**1.1 Wine, quality and aroma**

Since ancient times, wine has had a fundamental role in diet for several reasons. It is a good method of liquid conservation because its composition prevents the development of microorganisms and rot, it presents properties against certain diseases and provides health benefits, as long as its consumption is moderate. Wine is rich in antioxidants, mainly phenolic compounds, which are natural bioactive compounds related to its diverse properties. Numerous epidemiological studies have

associated regular and moderate consumption of wine with a lower incidence of mortality and morbidity from cardiovascular diseases in European countries, mainly in the Mediterranean [1].

• Yield per hectare.

• Analysis and evaluation of sensory characteristics.

**1.2 Accumulation of aroma compounds**

*DOI: http://dx.doi.org/10.5772/intechopen.92973*

immersed in a hydroalcoholic solution [7].

changes during ripening [9].

**49**

**1.3 Main factors affecting aroma quality**

tant in the development and accumulation of the aroma compounds.

*Management of Wine Aroma Compounds: Principal Basis and Future Perspectives*

nomena (oxidations, hydrolysis) and the fermentative metabolism of

Therefore, the quality of a wine will depend on many factors such as soil, type of grapes, presence of grape diseases, weather conditions, flavor complexity, alcoholic strength, balance, longevity, etc. (**Figure 1**) [4, 5]. These factors will also be impor-

The aroma of wine is complex, a particular wine contains more than 800 volatile compounds. When wine is ingested, these volatile compounds are dissolved in the palate and pharynx mucosa. Then, they reach the pituitary gland through the Eustachian tube. The perception of this odorous stimulus is the aroma of a wine and it cannot be evaluated without tasting it [6]. The concentration of these compounds may range from a few nanograms per liter to a few hundred micrograms or milligrams. They conform to a complex mixture of many different chemical compounds

Different factors determine the wine aroma such as the grape metabolism, the grape variety, the graft, the year, the weather conditions, the location of the vineyard, the region, the soil, cultural practices, the pre-fermentative biochemical phe-

microorganisms (conservation, aging) [8]. Since wine production is a long process that involves different stages, aromatic compounds from grapes can be transformed or revealed and many can be produced during alcoholic fermentation. In the case of aging wines in wood barrels, many reactions will occur in the wine forming new aroma compounds that will interact with the wood extracted aroma compounds. The ripening of grapes also plays an important role since many compounds of interest are synthesized at the skin, such as terpenoids, linalool, alpha-terpineol, and geraniol, which will influence the final chemical composition and therefore, the accumulation of wine's aroma. The concentration of volatile compounds in grapes increases in advanced stages of ripening, when sugar accumulation in berries slows down. However, this cumulative process varies from red grapes to white grapes. In red ones, the maximum amount of varietal volatile compounds is reached at maturity and remains constant in the following weeks; whereas, in white grapes varietal volatiles content cannot be related to a maturity stage, because of its concentration

As mentioned before, different factors influence the wine quality: type of soil, grape variety, grape diseases, weather, balance, longevity, etc. (**Figure 1**) [10]. Thermal variation is an important factor since it affects grape ripening. Slight thermal variations along grape development will suppress grapes acidity, while stronger thermal fluctuations will yield grapes with better balance. Not just thermal variations but hours of sunshine exposition are another parameter to consider. Environmental conditions affect the grape taste and quality and they also influence the quantity and availability of nutrients in the soil. A deficiency of nutrients affects negatively to the development of vines and to the production and the quality of the wine. Regarding soil characteristics, granularity and texture are two important factors. Stony soils are considered favorable for wine quality, but unfavorable for

The general term "quality" is a complex idea, which is not simpler when applied to wine. Throughout history, different institutions and laws have tried to regulate this concept. The International Organization of Vine and Wine (OIV) considers wine quality as the set of characters that differentiate one wine from another, being one of these characters the consumer taste [2]. According to this definition, the quality of a wine is relative and may vary over time, depending on several factors, such as the country of consumption, its habits, or new advances in the wine industry, among others.

