A bacteriological study was made of a number of prepared foods that were bought ready-to-eat, for home consumption, from several food establishments in Dallas, Texas. The purpose of this study was to show whether these foods could be a potential source of food poisoning; whether there are any particular foods that should have greater care than others in order to protect their quality; and whether the bacteriological contamination could have been prevented by strict observance of the city regulations for handling foods.

ABSTRACT The aim of this work was to determine the bacteriological status of selected RTE foods, associated preparation surfaces and cleaning tools sampled from four retail delicatessens in Johannesburg. An initial pilot study of four RTE foods such as filled baguettes, assorted salads, sliced processed meats and hot meals was conducted in order to set the parameters for the remainder of the study. Results showed that filled baguettes and assorted salads contained the highest bacterial counts and incidences of potential foodborne pathogens. Bacterial counts were obtained from the associated preparation surfaces, whilst cleaning tools were associated with coliform and Escherichia coli, suggesting they may harbour potential foodborne pathogens. For the main study, 60% filled baguettes and assorted salads complied with the microbiological guidelines recommended by the retailer, however fruit salads had the lowest bacterial counts overall. Furthermore, of the food contact surfaces plastic chopping boards were identified as the greatest reservoir for RTE food contamination. Bacteriological analysis in conjunction with scanning electron microscopy showed potential foodborne pathogens associated with cleaning tools. Low numbers of aerobic bacteria and Staphylococcus aureus were associated with disposable plastic gloves, suggesting that good glove practices are used by the food handlers.

No description available.

This thesis investigates the economic impact of food safety recalls on the capital share returns of publicly traded meat processing firms using the 2008 Listeria monocytogenes recall in Canada as a case study. The event study method was applied to this study to identify the size, direction and duration of abnormal returns to Maple Leaf Foods Inc. and Premium Brands Holdings which may have resulted from the Listeria recall. Results show that capital share returns to Maple Leaf Foods Inc. and Premium Brands Holdings were negatively impacted by the recall during the event window. Abnormal returns calculated during the post-event window provided evidence that Maple Leaf’s reaction to the announcement may have restored investor confidence in Maple Leaf shares to some degree and that Premium Brands Holdings lack of communication about their meat processing safety protocols may have negatively impacted Premium Brands share returns.

No description available.

Master of Science / Food Science Institute -- Animal Science & Industry / Daniel Y.C. Fung / In February 2008, the FDA released a draft Compliance Policy Guide (CPG) on Listeria monocytogenes and proposed that ready-to-eat (RTE) foods that do not support the growth of L. monocytogenes may contain up to 100 CFU/g of this pathogen. Frozen foods such as ice cream fall in that category since they are consumed in the frozen state. However, other frozen foods, such as vegetables and seafood that are thawed and served at salad and food bars, may support the growth of Listeria and would not be allowed to contain 100 CFU/g according to the draft CPG. In the current study, growth curves were generated for L. monocytogenes inoculated onto four thawed frozen foods - corn, green peas, crabmeat, and shrimp - stored at 4, 8, 12, and 20ºC. Growth parameters, lag phase duration (LPD), and exponential growth rate (EGR) were determined using a two-phase linear growth model and the Square Root Model. The results demonstrated that L. monocytogenes has a very short LPD on these thawed frozen foods during refrigerated storage and that there would be several orders of magnitude of growth (i.e., more than 1.7 log increase at 4 ºC) of the organism before the product is found to be organoleptically unacceptable. Although it would not be possible to take advantage of any extended lag phase duration caused by freeze injury to the organism, frozen foods containing less than 100 CFU/g of L. monocytogenes that are thawed, or thawed and cooked, and then consumed immediately, should not represent a public health hazard.

