Characterisation of some mushroom and earthy off-flavours found in wine made from ripe rot affected grapes
Ripe rot of grapes caused by the fungus Colletotrichum acutatum is a subtropical fungal bunch rot disease that results in the formation of off-flavours in wine. The chemical natures of the off flavours have not been fully characterised. The aim of this study was to identify and quantify some of the volatile compounds potentially responsible for mushroom or earthy odours in wine made from grapes infected with C. acutatum and investigate possible methods of amelioration. Cabernet Sauvignon wines were vinified from healthy and ripe rot affected grapes sourced from the Hastings Valley, NSW. These wines were analysed by headspace-solid-phase micro-extractionNDASHgas chromatographyNDASHmass spectrometry (HS-SPME-GC-MS). Geosmin, 1-octen-3-ol, 1-octen-3-one, and 2-methylisoborneol (MIB) were significantly higher in wines (P<0.05) made from ripe rot affected grapes than wines made from apparently disease-free, healthy grapes. MIB concentration in wines made from ripe rot affected grapes was higher than its reported sensory perception threshold. This suggests that MIB may contribute to the off-flavours found in wines made from ripe rot affected grapes. The fining agents, polyvinylpolypyrrolidone (PVPP), carbon and bentonite, were investigated at two concentrations for remediation of wines affected by ripe rots. All fining agent significantly reduced Geosmin, 1-octen-3-ol, 1-octen-3-one concentrations in affected wine but had no impact on the concentration of MIB.
Sadoughi, N., Blackman, J.W., Steel, C.C. and Schmidtke, L.M. (2016). Characterisation of some mushroom and earthy off-flavours found in wine made from ripe rot affected grapes. Acta Hortic. 1115, 259-264
Colletotrichum, fungal off-flavour, GC-MS, fining agents, geosmin, 2-methylisoborneol