In recent years, an undesirable premature “aged” character has been noticed in a growing number of young Riesling wines, associated with extreme weather conditions leading to increased radiation intensity and/ or sun exposure of grapes. One of the compounds responsible for rapid aging is 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN), a grape derived C13-norisoprenoid formed as biodegradation product of carotenoids that participate in light harvesting and are essential for photoprotection against excess light in the blue and green wavelength region (350–550 nm).
Our interest in carotenoids as aroma precursors led us to examine the effect of qualitative light manipulation in the vineyard by coloured shade cloth (green, red and black) on carotenoid profile and accumulation in grapes during the ripening season. Through wavelength modulation of the radiation reaching the vines and therefore regulate the key absorbance maxima of the carotenoids, it was possible to reduce TDN concentrations in finished wines.
This presentation describes HPLC-MS analysis of carotenoids in grapes and will focus on selected carotenoids potentially associated with the formation of TDN.
Authors: Yevgeniya Grebneva, Josh Hixson, Kathrin Vollmer, Cory Black, Markus Herderich
The Australian Wine Research Institute PO Box 197 Glen Osmond SA 5064, Australia
Keywords: Carotenoids, TDN, Riesling, HPLC-MS