Hplc-ms analysis of carotenoids as potential precursors for 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) in riesling grapes

Table grape production requires adequate nitrogen (N) supply to sustain vine performance and obtain high yields. However, excess agricultural N fertilization is a major source of groundwater contamination and air pollution. Therefore, there is a strong need for empirically based precision N fertilization schemes in vineyards, for optimizing grape yield and quality while minimizing their environmental impact.
Our aim was to unequivocally quantify table grape N requirements, elucidate the drivers of daily N uptake, and quantify the relationship between fertigation N levels and vine growth, fruit yield, composition, and quality. For this, forty ‘Early Sweet’ (early-maturing, white) and ‘Crimson seedless’ (late-maturing, red) vines were grown in 500L drainage-lysimeters for 2 fruiting seasons, while subjected to five continuous N fertigation treatments ranging from 10 to 200 ppm.

Taints and off-flavours are one of the major concerns in the wine industry and even if the issues provoked by them are harmless, they can still have a negative impact on the quality or on the visual perception of the consumer. Nowadays, the frequency of occurrence of mousy off-flavours in wines has increased.
The reasons behind this could be the significant decrease in sulphur dioxide addition during processing, the increase in pH or even the trend for spontaneous fermentation in wine. This off-flavour is associated with Brettanomyces bruxellensis or some lactic acid bacteria metabolisms.

The interaction between tannins and salivary proteins is considered to be the basis of the phenomenon of wine astringency. Recently, some authors have revealed that some anthocyanins can also contribute to this mouthfeel sensation by interacting with proline rich proteins (PRPs). However, more studies are needed in order to elucidate the affinity of anthocyanins with these proteins.

The global warming phenomenon involves the frequency of extreme meteorological events accompanied by a change in rainfall distribution. Irrigation frequency (IF) affects the spatial and temporal soil water distribution but its effects on the phenolic composition of the grape have been scarcely studied. The aim of this work was to evaluate the effects of four deficit irrigation frequencies of 30 % ETo: one irrigation per day (T01), two irrigations per week (T03), one irrigation per week (T07) and one irrigation every two weeks (T15) on berry phenolic composition at harvest.

In field conditions, grapevine roots are colonized by arbuscular mycorrhizal fungi (AMF). Little is known about the species composition of AMF communities associated to grapevine.