Red wine astringency: evolution of tribological parameters during different harvest dates

UV-Visible spectroscopy in conjunction with chemometrics, was successfully applied to objectively differentiate sparkling wine press juice fractions of Pinot noir. Two measurements methods were applied: reflectance using a fibre optic probe in-line and transmission using a benchtop spectrophotometer.

Must clarification is an important step occurring just after grape extraction in the elaboration of white wine, consisting in a solid-liquid separation. Traditionally, low must turbidity, around 50-150 NTU, is generally reached in white winemaking in order to prevent reductive aromas and facilitating alcoholic fermentation. Alternatively, a higher turbidity (300 NTU or above) can be sought for reasons such as a better expression of grapes identity (terroir), or for getting a must matrix that could supposedly lead to wines having greater ageing potential.

Preliminary experiment of harvest timing was carried out in Eger wine district, Hungary in 2009. In situ physiological responses, berry quality parameters and wine quality of the Kékfrankos grapevine were studied at two growing sites (Eger-K6lyuktet6 – non-stressed, flat vineyard, and Eger-Nagyeged hill – water stressed, steep slope vineyard).

Grapes (Vitis vinifera L.) are a fruit crop of high economic significance globally. Each grapevine cultivar is characterized by its distinctive grape aroma, affecting the wine quality. In several cultivars, the aroma is shaped by terpenoid (mono- and sesqui-terpenoids). Their profile is controlled by terpene synthases (TPS), which are part of a largely expanded gene family. How the variation in TPS copy number and sequence among cultivars determines terpenoid profiles of grapes remains largely unexplored. We annotated TPS in the haplotypes of seven genomes (Riesling, Albariño, Fiano, Gewürztraminer, Pinot Noir, Cabernet Sauvignon, and Viognier) using BLAST, GMAP, PFAM, and phylogenetic analyses. Further, TPS expression patterns and terpenoid accumulation during berry development and ripening were characterized using RNA-Seq and SPME/GC-MS platforms, respectively. Variation in TPS copy number exists among cultivars. Specifically, the TPS counts span a range of 251 to 150 for Riesling and Fiano, respectively, when considering combined haplotypes within each cultivar. Total terpenoid accumulation patterns throughout development were consistent among the five aromatic cultivars, marked by high concentrations in flowers, followed by a decline and subsequent rise during berry development and ripening, respectively. Conversely, non-aromatic cultivars exhibited no substantial increase in terpenoid concentration during ripening. Transcriptome and network analyses are currently employed to determine which TPS are expressed in the berry and determine the terpenoid profile of the specific cultivar. These findings shed light on the genomic determinants of grape aroma in major cultivars, and allow future studies focused on cultivar-specific responses of terpenoid biosynthesis to environmental stresses.

Viticulture is exposed to a range of new stressors, that are challenging its sustainability and disrupting famous and well-established production regions. Steady increase of average temperature, recurring heat waves, altered rainfall seasonal distribution, drought spells, increased pathogens pressure, they all mix up with increased frequency, making every growing season a special challenge and calling for new approaches to cope with worrying scenarios.