the growth of pathogenic bacteria like Salmonella enterica. Once...
Show moreDehydrated plant foods have low water activities and do not support the growth of pathogenic bacteria like Salmonella enterica. Once rehydration, the water activities will increase to > 0.92, and along with their neutral pHs, plant foods may be able to support the growth of S. enterica. Therefore, product assessments are required to determine the extent to which these products support growth of S. enterica. The purpose of this study was to determine the growth kinetics of S. enterica during rehydration with 5 or 25 °C water, and subsequent storage of dehydrated potatoes, carrots, and onions at 5, 10, and 25 °C. Fresh plant foods were dehydrated at 60°C (140°F) for 24 h. Dehydrated plant foods were inoculated with 4 log CFU/g of a 4-strain cocktail of S. enterica and dried for 24 h. Samples were rehydrated using 4-volumes of 5 or 25 °C water for 24 h. During rehydration, 30 g of sample was removed and drained for 10 min. Ninety mL of BPB was added to triplicate 10-g samples. Serial dilutions of the homogenate were plated onto TSA overlaid with XLD agar for enumeration of S. enterica. After 24 h rehydration, the remaining samples were drained and stored in containers at 5, 10, and 25°C for 7 d. S. enterica was enumerated at 1, 3, 5, and 7 d. Three independent trials were conducted. Growth kinetics were determined using DMFit and data were statistically analyzed using Student’s t-test (α=0.05). Overall, the growth rates of S. enterica when 5 °C water was used for rehydration were higher than when 25 °C water was used for potatoes and carrots. The highest growth rate of S. enterica was 3.74 log CFU/g per d on potatoes, leading to a 1 log CFU/g increase in S. enterica after only 0.27 d (16 h) which occurred during storage at 25 ℃ after 5℃ water rehydration. The highest growth rate on carrots was 1.98 log CFU/g per d (requiring only 0.51 d to increase 1 log CFU/g) when rehydrated with 5℃ water and stored at 25 ℃. The growth rates were the lowest during the storage of rehydrated onions. S. enterica required 12.5 d to increase 1 log CFU/g (the growth rate was 0.61 log CFU/g per d) when the onions were rehydrated with 25 ℃ water and stored at 25 ℃. The results of this study determined that S. enterica could survive and grow in dehydrated plant foods during rehydration and storage, highlighting the need for product assessments for these types of foods.
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Title: Effect of organic acid treatment in reducing Salmonella on six types of sprout seeds
Creator: Yang, Dachuan
Date: 2023
Description: Fresh sprouts present a special food safety concern as their growing conditions also favor the growth of pathogens such as Salmonella....
Show moreFresh sprouts present a special food safety concern as their growing conditions also favor the growth of pathogens such as Salmonella. Contamination in sprouts often originates from the seeds used for sprouting. The Produce Safety Rule requires that seeds used to grow sprouts be treated to reduce pathogens. The treatments may be applied by sprout growers or by seed suppliers. Although 20,000 ppm calcium hypochlorite is the most used seed treatment method, the high chlorine level can be hazardous to workers and the environment. Alternative seed treatment methods that are safe and environmentally friendly are needed. In addition, a post-treatment drying step is needed when seed suppliers are using chemical seed treatment methods. This study evaluated the efficacy of an organic acid solution for reducing Salmonella on six types of seeds (alfalfa, clover, radish, mung bean, onion, and broccoli). The impact of treatment on seed germination and sprout yield was also examined. Ten grams of seeds inoculated with a five-serotype cocktail of Salmonella were pre-rinsed with 40 ml of water twice and treated with 75.7 ml of the organic acid solution for 1 hour. The treated seeds were either not rinsed or rinsed with 40 ml of water twice before being dried in the biological safety cabinet for 24 hours. The Salmonella level, germination percentage, and sprout yield of seeds treated with water, seeds treated with the organic acid solution, seeds treated with organic acid, dried, and rinsed, and seeds treated with organic acids, dried, and not rinsed were compared. Salmonella reductions that could be achieved with this organic acid solution treatment were less than 0.5 log CFU/g without drying, 0.6-2.0 log CFU/g with drying and rinse, or 1.6-2.9 log CFU/g with drying and no rinse. Drying significantly enhanced the treatment efficacy (p < 0.05 ) on alfalfa, radish, mung bean, and onion seeds. If seeds were not rinsed after treatment, the log reductions achieved on mung bean and onion seeds were significantly higher (p < 0.05). If seeds were treated and rinsed, the germination rates of six types of seeds were not affected (p > 0.05) regardless of whether the seeds were dried or not. All treatments significantly decreased the sprout yield of clover seeds by 13% (p < 0.05 ). If seeds were not rinsed after treatment, the germination rates of clover and broccoli seeds were reduced by 7 and 9%, respectively, and the sprout yield of alfalfa seeds was reduced by 35%. Overall, the organic acid solution was ineffective when compared with 20,000 ppm calcium hypochlorite in reducing Salmonella on sprout seeds, although the drying step after treatment could improve the treatment efficacy.
