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.

Doctor of Philosophy / Food Science / Daniel Y.C. Fung / James L. Marsden / The ubiquitous nature and continued presence in food processing environments makes Listeria monocytogenes a significant threat in ready-to-eat (RTE) food products. This study was performed in two phases; Phase 1 studied lauric arginate (LAE) as an antimicrobial on food contact surfaces and shredded mozzarella cheese, and use of glucose oxidase (GOX), sodium lactate (SL), and acidified calcium sulfate (ACS) as preservatives in mozzarella cheese; Phase 2 evaluated efficacy of Photohydroionization (PHI) technology to control L. monocytogenes on food contact surfaces, sliced American cheese, and ready-to-eat turkey. Stainless steel coupons, mozzarella cheese, American cheese, and turkey were surface inoculated with a three- or five-strain cocktail of L. monocytogenes. Coupons were treated with 100 and 200 ppm solution of lauric arginate for 5 and 15 min. Mozzarella cheese was treated with different combinations of treatments comprising LAE, GOX, SL, ACS, dextrose, and anticaking agents (free flow 1031 and cellulose). Results indicated up to 2.5 log CFU/coupon reductions and it was concluded that LAE was effective in controlling low levels of contamination of L. monocytogenes on food contact surfaces. In mozzarella cheese, results indicated that lauric arginate provided no additional antimicrobial effect (P > 0.05) as compared to GOX + dextrose. The antimicrobial blends with GOX, SL, and ACS were different (P < 0.05) from the controls but showed no differences (P > 0.05) in their effect in controlling bacterial populations. Results from treatment with PHI unit showed significant (P < 0.05) reduction in bacterial populations. L. monocytogenes populations reduced by 4.37 log CFU/coupon on stainless steel surfaces after 15 min of treatment; 2.16 and 2.52 log CFU/sample reduction on American cheese and ready-to-eat turkey, respectively, after short treatment time of 5 min. Lipid oxidation analyses performed on cheese and turkey samples indicated that the PHI treatment did not affect (P > 0.05) TBAR values. These studies suggest that LAE and GOX as antimicrobials and PHI treatment can be used as intervention strategies in an integrated process to ensure safe production of food. Further research is needed to evaluate applicability of SL and ACS in mozzarella cheese.

