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Contribution of grape berry lipids to wine aroma

Blackford, Christopher Lawrence (2020) Contribution of grape berry lipids to wine aroma. PhD thesis, Murdoch University.

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Understanding how the composition of wine grapes influences the formation of wine volatiles is important for predicting and manipulating wine quality. The objective of this research was to develop an understanding of how non-varietal wine aroma compounds are affected by compounds sourced from grapes. Chemically defined grape juice musts were supplemented with material of interest and the volatile profile of the fermented wines analysed with head-space solid phase micro-extraction (HS-SPME) gas chromatography-mass spectrometry (GC-MS). Supplementing model must with different grape tissues was carried out to determine where volatile-influencing compounds are located in the berries, and variations in amino acid and lipid profiles identified as probable influences on wine aromas made by yeast. In order to isolate and identify grape compounds that increase fatty acid ethyl ester (FAEE) concentrations in wine, fractions of grape extract were separated by liquid chromatography and used to supplement model musts, resulting in the identification of the poly-unsaturated triglyceride TG 54:6 as a major component of fractions that induced high FAEE production during fermentation. The effect of supplementing model must with glycero-lipids on FAEE production was investigated and a positive impact of exogenous poly-unsaturated glycero-lipids on yeast-mediated FAEE production confirmed. A lipidomic profiling study of grape tissues, and of berry and seed development, was carried out by positive-mode liquid chromatography quadrupole time-of-flight MS (LC-QTOFMS). This study indicated: that there are few differences in lipid profile between mature Riesling and Cabernet Sauvignon grapes; that seeds and berry tissues have distinctive lipid profiles; and that lipid profiles change during berry development in both seeds and berry tissues. The results of these studies highlight the need for research into establishing optimal grape lipid profiles to produce wines with targeted wine aroma profiles.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Chemistry and Physics
Supervisor(s): Trengove, Robert and Boss, P.
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