Bibliography: pages 79-86. / Flavour in wines is perhaps the most important factor affecting wine quality, with monoterpenoids being among the compounds contributing to flavour. In grapes there exists glycosidically-bound forms of these monoterpenes, representing a latent source of aroma. This project is a study on the ability of different enzymes to release these monoterpenes in Muscat d'Alexandrie and Weisser Riesling grapes. Different commercial enzyme preparations were characterised with respect to their catalytic properties and fractionated by ion exchange chromatography in the most active fractions. Amongst those commercial preparations tested, Rohapect C was found to be the most effective at conditions prevalent during wine making. These purified fractions were added to the above mentioned grapes to determine their effect on the release of different monoterpenes. Even though the enzymes were active on synthetic substrates, limited release of terpenes from must could be detected. Possible causes for this apparent inability to release monoterpenes were investigated. Product inhibition due to the presence of high concentrations of glucose in the must appeared to be the main cause of limited enzyme activity. In an attempt to overcome this problem, glucose in the above mentioned cultivars was oxidised to gluconic acid by glucose oxidase, prior to attempting monoterpene release by Rohapect C. Although no marked increase in the release of total terpenes occured, a significant increase in the concentrations of some individual terpenes could be observed. The effect of this on wine quality remains to be ascertained.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/22185 |
| Date | January 1989 |
| Creators | Strauss, Lindie Helene |
| Contributors | Botes, DP |
| Publisher | University of Cape Town, Faculty of Science, Department of Molecular and Cell Biology |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Master Thesis, Masters, MSc |
| Format | application/pdf |
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