Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 53-55). Also available via the Internet.

Thesis (Ph.D.) -- University of Western Sydney, Hawkesbury, 1999. / Thesis submitted for the degree of Doctor of Philosophy. Copies of related publications in back. Includes bibliographical references (leaves 341-365).

Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains vii, 90 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 78-88).

No description available.

Comparative physiological and biochemical studies were conducted with apple varieties which were susceptible (Granny Smith and Lady Williams) and resistant (Crofton) to superficial scald, to understand the mechanisms of scald aetiology. This provided a basis for the development of alternatives to diphenylamine to control the disorder in cool stored apples. The research confirmed earlier research, which showed that the typical scald symptoms were the result of the deposition of brown pigments on the tonoplast in hypodermal and epidermal cells. It has been generally accepted that these pigments were formed by the action of polyphenol oxidase (PPO) following its release from chloroplasts, as a result of membrane damage caused by the oxidation products of alpha-farnesene. However, intact and functional chloroplasts were observed in severely scalded peel tissue. It was proposed that peroxidase (POD) might play a more important role in scald development. The concept that the concentration of alpha-farnesene or its products was related to the severity of scald was examined, and results indicated that differences in scald susceptability were related to the ability of apple tissue to cope with oxidative stress at low temperatures rather than the concentration of alpha-farnesene. If alpha-farnesene has a scald promoting role, it may be as a participant in a free radical chain reaction rather than an initiator. Studies were conducted on the phenolic compounds present in apple peel, which led to the proposal that phenolics might confer scald resistance by conserving other antioxidants and preventing peroxidation of membrane lipids. An holistic model of scald development was proposed, which indicated that scald results from a chilling stress since scald only occurs at temperatures below 4 degrees C and only in apples in which the capacity to protect membranes from oxidative stress is low. The model proposed that POD may have a more important role than PPO in scald development than previously thought. / Doctor of Philosophy (PhD)

One objective of the present investigation was to compare Salmonella and Campylobacter recovery incidence from commercially processed turkeys immediately prior to and following pre-chill and immersion chiller intervention strategies being used in three distinct turkey processing facilities. In each plant, on a single day of processing, 100 carcass rinse samples prior to and following each post-evisceration, pre-chill intervention and following immersion chilling were obtained for Salmonella and Campylobacter recovery. Two of three plants demonstrated a trend of decreased Salmonella on carcasses following the Inside Outside Bird Wash (IOBW), with reductions of 13%, and 11% being observed for Plants 1 and 2, respectively. Results for reductions of Campylobacter contamination were not as straightforward, with only Plant 3 showing decreased levels (11% reduction) following the IOBW. Plant 2 used an additional pre-chill intervention, a low pressure, acetic acid final wash, which was not shown to be effective in causing an additional reduction in either Salmonella or Campylobacter on carcasses. In all three plants, properly managed immersion chilling systems were the most effective microbial intervention for achieving Salmonella andCampylobacter reduction on processed turkey carcasses. While not as effective, the IOBW present in each plant likely contributed to the effectiveness of immersion chiller interventions. If managed properly these intervention points have demonstrated themselves as a viable means to effectively reduce Salmonella and Campylobacter on processed turkeys. Another objective was to modify the scalder environment to an alkaline pH and determine the effects of thermal killing of Salmonella and Campylobacter. In each plant, on a single day of processing, 50 carcass rinse samples prior to and following scald tank immersion and following feather removal were obtained for Salmonella and Campylobacter recovery. Modification of the scald water to alkaline conditions (pH 9- 10) did not result in increased thermal killing of Salmonella or Campylobacter on turkey carcasses, as hypothesized before the investigation. Alkaline conditions are known to facilitate a more efficacious pluck and aid in the detachment of bacteria. Due to this, the bacteria that were recovered at these points on the processing line could have had an impact on the observed data.

No abstract available. / Thesis (M.Sc.)-University of Durban-Westville, 1989.

Bibliography: leaves 218-232. / 232 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis investigates the resistance response of barley towards R. secalis by examining the in vitro interaction between various components of the apoplastic fluid and the fungus. / Thesis (Ph.D.)--Adelaide University, Dept. of Applied and Molecular Ecology, 2001

Thesis (M. Ag. Sci)--University of Adelaide, Dept. of Plant Science, 1992. / Includes bibliographical references.

