Impact of glutathione and elemental sulphur juice addition on the volatile thiol production in South African Sauvignon blanc wine

Beihong and Beimei are two wine cultivars from ‘Muscat Hamberg’ (V. vinifera L.) and wild V. amurensis Rupr., which were released in China in 2008. Here，two enology practices were reported. Firstly, the impact of different yeasts including D254, GRE, K1, D21 and BDX on dry wine quality of Beihong and Beimei was investigated. For Beihong, among wines fermented by all yeasts, residual sugar content was the lowest, total anthocyanin and resveratrol contents were the highest in the wine by D254. However, the wine by D254 had lower titrable acid than those by the other yeasts except BDX.

Filtration is a critical step in ensuring the clarity and microbial stability of wine prior to bottling. However the process of filtering potentially reduces red wine quality by removing some of the macromolecules that contribute to the texture of the wine. Commercial red wines, Cabernet Sauvignon (CAS) and Shiraz (SHZ), of two vintages and two grades (premium grade wines from the older vintage: CAS13 and SHZ13; and standard grade wines from a younger vintage: CAS14 and SHZ14) were filtered through industrial-scale commercial filtration units prior to bottling. Samples were taken before and after cross-flow filtration, lenticular filters, 0.65 µm and 0.45 µm pore size nylon membrane filters. The concentration and composition of macromolecules, including tannins and polysaccharides, were measured in all samples as well as particle size distribution and wine colour.

All along the winemaking process, conditioning and aging, wine is susceptible to be contaminated by different molecules. Contaminations can have various origins, related to wine microorganisms or as a result of an exogenous contamination. The aforementioned contamination of the wine can be caused by the migration of molecules from the materials in contact with the wine or by a contamination from exogenous molecules present in the air. Regardless of the source of the contamination, mainly two types of consequences can be observed.

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.

Many parameters affect the organoleptic characteristics of wine: internal parameters like the chemical composition or polyphenol content and external as for example storage conditions or the type of obturator. The aim of this study was to characterize sensorally the impacts of several type of obturator on a white wine: Chasselas. To determine the organoleptic characteristics of this wine, a quantitative descriptive analysis could be used. But rapid sensory methods were preferred in this project. Indeed these methods are an appropriate alternative to conventional descriptive methods for quickly assessing sensory product discrimination.