Master of Science / Food Science / Kelly J.K. Getty / Listeria monocytogenes has the potential to contaminate ready-to-eat (RTE) meat and poultry products. Listeria monocytogenes contamination is a hazard that can potentially occur after post-lethality treatment in a processing environment during slicing or packaging of RTE meat products. United States Department of Agriculture’s Food Safety and Inspection Service (USDA/FSIS) requires facilities to have intervention strategies to demonstrate control of this pathogen in RTE meat and poultry products. FSIS categorizes different intervention strategies into Alternative 1, 2, or 3. If an establishment chooses Alternative 1, it must use a post-lethality treatment that reduces or eliminates microorganisms on the product and an antimicrobial agent or process that suppresses or limits the growth of L. monocytogenes. If an establishment chooses Alternative 2, it can either use a post-lethality treatment or an antimicrobial agent or process that suppresses or limits growth of L. monocytogenes. Under Alternative 3, the establishment must have a detailed sanitation program as its intervention strategy. As establishments increase the number of interventions or change from Alternative 3 to 2 to 1, the frequency of FSIS sampling of RTE meat and poultry products for safety and wholesomeness decreases. The effectiveness of post-package decontamination technologies such as high-pressure processing, ultraviolet C light, and pre/post-package surface pasteurization have been researched for controlling L. monocytogenes in RTE products. Formulating meat products with antimicrobial additives such as lactates, sodium lactate and sodium diacetate, potassium lactate and sodium diacetate, sodium levulinate, lauric arginate, glucono-delta-lactone, or organic acids is another common approach to control L. monocytogenes in RTE meat products. Also, a combination of sodium lactate and sodium diacetate in a formulation is an acceptable antimicrobial strategy to provide Alternative 2 status. Bacteriocins such as nisin can also be added to the formulation of RTE meat and poultry products for controlling L. monocytogenes. In addition nisin can be applied as packaging film coating. Another approach for controlling L. monocytogenes in products such as jerky, kippered steaks, snack sticks and turkey tenders is the use of packaging environments and holding times prior to shipping. In conclusion, there are various approaches for controlling L. monocytogenes in RTE meat and poultry products post-lethality and processors should consider these options rather than relying on sanitation alone.

Doctor of Philosophy / Food Science Institute / Elizabeth A. E. Boyle / A total of three studies were conducted to evaluate the effects of different packaging systems and storage times on reduction of Listeria monocytogenes on ready-to-eat meat snacks. Study 1 was conducted to determine the effects of four packaging systems [heat sealed (HS), heat sealed with oxygen scavenger (HSOS), nitrogen flushed with oxygen scavenger (NFOS), and vacuum (VAC)] and storage times (24, 48, and 72 h, and 14 and 30 d) on reduction of L. monocytogenes in turkey jerky in the presence or absence of sodium nitrite. Inclusion of sodium nitrite in turkey jerky did not affect (P>0.05) L. monocytogenes log reductions regardless of packaging type or storage time. After 14 d of storage in HSOS, NFOS, or VAC, and 48 or 72 h in HS, a reduction of >1.0 log CFU/cm² of L. monocytogenes was achieved. Processors could use HS in conjunction with 48 h of ambient storage and be in compliance with the United States Department of Agriculture Food Safety and Inspection Service Listeria Rule of post-lethality treatment in achieving at least 1 log reduction of L. monocytogenes. Study 2 was conducted to investigate attachment of L. monocytogenes to uncured and cured turkey jerky packaged in HS, HSOS, NFOS, or VAC using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The SEM examination showed that L. monocytogenes is capable of adhering to uncured or cured turkey jerky surfaces. Elemental maps from EDS analysis revealed that no element was unique or elevated at sites of L. monocytogenes attachment. Elemental composition showed the presence of elemental sulfur and could be an indication of the presence of sulfur-containing amino acids in turkey jerky. Finally, Study 3 evaluated the affects of two packaging types (HSOS and NFOS) and four ambient storage times (24, 48, and 72 h, and 14 d) on reduction of L. monocytogenes on five commercial RTE meats and poultry snacks (beef tenders, beef jerky, beef sausage sticks, pork jerky, and turkey sausage sticks). A mean reduction of >1.0 log CFU/cm² of L. monocytogenes was achieved on all products, regardless of packaging or storage time. Correlation analysis provided some indication that reduction of L. monocytogenes increased with fat content. However, the strength of linear correlation was not sufficient to account for the differences in log reduction in L. monocytogenes. In study 1, a holding time of 24, 48, or 72 h for HSOS or NFOS packaging of was not effective for reducing L. monocytogenes by at least 1 log on turkey jerky. In contrast, packaging beef tenders, beef jerky, beef sausage sticks, pork jerky, and turkey sausage sticks in HSOS or NFOS for at least 24 h ambient storage was sufficient to achieve at least 1 log reduction in L. monocytogenes population. Specific components such as sulfur-containing amino acids in turkey jerky might be contributing to <1 log reduction of L. monocytogenes population on turkey jerky after 24, 48, or 72 h of ambient storage. Overall, nitrite was not an effective ingredient to control L. monocytogenes in turkey jerky. However, packaging such as HS, HSOS, NFOS or VAC and at least 24 h holding time were effective hurdles for controlling L. monocytogenes at post-lethality.

