Effect ofColletotrichum acutatumripe rot on the composition and sensory attributes of Cabernet Sauvignon grapes and wine

Abstract

Background and Aim: The impacts of the fungal bunch rot pathogen Colletotrichum acutatum (ripe rot) on grape growing are documented; however, little is known about how the disease affects the resulting wine. This work aimed to investigate how ripe rot affects wine composition and sensory properties. Methods and Results: Wine was made using Cabernet Sauvignon grapes grown in the Hastings Valley (NSW). Berries with ripe rot tended to shrivel and acquired a distinctive off flavour and bitterness, described as hessian sack and musty. Wine made from the infected fruit had a higher pH and a higher level of residual sugar, but lower titratable acidity. Volatile acidity in wine made from uninfected fruit was 0.57 g/L, but increased to 0.83 and 1.06 g/L with 1.5 and 3% infection, respectively. Wine made from infected fruit had higher levels of both glycerol and gluconic acid indicative of fungal contamination. Alcohol concentration was also higher in wine made from infected fruit. Sensory analysis indicated that wine made from as low as 3% infected fruit had a similar colour density to control fruit, but a distinctive off-flavour, and browner colour hue. Conclusions: As far as we are aware of, this is the first report of a correlation between the level of grape infection by C. acutatum and wine composition in Australia. Significance of the Study: These results underline the problems of red grapes infected with C. acutatum. It provides viticulturists and winemakers with information to be considered when assessing grape quality and winemaking process for red wines.