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Title: Evaluating antimicrobial efficacy of GS-2 on reusable food packaging materials
Creator: Birje, Nupoor Prasad
Date: 2024
Description: Packaging plays an important role in maintaining the quality and safety of fresh produce throughout storage, transportation and end-use by...
Show morePackaging plays an important role in maintaining the quality and safety of fresh produce throughout storage, transportation and end-use by consumers. Single-use packaging poses several environmental impacts; therefore use of reusable packaging is being encouraged in the fresh produce supply chain. However, the utilization of harmful chemicals and inadequate sanitation standards limit the reuse of packaging materials. To overcome these limitations, this study focuses on testing a non-toxic, water-soluble antimicrobial; GS-2 coating to facilitate the reuse of food packaging and reduce the risk of microbial contamination. In this study, the antimicrobial activity of GS-2 was evaluated against foodborne pathogens; Escherichia coli, Listeria monocytogenes and Salmonella enterica on plastic and cardboard coupons at 1 h and 15 min treatment times and 0.3%, 1% and 3% concentration. These coupons were also stored at 4℃ and 90% R.H. and 18℃ and 45% R.H. inoculated on different days up to 42 d with E. coli or L. monocytogenes to study retention of activity of GS-2. Additionally, the efficacy of GS-2 to reduce transfer of bacteria from cardboard and plastic to tomato was investigated. The initial level of inoculum was 9 log CFU/surface for all experiments. Cardboard and plastic without GS-2 were used to compare the reduction of bacteria on the treated surfaces. The differences in the population of bacteria were evaluated using Student’s T-Test and ANOVA; p <0.05 was considered significant. With 3% GS-2 concentration on plastic, there was > 4.50 log CFU/surface reduction of all three bacteria in 1 h. There was a lower reduction of the population on cardboard as compared to plastic for all bacteria, the reduction obtained was 1.83, 2.65 and 3.42 log CFU/surface for E. coli, L. monocytogenes and S. enterica, respectively, in 1 h. There was no significant difference between 15 min and 1 h treatments for cardboard. Further, the highest reduction of bacteria was obtained with 3% GS-2 on plastic. For cardboard, no significant difference in population reduction was obtained for E. coli or S. enterica, with 1% or 3% GS-2. However, for L. monocytogenes there was a higher reduction with 3%. GS-2 remained active on the surface of plastic and cardboard for a period of six weeks. For cardboard, there was a lower reduction of bacteria and there was no trend in the population reduction from 0 to 42 d, with the populations remaining within a range of 4-5 log CFU/surface. There was a significant transfer of E. coli or L. monocytogenes from plastic surfaces without GS-2 to tomato at 5-6 log CFU/tomato. However, the transfer of bacteria from the GS-2-coated plastic to the tomato was below the limit of enumeration. For cardboard, the population was below the limit of enumeration, irrespective of the GS-2 coating. Based on the results, GS-2 is a promising antimicrobial that reduces the microbial load on packaging surfaces and prevents cross-contamination of fresh produce. The retention of GS-2 activity makes it suitable for reusable packaging applications.
