Browsing by Author "Sofos, John, advisor"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Open Access Control of Escherichia coli O157:H7 and Listeria monocytogenes in meat and poultry products with chemicals and heating treatments(Colorado State University. Libraries, 2010) Shen, Cangliang, author; Sofos, John, advisor; Kendall, Patricia, committee member; Belk, Keith, committee member; Scanga, John A., committee memberObjectives of studies included in this dissertation were to evaluate the effects of chemical antimicrobials, such as cetylpyridinium chloride, lactic acid, hops beta acids, commercial salad dressings, and heat treatments including cooking with various appliances and microwave oven heating to control Escherichia coli 0157:H7 in moisture enhanced noninact beef and Listeria monocytogenes on ready-to-eat (RTE) meat and poultry products. In the first study, the effect of different cooking appliances on thermal inactivation of E. coli 0157:H7 in nonintact beef steaks of different thickness was evaluated. In general, the thicker the steaks, the higher the reduction levels reached, and roasting in a standard kitchen oven showed the best inactivation effect compared to the other cooking appliances. The second study evaluated thermal inactivation of E. coli 0157:H7 in nonintact beef steaks with pan-broiling or roasting appliances set at different temperatures. Results showed that setting the cooking appliances at higher temperatures resulted in higher reduction levels of E. coli 0157:H7 cells in nonintact beef steaks compared to the lower ones. The third study involved comparison of inactivation of different types of stress-adapted or unstressed E. coli 0157:H7 cells, inoculated in moisture enhanced nonintact beef steaks with various brining solutions and cooked by pan-broiling on an electric skillet. It was evident that acid stress-adapted cells were more resistant to heat treatment, while cold or desiccation stress-adapted cells were more Hi sensitive to heat treatment than controls. The lowest pathogen counts survived during cooking of beef steaks moisture enhanced to include cetylpyridinium chloride or lactic acid for all stressed inocula tested, thus, indicating that cetylpyridinium chloride and lactic acid could be considered as potential antimicrobial agents for use in beef brining solutions. An additional study evaluated the antilisterial activity of hops beta acids (HBA) in broth medium. HBA exhibited promising antilisterial activity in culture broth, and its activity was increased with increasing concentrations (0.5 to 5.0 pg/ml), and when combined with potassium lactate (1%), sodium diacetate (0.25%), or acetic acid (0.1%), at 4°C. In a subsequent study, HBA applied as dipping solutions (0.03 to 0.10%) on frankfurters, inoculated with L. monosytogenes, vacuum packaged and stored at 4 or 10°C, inhibited pathogen growth for 30 to 50 (4°C) or 20 to 28 days (10°C). The last two studies were designed to detect the antilisterial effects of commercial salad dressings, oil with vinegar or lemon juice, on artificially inoculated frankfurters, diced ham and turkey breast during simulated home storage, without or with prior microwave heating for 30 s or 45 s. Results indicated that microwave heating followed by immersing in salad dressings, especially oil with vinegar, could potentially contribute to control of L monocytogenes on RTE meat and poultry products in the home environment. The results of all studies in this dissertation indicated that certain chemical antimicrobials and heating treatments could be effectively to control E. coli 0157:H7 and L. monocytogenes in meat and poultry products.Item Open Access Fate of Listeria monocytogenes on ready-to-eat meat products, treated with antimicrobials, and under conditions simulating passage through the human stomach and small intestine(Colorado State University. Libraries, 2008) Barmpalia-Davis, Ioanna Maria, author; Sofos, John, advisorTo cause infection, the foodborne pathogen Listeria monocytogenes must overcome stresses associated with food processing, storage, and preparation, as well as various defense elements of the human body. In this work, we examined factors that may affect growth and survival properties of this pathogen on foods and during passage through a simulated stomach and small intestine.Item Open Access Prevalence and control of Listeria, Salmonella and Escherichia coli O157:H7 in Colorado rural households(Colorado State University. Libraries, 2009) Rodríguez Marval, Mawill R., author; Belk, Keith, advisor; Sofos, John, advisorThe household environment has been linked to multiple outbreaks of foodborne illnesses, including listeriosis and salmonellosis. The food handling habits of consumers play a critical role in the food chain continuum, and need to be investigated to better