Executives...FYI.

Scientists have examined how fungal infection affects wine produced from the grape varieties White Riesling, Red Riesling, and Gewurztraminer. They also examined the effect of powdery mildew on wine made from the unsprayed hybrid grape type Gm 8622-3.

They found that while bunch rot actually led to more positive aroma ratings due to the increased levels of fruity- and vanilla-like notes, powdery mildew decreased the level of pleasant notes in the wine, so that it received more negative ratings from the test panel, who found the infected wine to be less interesting than the healthy sample.

The researchers performed a series of tests, including comparative Aroma Extract Dilution Analysis, as well as sensory evaluation by a panel of 10 participants who had received extensive training in identifying different wine odorants. They found that both bunch rot and powdery mildew caused nuanced changes in the composition of chemical aroma substances, changing the odor of the wines to the point at which the wines' aroma quality was significantly affected. These changes were not linked to changes in any key chemical compound, but rather were a result of an interplay of subtler changes in multiple aroma active substances in each wine.

The researchers found that bunch rot infection increased the peach-like fruity, floral and liquorlike toasty aroma notes in all of the affected wine samples, leading the panel to rate its odor as more pleasant than the healthy control samples. Chemically, the change in aroma was caused by a complex variety of changes in the presence of aroma compounds.

But powdery mildew decreased vanilla-like notes, due to a variety of quite subtle chemical changes, including decreased levels of the flavor dilution factor of vanillin and decanoic acid, and a decrease of the esters ethyl isobutanoate, ethyl 2-methylbutanoate and 3-methylbutyl acetate.

Contact: Andrea Buettner, Department of Chemistry and Pharmacy, Friedrich-Alexander-Universitat Erlangen-Nurnberg, HenkestraBe 9,91054 Erlangen, Germany. Phone: +49 9131 85-22739. Email: [email protected].

Please Note: Illustration(s) are not available due to copyright restrictions.