**1. Introduction**

The study of the yeasts involved in the wine fermentation process has shown that the main yeasts genera are *Saccharomyces, Candida, Debaryomyces, Hanseniaspora, Kloeckera, Pichia* and *Torulaspora* [1]. Despite this large number of genera involved in this process, it has been identified that the species responsible for alcoholic fermentation is *Saccharomyces cerevisiae*.

Starter cultures of *S. cerevisiae* are currently used by winemakers in order to homogenize the microbiota and to prevent unwanted yeast species from prevailing in the fermentation process. These cultures quickly position themselves against the rest of the yeasts, thus ensuring the quality of the final product without being conditioned by the other microorganism species present in the fermentation.

Due to the importance of the aromatic products obtained during the fermentation process, numerous works have been carried out correlating the strain of *S. cerevisiae* used versus the aroma of the wine obtained [2]. Thereby, several studies carried out in the field of wine microbiology have reported that not only *S. cerevisiae* has an effect on the sensory quality of the wine, but also the metabolic activity of other genera and species of yeast, called non-*Saccharomyces*, would positively affect sensory quality.

In this way, the sequential action of these different genera and yeast species contributes to the wine aroma and flavor, determining the final sensory quality. The wine aroma and flavor are mainly obtained by many volatile compounds formed during the alcoholic fermentation, including alcohols, esters, organic acids, phenols, thiols, monoterpenes and norisoprenoids.

In this context, *Candida stellata* and *Kloeckera apiculata* stand out for their high glycerol production. This compound provides sweetness and fullness in wines, but the perception of these sensations depends on the concentration and on the wine [3].

*Candida colliculosa* stands out for its production of acetaldehyde and n-propanol, which can have a positive influence on the quality of the wine. Likewise, other non-*Saccharomyces* species possess ß-glucosidase activity, an enzyme that can hydrolyze aromatic precursors [2, 4]. In this way, the initial activity of these yeasts in the must is considered essential for the final wine aroma profile, because they are responsible for different reactions in the development of a wide range of volatile and nonvolatile products. As mentioned before, partially, it has been reported that the use of non-*Saccharomyces* yeasts in wine fermentation improves several parameters associated with the final wine quality, such as the increase in glycerol content [5], aromatic complexity [6], acidity [7] and anthocyanin content [8].

However, despite the aromatic potential of non-*Saccharomyces* yeasts, most of them have a low fermentative capacity, due to their low tolerance to alcohol, being unable to finish the fermentation. These characteristics have limited their use in the industry, despite their potential.

Currently, one of the strategies is the use of mixed cultures of non-*Saccharomyces* species with *S. cerevisiae* strains. This represents a useful tool that allows taking advantage of the sensory qualities of non-*Saccharomyces* species and the fermentative fitness of *S. cerevisiae*, favoring the sensory complexity and, therefore, the quality of the wine obtained [9]. Studies of mixed cultures of *Candida cantarelli* and *S. cerevisiae* reported that the use of sequential inoculation of these yeasts contributes to the improvement of the sensory characteristics of Syrah variety wine [10]. Likewise, Jolly et al. [4] observed that the aromatic profile of Chenin Blanc wines was improved with mixtures of *Candida pulcherrima* and *S. cerevisiae*. García et al. [11] reported similar observations for Chardonnay wines. Regarding fermentation of musts with a high concentration of sugar, it has been reported that the use of *T. delbrueckii* and *S. cerevisiae* reduced the volatile acidity and improved the analytical profile of the wine [12]. Also, the combined use of *Debaryomyces vanriji* and *S. cerevisiae* increased the concentration of geraniol [13]. An increase in varietal thiols was observed in cofermentation with *Pichia kluyveri* and *S. cerevisiae* [14]. Clemente-Jimenez et al. [15], using sequential inoculum of *Pichia fermentans* and *S. cerevisiae,* observed an increase in the concentration of specific aromatic components.

