Carotenoid breakdown products the-norisoprenoids-in wine aroma.

In recent years there has been much interest in the role that products of carotenoid breakdown--the norisoprenoids--may play in wine aroma. The basis for this interest is that norisoprenoids have very low olfactory perception thresholds and so have a high sensorial impact on wine aroma. The norisoprenoids can be formed by direct degradation of carotenoids such beta-carotene and neoxanthin or they can be stored as glycoconjugates, which can then release their volatile aglycone during fermentation via enzymatic and acid hydrolysis processes. The norisoprenoids identified in wine with important sensory properties are: TCH (2,2,6-trimethylcyclohexanone), beta-damascenone, beta-ionone, vitispirane, actinidiol, TDN (1,1,6-trimethyl-1,2-dihydronaphthalene), riesling acetal and TPB (4-(2,3,6-trimethylphenyl)buta-1,3-diene). The grape carotenoid profile, fermentation process and wine storage conditions, are determinant factors for the aroma of wine. The mechanisms involved in overall aroma development from grapes through fermentation to wine are yet to be defined. Progress in this area will be reviewed.