High-resolution aerial thermography for water stress estimation in grapevines

In the global economic context, an Appellation d’Origine Contrôlée must now more than ever control the typicity and originality of the wines it produces. It is in this spirit that the Côtes du Rhône have decided to acquire the means necessary for this control.

Chitosan is a polysaccharide produced from the deacetylation of chitin extracted from crustaceous and fungi. In winemaking chitosan is mainly used in the clarification of grape juice and wine, stabilization of white wines, removal of metals and to prevent wine spoilage by undesired microorganisms. The addition of chitosan to model wine systems was able to retard browning, reduce levels of metallic ions (Fe and Cu) and to protect varietal thiols due to its antiradical activity1. The present experiment was planned in order to evaluate the use of chitosan as a secondary antioxidant at three different stages of Sauvignon blanc fermentation and winemaking. Sauvignon blanc juices from three different locations were obtained at a commercial winery in Marlborough, New Zealand. One lots of grapes was collected from a receival bin and pressed into juice with a water-bag press, and a further juice sample was collected from a commercial pressing operation. Chitosan (1 g/L, low molecular weight, 75 – 85% deacetylated) was added to the juice after pressing, after cold settling, after fermentation, or at all these stages. Controls without any chitosan additions were also prepared.

The recent effects on temperature and rainfall caused by global warming pose a serious threat to the wine industry worldwide, mainly in terms of a loss of quality in the wines produced.

The crunchy texture of table grapes is one of the key quality parameters during production. This varies from cultivar to cultivar, stage of harvest and vineyard performance. Cell wall properties are key drivers of berry quality (e.g., pericarp firmness and intactness) at harvest and beyond. Common practise amongst producers is to continuously monitor firmness by evaluating pericarp appearance of cross-sectioned berries prior to harvest. These qualitative methods can be quite arbitrary and imprecise in their execution, but more quantitative, yet simple and high-throughput methods to evaluate these cell wall polymers are not yet readily available.

The application of different winemaking techniques helps to modify the basic parameters, phenolic profile, and aroma components influencing the final wine quality. In particular, pre-fermentative processes aim to increase the extraction and preservation of grape native compounds. Among them, cold liquid stabulation (macération sur bourbes) consists in maintaining the grape juice on its lees, in suspended condition at low temperature (0-8 °C) for a variable time (generally from 7 to 21 days). The aim of this work is to apply the cold liquid stabulation on two Italian white grape varieties, Arneis and Cortese, to evaluate the impact on basic parameters, color, polyphenolic compounds (TPI), antioxidant power (DPPH), total polysaccharides, and free and glycosylated volatile compounds (GC-MS analysis) during and after the process.