Valorization of wine lees for oenological interest by eco-responsible processes

Phenolic compounds play a central role in sensory characteristics of wine, such as colour, mouthfeel, flavour and determine its shelf life. Furthermore, the major non-enzymatic wine oxidation process is due to the catalytic oxidation of phenols in quinones. Due their importance, during the years have been developed different analytical methods to monitor the concentration of phenols in wine, such as Folin-Ciocalteu method, spectrophotometric techniques and HPLC. These methods can also be used to follow some oxidation-related chemical transformations.

From the effect of global climate change, wildfire occurrence during grape ripening has increased. These wildfires produce smoke that can carry organic compounds to a vineyard. These smoke compounds are adsorbed in the grape berry and result in wines with elevated levels of smoke-related phenols. These wines are described as having a smokey, burnt, and dirty aroma (Kristic et al, 2015). Not only are volatile phenols carried by smoke, but additionally glycoconjugate forms of these phenols are present as will. These have been found to have a large impact on the flavor of wines, being the cause of a lasting ashy aftertaste post consumption (Parker et al, 2012). When evaluating the sensory profile of these wines when tasted one after the other, there is an observed problem due to the lasting nature of these undesirable attributes and high level of carry-over from sample to sample. The aim of this work is to evaluate the extent this carryover occurs, along with the best sensory practices to mitigate its influence via different inter-stimulus rinse protocols.

Bois noir is the most widespread phytoplasma grapevine disease in Europe. It is associated with ‘Candidatus Phytoplasma solani’. In symptomatic grapevines cv. ‘Zweigelt’ infected with ‘Ca. P. solani’ compared with uninfected grapevines, metabolic pathways associated with phosphorylated sugar production were induced both at the transcriptional level and at the level of activity of the corresponding enzymes (Dermastia et al., 2021, Int. J. Mol. Sci. 22: 3531). In particular, the expression of gene coding for phosphoglucoisomerase was upregulated, resulting in increased phosphoglucoisomerase enzyme activity.

The use of soil conservation practices in wine grape production is becoming common throughout the world in response to an increased awareness of the value of soil health to maintain crop productivity and environmental quality. However, little information is available on the meaning of soil health within a viticultural context, and what soil properties should be targeted to achieve both the agronomic and environmental goals of wine grape producers. Conservation practices lead to increases in soil organic matter which may improve soil water retention, and increase soil C content therefore constituting a potential avenue to adapt to droughts and sequester C. Well-known management practices such as the use of cover crops, compost or no-till, although effective, seem to result in highly variable outcomes in soil organic matter and other soil health indicators. This variability is likely associated to the application of the practices in different soils and climates. Thus, integration of soil health building practices needs a thorough understanding of their efficacy under different conditions. Furthermore, additions of soil organic matter could trigger emissions of CO2 and N2O, a potent greenhouse gas that could represent a potential tradeoff of soil conservation practices. Finally, nutrient and water availability may be affected by the increase in soil organic matter having consequences for vine balance and grape quality.

The research includes an analysis of the impact of weather conditions on phenological development of the vine and grape quality, through monitoring of four experimental cultivars (Chardonnay, Graševina, Merlot and Plavac mali) over two production years. In each experimental vineyard, which were evenly distributed throughout the regions of Slavonia and The Croatian Danube, Croatian Uplands,