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Item The influence of cations on biofilm formation of Listeria monocytogenes persistence strains : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology, Institute of Food Science and Technology, Massey University, Manawatū, New Zealand(Massey University, 2024) Chalke, SailiListeria monocytogenes is a Gram-positive pathogen, that possess a considerable risk to the human health with a high mortality rate. The persistence of pathogens through severe environmental conditions could be associated with their biofilm forming abilities. In this study, four different L.monocytogenes isolates from the seafood industry, were examined for their biofilm formation ability in the presence of three the cations: magnesium, calcium and sodium that are readily available in the seafood industry. Out of four the two isolates 15G01 and 33H04, were the persistent isolates from different seafood industry in New Zealand. Isolate 15A04 was a low biofilm former and the last isolate 16A01 was associated with a mussel contamination outbreak. The divalent cations, magnesium and calcium had a significantly greater effect on biofilm formation compared to the monovalent cation, sodium, especially at a concentration of 50mM. To further understand the effect, comparative transcriptomics was used on L.monocytogenes isolate 15G01 (a persistent and high biofilm forming isolate) and 15A04 (a low biofilm former). Both the isolates were exposed to 50mM concentrations of magnesium and sodium. In the presence of magnesium, various genes related to the phosphotransferase system, flagellar assembly, chemotaxis and various signal transduction receptors were upregulated. In case of sodium, the results indicated limited effect on gene expression for both the isolates. As biofilm is a community of bacteria enclosed in a self-induced matrix called EPS (extracellular polymeric substances), understanding the influence of cations on the composition of the EPS and the structural stability of biofilm is important. Magnesium enhanced the polysaccharide content, thus enhancing biofilm formation particularly in 15G01. eDNA concentration increased in the presence of cations however there were no significant differences among the cations. A unique hexagonal structure with voids were observed for the first time in the presence of magnesium and calcium for isolate 15A04. These findings contribute insights into the role of cations in biofilm formation, their involvement in regulating the complex network in biofilms and maintaining their structural integrity.Item Organisational learning and food safety crises : a critical case study of the Sanlu and Fonterra crises : a thesis presented in fulfilment of the requirements for the degree of Doctor of Philosophy, Massey University, New Zealand(Massey University, 2022) Ding, GuoyuThis study explores crisis-induced organisational learning in the Chinese and the New Zealand food safety authorities, or CFSA and NZFSA. While many crisis management scholars have sought to examine food safety crises, including the 2008 Sanlu melamine infant formula scandal and the 2013 Fonterra botulism scare, from the perspective of business organisations, food safety government agencies’ role in handling such crises, especially crisis-induced learning in the food safety authorities to prevent or better prepare for future crises, has been neglected. This thesis seeks to address this research gap by examining the two food safety crises under the lens of crisis-induced organisational learning to investigate changes in CFSA and NZFSA triggered by the biggest-ever food safety crises happened in China and New Zealand. Qualitative content analysis approach is employed to analyse the data corpus consisting of news articles and government documents recording the dairy food safety incidents and their socio-economic and political contexts and ensuing policy changes. A comparison between the two cases offers a deep understanding of the dairy food safety landscapes in the two countries and approaches employed by the government agencies in handling the dairy food safety crises. It also provides insights into dynamics of internal and external factors facilitating or inhibiting crisis-induced organisational learning in the two dairy food safety authorities. Though the two crises in this research have different socio-economic and political roots, they both caused unprecedented reputational damage not only to the dairy industries but to the whole food sectors in China and New Zealand. This research identifies multiple loopholes and underlying problems in the two dairy food safety regulatory systems leading to the incidents in question. It also finds systemic changes in the food safety authorities and the dairy food safety regulatory systems to address the loopholes. Political pressure and social emotion provoked by the dairy product crises are found to be the main factors facilitating learning in the public organisations. Conflict of interest incorporated into the dairy food safety system is seen as a key factor inhibiting deep learning in the two food safety authorities. This study therefore argues double-loop learning needs to happen in CFSA and NZFSA to uproot the underlying problem that led to lax regulation and other dairy food safety regulatory problems.Item Microbiological and chemical risk assessments of the addition of selected cereal grains as non-dairy ingredients to dairy products : a thesis presented in partial fulfilment of the requirements for the degree of Master in Food Technology at Massey University, Manawatū, New Zealand(Massey