Dissertation submitted in fulfilment of the requirements for the degree Master of Technology: Environmental Health in the Faculty of Applied Sciences at the Cape Peninsula University of Technology, 2011 / The retail sector in South Africa is increasingly evolving into a dynamic industry, driven by changes in technology, saturating markets and globalisation. A major phenomenon in South Africa has been the evolution of hypermarkets, which sell large quantities of almost all consumer goods on a self-service basis. The South African consumers are becoming increasingly health conscious and, as such, the demand for wellness foods, health and convenience food has escalated. Convenience foods are expected to remain popular with consumers and supermarkets and will therefore increase the amount of ready-to-eat food items offered. As the retail industry has changed over the last two decades, so has the epidemiology of foodborne illnesses, with an increase in the incidence of bacterial infections caused by emerging organisms. In addition, there are certain food safety issues specifically associated with ready-to-eat foods. In recent years, incidences of enteric diseases associated with meat consumption have risen. The emergence of several new foodborne diseases has led to an increased focus attention on the issue of food safety by consumers and the industry. The most commonly implicated foods in these disease outbreaks have been meat and dairy products. The microbial load of eight convenience food manufacturing plants was determined by firstly sampling stainless steel food contact surfaces after they had been cleaned and sanitised at the end of a day‘s shift. The samples were analysed for Total Plate Count (TPC), Escherichia coli, Salmonella species and Staphylococcus aureus and Listeria. The results showed that 59 % of the total areas sampled for TPC failed to comply with the legal requirements for food surfaces specified in the South African Health Act (< 100 cfu.cm-2). Listeria was detected in 23 % of the samples taken and E.coli was found in 1.3 % of the samples, while S. aureus was not detected in any of the samples. Fifty percent of the plants applied conventional cleaning methods for cleaning and sanitation and the remaining 50 % used the low-pressure foam (LPF) method. The bacterial results of the two cleaning methods were statistically compared and a statistically significant difference (P ≤ 0.05) was found between the TPC means of the cleaning methods after cleaning. No statistically significant difference (P > 0.05) was found in terms of the Listeria species counts after both cleaning processes. The LPF method proved to be the superior cleaning option for reducing TPC counts. Secondly surface samples were collected from washed and sanitised dominant hands of food handlers and analysed for the presence of total plate counts, S. aureus and E. coli. The study aimed to evaluate the efficacy of hand washing practices and sanitation before commencing work. A total of 230 samples were collected, involving 100 % of the food handlers in selected convenience food outlets. The highest bacterial count taken from handswas 7.4 x 10-3 cfu.cm-2 and the lowest showed no detectable growth. Forty percent of the TPC analysed complied with the legal limit of < 100 cfu.cm-2 and only 18 % of the food handlers had no detectable bacteria present on their hands. One hand sample tested positive for E. coli, which is generally viewed as an indication of faecal contamination. S. aureus could not be detected on the hands of any of the food handlers. The results of this study indicated that hand hygiene is unsatisfactory and underlined the importance of further training to improve food handlers‘ knowledge of good hand washing practices. The study also aimed to present data on the food hygiene knowledge and practices of food handlers based on a representative sample from convenience food outlets in the Gauteng area. The management, as well as food handlers, were interviewed without prior announcement and managers were interviewed prior to starting their shifts, followed by food handlers, after they had passed through the change room and hand wash facilities. Although the majority of food handlers adhered to basic hygiene principles, the results highlighted a need for proper and continuous training in hygiene practices, not only for food handlers, but also for management. Furthermore, all food handlers should adhere to a formal cleaning schedule and specific courses should be planned for food handlers. Most training is done away from the workplace and the workers might find it difficult to translate theory into practice. Although food safety training programmes are essential, behavioural changes will not occur merely as a result of having received training but rather continuous development of food handlers. In conclusion, the popularity of convenience food is bound to increase with the growing appeal for modern foods. Consumers in South Africa nowadays demand good quality and safe products at a reasonable cost. Due to continuous time constraints, convenience food is the food of the future for the working mother. It is clear that managing foodborne disease is a challenge and an economic problem subject to various constraints. Food safety has too often become a hit-or-miss gamble, with parents obliged to roll the dice when it comes to the safety of their children‘s food and consumers in general. The food industry therefore needs to improve food safety processes to prevent the contamination of foods and use methods to ensure safe food for consumers. Better training, more testing and better methods of tracking food must be utilised to verify that the processes are working. This study endeavoured to add to the understanding and improvement of hygiene processes as well as food handlers‘ practices in the convenience food industry in the Gauteng Province.

Control of the pathogen Listeria monocytogenes in ready-to-eat (RTE) meats is a major concern in the food industry. The objective of this study was to compare the growth of L. monocytogenes on refrigerated RTE meats containing sodium levulinate (4-oxopentanoic acid, a five carbon organic acid with GRAS status), sodium lactate, or a combination of sodium lactate and sodium diacetate. Turkey roll and bologna were prepared to contain (wt/wt) sodium lactate (2%); sodium lactate in combination with sodium diacetate (1.875% sodium lactate, 0.125% sodium diacetate); sodium levulinate (1, 2, or 3%); or no antilisterial additive. Samples were sliced, inoculated with a 5-strain cocktail (102 to 103 CFU/cm2) of L. monocytogenes, vacuum packaged, and stored at 2°C for 0-12 weeks. Triplicate packages of each treatment were analyzed bi-weekly for growth of the pathogen. Bacterial counts exceeded 105 CFU/cm2 in controls after 4 weeks in turkey and over 106 CFU/cm2 after 8 weeks in bologna. In turkey, L. monocytogenes showed significant growth in samples containing sodium lactate after 6 weeks(>104 CFU/cm2) and after 8 weeks when used in combination with diacetate. Further, samples containing 1% sodium Jevulinate did not show significant growth of the pathogen for 10 weeks (~104 CFU/cm2), while those containing 2% and 3% levulinate inhibited growth for 12 weeks. In bologna, adding any antimicrobial inhibited growth for 12 weeks. Finally, Listeria-free samples of turkey roll and bologna, containing the various organic acid salts, were evaluated by members of consumer taste panels. Statistical analysis (ANOV A) showed that there were no differences in overall liking of samples of turkey roll (p = 0.19) or bologna (p = 0.42). In turkey, sodium levulinate was more effective at preventing growth of L. monocytogenes, while in bologna it was as effective as the current industry standards lactate and diacetate. Addition of levulinate did not alter the sensory acceptability of either product