However, the Regulation (EEC) No 823/87 has established a more permanent concept of wine quality, through the definition of the following requirements:


**Figure 1.**

*Environmental and viticultural factors that influence the composition of the wine. Adapted from [3].*

*Management of Wine Aroma Compounds: Principal Basis and Future Perspectives DOI: http://dx.doi.org/10.5772/intechopen.92973*

• Yield per hectare.

associated regular and moderate consumption of wine with a lower incidence of mortality and morbidity from cardiovascular diseases in European countries,

*Chemistry and Biochemistry of Winemaking, Wine Stabilization and Aging*

The general term "quality" is a complex idea, which is not simpler when applied to wine. Throughout history, different institutions and laws have tried to regulate this concept. The International Organization of Vine and Wine (OIV) considers wine quality as the set of characters that differentiate one wine from another, being one of these characters the consumer taste [2]. According to this definition, the quality of a wine is relative and may vary over time, depending on several factors, such as the country of consumption, its habits, or new advances in the wine

However, the Regulation (EEC) No 823/87 has established a more permanent concept of wine quality, through the definition of the following requirements:

*Environmental and viticultural factors that influence the composition of the wine. Adapted from [3].*

mainly in the Mediterranean [1].

industry, among others.

• Delimitation of the production area.

• Cultivation systems and uses.

• Vinification methods.

**Figure 1.**

**48**

• Distribution of varieties within the wine area.

• Minimum natural volumetric alcoholic strength.

• Analysis and evaluation of sensory characteristics.

Therefore, the quality of a wine will depend on many factors such as soil, type of grapes, presence of grape diseases, weather conditions, flavor complexity, alcoholic strength, balance, longevity, etc. (**Figure 1**) [4, 5]. These factors will also be important in the development and accumulation of the aroma compounds.

## **1.2 Accumulation of aroma compounds**

The aroma of wine is complex, a particular wine contains more than 800 volatile compounds. When wine is ingested, these volatile compounds are dissolved in the palate and pharynx mucosa. Then, they reach the pituitary gland through the Eustachian tube. The perception of this odorous stimulus is the aroma of a wine and it cannot be evaluated without tasting it [6]. The concentration of these compounds may range from a few nanograms per liter to a few hundred micrograms or milligrams. They conform to a complex mixture of many different chemical compounds immersed in a hydroalcoholic solution [7].

Different factors determine the wine aroma such as the grape metabolism, the grape variety, the graft, the year, the weather conditions, the location of the vineyard, the region, the soil, cultural practices, the pre-fermentative biochemical phenomena (oxidations, hydrolysis) and the fermentative metabolism of microorganisms (conservation, aging) [8]. Since wine production is a long process that involves different stages, aromatic compounds from grapes can be transformed or revealed and many can be produced during alcoholic fermentation. In the case of aging wines in wood barrels, many reactions will occur in the wine forming new aroma compounds that will interact with the wood extracted aroma compounds.

The ripening of grapes also plays an important role since many compounds of interest are synthesized at the skin, such as terpenoids, linalool, alpha-terpineol, and geraniol, which will influence the final chemical composition and therefore, the accumulation of wine's aroma. The concentration of volatile compounds in grapes increases in advanced stages of ripening, when sugar accumulation in berries slows down. However, this cumulative process varies from red grapes to white grapes. In red ones, the maximum amount of varietal volatile compounds is reached at maturity and remains constant in the following weeks; whereas, in white grapes varietal volatiles content cannot be related to a maturity stage, because of its concentration changes during ripening [9].

#### **1.3 Main factors affecting aroma quality**

As mentioned before, different factors influence the wine quality: type of soil, grape variety, grape diseases, weather, balance, longevity, etc. (**Figure 1**) [10]. Thermal variation is an important factor since it affects grape ripening. Slight thermal variations along grape development will suppress grapes acidity, while stronger thermal fluctuations will yield grapes with better balance. Not just thermal variations but hours of sunshine exposition are another parameter to consider. Environmental conditions affect the grape taste and quality and they also influence the quantity and availability of nutrients in the soil. A deficiency of nutrients affects negatively to the development of vines and to the production and the quality of the wine. Regarding soil characteristics, granularity and texture are two important factors. Stony soils are considered favorable for wine quality, but unfavorable for

the plant production capacity due to its lower fertility. Clay soils are related to aromatic, well colored and, often thick, wines [11].