These results show that there is a huge potential for the application of non-*Saccharomyces* yeasts in oenology and strong evidence that their use contributes to the production of specific volatile compounds improving the aromatic composition of wines (**Table 1**).

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*Formation of Aromatic and Flavor Compounds in Wine: A Perspective of Positive and Negative…*

**Species Metabolites References Increase Decrease**

[16, 17]

[33–35]

[16, 41]

[55–60]

[5, 6, 18–30]

Acetic acid Acetaldehyde Ethanol Higher alcohols

Acetic acid [31, 32]

2-phenylethanol [44–48]

C6 alcohols [48–54]

Ethyl esters (caprylate)

3-methylthio-1-propanol

Monoterpenic alcohols 2-phenylethanol Carboxylic acids Ketones Furans Isoamyl acetate

2-phenylethanol Phenethyl acetate Ethyl acetate

Acetate ester Ethyl acetate Sulfur compounds Hydrogen sulfide

*K. lactis* Monoterpenoids [36–40]

*H. uvarum* Acetic acid [42] *H. guilliermondii* Acetate ester [43]

> 2-phenylethyl acetate β-damascenone Isoamyl acetate Phenylacetaldehyde

Biogenic amines (histamine, tyramine and putrescine) Acetate esters β-damascenone Higher alcohols (isobutanol and

2‐ethyl‐3,4,5,6‐tetrahydropyridine

Free terpenes Linalool Geraniol Nerol Citronerol Alpha-terpineol

phenylethanol)

2‐acetyl‐3,4,5,6‐ tetrahydropyridine 2‐acetyl‐1,2,5,6‐ tetrahydropyridine

Isoamyl alcohol Isoamyl acetate Esters

*Brettanomyces bruxellensis* Volatile phenols (4-ethylphenol)

Ethyl propanoate Ethyl isobutanoate Ethyl dihydrocinnamate

Thiols Terpenes Glycerol

4-MSP

Esters

*DOI: http://dx.doi.org/10.5772/intechopen.92562*

*Saccharomyces cerevisiae* Acetaldehyde

*Torulaspora delbrueckii* Fruity esters

*Kluyveromyces spp* Lactic acid

*K. marxianus* Polygalacturonases

*H. vineae* Acetate and ethyl ester

*Hanseniaspora spp* Acetic acid

*Metschnikowia pulcherrima*

**Species Metabolites References Increase Decrease** *Saccharomyces cerevisiae* Acetaldehyde Ethyl esters (caprylate) [16, 17] *Torulaspora delbrueckii* Fruity esters Ethyl propanoate Ethyl isobutanoate Ethyl dihydrocinnamate Thiols Terpenes Glycerol 3-methylthio-1-propanol 4-MSP Acetic acid Acetaldehyde Ethanol Higher alcohols [5, 6, 18–30] *Kluyveromyces spp* Lactic acid Esters Monoterpenic alcohols 2-phenylethanol Carboxylic acids Ketones Furans Isoamyl acetate Acetic acid [31, 32] *K. marxianus* Polygalacturonases 2-phenylethanol Phenethyl acetate Ethyl acetate [33–35] *K. lactis* Monoterpenoids [36–40] *Hanseniaspora spp* Acetic acid Acetate ester Ethyl acetate Sulfur compounds Hydrogen sulfide [16, 41] *H. uvarum* Acetic acid [42] *H. guilliermondii* Acetate ester [43] *H. vineae* Acetate and ethyl ester 2-phenylethyl acetate β-damascenone Isoamyl acetate Phenylacetaldehyde 2-phenylethanol [44–48] *Metschnikowia pulcherrima* Free terpenes Linalool Geraniol Nerol Citronerol Alpha-terpineol Biogenic amines (histamine, tyramine and putrescine) Acetate esters β-damascenone Higher alcohols (isobutanol and phenylethanol) C6 alcohols [48–54] *Brettanomyces bruxellensis* Volatile phenols (4-ethylphenol) 2‐acetyl‐3,4,5,6‐ tetrahydropyridine 2‐acetyl‐1,2,5,6‐ tetrahydropyridine 2‐ethyl‐3,4,5,6‐tetrahydropyridine Isoamyl alcohol Isoamyl acetate Esters [55–60]

*Formation of Aromatic and Flavor Compounds in Wine: A Perspective of Positive and Negative… DOI: http://dx.doi.org/10.5772/intechopen.92562*

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

affect sensory quality.

wine [3].

nols, thiols, monoterpenes and norisoprenoids.

complexity [6], acidity [7] and anthocyanin content [8].

industry, despite their potential.

