Thesis
Fatty acid derived ester related gene expression, activities, and volatiles for on-tree ripening and storage of apples
Washington State University
Master of Science (MS), Washington State University
2009
Handle:
https://hdl.handle.net/2376/102106
Abstract
Although apple fruit ripening has been the focus of many studies, many questions about the regulation of the ripening process remain unresolved. Most studies do not focus on freshly harvested fruit during the transition to autocatalytic ethylene production, which marks the beginning of many ripening-related processes, including the increased production of volatiles. To provide insight into the regulation of apple fruit volatile production during ripening, apple samples were taken off the tree every 3-4 days during and just after the transition to autocatalytic ethylene production. The lipoxygenase (LOX) and alcohol acyltransferase (AAT) enzymes, which are important to the production of straight-chain ester volatiles and the focus of much attention in apple flavor studies, were examined at both the enzyme activity and gene expression levels. Aldehydes and esters, which are products of LOX and AAT, respectively, and alcohols, which are substrates for AAT, were also examined in both headspace emissions and juice content. Headspace emissions were found to be a more reliable method of measuring physiological changes. While the LOX isoform examined in this work increased in early ripening, LOX activity decreased, along with headspace aldehydes. AAT gene expression and activity increased in late ripening, after the increase in headspace esters, indicating a role for AAT activity in regulating later ripening. Acetyl-coA carboxylase (ACCase) gene expression was also measured to try to determine any involvement in the regulation of flavor volatiles. Results showed changes in gene expression during ripening. Attempts were made to measure ACCase activity, but none was detected. Apple fruit were placed in 1.5% O2 controlled atmosphere (CA) storage, and the measurements taken in freshly harvested fruit were also taken just after removal from storage and during ripening afterwards. Esters and alcohols increased during CA storage, while aldehydes decreased. During ripening after CA storage, AAT activity does not reach the level it reaches in ripe fruit, while LOX activity does. Esters, including butyl acetate and hexyl acetate, make a strong recovery after CA storage, indicating a strong recovery of the straight chain ester synthesis pathway.
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Details
- Title
- Fatty acid derived ester related gene expression, activities, and volatiles for on-tree ripening and storage of apples
- Creators
- Christopher Daniel Starr
- Contributors
- John K. Fellman (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Program in Molecular Plant Sciences
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525088201842
- Language
- English
- Resource Type
- Thesis