The variety of graft inserted in the vine is also important since the combinations of different varieties allow the obtaining of wines with greater complexity and creativity. Fruit physicochemical characteristics and, therefore wine properties define each variety [12].

branches and increases airflow and insulation within the foliage [13]. Additionally, the removal of leaves may increase the content of total and phenol-free glycosides (one group of compounds that influence the aroma) [21]. In fact, wines obtained from defoliated grapes usually present higher fruity notes [22, 23]. Leaf-plucked grapes show the highest values of terpene and norisoprenoids compounds in Tempranillo, Merlot, and Gewürztraminer varieties where the synthesis of precursors is higher in warmest years and in grapes with more exposure to the sun [13]. As it has been previously described, soil and weather have an important effect on wine aroma, and this is mostly mediated by water. In general terms, water deficit has been proved to improve wine quality, enhance color, flavor and/or aroma [24]. However, no definitive scientific results can prove that the lack of water has such direct and positive impact on the quality since the effect of water depends on the species. For instance, during the maturation of Riesling grapes, the accumulation of terpene precursors is lower under irrigation [25]. In Tempranillo grapes, a positive correlation between irrigation and aroma potential at harvest has been detected [26, 27]. In Agiorgitiko grapes, precursors'synthesis is promoted by the limited availability of water [28]. There are several studies about the impacts of irrigation on fruit composition and wine sensory properties. However, the majority of these studies have been conducted in arid regions where irrigation is considered necessary and only a few have been carried out in humid regions where irrigation is

*Management of Wine Aroma Compounds: Principal Basis and Future Perspectives*

*DOI: http://dx.doi.org/10.5772/intechopen.92973*

Among the nutritive compounds of must, the amino acids are of great importance. They can serve as precursors of esters and also may play an indirect role in supporting cellular metabolic activities [30]. Consequently, wine growers can also modify soil fertilization to change the aromatic profile of the resulting wine. The nitrogen soil composition can lead to excessive vine vigor and susceptibility to gray rot, but can also enhance aroma expression since yeasts use that same nitrogen [31]. Nevertheless, when juice presents a sufficient amount of nitrogen, the addition of amino acids does not improve the volatile composition of wine, therefore the excess of the amino acids will probably be consumed by other cellular processes [30].

As wine quality strongly depends on the grape quality, it is necessary to process healthy grapes at the correct ripeness stage in order to obtain high-quality wines. For this reason, winegrowers have to be especially careful in the prevention of parasite attacks on the grapevine. Fungicide treatments are applied to prevent diseases such as botrytis, powdery mildew or downy mildew, which cause serious problems in the production. However, these fungicides can pass to wines at trace levels and can affect the aroma, and also the safety of the wine [9]. In addition, pesticide residues on grapes can be transferred to the must and influence the selection and development of yeast strains. On the other hand, yeast can reduce the levels of the pesticides in the wine or adsorb them on the dregs of the wine. The persistence of pesticides depends on several factors such as the chemical character-

istics of the active ingredients, photodegradation, thermodegradation, co-

orient the preferences of winegrowers for one or another fungicide.

**2. Determination of aroma compounds**

**51**

distillation and enzymatic degradation [32]. However, more studies are needed to

The analysis of the food aroma can be performed through tastings or instrumental methods, being necessary to correlate the latter with the former (**Figure 2**). Traditionally, sensory analysis was used to carry out the aroma determination. However, this method has the disadvantage (**Table 1**) of being subjective, and so,

mostly not necessary [29].

Grape production, transformation and certification techniques may be considered, too. A good production is defined by several parameters. Grapes might be whole, healthy and mature. They should be grown following respectful cultivation and be manufactured using proper mechanization procedures. In addition, using appropriate technologies, oenological assessments should be performed for keeping high levels of quality along the control systems. As a result of all this chain of processes, a specific wine will be produced and therefore all these parameters will define its brand, image, authenticity and origin, among other aspects. All these factors lead to a new term "terroir", which is used to express the distinctive characteristics that encompass the physical and biological environment and the applied wine practices that allow producing this wine in this situation [2].
