Assessing the effect of oak derived aromas on mouthfeel perception in Chardonnay wine

Despite the extensive research performed during the last decades, the multifactorial mechanism responsible for the white wine protein haze formation is not fully characterized. Herein, a new model is proposed, which is based on the experimental identification of sulfur dioxide as a major modulating factor inducing wine protein haze upon heating. As opposed to other reducing agents, such as 2-mercaptoethanol, dithiothreitol and tris(2-carboxyethyl)phosphine hydrochloride (TCEP), the addition of SO2 to must/wine upon heating cleaves intraprotein disulfide bonds, hinders thiol-disulfide exchange during protein interactions and can lead to the formation of novel inter/intraprotein disulfide bonds. Those are eventually responsible for wine protein aggregation which follows a nucleation-growth kinetic model as shown by dynamic light scattering [1].

2,5-Dimethyl-4-hydroxy-3(2H)-furanone (furaneol) is an important aroma compound in fruits, such as pineapple and strawberry, and is reported to contribute to the strawberry-like note in some wines. Several grapevine species are used in winemaking, and furaneol is one of the characteristic aroma compounds in wines made from American grape (Vitis labrusca) and its hybrid grape, similar to methyl anthranilate. Muscat Bailey A is a hybrid grape variety [V. labrusca (Bailey) x V. vinifera (Muscat Hamburg)], and its wine is one of the most popular in Japan. The inclusion of Muscat Bailey A in the ‘International List of Vine and Varieties and their Synonyms’ managed by the ‘International Organisation of Vine and Wine (OIV)’ in 2013 has further fueled its popularity among winemakers and researchers worldwide.

Consumers typically prefer wines with floral and fruity aromas over those presenting green-pepper, vegetal or herbaceous notes. Pyrazines have been identified as causatives for herbaceous notes in wines, especially Bordeaux reds. However, pyrazines are not universally responsible for herbaceousness, and several other wine volatile compounds are known to produce distinct vegetal/herbaceous aromas in wines. Specifically, volatile aldehydes elicit sensations of herbaceousness or grassiness and have been described in wines well above their perception thresholds.

Volatile thiols contribute largely to the organoleptic characteristics and typicity of Sauvignon blanc wines. Among this family of odorous compounds, 3-sulfanylhexan-1-ol (3SH) and 4-methyl-4-sulfanylpentan-2-one (4MSP) have a major impact on wine flavor. These thiols are formed during alcoholic fermentation by the yeast from odorless and non-volatile precursors found in the berry and the must. The effect of vine nitrogen status on 3SH and 4MSP in Sauvignon blanc wine and on the glutathionylated and cysteinylated precursors of 3SH (Glut-3SH and Cys-3SH) was investigated in this study.

Contribution Sparkling wines elaborated following the traditional method undergo a second fermentation in closed bottles of base wines, followed by aging of wines with lees for at least 9 months. Most of the sparkling wines elaborated are white and rosé ones, although the production of red ones is highly increasing. One of the initial problems in red sparkling wine processing is to obtain suitable base wines that should have moderate alcohol content and astringency and adequate color intensity; which is difficult to obtain when grapes must be harvested at low phenolic and industrial maturity stage. The low phenolic maturity degree in the red grapes makes essential to choose an adequate winemaking methodology to obtain the base wines because the extracted polyphenols will vary according the winemaking technique: carbonic maceration or destemmed-crushed grapes.