Sunday, July 23, 2006

Botrytis under microscope

During my residential block in Australia last week, we spent sometime reading about Botrytis, getting to know its microscopic form and how this fungus can be a friend and a foe to winemaking. Most of us hear about Botrytis from late harvest wine, one that has the honey nose and sweet on the palate. The taste often reminds one of raisins because the grapes are left to dry on the vines before being harvested. These grapes are not necessarily botrytised but those that are command a much higher price.

Botrytis, sometimes known as grey rot, is a fungal disease spread by damp, humid conditions. It tends to affect mostly immature berries with broken skins which are either caused by the scar left on the caps during flowering or mechanical equipment mishandling or weather conditions (e.g hail, wind or excessive sunburn). Skin damages provide the least resistance path for the fungus pathogen to infect the plant tissue. Yield and grape quality are most affected once grey rot sets in. Thin-skinned berries are most susceptible to grey rot. However, in the right conditions, i.e damp mornings and dry afternoons, the benevolent form of the fungus known as noble rot is welcome. The famous sweet wines of Sauternes and Germany are results of noble rot infected grapes. In this form, botrytis affect ripe grapes, consume water from the fruits through the pores of the skins (microscope filaments). As a result, sugar concentration increases, reducing the grapes into shriveled raisins. Wines made from these raisins are sweet and carry a unique flavor. The highest quality German classification for such wine is known as Trockenbeerenauslese (TBA). They are produced in minute quantities, in only the finest vintages. The sugars in these grapes can contribute about 21.5% alcohol volume (ABV) but after fermentation, the resultant wine rarely goes beyond 8% ABV as it is matched with high levels of acidity to produce a balanced wine. Top quality TBAs are among the world’s most expensive and worthy wines. And Yes, TBAs are great with cheese and desserts.

By Cher Lim
Wine Treasures Pte Ltd



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