University, 2019) Fatima, FitryFood poisoning cases involving non-dairy ingredients such as cereal grains have been reported. The addition of cereal grains to dairy products in the dairy industry has increased in recent years. This has the potential to contaminate final products with pathogenic, spoilage and toxic chemical contaminants. In this study, the microbial and chemical risks involved in the addition of cereal grains to dairy products were assessed using semi- quantitative risk assessment method. The results showed that the most critical microbiological hazard in the selected cereal grains is Bacillus cereus due to its ability to form spores and persist in cereal grains. The addition of cereal grains to dairy products with high water activity/moisture content such as liquid breakfast products were found to pose the highest risk. Cyanogenic glycosides (hydrocyanic acid) were found to be the most critical chemical hazard among natural plant toxins in selected cereal grains due to their adverse health effects and abundance in most cereal grains. The addition of cereal grains to dairy products with high solid content was found to pose a very low risk. The results have identified some knowledge gaps in conducting risk assessments and have also provided background information about the microbial and chemical risks involved in the addition of cereal grains to dairy products. The results highlight the importance of effective implementation of Hazard Analysis and Critical Control Point (HACCP), Good Manufacturing Practices (GMP) and Good Hygienic Practices (GHP) in the dairy industry.Item Surface pasteurisation of fresh chicken meat using UV-C technology : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Albany, New Zealand(Massey University, 2019) Philip, Arthur JonathanFresh chicken meat is highly susceptible to contamination by spoilage and pathogenic microorganisms due to its high-water activity and rich nutrients. Following processing, aerobic mesophilic count (AMCs) on the surface of fresh chicken samples ranges from 3.00 to 4.00 log CFU/cm2. The New Zealand food safety guidelines stipulate that aerobic mesophilic counts (AMCs) present on surfaces of fresh chicken portion should be <6 log CFU/cm2 by end of shelf-life (6-7 days) when stored at 4°C. Hence, the safety and shelf-life of fresh chicken meat pose challenges for the industry. The UV-C technology, is a novel food processing technique that has lethal germicidal capability at 280-290 nm. Therefore, the technology has a potential to decontaminate suitable food products including the surfaces of fresh poultry portions. This study investigated the effect of UV-C light processing on untreated fresh skinless and skin-on chicken portions. The study was conducted in 2 phases to optimise the processing technology and determine its effects on fresh chicken samples during storage (4°C). One day old fresh chicken samples (skinless breast fillet, skinless thigh fillet, skin-on breast fillet, and skin-on thigh fillet) were obtained from a commercial processing factory and transported to Massey University, Auckland Campus, under chilled conditions (4°C) within an hour. In phase one, the fresh chicken samples were treated with four UV-C dosages (50, 100, 200, and 300 mJ/cm2) at ambient temperature (20°C) using a commercial UV disinfection system. AMCs were determined by swabbing the fresh chicken samples using swabs and 5-cm2 templates. Suitable dilutions (10-1 up to 10-6) of the swabbed samples were enumerated on standard plate agar with incubation at 30°C/72 h and grown colonies were expressed as log CFU/cm2. Temperature of the chicken samples before and after UV-C treatments was measured using a 20-cm probe thermometer. Treatment time was recorded automatically by the UV-C equipment. Phase one results showed that 50 mJ/cm2 was capable of maximum microbial reduction (skinless: 1.69 log CFU/cm2; skin-on: 0.21 log CFU/cm2) with minimal temperature changes (skinless: 3.14°C; skin-on: 3.32°C) and lowest exposure times (skinless: 2.17 minutes; skin-on: 2.22 minutes.). Therefore, 50 mJ/cm2 was selected as the optimum dosage for skin-on and skinless fresh chicken samples. In phase 2, the effect of optimised UV-C light dosage (50 mJ/cm2) on fresh chicken samples stored at 4°C/7 days was investigated. Instrumental color analysis, AMCs and lipid oxidation were determined at 4 different time points (day 0, 3, 5, 7) during storage (4°C). AMCs were analysed as previously described. The detection of E.coli, S. aureus, L. monocytogenes, Campylobacter spp. and Salmonella spp. were conducted at 0 and 7 days of storage using standard methods, while colour was measured by a colorimeter. Lipid oxidation was analysed by the thiobarbituric acid (TBA) method. Consumer sensory evaluation was carried out to evaluate raw and cooked chicken samples during storage. Raw chicken samples were evaluated by a focus group consisting of 5 semi-trained panelists at days 1, 5, and 7 while cooked samples were evaluated on days 1 and 7 by 30 panelists using a 9-scale hedonic test. For cooked chicken portions, samples were cooked to an internal temperature of 75°C using a convection oven. The cooked chicken samples were cooled to between 30 – 40°C before being served to the sensory panelists. The result of phase 2 showed that the initial mean AMCs were 3.31 ± 0.11 (skin-on) and 3.80 ± 0.35 (skinless) log CFU/cm2. After UV-C treatment, the AMCs of UV-treated chicken samples were reduced to 1.87 ± 0.98 (skinless) and 3.07 ± 0.34 (skin-on) log CFU/cm2, indicating that the AMCs for skinless and skin-on chicken samples decreased by 1.93 log and 0.24 