Eating disorders affect individuals from most ethnic backgrounds. Research suggests that White females experience the greatest levels of disordered eating and body dissatisfaction. Studies examining Chinese females found they experienced similar levels of disordered eating but less body dissatisfaction to White females. This study was conducted to examine the prevalence of eating disorder symptomatology in Chinese and Other ethnicities in New Zealand. A sample of female university students at the University of Waikato completed questionnaires (N=116) to assess disordered eating and body dissatisfaction. In contrast to previous findings Chinese females actually exhibited more disordered eating behaviours and body dissatisfaction attitudes than did other females living in New Zealand. Also, fear of weight gain was more likely to be exhibited by Chinese females than other females. Pressure to be thin came from similar sources for both Chinese and other female students. While, length of time living in New Zealand did not appear to alter Chinese females' levels of disordered eating and body dissatisfaction. However in keeping with previous research, the present findings did suggest that the data from this study support the suggestion that the EAT-26 may not be an appropriate measure for Chinese females when assessing eating disorders. These findings have important implications for future research on ethnicities and eating disorders, and for clinicians working with Chinese female clients.

Listeriosis has the highest fatality and hospitalization rate among foodborne illnesses. Listeria monocytogenes causes listeriosis and is a difficult bacterium for ready-to-eat food processors to eliminate because of its ability to grow in the absence of oxygen and under refrigeration. Recently, milk and its proteins have gained recognition as the largest source of biologically active peptides, and, it stands reason that several antimicrobial peptides (AMP) can be released from casein as it is the most abundant milk protein. AMPs are commonly obtained by cutting the whole protein into peptide fragments using enzymes or by acidification. The objective of this study was to predict potential AMPs through computer aided tools, improve hydrolysate preparation, and determine trypsin and pepsin-casein hydrolysate antimicrobial activity in growth media and on frankfurters against two strains of Listeria monocytogenes (Scott A and 310) and Escherichia coli O157:H7 (Salami strain). The prediction study procedure was to identify the most common variants of primary peptide sequences. The sequences were analyzed for greatest possible enzyme cuts on the protein, peptide masses, isoelectric point, net charge and percent hydrophilic residues using online proteomics programs. The fragments were explored for AMP commonalities: fragment length of 3 to 50 amino acids, positive (cationic) net charge, and hydrophilic residues between 25 and 50%. This technique identified 16 potential AMPs which proved that it is possible to screen for AMPs. The method used to determine the trypsin-casein hydrolysate (TCH) and pepsin-casein hydrolysate (PCH) antimicrobial activity was to hydrolyze sodium caseinate with pepsin or trypsin. L. monocytogenes (strains Scott A and 310) were incubated in 0, 10, 20, and 40% PCH and 0 and 50% TCH concentrations over a 24 hour period. PCH suppressed growth of L. monocytogenes Scott A by 1.76 log CFU/mL and reduced initial populations of L. monocytogenes 310 and E. coli O157:H7 by 0.52 and 0.62 log CFU/ml, respectively. TCH had little or no effect on growth suppression of any of the three test organisms. The frankfurter study was conducted by spot inoculating frankfurters with L. monocytogenes Scott A and then dipping frankfurters into one of five treatments (deionized water, pH 2.7 buffer, pH 5.1 buffer, pH 2.7 PCH, and pH 5.1 PCH) for 30 seconds; inoculated frankfurters that were not dipped served as controls. Frankfurters were incubated at 32°C for seven days. The results showed that there was no significant difference (p>0.05) in antimicrobial effectiveness among the treatments and control. This study demonstrated that enzymatically derived casein hydrolysates somewhat inhibit growth of L. monocytogenes and E. coli O157:H7 in culture media, but were ineffective when applied to frankfurters. Casein hydrolysate solutions can be easily made in a processing facility for application in fluid systems such as an antimicrobial spray on beef carcasses and in milk, juice, sports drinks, soda, soups, and yogurt. It also could be used in solid systems such as frankfurters, cheese, ground beef, and processed or RTE foods.

Denna uppsats vill beskriva två olika typer av konst- och vetenskapsorganisationer som sammanför konstnärer och vetenskapsmän. Olika händelser från dessa organisationer beskrivs dels för att verksamheten har varit banbrytande av olika slag. Dels innebär verksamheten någonting nytt på i alla fall i organiserad form. Det andra är att ställa E.A.T. och ASCI mot den linjära spridningsmodellen. Vad innebär tillkomsten av organisationer som E.A.T. för den linjära spridningsmodellen? Det som framkommer är att dessa två organisationer avviker från den linjära spridningsmodellen då konstnärer skapar och/eller förmedlar vetenskap istället för skapande vetenskapsmän och förmedlande journalister.