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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: Efficacy and Mechanisms of Power Ultrasound-Based Hurdle Technology for Reduction of Pathogens in Fresh Produce
Creator: Zhou, Xinyi
Date: 2023
Description: Minimally processed produce is frequently contaminated with foodborne bacterial pathogens. Power ultrasound is a non-thermal and cost...
Show moreMinimally processed produce is frequently contaminated with foodborne bacterial pathogens. Power ultrasound is a non-thermal and cost-effective technology that can be combined with other chemical sanitization methods. This study investigated the reduction of Listeria monocytogenes and Salmonella Newport on grape tomato, romaine lettuce, and spinach washed with water, chlorine, or peroxyacetic acid alone or in combination with 25 or 40 kHz power ultrasound for 1, 2, or 5 min. Produce items were inoculated with selected pathogens at approximately 10 log CFU/g, air dried for 2 h, and then treated. Combined treatment of ultrasound and sanitizers resulted in 1.44-3.99 log CFU/g reduction of L. monocytogenes and 1.35-3.62 log CFU/g reduction of S. Newport on washed produce items, with significantly higher reductions observed on grape tomato. Synergistic effects were achieved with the combined treatment of power ultrasound coupled with the chemical sanitizers when compared to the single treatments. An additional 0.48-1.40 log CFU/g reduction of S. Newport was obtained with the combined treatment on grape tomato. In general, no significant differences (p<0.05) were observed in pathogen reductions between the selected ultrasound frequencies, sanitizers, or treatment lengths. Results from this study suggest that incorporation of power ultrasound to current treatment can enhance bacterial pathogen reduction on fresh produce surface, but cannot completely eliminate bacterial pathogens. Transcriptomic study revealed significant (|Log2 fold change|<1 and false discovery rate < 0.05) transcriptional changes in L. monocytogenes LS810 in response to the 2 min power ultrasound treatment. The up-regulation of genes encoding TPI, LLO, and PTS indicates increased energy requirements, enhanced virulence, and demand for sugar sources in bacteria. On the other hand, the down-regulation of genes involved in cyclic dimeric GMP hydrolysis and transcriptional regulation suggests a modulation of intracellular signaling, cellular processes, and metabolisms to enhance survival and recovery. The GO and KEGG analysis demonstrated defense mechanisms against ultrasound stress more comprehensively. L. monocytogenes adjusts its metabolism, repairs cell membranes, and conserves energy for survival. These findings enhance our understanding of its adaptation to environmental stress. Results of this study can be used as a start point for optimizing the efficacy of ultrasound-based hurdle treatments for fresh produce disinfection.
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Title: Evaluation of the Native Microbiota and Comparative Analysis of a Known Cronobacter Sakazakii and a Newly Isolated Bacillus Cereus Strain in Powdered Infant Formula
Creator: Patil, Sonali Prashant
Date: 2024
Description: There have been numerous reports of Powdered Infant Formula (PIF) recalls and outbreaks due to the absence of a kill step in the post...