log CFU/cm2 after UV-C (50 mJ/cm2) treatment, respectively. At the end of storage, the AMCs on skin-on chicken breast samples were 8.57 ± 0.34 (untreated) and 7.48 ± 0.07 (UV- treated) log CFU/cm2. Whereas, AMCs on skinless breast fillet were 8.62 ± 0.35 (untreated) and 6.73 ± 1.10 (UV-treated) log CFU/cm2, respectively. The results indicated that the growth of AMCs on untreated chicken samples exceeded the recommended limit on day 5, while UV-treated chicken samples were higher than the recommended limit on day 6 (skin- on) and day 7 (skinless). In addition, the AMCs results suggested that UV-C treatment was more effective on skinless chicken portion. Furthermore, pathogenic bacteria (E.coli, S. aureus, L. monocytogenes, Campylobacter spp., and Salmonella spp.) were not detected on untreated and UV-treated chicken samples on days 0 and 7 of storage, indicating the effectiveness of the chlorinated chilling processing step. Based on the Hunter L*, a*, b* colour readings and TBA (TBARS) results, the applied UV-C dose (50 mJ/cm2) had minimal impact on the color and lipid oxidation of both skin-on and skinless chicken samples during storage. However, a faint burnt odor was detected by sensory panelists during evaluation of UV-C treated fresh (raw) chicken samples stored (4°C) for day 1. The panelists did not detect any unpleasant odor from the cooked chicken samples during storage. Therefore, the results suggested that UV-C light may offer good prospects for shelf-life extension of fresh chicken samples. In addition, the results also indicated that UV-C light surface pasteurisation was more effective for skinless chicken samples, compared to its skin-on counterparts.Item Investigation of hygiene aspects of pig processing using the HACCP concept : a dissertation presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies in Veterinary Public Health at Massey University(Massey University, 1999) Vu, Quynh NContamination of fresh meat by pathogenic and spoilage microorganisms can occur at any stage of the slaughter process. Pathogens which are frequently found in fresh meat and which pose a public health problem include Salmonella spp. Campylobacter spp. and Yersinia spp. Contamination with spoilage bacteria affects the storage stability and shelf life of meats. Factors that contribute to meat spoilage include physical damage, biochemical changes in the meat tissues and the activity of microorganisms, of which bacteria are undoubtedly the most important. Fresh meats present a rich medium for the support of microbial growth and will ultimately be rendered unacceptable to consumers as a consequence of spoilage due to such growth. The source of spoilage bacteria can be the slaughter animals themselves, the environment, water and personnel working in the processing plants. This study was conducted to determine the effect of some processing operations on the level of contamination of the pig carcass with aerobic bacteria and to establish microbial quality control points based on the Hazards Analysis Critical Control Point (HACCP) principles. As a component of the HACCP system and a step in the setting up of an HACCP plan for microbial quality control of fresh carcass meat, this study aims at identifying hazards at various stages of processing, evaluating preventive measures and establishing critical control points. Where appropriate, corrective measures to ensure that bacterial contamination is within an acceptable level are recommended. The study was carried out at a processing plant in the North Island of New Zealand during the period April to July 1998. Based on observations at the plant, a flow chart of pig processing was drawn up. A number of processing stages were selected as points where potential risks of bacterial contamination were most likely to occur. These points initially included dehairing, polishing and scraping, evisceration, and inspection. Eight visits to the abattoir were made and a total of 32 paired swab samples from carcasses at each process stage were collected. With four process stages selected for sampling, the total number of samples was 128. In addition, 12 scalding tank water samples were collected for analysis. All samples were processed in the Microbiology Laboratory at Massey University. The aerobic plate count (APC) technique employing incubation at 30°C for 3 days was used for enumeration of aerobic bacteria. A matrix table was designed for entering APC data after each count. The mean of colony forming units per square cm (CFU/cm2) for pig carcass surfaces and CFU/ml for scalding water were calculated and log10 transformation was performed. The highest mean APC was found after the carcasses had passed the dehairing machine (5.1 log10/cm2, ST.D. = 0.57) and the lowest number before the dehairing step (4.31 log10/cm2, ST.D. = 0.61). A rapid increase in APC at the dehairing stage indicated a heavy recontamination of the pig carcass with bacteria from the equipment and from detritus accumulated during the operation. After the operation, the count gradually decreased to 4.4 log10/cm2, ST.D. = 0.38 at the post-evisceration point but then slightly rose again to 4.5 log10/cm2, ST.D. = 0.4 at the post-inspection step. The increase in the APC at the dehairing stage by 0.8 log10/cm2 (p = 0.0002, n = 16) is significant. There was little change in the APC at the polishing and scraping and evisceration stages. There was an insignificant difference of 0.2 log10/cm2 in the APC between samples taken at the start and at the end of the shift. The scalding water temperature fluctuated between 60°C and 67.5 °C (mean = 63.2, n = 12). Bacterial