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

Viticulture is threatened by the environmental modification caused by climate change. Higher temperatures determine an acceleration of the ripening process, which can be detrimental to wine quality. In the mediterranean area, heat waves are also increasingly frequent, with consequent blocking of the vegetative activity of the vines and increased susceptibility to sunburn damage. thus, adaptation strategies are necessary to reduce stress and improve the quality of grape production. Amongst the various techniques available, shading nets represent an interesting alternative for their effects on canopy microclimate (i.e., reduction of photosynthetic activity, improvement of water use efficiency, and slowing down in the ripening process).

Aims: Microscopic bud dissection is a common tool used to assess grapevine bud fertility and therefore to predict the yield of the following season

The grape variety Gewürztraminer is known to be affected by two physiological disorders namely berry shrivel and bunch stem necrosis. During the season 2014 we noticed a new symptomatology type of ripening disorder on the variety. The new symptom showed not all berries fallowing the normal maturation stages, but single berries remaining at a soft but green stage till harvest. The broad distribution of these so called “green berries” symptoms in different production sites of our region, caused huge damage due to the difficulty of eliminating single berries per bunch before harvesting. Therefore, the Research Centre Laimburg began to investigate the reasons and origins of this new symptom. This work shows the results of first attempts to find causes for the symptom as well as the resulting approach to mitigate symptoms. Applications of magnesium leaf fertilizer showed first promising results against this putative disorder. To study the causal effect of the green berries 30 symptomatic vineyards in 2014 have been selected for a monitoring during the season 2016. To evaluate the foliar nutrient treatment two vineyards have been selected for application of magnesium sulfate and magnesium chloride. Leaf and berry nutrient analysis, as well as the main quality parameters during ripening have been performed. As soon as “green berries” symptoms appeared, incidence and severity have been evaluated. Most of the symptomatic vineyards of the 2016 monitoring showed light to clear magnesium deficit symptoms on their foliage. Only during the seasons 2020 and 2021 “green berries” symptoms could be found in the leaf fertilizer treatment vineyards. Both seasons showed a significant effect of the magnesium treatments to reduce the incidence and severity of the symptom. It seems that the appearance of the “green berries” symptom on Gewürztraminer is correlated to a disturbed uptake of magnesium of the vines.

In this work, results about the composition in polyphenols and polyamines in important wine-grape cultivars from the Emilia-Romagna region are presented. Spectrophotometric and HPLC analyses suggest that especially coloured berries are particularly rich of antioxidant species (stilbenes and catechins). Potential allergenic capability of biogenic amines was also characterized.

The foliar application of urea has been shown to be able to satisfy the specific nutritional needs of the vine as well as to increase the nitrogen composition of the must. On the other hand, the use of nanotechnology could be of great interest in viticulture as it would help to slow down the release of urea and protect it against possible degradation. Several studies indicate that cell wall synthesis and remodeling are affected by nitrogen availability.