1.4.1 Chemical evolution of stored wine: Kinetics of SO2 and anthocyanin degradation

As SO2 plays an important protective role against oxidation in wine, the chemical degradation of this compound during storage may represent a good index of the oxidative processes occurring in the product as a function of the packaging used [39, 44].

Generally, in wine, SO2 can exist in many interconvertible forms represented by a variety of "free" (FSO2) and "bound" (BSO2) forms. The actual protective concentration of SO2 during wine evolution and aging depends on many factors (i.e., pH, level and type of binding compounds, oxygen concentration, and so on). Thus, the total SO2 concentration (TSO2 = FSO2 + BSO2) can be considered an index of the oxidative damage caused by storage conditions. Indeed, FSO2 is an intermediate product which concentration is influenced by various chemical reactions different from the oxidative ones.

As reported in [26], the time evolution of TSO2 concentration could be described by a first-order kinetic equation:

$$[-d[TSO\_2]\_{t=t}/dt = kTSO\_2 \bullet [TSO\_2]\_{t=t} \tag{2}$$

where kTSO2 is the kinetic constant related to TSO2 degradation and [TSO2]t=t is the concentration of total SO2 at the generic reaction time t = t.

After integration, the following equation can be obtained:

$$[TSO\_2]\_{t=t} = [TSO\_2]\_{t=0} \bullet^{-kTSO2\star t} \tag{3}$$

where the two functional parameters k and [TSO2]t=0 may be considered a valid measure of the effect induced by oxidation during wine storage as a function of the packaging and storage temperature used.

Color is one of the most important organoleptic characteristics of red wines and affects the quality evaluation of the product [45]. Anthocyanins (Ant) are the most important molecules responsible of the young red wines' color. The color change from red-purple to brick-red hues is strongly related to the concentration of oxygen present in the stored wine [46].

The same experimental approach reported above to describe TSO2 time evolution can be also followed to describe the time evolution of total anthocyanin concentration (TAnt) that may represent a second index of oxidative degradation of the product as a function of packaging.

#### 1.4.2 Chemical evolution of stored wine: Antioxidant capacity

As polyphenols are widely known to play a protective action on the organism against cardiovascular and degenerative diseases [47], the moderate consumption of wine, especially red and rosé ones, has been associated with the reduction of mortality caused by many chronic diseases, a phenomenon that is commonly known as the "French paradox" [48]. In this context, the health properties of wines have been mainly interpreted on the basis of the antioxidant properties of the flavonoid fraction, which are related to both free radical scavenging and transition metal chelating mechanisms [49].

#### 1.4.3 Sensorial evolution of stored wine

In the field of sensory science, sensory analysis was initially adopted as a tool for quality control [50]. Since then, it has evolved in one of the most diffused and sophisticated toolkits, allowing to achieve an exhaustive description of the characteristics of the products [51]. According to Stone et al. [52], "Sensory evaluation is a scientific discipline used to evoke, measure, analyze and interpret reactions referable to those characteristics of products as they are perceived by the senses of sight, smell, taste, touch, and hearing" [50].

2.1 Case of study 1a, 1b, and 1c: Influence of storage conditions (temperature, packaging material, and volume of packaging) on the time evolution of a

Main Operating Conditions That Can Influence the Evolution of Wines during Long-Term Storage

The red wine (Table 2) was packed in different packaging materials at the same time in a commercial winery bottling line using a fully automated bottling/filling

Parameter Mean value c.i.\* Alcohol (%v/v) 11.46 0.06 pH 3.62 0.01 Titratable acidity (g/L as tartaric acid) 4.82 0.70 Net volatile acidity (g/L as acetic acid) 0.550 0.003 Total SO2 (TSO2) (g/L) 0.106 0.001 Total phenols (g/L as gallic acid) 2.140 0.064 Total anthocyanins (g/L as malvin) 0.470 0.006

As reported in Table 3, after 12 months of storage, it can be observed that the aging of red wine was significantly delayed at the lowest temperature, regardless of the packaging solution adopted. The only exception was represented by the wine

red wine over a storage period of 12 months

Cases of study 1a, 1b, and 1c: graphical abstract—Experimental setup.

DOI: http://dx.doi.org/10.5772/intechopen.85672

2.1.1 Case of study 1a: Influence of storage temperature

stored in glass bottles closed by natural corks [56].

station, as described in Figure 1.

\*c.i., confidence interval = P < 0.05.

Initial chemical composition of the red wine.

Table 2.

215

Figure 1.

In this context, it is possible to introduce the "sensory shelf life" concept of a product [53]. This can be defined as the storage time at which overall quality, or the intensity of a specific sensory attribute, reaches a predetermined value or "failure criterion," assuming that once the product has reached this point, it is no longer saleable [54].

As a function of specific characters, sensory analysis should also be performed in parallel with microbiological and/or chemical-physical shelf life analysis to monitor the sensory profile of the product for potential deleterious sensory attribute changes [53]. Thus, sensory variables used during sensory shelf life testing could include the monitoring of specific sensory attributes related to visual, aroma, and taste attributes which can be used as indices of sensory quality.

As reported by Jackson [55], most sensory changes that negatively affect wine shelf life are those associated with oxidation and hydrolysis of esters. Such changes are involved in reduction, polymerization, structural rearrangement, and volatility modifications; their relative importance depends on wine style, production techniques, varietal origin, storage conditions, and consumer expectation [55].

### 2. Experimental evidences

With the aim to better understand the time evolution of wines during bottle aging as a function of storage conditions, among the literature available on the topic, we selected and discussed two real case reports recently developed by our group (Figure 1; Table 2).

Main Operating Conditions That Can Influence the Evolution of Wines during Long-Term Storage DOI: http://dx.doi.org/10.5772/intechopen.85672

Figure 1. Cases of study 1a, 1b, and 1c: graphical abstract—Experimental setup.
