Odors botrytic

Numerous y- and 8-lactones were identified in Tokaji aszu grapes (Miklosy and Kerenyi, 2004 Miklosy et al., 2004). The odor notes of the y-lactones were described as resin- and caramel-like, roasted, or honey, while the 8-lactones exhibited characteristic notes of coconut, chocolate, and peach. The same lactones had been identified earlier from botrytized wines but not from normal wines (Schreier et al., 1976). Lactones are mostly found in oxidatively aged wines but seem to develop in fruit due to the oxidizing effect of B. cinerea, water loss, or Maillard reactions (Miklosy et al., 2004). 

The main aroma compounds identified as specific botrytized odorants are indicated in Table 6.6. It seems that while the terpene content decreases, numerous hydroxy-, oxo-, and dicarboxylic acid esters, acetals, and lactones form, all typically in lower concentrations or absent in normal wines (Miklosy and Kerenyi, 2004 Miklosy et al., 2000, 2004 Schreier et al, 1976). 

In addition to GC-MS, recent studies have focused on the identification and quantitative analysis of impact odorants in botrytized wines using gas chromatography-olfactometry (GC-O) analysis. Sarrazin et al. (2007a) investigated numerous botrytized and nonbotry-tized Sautemes wines. They could identify several key odorants that were responsible for the sensory differences between the wines, notably 3-mercaptohexan-l-ol, various furanons, ethyl-hexanoate, methional, phenylethanol, phenylacetaldehyde, sotolon, p-damascenone, and 2-methyl-3-furanthiol. 

The nature of the Botrytis aroma compounds has been subjected to extensive research. In addition to the older findings about the importance of hydroxy-, oxo-, and dicarboxylic acid esters, acetals, and some special y- and 8-lactones, the role of volatile thiols has recently been elucidated. Nonetheless, additional research is needed to identify odor active compounds that are specific for botrytized wines. 

Sarrazin, E., Shinkaruk, S., Tominaga, T., Bennetau, B., Frerot, E., and Dubourdieu, D. (2007b). Odorous impact of volatile thiols on the aroma of young botrytized sweet wines Identification and quantification of new sulfanyl alcohols. /. Agric. Food Chem. 55,1437-1444. 

As with dry white winemaking, overclarification can lead to large fermentation problems and increased acetic acid production. Must turbidity should not be as low as in dry white winemaking (100-200 NTU) 500-600 NTU or even a slightly higher turbidity is perfectly acceptable. Moreover, botrytized sweet wines are not subject to the same problems related to insufficient clarification as dry white wines—the development of reduction odors and vegetal tastes, oxidability, etc. 

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