Ethyl esters interact with the major wine Thaumatin Like Protein VVTL1

The use of glutathione (GSH) in winemaking has been legitimated recently, according to OIV resolutions OENO 445-2015 and OENO 446-2015 a maximum dose of 20 mg/L is now allowed to use in must and wine. Several studies have proven the benefits of GSH, predominantly in Sauvignon blanc. Thus, oxidative coloration of must and wine is limited, aroma compounds such as volatile thiols are preserved, and the development of ageing flavors such as sotolon and 2-aminoacetophenone is impeded. The protective effect may be explained by the high affinity of GSH to bind o-quinones which are formed during phenolic oxidation and which are known to initiate browning and other oxidative changes. Some researchers have proposed the hydroxycinnamic acid to GSH ratio (HGR) as an indicator of oxidation susceptibility of must and could show that lower ratios yielded lighter musts.

Three compounds, 3-mercaptohexanol (3MH), 3-mercaptohexyl-acetate (3MHA) and 4-mercapto-4-methylpentan-2-one (4MMP), also known as varietal thiols, have been identified to contribute positively to wine aroma and are responsible for the distinct gooseberry, grapefruit, guava and box tree character found in Sauvignon blanc wines. Certain volatile thiol compounds though, can cause off-aromas of onion, garlic, rubber and rotten egg, this group of molecules is known as reductive sulphur compounds (RSC). This study looks into how the addition of sulphur-compounds to Sauvignon blanc juice contributes to the varietal thiol (3MH and 3MHA) concentration and reductive sulphur compound concentration in South African Sauvignon blanc wine.

Adrenaline (epinephrine) belongs to catecholamine class. It is a neurotransmitter and both a hormone which is released by the sympathetic nervous system and adrenal medulla in response to a range of stresses in order to regulate blood pressure, cardiac stimulation, relaxation of smooth muscles and other physiological processes. Adrenaline exhibits an effective antioxidant capacity (1). However, adrenalin is capable to auto-oxidation and in this case it generates toxic reactive oxygen intermediates and adrenochrome. Under in vitro conditions, auto-oxidation of adrenaline occurs in an alkaline medium (2).

The aromas found in young Bordeaux red wines made with Merlot and Cabernet Sauvignon suggest a complex mixture of aromas of fresh red fruits such as cherry or blackberry for Merlot, and strawberry or blackcurrant for Cabernet Sauvignon. The aromas of these wines are closely linked with the maturity of the grapes. The climate change that has occurred during the last decade in Bordeaux has induced changes in the ripening conditions of grape berries. It is now widely admitted that over-ripening of the berries during hot and dry summers results in the development of characteristic flavors reminiscent of cooked fruits (fig, prune). The presence of these overriding odors found in both musts and young wines affects the quality and subtlety of the wine flavor and may shorten its shelf life.

During wine aging, several complex phenomena of gas transfer take place in barrels due to the wine/oak contact. The efficiency of this gas transfer varies according to oak wood’s intrinsic physical properties. This research aims to better understand oxygen transfer phenomena through dry oak staves and especially through stave gaps, in order to reevaluate the importance of barrel-making on a barrel’s supply of oxygen. Experimentation was based on the development of an innovative permeameter of laboratory scale, for which the principal operating conditions concerning applied pressure, the choice of liquid phase/gas phase, and the grain type of oak are taken into account and investigated. With a specially developed tightening system, the existing pressure at stave gaps in a barrel could be reproduced on a laboratory scale in order to estimate its influence on oxygen transfer efficiency.