Show moreThere have been numerous reports of Powdered Infant Formula (PIF) recalls and outbreaks due to the absence of a kill step in the post-pasteurization processing, improper handling pre and post processing and/or reconstitution, and lack of effective sanitization and cleaning of the food contact surfaces in the manufacturing facilities. The objectives of this present study were to 1) survey and identify background microflora in commercial PIF products through microbiological analysis, 16S rRNA, and whole genome sequencing (WGS); 2) compare the survival rate of a known Cronobacter sakazakii and a newly isolated Bacillus cereus DFPST-SP1 in PIF under a humidity level of 33 ± 3% over a period of 28 d; 3) examine the relative resistance of these two strains to thermal treatments at temperatures 40, 70, and 100 °C followed by storage at room temperature (RT) for 30 min; and 4) evaluate the bactericidal effect of 70% ethanol on the two artificially deposited bacterial strains on stainless steel (SS) and plastic coupons. Three biological trials were conducted for each study. To determine whether the increase, decrease, or difference in the bacterial populations and other parameters like water activity (aw) was statistically significant, a T-test was performed (p ≤ 0.05 was considered significant). Results of 16S rRNA sequencing revealed the presence of certain bacterial species in PIF, such as Lactococcus lactis, B. cereus, Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica, etc. distributed across a relative abundance of >25%, <25%, and ≤3%. After the enrichment and isolation as per Bacteriological Analytical Manual (BAM), C. sakazakii or S. enterica were not detected, while colonies exhibiting a blue-green appearance resembling Listeria spp. and certain Bacillus spp. were subjected to WGS for species-level identification. The assembly_1 from formulation 1 was confirmed as B. cereus sequence type 2255 and was renamed as B. cereus DFPST-SP1 in the contribution of this thesis work. The storage study conducted on PIF inoculated with C. sakazakii and B. cereus DFPST-SP1 at 33% RH showed that there was 0.25-0.27 log CFU/g reduction towards the end of 28 d, but no significant difference was observed between the two strains. The thermal challenge study revealed that the newly isolated B. cereus strain and C. sakazakii used in this study were highly thermotolerant. Based on the sanitizer challenge study, 70% ethanol was significantly more effective in reducing populations of C. sakazakii as compared to B. cereus. Moreover, higher log reductions of C. sakazakii 587 populations on stainless steel coupons compared to plastic coupons were observed, indicating that bacteria adhere more tightly to plastic surfaces than stainless steel (SS). Overall, the findings of this study shed new light on bolstering the safety standards of PIF and highlight the need for improved cleaning and sanitization procedures within manufacturing facilities in order to ensure the safety of reconstituted PIF, thereby enhancing public health, particularly infants and neonates.
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Title: Evaluation of the efficacy of power ultrasound technology coupled with organic acids to reduce listeria monocytogenes on peaches and apples
Creator: Joshi, Mayura Anand
Date: 2024
Description: Fresh fruits and vegetables are prone to microbial contamination throughout different phases of human handling, processing, transportation,...
Show moreFresh fruits and vegetables are prone to microbial contamination throughout different phases of human handling, processing, transportation, and distribution. Emerging technologies, such as power ultrasound, have received attention due to their capacity to reduce or eliminate foodborne bacterial pathogens on these commodities. Power ultrasound, when combined with certain antimicrobials, has demonstrated its effectiveness as a valuable tool for washing fresh produce. The objective of this study was to examine the effectiveness of power ultrasound combined with organic acids on the reduction of Listeria monocytogenes on fruits. In this study, peaches and apples were subjected to surface inoculation with a four-strain cocktail of L. monocytogenes and dried for 1 h. Stomacher bags, containing 225 mL of citric, lactic, or malic acids at concentrations of 1%, 2%, or 5%, were employed for treating inoculated peaches and apples. The acid treatment was used alone, or in combination with power ultrasound for 2, 5, or 10 min. Water was used for controls. Before treatment, the initial population of L. monocytogenes on apples was lower compared to the initial population on peaches, with apples showing a 1.94 log CFU/fruit reduction. Water controls demonstrated no significant log reduction in both apples and peaches. The greatest L. monocytogenes reduction on apples occurred when treated with 1% citric acid for 2 min with power ultrasound where L. monocytogenes was significantly reduced from 6.98±0.88 log CFU/fruit to 5.56±0.91 log CFU/fruit. The greatest L. monocytogenes reduction on peaches occurred when treated with 5% citric acid for 5 min with power ultrasound where L. monocytogenes was significantly reduced from 7.44±0.45 log CFU/fruit to 6.68±0.40 log CFU/fruit. Overall, the combined effect of acid and power ultrasound was more pronounced in apples than in peaches. The survival of L. monocytogenes on apples and peaches appeared to be highly dependent on the specific treatment and hurdle technology applied. The combination of ultrasound hurdle technology with acid washing has proven effective in reducing L. monocytogenes on both peaches and apples, with a more significant impact observed on apples. While acid washing is a more economical option compared to ultrasound technology, the efficiency of microorganism reduction is considerably enhanced when power ultrasound is combined with organic acids. Looking ahead, the development of cost-effective power ultrasound methods could facilitate widespread adoption of ultrasound hurdle technology in the produce industry.
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