Differences in fruit and wine composition (Vitis vinifera L. 'Pinot Noir') detected through non-invasive fluorescence sensor technology

The main objective of this study was to find a method assessing non-destructively the phenolic composition of fruit and wine providing a tool to better estimate the variability within a vineyard. A rootstock trial established at Geisenheim (Germany) with Vitis vinifera L. 'Pinot Noir' grafted onto six different rootstocks was used to test if differences induced by the rootstock could be detected through non-invasive sensor technology. A hand-held MULTIPLEX RESEARCH MXH optical sensor (Force-A, Orsay, France) based on chlorophyll fluorescence screening was used to measure randomly selected and representative berry samples. These measurements were compared on bunches measured directly in the field. Investigations of phenolics in 'Pinot Noir' berries during three vintages (2012-2014) showed that for scions grafted on a high vigor rootstock (SO4) both seed and skin tannins were 15% higher compared to lower vigor rootstocks (Riparia), following the trend in leaf chlorophyll. A micro-scale fermentation technique was developed to produce wine from each field replicate. The MXH chlorophyll index (SFR_R) was inversely linearly related to the total soluble solids (°Brix). Furthermore, the MXH anthocyanins index (ANTH_R) was correlated with the concentration of anthocyanins (R²=0.91). 'Pinot Noir' leaf composition was measured both manually (MXH) and on-the-go (MXM) and was not completely related to berry and wine phenolic composition. Understanding the interaction between rootstock nitrogen uptake efficiency and scion berry/wine phenolic composition will allow a better selection of suitable rootstocks matching the desired wine profile.