Apple is one of the most valuable fruit consumed worldwide due to its excellent quality features and high degree of acceptation by consumers. However, apples are susceptible to various postharvest disorders, leading to significant economic losses. To slow down food decay and provide constant fresh food to the market, postharvest strategies including decreasing the temperature can slows down the metabolism of fruits, but in parallel can also trigger the occurrence of typical chilling injury related disorders. Among all the physiological disorders, superficial scald is one of the most challenging, causing discoloration and skin browning triggering therefore consumers unacceptance. The development of superficial scald in apple fruit is a complex process influenced by various factors, including genetic background, storage conditions and preharvest management practices. Recent research partially disclosed the molecular mechanisms underlying the development of superficial scald in apple fruit. It has been shown that this disorder is associated with the accumulation of reactive oxygen species (ROS) and the oxidation of alfa-farnesene, a sesquiterpene largely considered as a major actor in the onset of this disorder. Various postharvest treatments have been used to control the development of superficial scald in apple fruit, such as including the application of the ethylene competitor 1-methylcyclopropene (1-MCP) or controlled atmosphere storage. This thesis aimed to identify and characterize the genetic factors involved in symptoms development and to disclose the regulation of this phenomenon. To this end, a comparative multidisciplinary study integrating transcriptomics and metabolomics analysis have been performed in a wide range of storage conditions and across different genetic background. The mechanism of action and effectiveness of two preventing strategies, such as the exogenous application of 1-MCP and storage at low oxygen concentration were assessed in two apple cultivars, ‘Granny Smith’ and ‘Ladina’. The metabolite and transcriptomic profiles revealed that 1-MCP treatment actively stimulated the production of unsaturated fatty acids such as oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3), thereby successfully preventing the development of superficial scald in ‘Granny Smith’. ‘Ladina’, on the other hand, was less responsive to these strategies and was characterized by a higher accumulation of very long chain fatty acids (VLCFAs), together with an increased level of fatty acid saturation. Additionally, the integration of the transcriptomic survey and VOCs assessment underlined that storage at low oxygen concentration stimulated the expression of genes involved in anaerobic respiration, such as malate, alcohol dehydrogenase, and pyruvate decarboxylase, leading to the accumulation of ethanol and acetaldehyde in both cultivars. The expression of three members of the VII subgroups of ERF genes was also observed in ‘Granny Smith’, which coordinate the acclimation process to hypoxia in plants. The effect of controlled atmosphere in the prevention of superficial scald was furthermore investigated in fruit of ‘Granny Smith’ stored for different time and employing both a static and dynamic controlled atmosphere approach. The transcriptome analysis found that the duration of storage had an important effect on the coordination of gene expression, and the expression patterns of DEGs identified a distinct networks and types of transcriptomic hubs. Samples that developed superficial scald were characterized by higher concentration of chlorogenic acid and a time-specific increase in the expression of PAL and PPO genes. Prevention of superficial scald was related to a peculiar realigning episodes that involved the accumulation of specific antioxidant metabolites, very long chain fatty acids, and the expression of genes that coordinate the hypoxia acclimation process, such as RAP2-like and PCO. A complementary research was conducted to investigate the connection between the application of 1-MCP, low oxygen, and superficial scald. The study highlighted the possible application of genes involved in key fruit ripening pathways, including ethylene-related pathways and sugar/fermentation metabolism, as potential biomarkers for molecular characterization of the major changes that occur during fruit storage. The specific expression of polyphenol oxidase, along with sorbitol-6-phosphate dehydrogenase, were also used to investigate the onset of superficial scald in apples and correlated with the accumulation of the sugar alcohol sorbitol, which plays a protective role against chilling injuries. Assessing the transcriptional signature of these biomarkers can contribute to the development of new tools for a more informed understanding of the physiological progression of postharvest ripening in apples. Overall, these studies provide insights into the genetic and metabolic mechanisms underlying the development and prevention of superficial scald in apple cultivars during storage. The results obtained here paved the way for the identification of a core set of genes to be used as functional marker suitable to better comprehend this phenomenon and to select new accession characterized by a superior fruit quality and postharvest performance.