Microwave treatment of grapes: effect on the must and red wine polysaccharide composition

The hot and dry climate of the Demarcated Region of Douro (DRD), Portugal, particularly during the summer, induces soil water deficits that influence the growth and development of grapevines.

The frequency of water deficits is increasing in many grape-growing regions due to climate change.

The use of cover crops in viticulture has increased in recent decades as growers seek to reduce herbicide use, improve soil organic matter and biodiversity, and minimize soil-related agronomic issues such as compaction and erosion.

Aim: The eastern foot of Helan Mountain, Ningxia, China is one of the most important wine production regions in China and grape cultivation has spread in several sub-regions with different soils and cultivars. Large diversity in wine aromas have been observed at Ningxia region but which terroir factors drive those diversity in aromas remain to uncover. This study aims to investigate the impacts of grape varieties and soil chemical properties on wine aromas at Ningxia, in order to characterize the aromatic typicality of Ningxia wines and provide foundation for developing a ‘Protected Designation of Origin’ system. 

As elsewhere, southwestern France vineyards face more recurrent summer heat waves these last years. Among the possibilities of adaptation to this climate changing parameter, the use of net shading is a technique that allow for limiting canopy exposure to radiations. In this trial, we tested net shading installed on one face of the canopy, on a north-south row-oriented plot of cv. Gros Manseng trained on VSP system in the PDO Pacherenc-du-Vic-Bilh. The purpose was to characterize the effects on the ambient canopy temperatures and radiations during the season and to observe the consequences on the composition of grapes and wines. Two sorts of net were used with two levels of obstruction (50% and 75%) of the photosynthesis active radiation (PAR). They have been installed on the west side of the canopy and compared to a netless control. Temperature and PAR sensors registered hourly data during the season. On specific summer day (hot and sunny) manual measurements took also place on bunches (temperature) and in different spots of the canopy (PAR). The results showed that, on clear days, the radiation is lowered by the shade nets respecting the supplier criteria. The effects on the ambient canopy temperature were inconstant on this plot when we observed the data from the global period of shading between fruit set and harvest. However, during hot days (>30°C), the temperature in the canopy was reduced during afternoon and the temperature of the bunch surface was reduced as well comparing to the control. A decrease of the maturity parameters of the berries, sugar and acidity, was also observed. Concerning the wine aromatic potential, no differences clearly appeared.