La família del CD150 es troba constituïda per nou proteïnes expressades en la superficie dels leucòcits implicades en l'activació dels limfòcits i que pertanyen a la superfamília de les immunoglobulines. Els receptors CD84, CD150 (SLAM), CD229 (Ly9), CD244 (2B4), NTB-A i CS1 s'associen amb els adaptadors SAP (SLAM-associated protein) i EAT-2. L'adaptador SAP és una proteïna intracel·lular que es troba mutada en malalts amb el síndrome d'immunodeficiència lligat al cromosoma X (XLP).Aquest estudi s'ha analizat l'expressió de CD84, CD150, CD229 i CD244 en diferents leucòcits i poblacions limfocitàries mitjançant citometria de fluxe. El CD84 i el CD150 estaven presents en timòcits, cèl·lules T madures i cèl·lules presentadores d'antígen. L'expressió de CD84 i CD150 era elevada en cél·lules T memòria. L'expressió de CD150 s'incrementava molt després de l'activació. Al contrari que el CD84, el CD150 es trobava absent en monòcits en repòs i en cèl·lules dendrítiques immadures. El CD229 presentava un patró d'expressió restringit a limfòcits. El CD244 s'expressava de forma preferencial en cèl·lules NK, limfòcits CD8+ efectors, monòcits en repòs, basòfils i eosinòfils. Nosaltres hem descrit una distribució de CD84, CD150, CD229 i CD244 més àmplia que la prèviament descrita i hem demostrat que aquestes molècules s'expressen de forma diferencial en les cèl·lules hematopoiètiques. L'expressió heterogènea d'aquests receptors indica que deuen tenir funcions no redundants en la regulació tant del sistema immune adaptatiu com de l'innat.Amb la finalitat d'identificar el lligand de CD84, es va generar una proteïna de fusió soluble constituïda pels dominis extracel·lulars de CD84 i dos dominis immunoglobulina constants de la IgG humana (CD84-Ig). Degut a que ja havien estat descrites diverses interaccions entre membres de la mateixa família CD2 / CD150, es va assajar la interacció de la proteïna de fusió CD84-Ig amb cèl·lules COS transfectades amb els cDNAs de diferents membres de la família CD2 / CD150. La proteïna de fusió CD84-Ig interaccionava amb cèl·lules transfectades amb el cDNA de CD84, però no s'observava cap interacció amb la resta de membres de la família del CD2 / CD150. Així doncs, el CD84 interaccionava amb ell mateix. Els anticossos contra CD84 que reconeixien el primer domini V-like, bloquejaven la interacció de la proteïna de fusió de CD84 en les cèl·lules transfectades amb el cDNA de CD84 i en plaquetes. A més a més, els resultats obtinguts amb quimeres humà / murí dels dominis extracel·lulars de CD84, demostren que únicament el primer domini extracel·lular N-terminal és el responsable de la interacció homofílica. La interacció CD84-CD84 és independent de la seva cua citoplasmàtica. Finalment, la co-lligació del CD84 amb anticossos contra CD84 o la proteïna de fusió CD84-Ig i anticossos contra CD3, incrementen la secreció de IFN-gamma en limfòcits humans. Així, CD84 interacciona de manera homotípica i actua com a molècula coestimuladora.Amb l'objectiu d'indentificar el lligand de CD229, es va generar una proteïna de fusió soluble que contenia els dos dominis Ig N-terminals del receptor CD229 (CD229-Ig). La proteïna de fusió CD229-Ig s'unia a les cèl·lules transfectades amb el cDNA de CD229 però no es va detectar cap interacció amb les cèl·lules que expressaven la resta dels membres de la família del CD150, demostrant així que CD229 interaccionava de manera homofílica. Tant el CD229 humà com el de ratolí interaccionen amb ells mateixos. Amb mutants en que es deleccionaven els dominis Ig es va demostrar que el domini immunoglobulina N-terminal mitjançava l'adhesió homofílica. La interacció CD229-CD229 es veia severament compromesa quan es mutaven tres aminoàcids carregats del domini Ig N-terminal: E27 i E29 en el "loop" B-C i R89 en el "loop" F-G, localitzacions predites mitjançant anàlisi computacional. De manera sorprenent, la mutació R44A augmentava la interacció homofílica. Imatges obtingudes per microscopia confocal revelaven que el CD229 es relocalizava en les zones de contacte entre les cèl·lules B i T durant la formació de la sinapsi immunològica. Per tant, CD229 interacciona de forma homotípica i participa en la sinapsi immunològica.