/library/oar/handle/123456789/13229 Sat, 07 Nov 2026 10:12:05 GMT 2026-11-07T10:12:05Z /library/oar/handle/123456789/101275 Title: Ultrasound and cold atmospheric plasma disinfection technologies for the production of safe and high quality fresh produce Abstract: Non-thermal technologies have drawn the attention of both researchers and the food industry in recent years. Notable interest has been shown by the fresh produce industry in particular. The fresh fruit and vegetable industry is constantly looking for new processes in order to produce fresh produce which is safe with respect to the microbial levels and the retention their quality properties. In addition, consumers' concerns about the use of chemical products such as chlorine and its derivatives in the disinfection of fresh produce have highlighted the need for the development of new methods for fresh produce production. Therefore, non-thermal technologies, which have been reported to be effective in inactivating the microorganisms and are able to retain the organoleptic properties of the fresh produce can be applied by the fresh produce industry. Furthermore, these technologies have been also classified as environmentally friendly due to the fact that less energy and water consumption is required. Their application across different steps in the food chain (e.g., during processing and post-processing) can contribute to control better the production of safe fresh produce while resulting in less adverse environmental impacts. Ultrasound is a non-thermal technology able to inactivate microorganisms based on physical mechanisms. Moreover, the efficacy of this technology can be enhanced by its combination with another antimicrobial process. In this thesis It was found that the combination of ultrasound (20 kHz, 90 µ111, 200 W) and essential oils significantly increased the rates of reduction of Escherichia coli and Salmonella enterica inoculated on Romain lettuce leaves, especially when a critical concentration of 0.018% (v/v) of essential oil of thyme and essential oil of oregano was used. Additionally, the impact of ultrasound treatment on the lettuce leaves was assessed by SEM and histological cross sections, has shown no damage on the biological structure of the leaves. The efficacy of ultrasound was also evaluated in other fresh produce. E. coli and S. enterica inoculated on alfalfa and mung bean sprouts were treated by ultrasound and the combination of ultrasound with CI02. An additive effect in the reduction of Salmonella on inoculated alfalfa and mung bean sprouts for the combination of ultrasound and CI02 was found, resulting in microbial reductions of 1.93±0.42 and 2.06±0.23 log CFU/g, respectively. Application of the same treatments on E. coli inoculated alfalfa and mung bean sprouts also resulted in additive effects, i.e., 2.61±0.02 and 2.07±0.02 log CFU/g reductions, respectively. Similarly, an additive effect was observed in terms of total inactivation (accounting for both the presence of the bacteria on the surface of the sprouts and the treated water) both for Salmonella and E. coli in alfalfa (i.e., 1.56±0.40 and 1.90±0.33 log CFU/sample, respectively) and mung bean sprouts (i.e., 1. 78±0.10 and 2.05±0.02 log CFU/sample, respectively). Ultrasound requires the use of water as a mean to decontaminate fresh produce. Cold Atmospheric Plasma (CAP) is an alternative dry (i.e., it does not require the use of water) decontamination technology which is based on the generation of ionized air. This can inactivate bacteria through different mechanisms. However, bacteria have different repair and defend mechanisms. In the course of this thesis the main antimicrobial species generated by a CAP (operating at 230V, 50 Hz, carried gas air) were identified and the effect of these reactive species on the growth rate, µmax, of different E. coli mutants was determined. Furthermore, the effect of CAP on E. coli inoculated on butter head lettuce leaves was assessed and it was found that treatments of 60 and 90 s were able to reduce the bacteria by more than 1.5 log CFU/cm2 Safety of produce is as important as the safety of the water effluents produced during decontamination treatments. UV-C light has been widely applied for water disinfection. However, the presence of organic matter can decrease the antimicrobial efficacy of this process. In order to avoid this drawback, an ultrasound system, which has been reported to be effective in reducing conglomerates, was applied in combination with UV-C during the current research. Lettuce wash water treated by the combination of both systems resulted in the highest bacterial inactivation (i.e., 3.57±0.39 log CFU/ml), colour reduction (43.31 ±7.02%) and reduction of organic matter (29.86±5.39%) after 30 min of treatment. As a general conclusion, non-thermal technologies show a high potential for application in fresh produce decontamination in terms of their antimicrobial efficacy either in processing or post processing environments. These observations have been assessed by a range of microbial, structural and biochemical tests and support further investigations at industrial