# Pairing Red Wine and Closure: New Achievements from Short-to-Medium Storage Time Assays
## 3 Results and Discussion  
### Determination of the Oxygen Transfer Rate  
The OTR, expressed as milligrams of oxygen per bottle, was monitored over 210 days (Figure 1) for natural and micro-agglomerated cork stoppers. At the end of this period, Natural Cork 1 reached 1.971 \(\pm\) 0.854 mg of O\({}_{2}\), Natural Cork 2 achieved 1.546 \(\pm\) 0.846 mg of O\({}_{2}\), Micro A recorded 1.200 \(\pm\) 0.446 mg of O\({}_{2}\), and Micro E showed 1.627 \(\pm\) 0.121 mg of O\({}_{2}\), corresponding to variability, expressed as standard deviation, of 43%, 55%, 37%, and 5%, respectively. Compared with the existing literature, the observed OTR values are within the generally reported range of 1 to 3 mg of O\({}_{2}\) per year for natural cork stoppers [18; 27; 28; 29], closer to the lower limit of this range. These results can be explained by the duration of the assay (210 days), as the trend lines presented for natural cork stoppers show that OTR values are still increasing. Other studies report that the OTR can fluctuate over the years of storage, with some findings indicating broader ranges of oxygen transfer that extend beyond the values typically observed during short- to medium-term assessments [1; 27; 30; 31]. For micro-agglomerated cork stoppers lower OTR values have been reported, ranging from 0.38 to 2.0 mg of O\({}_{2}\) per year, depending on the stopper dimension [1; 9]. Natural Cork 1 exhibited tendentially higher OTR; however, analysis of variance found no statistically significant differences between the stoppers (\(p>0.05\)), suggesting similar OTR behavior across stopper types under the study conditions. The Natural Cork 1 presents a lower length (45 \(\times\) 24 mm--length \(\times\) diameter), compared with the others (49 \(\times\) 24 mm), which may explain the tendentially higher OTR values. In fact, factors such as the cork stopper size and cork-glass interface conditions can influence oxygen ingress [18; 32]. Namely, the size of the stopper is relevant, as it determines its available surface (diameter) and filter thickness (length) [1; 33]. The greater variability among natural cork stoppers is likely attributed to the natural heterogeneous morphology of natural cork, where differences in pore structure and density influence oxygen permeability [1; 4; 34]. Micro-agglomerated corks, such as Micro A, and especially Micro E, demonstrated lower variability due to their uniform structure derived from adhesive-based manufacturing processes, which allowed for improved control over the gas transference from and to the wine [1]. Also, OTR variability depends on factors such as cork quality, structural uniformity, and sealing conditions [4; 29; 34; 35]. General Physicochemical Characteristics and Sensorial Properties of Wines Sealed with Different Types of Closures  
For this section and the following ones, the discussion of the results begins with the data obtained from the Douro blend wine stored for 35 months using natural and micro-agglomerated cork stoppers. In this case, a simpler model was studied, which involves two very common closures used to seal bottles containing red wines, allowing for a detailed assessment of the effects of medium-term storage. After that, we discuss the  
Figure 1: Oxygen transfer rate (OTR), expressed in mg of oxygen, for different stoppers (Natural Cork 1, Natural Cork 2, Micro A, and Micro E), determined over 210 days, under controlled environmental conditions. Error bars represent the standard deviation of five measurements taken per analysis time and closure type. No statistically significant differences (\(p>0.05\)) were observed between the four types of stoppers. results obtained from the Burgenland red wines stored for a shorter period of 5 months. This assay included the addition of the screw cap closure recommended for relatively short storage times.