Title: Thermally tolerant pectin methylesterase, juice cloud loss and greening Authors
Submitted to: Subtropical Technology Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 1, 2008
Publication Date: October 16, 2008
Citation: Cameron, R.G., Savary, B.J., Vasu, P., Mccollum, T.G. 2008. Thermally tolerant pectin methylesterase, juice cloud loss and greening. Subtropical Technology Conference Proceedings.59:29. Technical Abstract: Multiple forms of pectin methylesterase (PME) have been isolated and characterized from citrus fruit tissue. PME is the causative agent responsible for destabilization of citrus juice cloud, a serious product quality defect. This report will present an up to date state of our knowledge regarding the thermally-tolerant PME (TT-PME) found in citrus and present preliminary data on the effects of HLB infection on PME activity in juice and juice cloud stability. Using affinity purified TT-PME two glycoforms have been identified. These were submitted to peptide finger printing techniques utilizing MALDI-TOF/TOF analysis. Sequence data obtained was used to construct primers for use with PCR amplification of the corresponding gene from a Citrus EST library. Subsequently cDNA and genomic clones have been sequenced from valencia, grapefruit and tangerine. These genes are distinctly different from other, previously sequenced citrus PME genes. Comparison of cloud stability in raw Valencia juices extracted from healthy and HLB (non-symptomatic) suggest that juice obtained from HLB infected trees is less stable than juice extracted from healthy fruit. Although total PME activity appeared to be equal in juice from both healthy and HLB infected fruit, two of three HLB infected samples had only approximately one-half of the TT-PME activity as found in healthy juice.