UNEXPECTED PRODUCTION OF DMS POTENTIAL DURING ALCOOLIC FERMENTATION FROM MODEL CHAMPAGNE-LIKE MUSTS

Lately, rosé wine is rapidly increasing its popularity worldwide. Short-time macerations with the red skin of the grapes cause the partial extraction of anthocyanins, which are responsible for the pinki-sh-salmon hue of rosé wines. However, the low quantity of tannins (antioxidants) and richness in phenolic acids, which can be easily oxidized into yellowish pigments, tend to predispose rosé wines to an undesirable browning. Although the use of SO₂ for the prevention of oxidation is highly extended, this practice is expected to be reduced. Therefore, the search for alternative oenological adjuvants that prevent the oxidation and browning of rosé wines is highly desired.

Besides the increase in global mean temperature the second main challenge of a changing climate is the increase in atmospheric carbon dioxide (CO2) in relation to physiology and yield performance of grapevines. The benefits of increasing CO2 levels under greenhouse environment or open field studies have been well investigated for various annual crops. Research under free carbon dioxide enrichment on field-grown perennial plants such as grapevines is limited to a few studies. Further, chamber and greenhouse experiments have been conducted mostly on potted vines under eCO2 conditions.

Barrel fermentation and barrel-ageing of wine are commonly utilised practices in premium wine production. The wine aroma compounds related to barrel contact are varied and can enhance a range of wine aromas and flavours, such as ‘struck flint’, ‘caramel’, ‘red berry’, ‘toasty’ and ‘nutty’, as well as conventional oaky characters such as ‘vanilla’, ‘spice’, ‘smoky’ and ‘coconut’. A survey of commercially produced premium Shiraz, Cabernet Sauvignon, Pinot Noir and Chardonnay wines was conducted, assessing the prevalence of compounds that have been proposed as barrel-ageing markers¹ including oak lactones, volatile phenols, furanones, aldehydes, thiazoles2,3, phenylmethanethiol⁴ and 2-furylmethanethiol.⁵

Ultrafiltration is a process that fractionates mixtures using semipermeable membranes, primarily on the basis of molecular weight. Depending on the nominal molecular weight cut-off (MWCO) specifications of the membrane, smaller molecules pass through the membrane into the ‘permeate’, while larger molecules are retained and concentrated in the ‘retentate’. This study investigated applications of ultrafiltration technology for enhanced wine quality and profitability. The key objective was to establish to what extent ultrafiltration could be used to manage phenolic compounds (associated with astringency or bitterness) and proteins (associated with haze formation) in white wine.

Mannoproteins (MPs) are proteoglycans from the outmost layer of yeast cell walls released into wine during alcoholic fermentation and ageing on lees processes. The use of commercial preparations of mannoproteins as additives to improve wine stability with regards to the crystallization of tartaric salts and to prevent protein haze in the case of white and rosé wines is authorized by the OIV.
Regarding red wines and polyphenols, mannoproteins are described as able to improve their colloidal stability and modulate the astringent effect of condensed tannins. The latter interact with salivary proteins forming insoluble aggregates that cause a loss of lubrication in the mouth and promote a drying and puckering sensation. However, neither the interaction mechanisms involved in mannoproteins capacity to impact astringency nor the structure-function relationships related to this property are fully understood.