Heat berry: the influence of abiotic factors on the composition of berries, must and wine in Vitis vinifera L. CV Riesling

Abstract

It has been known for a long time that altering microclimate affects fruit composition and wine quality. The research project Heat Berry focuses on future scenarios of the climate change regarding higher temperatures and the risk of increasing sun radiation to the fruit. Field experiments were conducted in 2015 and 2016 at an experimental site at Geisenheim (Germany) using Riesling (clone 198-25 grafted to rootstock SO4). The aim of this study was to investigate and separate the effect of higher temperature to the fruit and higher light exposure in the bunch zone. Therefore, an experimental setup was designed to increase temperature inside the bunch zone (up to max. 3 °C on average) as well as defoliation and shading to influence the light exposure of the bunches. In addition, some physiological parameters and maturity measurements (Brix, yeast available nitrogen, organic acids) were determined. Aroma measurements focused on monoterpenes, C13-Norisoprenoids and polyphenols in berries as well as in samples of small scale vinification. A special focus lies on the C13-norisoprenoid TDN (1, 1, 6-trimethyl-1, 2-dihydronaphthalene). It is mostly present in mellow, aging Riesling wines and associated with a petrol taint in the sensory perception. Whether the origin of TDN is connected to viticultural and abiotic factors like temperature or sun exposure will be discussed.