## 4 Materials and Methods
### Winemaking and Sampling
#### 4.1.2 Winemaking and Sampling  
[PERSON] et al. [21] described the winemaking of 'Marselan' and 'Merlot' single-variety wines. Each monovarietal wine was fermented in one 20-kiloliter (kL) fully automated thermostatic fermenters along with 4.0 g/hL of K\({}_{2}\)S\({}_{2}\)O\({}_{5}\) and 2.0 g/hL of pectinase. In consideration of the distinctive characteristics of the grapes from this region, namely their low acidity and high sugar content, 150 g/hL and 110 g/hL of tartaric acid were incorporated into the musts of 'Merlot' and 'Marselan', respectively, before fermentation. This was done in accordance with the local production guidelines. The objective of the addition was to enhance the stability of the wine color and to improve its mouthfeel, while compensating for the low tittatable acid. Cold maceration was then carried out for 3 days at around 10 \({}^{\circ}\)C. At a temperature of 10 \({}^{\circ}\)C, 14.0 g/hL of pre-activated OKAY yeast (LALLEMAND, Niagara-on-the-Lake, ON, Canada) and XPURE yeast (Laffort, Bordeaux, France) were added to 'Merlot' and 'Marselan' fermenters, respectively, to initiate alcohol fermentation. The temperature was controlled at 20-25 \({}^{\circ}\)C. Additionally, the wine was punched every 8 h for 20 min from the beginning of cold maceration until the end of alcohol fermentation. Alcohol fermentation was considered complete when the specific gravity dropped to around 0.993 and residual sugar was less than 4 g/L. The residue was then separated by racking. The free-run wine was loaded into a 10 kL stainless steel fermenter, and 5 mg/L VP41 lactobacillus (Enartis, Niagara-on-the-Lake, ON, Canada) was added to initiate malactic fermentation, with a controlled temperature at 18-20 \({}^{\circ}\)C. Malolactic fermentation process was monitored by using the FOSS WineScan instrument (Foss Electric, Hillerod, Denmark) to examine the changes in malic acid concentration. The fermentation was deemed to be complete when the concentration of malic acid dropped below 0.3 mg/L in accordance with local regulations pertaining to wine making technology.  
The residual sugar, total acid, volatile acid (VA) and pH of the wines were measured using a fast scanning infrared Fourier transform spectrometer from Foss Winescan. The results indicate that the alcohol content of 'Marselan' and 'Merlot' wines was 14.88 \(\pm\) 0.04% (\(v/v\)) and 14.31 \(\pm\) 0.01% (\(v/v\)), respectively, while the residual sugar was 4.87 \(\pm\) 0.31 g/L and 3.63 \(\pm\) 0.29 g/L, respectively. According to the study, the total acid levels were 7.80 \(\pm\) 0.01 g/L and 6.80 \(\pm\) 0.01 g/L, while the volatile acid levels were 0.67 \(\pm\) 0.02 g/L and 0.67 \(\pm\) 0.01 g/L, respectively. The pH were 3.28 \(\pm\) 0.01 and 3.54 \(\pm\) 0.01, respectively. The tittatable acid content of the wines was found to exceed that of the grape juice, primarily due to the addition of tartaric acid prior to alcohol fermentation, as previously mentioned [21]. The wine samples were bottled and stored in an underground wine collar at a temperature of approximately 16 \({}^{\circ}\)C with a controlled relative humidity of 70%.  
The wine samples were collected at various stages of the winemaking process, including must, before cold maceration (BC), after cold maceration (EC), before heating (BH), before alcohol fermentation (BAF), specific gravity down to 1.00 (SG to 1), the end of alcohol fermentation (EAF), the beginning of malolactic fermentation (MLF start), and the end of malolactic fermentation (MLF end). Additionally, samples were taken during bottle storage stages at 3 months (3 m), 6 months (6 m), 9 months (9 m), and 12 months (12 m). For each sampling point, three bottles of 350 mL were taken and stored separately in a refrigerator at \(-40\)\({}^{\circ}\)C.