Master of Science / Food Science Institute - Animal Science & Industry / Fadi M. Aramouni / Determining the optimum cooking instructions for microwavable not-ready-to-eat foods requires an understanding of the factors that affect heating of foods in microwaves. Factors are often studied without consideration of interactions. Consumer-driven factors appear to be the least-studied. Microwave appliance, heat time, flip step, and plate material were studied to determine their effect on final temperature of a frozen hand-held calzone sandwich after heating. Initial studies to ensure wattage stability during testing and a study to narrow down the plates to be tested were also executed. In the central experiment, a calzone was heated on a microwavable plate for one minute, then flipped or not flipped and heated again for the remaining time in each of four microwave ovens. The microwave ovens differed in age and manufacturer, but were of similar stated wattage. Probes were attached to a data logger and temperatures were recorded every 5 seconds for 2 minutes post-heating to attain the average maximum temperature and lowest maximum temperature for each run. The data was evaluated by analysis of variance and significant differences were compared using Tukey means. All factors had significant effects on average maximum temperature and lowest maximum temperature with the exception of the flip step (p< .05). Plate type was the most critical factor. Calzones heated on paper plates were significantly hotter than those on stoneware plates (p<.05). Significant differences were also observed among microwaves and heat times (p<.05). An interaction between microwave and plate type indicated the effect of plate type was not consistent across all microwaves (p<.05). Although flip step, as tested, was not a significant factor, a follow-up experiment to de-couple the effect of the physical flipping of the calzone and the stopping of the microwave during the heating process indicated that the stopping of the microwave was more critical to heating than the actual flip step. A follow-up study of plate type, microwave and heat time in higher-wattage microwaves showed that microwave appliance and heat time again had significant effects on temperature (p<.05), however; plate type was not a significant factor in the higher-wattage microwaves. The effect of plate type was dependent on the exact microwave used. Various plate types and multiple microwaves in each wattage range should be used for development of microwavable frozen calzones because wattage alone cannot predict performance and because of the interaction between microwave and plate type.

There is demand for improved security of refrigerated ready-to-eat meats. Antimicrobial edible films and coatings could function as an added barrier against post-processing contamination. Hops and hop extracts are known for their antimicrobial efficacy which is attributed to key antimicrobial components including humulones, lupulones, xanthohumol and various terpenoids. Yet, hop ethanol extract has not been studied as an antimicrobial to incorporate into edible protein films and/or coatings. The overall objective of this research was to evaluate hop ethanol extract as an antimicrobial agent incorporated into edible soy protein isolate (SPI) films and coatings, and the influence on the shelf-life and sensory attributes of bologna. Hop ethanol extract was examined for minimum inhibitory concentration before the extract was incorporated into a 6% SPI solution at 0, 10, and 20% levels to determine antimicrobial efficacy as a cast film and simulated coating via zone of inhibition against Listeria monocytogenes strains ATCC 4644, UKADL and ATCC 49594. The results showed that hop ethanol extract alone was inhibitory of all three strains. Moreover, the hop ethanol extract, when incorporated at 10 and 20% (v/v) into edible soy protein isolate (SPI) films and simulated coatings, exhibited antimicrobial action against all three L. monocytogenes strains. Key antimicrobial components, as mentioned above, were identified in the hop ethanol extract via mass spectrometry. The SPI with 10% incorporated hop ethanol extract (SPI+10%hop) antimicrobial coating was applied to bologna, prepared in lab without L. monocytogenes inhibitors, where it exhibited a significant (P ≤ 0.05) bacteriostatic effect against strain ATCC 4644. The SPI+10% hop coating was then applied to a commercial bologna to examine effects on shelf-life and sensory attributes. Significant differences (P ≤ 0.05) were found in instrumental red and yellow colors, however not in sensory color. There was no significant difference (P > 0.05) found in measured lipid oxidation between the bologna with no coating, SPI coating or SPI+10%hop coating. The incorporation of hop did exhibit a slightly bitter taste. Overall, these findings indicate that the SPI+10%hop antimicrobial coating functioned as an inhibitor of L. monocytogenes while producing minimal effects on shelf-life and sensory attributes of bologna.