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Studies on the carotenoid and glycosidic precursors of aroma and flavour compounds in Boronia megastigma (Nees)

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Cooper, Chris(Christopher Mark) (2006) Studies on the carotenoid and glycosidic precursors of aroma and flavour compounds in Boronia megastigma (Nees). PhD thesis, University of Tasmania.

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Abstract

Studies relating to the carotenoid precursors of C-13 norisoprenoids resulted in the
identification of five C-27 apocarotenoids. The new compounds were 3-hydroxyapo-10'-carotenoic
acid, methyl 3-hydroxy-apo-10'-caroteno ate, apo-10'-carotenoic
acid, apo-10'-carotenal, and methyl apo-10'-carotenoate. This provided evidence for
site specific cleavage of C-40 hydrocarbon carotenoids and xanthophylls in the 9, 10
position. Changes in the levels of these apocarotenoids, P-ionone and C-40
carotenoids demonstrated that metabolism relating to carotenoid cleavage increased
during flower opening.
Glycosides of monoterpenes, C-13 norisoprenoids and cucurbates were detected in
boronia using an HPLC screening process followed by enzymatic hydrolysis of an
extract using both a pectinase and B-D-glucosidase. Release of these conjugates was
further demonstrated through a simple marc incubation process. The pattern of
change over a ten day period demonstrated initial release of the compounds over 4 -
6 days of incubation followed by their disappearance. A commercial trial of the
process demonstrated a 36% increase in the yield of extract after 4 days. GC /
Olfactometry indicated that many of the compounds in the new extract had aroma
properties compatible with the primary boronia extract. There was additionally
evidence that tiglamides, cinnamate esters and 8-hydroxy linalool esters that were
previously not considered as flavour and aroma compounds contributed positive
aroma sensations.
Endogenous fungi were isolated from boronia which have the capacity to breakdown
glycosides of flavour and aroma compounds including monoterpenols, C-13
norisoprenoids and cucurbates. These fungi were tested in a model system using
sterilised boronia marc. The impact of fungal treatment on 45 naturally occurring
boronia compounds was measured over a 4 day incubation period. The results
indicated a complex pattern of changes including hydrolysis of glycosides, further
metabolism of released compounds, and metabolism of volatile compounds
remaining after the primary flower extraction.

Item Type: Thesis (PhD)
Keywords: Boronia, Carotenoids, Glycosides
Copyright Holders: The Author
Additional Information:

No access or viewing until 7 June 2007. Thesis (PhD)--University of Tasmania, 2006. Includes bibliographical references

Date Deposited: 25 Nov 2014 00:54
Last Modified: 11 Mar 2016 05:54
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