Long-term effects of different starter yeasts on colour and natural antioxidant power of red wines

Eighty-seven red wines produced from red grapes of the grape variety Gaglioppo from the Calabria region (vintage 2009) were analysed by standard methods after 4 and 120 months of ageing. So, a total of 29 selected starters of Saccharomyces cerevisiae—3 wild type, 12 monoclonal cultures, and 14 hybrids—inoculated in triplicate were studied for their effects on colour and natural antioxidant power keeping of red wine. Wine ageing decreased the red component, the colour intensity, and the DPPH values while the colour hue values increased. This research has shown that the evolution of wine ageing is affected in a very different way by the starter yeast used and has allowed choosing the best yeast strain useful to produce red wine able to endure very long-time ageing, until 10 years.


Introduction
Moderate but regular consumption of red wine is proven to possess a positive effect on health, due to the presence of antioxidants and protective substances [1]. During ageing, these substances undergo an evolution, which involves changes in chemical and sensory characteristics of red wines [2]; the potential relevance of these changes to wine quality and complexity was assessed [3]. Particularly, the colour seems to provide information about defects, variation of quality parameters of wines during storage and polyphenolic composition, playing an important role in the evaluation of the perceived quality of wine [4]. The relation between colour components and antioxidant properties of wine is widely proven; it was reported that phenolic composition, as well as monomeric anthocyanins and co-pigments, effect the colour stability of wine [5]. The influence of different native grape varieties [6][7][8], and winemaking technologies [9][10][11][12][13][14] on the evolution of the chemical characteristics was diffusely investigated. The aim of this work was to study the influence of the yeast strain used as a starter on the evolution of the red component, colour intensity, colour hue, and antioxidant activity of red wine to assess its influence on long-term wine ageing. Several of the 29 yeast strains used and, in details, all the 14 hybrids were previously selected towards their effect on antioxidant phenolic compounds and towards a reduced absorption of wine phenolics.

Microorganisms
Three wild type, 12 monosporal cultures, and 14 hybrid strains of Saccharomyces cerevisiae, specifically obtained crossing selected strains with a low aptitude to adsorb grape pigments on their parietal mannoproteins were used. In details, the 14 hybrids were previously selected towards their effect on antioxidant phenolic compounds [15] and some of them are characterised by reduced absorption of wine phenolics [16].

Fermentation trials and analyses
Twenty kilograms of red grapes (vintage 2009) of the Calabrian cultivar Gaglioppo were given pre-fermentative maceration to extract pigments from skins and seeds. They were manually destemmed, crushed and macerated at 4 °C for 3 days, performing a punch down twice per day. The must obtained after pressing (pH 3.40, °Brix 22) was divided into aliquots of 100 mL and immediately inoculated at 5% in triplicate with 48-h precultures of each wine yeast. Microwinemaking trials were performed at 25 °C. At the end of fermentation, the wines were refrigerated at 4 °C and racked into125 mL plastic jars with a screw cap, under 10 ml of liquid paraffin, and keep in the dark at cellar temperature. After 4 and 120 months of ageing, the wines were analysed. The red component (Abs 520 nm), the colour intensity, and the colour hue were evaluated according to the Glories method [17]; the percentage of DPPH inactivation were evaluated according to Alén-Ruiz method [18].

