Noble rot

Laccase (EC 1.10.3.2), arising from fungal contamination by B. cinerea, which is the agent of gray and noble rot, also catalyzes reaction 2 and accepts a wider range of substrates, including, in particular, glycosylated flavonoids such as anthocyanins and also p-diphenols (oxidized to p-quinones). ... 

In a recent thorough investigation focused on dessert wine demand in the Florentine areas, Meucci (2008) reported that these consumers showed a clear preference (44%) for Vin Santo (Fig. 3.7). The preference of the remaining consumers was mainly for Passito di Pantelleria and for other Italian dessert wines (44% in all). Only a small share of consumers (around 7%) bought dessert wines from the noble rot, while the remaining 3% purchased from among all of the other Italian and non-Italian dessert wines. 

The aim of this review is to give an insight into the diversity of botrytized wines, the biochemical—physicochemical processes of noble rot, and the vinification process, with special regard to the alcoholic fermentation. The health concerns of botrytized wine consumption are also presented and discussed. 

The climatic conditions, cultivated varieties, and a late harvest favor the development of noble rot almost every year, although the vintage years are not equally good. To support the development of noble rot, very low fruit yields are set in most vineyards. 

The harvest in the region is typically very late (from the beginning of October to the end of November). In contrast to several other wine districts, in Tokaj, noble rot is desired to reach where desiccation creates extremely high concentration levels (Fig. 6.1). Optimally botrytized berries (locally called aszu berries) are brown, with violet hues, resinlike, and fully shriveled. Flardly any fungal mycelium and conidia are visible or are totally lacking on the surface of the skin. The total extract is above 60°Brix, which corresponds to 500-800 g/1 sugar in the juice (Bene, 2004). 

Beside Eszencia and Aszu, Tokaj specialty wines include three more types, Forditas, Maslas, and Szamorodni (Eperjesi, 2010 Kirkland, 1996). Szamorodni (meaning "as it was bom") is the most internationally well known. In vineyard sections where the selection of botrytized berries is unprofitable because of their limited presence or adverse weather conditions, noble-rotted and sound berries are harvested together. Vinification follows standard procedures, typical to other white wines. Depending on the initial sugar content of the must, the resulting wine is sweet or dry and is matured for 2 years (at least 1 year in oak barrels). 

TABLE 6.3 Modifications of some physical and chemical parameters of grape and juice by noble rot... 

Healthy Noble-rotted berry berry Healthy berry Noble-rotted berry BA Noble-rotted berry TBA Noble-rotted berry (Essencia Noble-rotted ) berry (Essencia)... 

The other appellations of SGN wines are Coteaux du Layon, and Coteaux de l Aubance in the Loire valley, Anjou. Coteaux du Layon produces sweet wine only, and the single variety here is Chenin blanc, a neutral, acidic grape cultivar. It is extremely prone to noble rot. The required initial sugar content of the must is 294 g/1 for SGN wines (INAO, 2007). Two individual AOCs within this region are Bonnezeaux and Chaume. Most of these SGN wines are very sweet, in comparison with the other French styles. 

The high prestige and superb quality of botrytized wines has inspired many winemakers, both within and exterior to Europe, to encourage noble rot and produce botrytized sweet wines. 

In California, the environmental conditions typically do not support the development of noble rot. Nonetheless, a few wineries are occasionally able to produce botrytized sweet wines, mainly by vineyard inoculation of grape clusters with Botrytis spores. 

Several other varietal properties influence susceptibility to noble rot. Very thin cuticles and the compact grape clusters favor gray rot, whereas thick cuticles resist Botrytis attack (Ribereau-Gayon et ah, 2000). High stomatal number, which is variety- or even clone-dependent, favors infection by Botrytis (Pucheu-Plante and Leclair, 1990 Pulcheu-Plante and Mercier, 1983). 

Most of the studies on Botrytis-specific aroma compounds have investigated the aroma composition of wines (Table 6.7). Only a few have focused on what occurs in the grape. On synthetic media, the main odorous compounds produced by B. cinerea are aromatic aldehydes (benzaldehyde, phenylacetaldehyde), and furfural (Kikuchi et al., 1983). Sarrazin et al. (2007a) confirmed the higher concentration of phenylacetaldehyde in noble-rotted grapes. 

---