Origin of (−)-Geosmin on Grapes: On the Complementary Action of Two Fungi, Botrytis Cinerea and Penicillium Expansum

Abstract

One of the consequences of rot on grapes is the development of volatile compounds giving fungal, mouldy or earthy odours. Among these compounds, (-)-geosmin (trans-1,10-dimethyl-trans-9-decalol), a powerful aromatic compound with an earthy smell is a persistent defect in grape juice and wines made with at least partially rotten grapes. A microbiota analysis of rotten grapes containing (-)-geosmin was carried out on sites from four French regions from 1999 to 2002, to clarify the involvement in geosmin appearance of Streptomyces spp. and Penicillium spp., two types of microorganisms present on grape, that are known for their ability to produce geosmin. In earthy grapes, Botrytis cinerea was largely present. Different species of Streptomyces were also isolated, but their pH sensitivity was an extremely limiting parameter for their development on grape juice, grapes or stem, and consequently for their potentiality to generate geosmin in the vineyard. Penicillium expansum, producing geosmin on a model medium, was omnipresent. Penicillium carneum, which is also a geosmin producer, was represented by a single colony during the 4 years of this study. P. expansum alone was able to produce geosmin on a model medium but not on grapes. However, after 7 days' pre-culture of some B. cinerea strains on grape juice, this juice became favourable to geosmin production by P. expansum. We demonstrated the necessary and complementary action of B. cinerea and P. expansum in geosmin production in grape juice and in crushed grape berries.

Contribution of Streptomyces in sediment to earthy odor in the overlying water in Xionghe Reservoir, China

“…Moreover, the Oscillatoria found in sediments has been observed not to produce geosmin in vitro. In addition to actinomycetes, fungi are generally predominant in terrestrial environments (Zaitlin and Watson, 2006), and some genera, such as Penicillium, Aspergillus and Botrytis (La Guerche et al, 2005;Dionigi and Ingram, 1994;Bö rjesson et al, 1993), have also been shown to produce geosmin and/or 2-MIB in the food industry. But no evidence shows that they are the dominant geosmin/2-MIB producers in water bodies.…”

Impact of the Botrytis cinerea strain and metabolism on (−)-geosmin production by Penicillium expansum in grape juice

“…The distribution of the microbiota associated with rotten grapes containing geosmin was studied on different sites (La Guerche et al , 2005b. Some microorganisms commonly present on grapes were isolated (Hewitt 1994, Serra et al 2005: fungi, e.g.…”

Research Note: Benefits and Drawbacks of Pre-bloom Applications of Gibberellic Acid (GA3) for Stem Elongation in Sauvignon blanc

“…Attacks can reduce grape yield, as well as wine quality, by causing off-flavours, unstable colour, oxidative damage, premature ageing and difficulties in clarification (Ribereau-Gayon, 1983;Smart & Robinson, 1991). Furthermore, berries infected by B. cinerea can readily be invaded by other fungi, such as Penicillium expansum, which further favours the risk of off-flavour development (Smart & Robinson, 1991;La Guerche et al, 2005).…”