Fining-Derived Allergens in Wine: from Detection to Quantification

The color of a red wine is one of the most important parameters of its quality, giving much information on its status, such as the grape variety used or the winemaking style. As the result of a complex equilibrium between different forms of anthocyanins and polymerization reactions which occur over the course of time, color can also serve as an indication of a wines’ age. For this purpose the “chemical age” i and ii indexes have been introduced by Somers in 1977. The chemical age index i measures the color absorbance after the addition of acetaldehyde while chemical index ii provides an indication of how much of the total red pigments are resistant to SO2 bleaching.

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.

In red wines, anthocyanins evolve during the wine-making process and ageing. They react with other compounds (such as vinylphenols, acetaldehyde, pyruvic acid…) to form a stable family of compounds called pyranoanthocyanins. Furthermore, the oxidation process can modify the anthocyanic profile of a red wine. It is also interesting to evaluate the occurrence of the different subclasses of pyranoanthocyanins and to characterize their chemical properties. The first objective of this study is to evaluate the occurrence of the different groups of pyranoanthocyanins in an oxidised Merlot wine by a centrifugal partition chromatography strategy. The second goal is to evaluate their relative impact in red wines from Bordeaux region by measuring their concentrations.

Proteins play a significant role in the colloidal stability and clarity of white wines [1]. However, under conditions of high temperatures during storage or transportation, the proteins themselves can self-aggregate into light-dispersing particles causing the so-called protein haze [2]. Formation of these unattractive precipitates in bottled wine is a common defect of commercial wines, making them unacceptable for sale [3]. Previous studies identified the presence of phenolic compounds in the natural precipitate of white wine [4], contributing to the hypothesis that these compounds could be involved in the mechanism of protein haze formation.

FNB Top 10 Sauvignon Blanc competition, presented by the Sauvignon Blanc Interest Group of South Africa and sponsored by First National Bank, is the country’s foremost platform for producers of this cultivar to showcase and benchmark their wines. Wines entered in the competition originated from all over the winegrowing regions of the country and the winning wines showed good representation of quality South African Sauvignon blanc wines. The ten selected wines were subjected to various chemical analyses including volatile thiol and methoxypyrazine determination, while the sensory profile of each wine was determined using projective mapping.