prevent foodborne illnesses that originate at home. The objective of this work was to identify risk factors associated with prevalence of Listeria, Salmonella and Escherichia coli 0157:H7 in the rural household environment, and to provide scientific data for the development of reheating instructions for frankfurters in the home setting. To study risk factors associated with Listeria, Salmonella and Escherichia coli 0157:H7 prevalence in rural Colorado households with or without ruminants, households were recruited, and samples from food and the environment, as well as behavioral data from the primary foods preparer in the house, were collected. Listeria was isolated from refrigerators, kitchen sinks, shoes soles, clothes washing machine and food samples, with higher prevalence in households with ruminants. No sample was found positive for E. coli 0157:H7, and Salmonella was isolated from one refrigerator, one washing machine, one working glove, and two shoe samples. Results indicated that behavior related to handling and cooking of perishable foods affected the probability of household samples testing positive tor Listeria, regardless of presence of ruminants. Personal cleanliness habits were related to presence of Listeria on shoe soles, clothes washing machine, and working gloves. Shoes testing positive in households with ruminants were more frequently associated with multiple positive environmental samples compared to households without ruminants. Results indicated that consumer education on handling and storing perishable foods, and animal handling to prevent contamination of the household through shoes or clothes may reduce prevalence of Listeria in home environments. Two studies evaluated reheating of frankfurters inoculated with L. monocytogenes with or without antimicrobials. In both cases, frankfurters were formulated with or without 1.5% potassium lactate and 0.1% sodium diacetate and were inoculated with a ten-strain composite of L. monocytogenes. After inoculation, frankfurters were vacuum packaged and stored under conditions simulating manufacturing/retail and consumer storage. In one study, after the appropriate storage time, frankfurters were placed in a bowl with water and treated in a household microwave oven. Exposure to high power for 75 s reduced pathogen levels (0.7±0.0 to 1.0±0.1 log CFU/cm2) to below the detection limit (<-0.4 log CFU/cm2) on frankfurters with actate/diacetate. On frankfurters without lactate/diacetate, initial levels of L. monocytogenes (1.5±0.1 to 7.2±0.5 log CFU/cm2) on untreated samples increased as storage in vacuum and aerobic packages progressed. For this formulation, the exposure to high power for 75 s produced reductions between >1.5 and 5.9 log CFU/cm2. Depending on the treatment and storage time, the water used to reheat the frankfurters had viable L. monocytogenes counts of <-2.4 to 5.5±0.5 log CFU/ml. Results indicated that levels of L. monocytogenes contamination <3.7 log CFU/cm2, on frankfurters can be significantly (P>0.05) reduced by microwave oven heating at high power for at least 75 s. Higher contamination levels, such as those found on frankfurters without lactate/diacetate and stored for a prolonged period of time, require longer exposure to microwave heating in order to render the product safe for consumption. In the other study, inoculated frankfurters were treated with hot water after different storage periods to evaluate the destructiveness of different time and water-temperature combinations L. monocytogenes. Treatments at 80°C (60, 120 s) and 94°C (30, 60 s) reduced pathogen counts on frankfurters with PL/SD to at/below the detection limit (<-0.4 log CFU/cm) from initial levels on control (immersed in 25°C water for 300 s) samples. For frankfurters without PL/SD, where pathogen numbers reached 6.1 log CFU/cm2 on 60-day old vacuum-packaged product stored aerobically for 7 days, hot water treatments reduced counts by 1.0 (30 s/80°C) to >6.0 (120 s/94°C and 300 s/94°C) log CFU/cmz. No survivors were detected in the heated water after any treatment (detection limit <-2.5 log CFU/ml). While low levels of L. monocytogenes on frankfurters can be inactivated with short exposure to hot water, increased contamination that may occur as the product ages needs longer times and/or higher temperature for inactivation.Item Open Access Survival and inactivation of Listeria monocytogenes, shiga toxin-producing Escherichia coli, and multidrug-resistant and susceptible Salmonella serovars exposed to heat and antimicrobials on food contact and food surfaces(Colorado State University. Libraries, 2013) Fouladkhah, Aliyar, author; Sofos, John, advisor; Nightingale, Kendra, advisor; Kendall, Patricia, committee member; Belk, Keith, committee memberTo view the abstract, please see the full text of the document.