Due to the importance of the aromatic products obtained during the fermentation process, numerous works have been carried out correlating the strain of *S. cerevisiae* used versus the aroma of the wine obtained [2]. Thereby, several studies carried out in the field of wine microbiology have reported that not only *S. cerevisiae* has an effect on the sensory quality of the wine, but also the metabolic activity of other genera and species of yeast, called non-*Saccharomyces*, would positively

In this way, the sequential action of these different genera and yeast species contributes to the wine aroma and flavor, determining the final sensory quality. The wine aroma and flavor are mainly obtained by many volatile compounds formed during the alcoholic fermentation, including alcohols, esters, organic acids, phe-

In this context, *Candida stellata* and *Kloeckera apiculata* stand out for their high glycerol production. This compound provides sweetness and fullness in wines, but the perception of these sensations depends on the concentration and on the

*Candida colliculosa* stands out for its production of acetaldehyde and n-propanol, which can have a positive influence on the quality of the wine. Likewise, other non-*Saccharomyces* species possess ß-glucosidase activity, an enzyme that can hydrolyze aromatic precursors [2, 4]. In this way, the initial activity of these yeasts in the must is considered essential for the final wine aroma profile, because they are responsible for different reactions in the development of a wide range of volatile and nonvolatile products. As mentioned before, partially, it has been reported that the use of non-*Saccharomyces* yeasts in wine fermentation improves several parameters associated with the final wine quality, such as the increase in glycerol content [5], aromatic

However, despite the aromatic potential of non-*Saccharomyces* yeasts, most of them have a low fermentative capacity, due to their low tolerance to alcohol, being unable to finish the fermentation. These characteristics have limited their use in the

Currently, one of the strategies is the use of mixed cultures of non-*Saccharomyces* species with *S. cerevisiae* strains. This represents a useful tool that allows taking advantage of the sensory qualities of non-*Saccharomyces* species and the fermentative fitness of *S. cerevisiae*, favoring the sensory complexity and, therefore, the quality of the wine obtained [9]. Studies of mixed cultures of *Candida cantarelli* and *S. cerevisiae* reported that the use of sequential inoculation of these yeasts contributes to the improvement of the sensory characteristics of Syrah variety wine [10]. Likewise, Jolly et al. [4] observed that the aromatic profile of Chenin Blanc wines was improved with mixtures of *Candida pulcherrima* and *S. cerevisiae*. García et al. [11] reported similar observations for Chardonnay wines. Regarding fermentation of musts with a high concentration of sugar, it has been reported that the use of *T. delbrueckii* and *S. cerevisiae* reduced the volatile acidity and improved the analytical profile of the wine [12]. Also, the combined use of *Debaryomyces vanriji* and *S. cerevisiae* increased the concentration of geraniol [13]. An increase in varietal thiols was observed in cofermentation with *Pichia kluyveri* and *S. cerevisiae* [14]. Clemente-Jimenez et al. [15], using sequential inoculum of *Pichia fermentans* and *S. cerevisiae,* observed an increase in the concentration of specific aromatic

These results show that there is a huge potential for the application of non-*Saccharomyces* yeasts in oenology and strong evidence that their use contributes to the production of specific volatile compounds improving the aromatic composition

**72**

components.

of wines (**Table 1**).


#### **Table 1.**

*Metabolites produced in wine by non-*Saccharomyces *yeasts in mixed fermentations compared to fermentations with* S. cerevisiae*.*