Results and discussion
The data presented in Table 1 show the red component of examined wines. After an ageing period of 4 months, the red component ranged (p < 0.01) from a minimum value of 0.354 (strain RC029A-1A) to a maximum value of 0.463 [strain RC029B-1C × RE078C-1C (4)]. Twenty strains (value highlighted in grey) exhibited a value ≤ 0.392 (the mean value). After an ageing period of 120 months, the red component ranged (p < 0.01) from a minimum value of 0.031 [strain RC026C-1C × RC039C-1C (4)] to a maximum value of 0.234 (strain RC026). Seventeen strains (value highlighted in grey) exhibited a value ≤ 0.127 (the mean value). The four strains are written in bold type exhibited in both the ageing periods values above average probably because they absorbed less anthocyanins than the others. Considering the variation of the value of the red component between 4 and 120 months, for each strain it highly significantly (p < 0.01) decreased after 10 years of ageing from a minimum of − 39.38% (strain RC026) to a maximum of − 91.82% [strain RC026C-1C × RC039C-1C (4)] and a mean value of − 67.68%. This decrease in red component with wine ageing has also been observed by other authors. Red wines produced from five red grapes varieties of Metohija regions (Serbia) were analysed after 0, 4, 8, and 12 months of ageing for the value of the red component [19]. It always decreased too, exhibiting variations of: (a) − 2.56% after 4 months, − 5.13% after 8 months, and − 8.97% after 12 months for Cabernet wine; (b) − 2.78% after 4 months, − 5.56% after 8 months, and -8.33% after 12 months for Game wine; (c) − 2.75% after 4 months, − 3.67% after 8 months, and − 5.50% after 12 months for Merlot wine; (d) − 3.85% after 4 months, − 7.69% after 8 months, and − 9.62% after 12 months for Prokup wine; (e) − 1.83% after 4 months, − 3.67% after 8 months, and − 5.50% after 12 months for Vranac wine. Red wines produced from two different grape batches, both Cabernet Sauvignon, of Langhorne Creek region (South Australia) with low (P low ) and high (P high ) initial tannin and anthocyanin concentration were analysed after 0 and 42 months of ageing for the value of the red component [20]. It always decreased too, exhibiting variations of: − 43.11% for P low wine and − 44.65% for P high wine. Red wines produced from red grapes of the Cabernet Sauvignon variety from Ribera del Duero region (Spain) were analysed after 6 and 12 months of ageing for the value of the red component [21]. It always decreased too, exhibiting a mean variation of -2.46%.
The data presented in Table 2 show the colour intensity of examined wines. After an ageing period of 4 months, the colour intensity ranged (p < 0.01) from a minimum value of 1.145 (strain RC026C-1B) to a maximum value of 1.443 [strain RE049B-1A × NA093B-1C (5)]. Twenty strains (value highlighted in grey) exhibited a value ≤ 1.245 (the mean value). After an ageing period of 120 months, the colour intensity ranged (p < 0.01) from a minimum value of 0.147 [strain RC026C-1C × RC039C-1C (4)] to a maximum value of 1.214 [strain RE049B-1A × RC039C-1C (8)]. Sixteen strains (value highlighted in grey) exhibited a value ≤ 0.675 (the mean value). The four strains written in bold type exhibited in both the ageing periods values above average probably because they absorbed less pigments than the others. Considering the variation of the colour intensity between 4 and 120 months, it always decreased after 10 years of ageing for 21 strains highly significantly (p < 0.01), for five strains significantly (p < 0.05), and for three strains not significantly, from a minimum of − 2.80% [strain RE049B-1A × RC039C-1C (8)] to a maximum of − 87.97% [strain RC026C-1C × RC039C-1C (4)] and a mean value of − 45.73%.
This decrease in colour intensity with wine ageing has also been observed by other authors. Red wines produced from five red grapes varieties of Metohija regions (Serbia) were analysed after 0, 4, 8, and 12 months of ageing for the colour intensity [19]. It decreased too, excluding the Cabernet wine, exhibiting variations of: (a) 0% after 4 and 8 months, and 1.80% after 12 months for Cabernet wine; (b) − 0.62% after 4 and 8 months, and − 1.85% after 12 months for Game wine; (c) − 1.33% after 4 and 8 months, and − 1.77% after 12 months for Merlot wine; (d) 0% after 4 months, − 4.96% after 8 months, and − 2.48% after 12 months for Prokup wine; (e) − 0.45% after 4, 8, and 12 months for Vranac wine. Eighty-four bottled samples of red wines, all produced using red grapes of Listán negro variety in the Canary Islands, were analysed after 12 and 24 months of ageing for the colour density [22]. It always decreased too, exhibiting, compared to the values after 12 months, a mean value variation of − 21.84%. Tempranillo wines made with grapes from two different vineyards of Rioja Alta (Spain) were analysed after 55 and 720 days of ageing for the colour intensity [23]. It always decreased too exhibiting, compared to the values after 55 days, a mean value variation of − 11.25%.
The data presented in Table 3 show the colour hue of examined wines. After an ageing period of 4 months, the colour hue ranged (p < 0.01) from a minimum value of 1.729 (strain RC026C-1B) to a maximum value of 1.987 (strain RC029A-1A). Thirteen strains (value highlighted in grey) exhibited a value ≥ 1.857 (the mean value). After an ageing period of 120 months, the colour hue ranged (p < 0.01) from a minimum value of 2.476 (strain RC026) to a maximum value of 6.712 (strain RC029B-1C). Thirteen strains (value highlighted in grey) exhibited a value ≥ 4.179 (the mean value). The ten strains written in bold type exhibited in both the ageing periods values below average because they better-protected wine from ageing. Considering the variation of the colour hue between 4 and 120 months, it always increased after 10 years of ageing for 20 strains highly significantly (p < 0.01), for six strains significantly (p < 0.05), and for three strain not significantly, from a minimum of 27.07% (strain RC039) to a maximum of 248.13% (strain RC029B-1C) and a mean value of 124.13%.

Conclusion
This research has shown that the evolution of wine ageing is affected in a very different way by the starter yeast used and has allowed choosing the best yeast strain useful to produce red wine able to endure very long-time ageing, until 10 years. Data clearly show that after 120 months of ageing wine variability linked to the starter biodiversity is notably increased.