scale levels. Description: PH.D. Fri, 01 Jan 2016 00:00:00 GMT /library/oar/handle/123456789/101275 2016-01-01T00:00:00Z /library/oar/handle/123456789/16712 Title: Dietary and physical activity assessment in 5-6-year-old Maltese children Abstract: Background: Most countries worldwide, including Malta, have increasing prevalence of childhood obesity. The most recent local prevalence data available for 6-year-old children was in 2007-2008, however, possible underlying causes of obesity related to food intake and activity levels have not yet been investigated in this age group. Aims: The aim of this study was to explore potential links between obesity and dietary intake and activity levels in a sample of 5-6-year-old Maltese children and possible associations with parental body mass index (BMI). Method: Stratified sampling from 15 schools (state, church and independent), conducted between March-June 2015, yielded a sample of 66 participants. Child and parent anthropometric data was collected and parents completed food, physical activity and sedentary behaviour diaries. The BMI-for-age was classified using International Obesity Task Force, World Health Organization and Centers for Disease Control criteria. The diaries were coded for energy intake, macronutrients and activity. Multiple regression related BMI and waist circumference (WC) with the diaries and Spearman correlation associated parental and child BMI. Results: A significant positive correlation (p < 0.001) was found between the children’s BMI and WC. Mean WC (p < 0.05) differed significantly between schools. Mean BMI (p > 0.05) and mean WC (p > 0.05) varied between genders. WC in girls was higher than the 90th percentile of British and European children (p > 0.05). Protein, saturated fats and non-milk extrinsic sugars (NMES) were significantly higher (p < 0.001) than the UK and Italian recommended values regardless of gender and socio-economic status. NMES were significantly higher in girls than in boys (p < 0.05). Physical activity and screen time were higher in boys than in girls (p > 0.05). Energy and macronutrient intake, activity and screen time varied between districts (p > 0.05). Multiple regression, showed a positive relationship between NMES and both BMI and WC and a negative relationship between physical activity and both BMI and WC. Paternal and child BMI were positively significantly correlated (p < 0.01). Conclusion: The results of this preliminary study suggest that this age group is a relevant group for monitoring obesity onset and prevalence, specific macronutrient and physical activity association and parental BMI association in Maltese children. This warrants further investigations using a larger sample size so as to work towards developing nutritional recommendations on a national basis. Description: M.SC.FOOD STUD.&ENV.HEALTH Fri, 01 Jan 2016 00:00:00 GMT /library/oar/handle/123456789/16712 2016-01-01T00:00:00Z /library/oar/handle/123456789/16710 Title: Characterisation of fungal contaminants affecting preservation properties of pirus communis var. bambinella Abstract: Fungal pathogens cause premature fruit spoilage of Bambinella, a fruit endemic to the Maltese islands, leading to the loss of fruit during the post-harvest phase. The objective of this study was to isolate, characterise and describe the growth kinetics of fungal contaminants of the Maltese June Pear and to produce a quasi-in-vivo model of Bambinella fruit to understand the growth dynamics of fungi on fruit. In total, 358 fungicide-free fruits were collected over 3 consecutive summers. The isolated fungi were identified and counted morphologically and molecularly. Fungi isolated from Bambinella in 2014 and 2015 included Cladosporium ramotenellum, Penicillium lanosum, Penicillium expansum, Alternaria arborescens and Aspergillus sydowii. All isolates are known to be causative factors of fungal disease in pears at various degrees. Mycelium diameter growth rate studies of the isolates were carried out on Sabouraud Dextrose Agar (SDA) at seven different temperatures ranging from 5- 35°C. The data collected was fitted with the modified Rosso model which showed that the optimal temperatures for growth of all the 5 fungi were in the range of 20- 22°C, while growth was slower at temperatures below 10°C and above 30°C. The order of most to least aggressive fungi was found to be: P. expansum, A. sydowii, P. lanosum, C. ramotenellum and A. arborescens. Spore germination studies were also performed for each isolate on in-house prepared Bambinella medium and the percentage of germination at 20°C was calculated. The rate of germination on Bambinella medium appeared to be similar to the rate of germination on SDA, suggesting that the fruit provides ample nutrients for fungal growth. Understanding the growth dynamics of Bambinella fungal pathogens can help in reducing the use of agricultural fungicides, which have been proven to cause clinical azole resistance in fungal organisms causing invasive infections. Description: M.SC.FOOD STUD.&ENV.HEALTH Fri, 01 Jan 2016 00:00:00 GMT /library/oar/handle/123456789/16710 2016-01-01T00:00:00Z