contamination of the scalding water remained almost unchanged with time (2.55 log10/ml at the beginning and 2.62 log10/ml at the end of the shift). An expected inverse correlation between scalding water counts and water temperature could not be verified. Although this study is confined to the microbiological assessment of only a few operational stages that can contribute to the storage quality of fresh pork, the results showed that recontamination of the pig carcass at the dehairing stage is serious and may pose potential safety and quality hazards. Control of bacterial contamination at this step is likely to have a beneficial effect on the microbial quality and safety of the final products. A quality Critical Control Point should be established at the dehairing step which can be considered as a safety CCP as well. However, some technological modification at this step such as installation of hot water showers to make the operation "specifically designed", may be needed to meet the criteria for establishing a CCP. At the polishing and scraping step the results of the study indicated a slight decline in bacterial numbers, provided that brushing and washing of the carcasses was done properly. Any deviation from the normal procedure e.g. inadequate water supply to the brush and scraping table, reduced frequency of hand and knife washing, or increased frequency of touching the carcass by the worker's hands, is likely to result in an increased level of bacterial contamination. Monitoring measures and corrective actions at this stage could be crucial for maintaining an effective CCP. At the evisceration step, preventive measures such as plugging or tying the anus should be considered. This step could be an important CCP for both quality and safety. Further investigations are required to assess the effect of meat inspection procedures on the spread of bacteria from multiple incisions of lymph nodes, internal organs and tonsils. If this step were to be considered a CCP, it would mainly have safety implications.Item Toxigenic fungi and mycotoxin production in Maldive fish (smoked dried tuna fish) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology, Massey University, Palmerston North, New Zealand(Massey University, 2013) Mohamed, ShazlaThis is the first study on the mycological safety of “Maldive fish”, a smoked dried tuna product that is both economically and nutritionally important to the Maldives. The most obvious concern with this product is the effect of fungal contamination. The initial aim of the current study was therefore to determine if Maldive fish supports the growth of toxigenic fungi and production of mycotoxins. The uncontrolled mycoflora on the product were characterised and related to the physiological parameters of the Maldive fish. Ninety six percent of the samples (n=25) were contaminated with one or more mycotoxigenic fungi with Aspergillus flavus (92%), A. tamarii (96%), A. niger (40%), A. ochraceus (12%) and Penicillium citrinum (60%) identified as the significant species. Subsequently, the potentially toxigenic isolates were screened for their corresponding mycotoxins aflatoxins, ochratoxin A (OTA), cyclopiazonic acid (CPA) and citrinin. A high proportion (72%) of isolates was able to produce toxic metabolites in vitro indicating possible contamination of the product with mycotoxins. Almost half (46%) of the A. flavus isolates were able to produce the potent carcinogen, aflatoxin B. All species on the surface were also found invading the product. The huge variability in aw levels (0.951 to 0.720) of the samples would support growth of a wide range of species. Furthermore, the slightly acidic pH (5.65 to 6.68) and low salt content (1.48 to 4.29%) together with the high ambient temperatures of the Maldives were eminently suitable for fungal growth and mycotoxin production. Quantification of aflatoxins from the product revealed two of the 25 samples to be contaminated above the legal limits and confirms potential exposure to significant levels of this toxin from Maldive fish infected with fungi. These results led to a new question: can fungal growth and mycotoxin production in Maldive fish be eliminated or reduced to safe levels? The most practical approach would be to reduce the aw to sufficiently low levels that inhibit fungal growth and mycotoxin production. The limiting aw levels for the most important species were therefore evaluated. The limiting aw for growth of A. tamarii was between 0.82 and 0.85 on NaCl media and between 0.79 and 0.75, on media containing sugars at ambient storage temperatures (25 to 35°C). The aw of Maldive fish should be maintained below 0.75 to prevent the growth of A. tamarii. The physiology of A. flavus has been extensively studied previously but the limiting values are dependent on the food matrix. A smoked fish agar was used to simulate Maldive fish for fungal growth (A. flavus) and mycotoxin production (aflatoxin and CPA) under varying conditions. No growth occurred at an aw of 0.75 while the toxin production was limited at an aw 0.80 under all incubation conditions (25°C to 40°C). Hence, control of A. flavus can be achieved by rapid drying of Maldive fish to an aw of 0.75 or below. This study has provided scientific evidence that the mycoflora on Maldive fish produce aflatoxins and other mycotoxins that are a food safety risk. Hence, control of toxigenic fungi is imperative and can be achieved through adequate drying. This information is crucial for the Maldives as well as other developing countries that consume hot smoked dried fish while it potentially has a broader application for other food products.