Enological Repercussions of Non-Saccharomyces Species 3.0

Innovations Using Non-Saccharomyces Species in Wine Biotechnology

The use of non-Saccharomyces in wine production has increased steadily since the commercial introduction of the first non-Saccharomyces strains produced as dry active yeasts at the beginning of the century by CHR Hansen and Lallemand (2004–2007) [1,2]. This is due to the development of the sensory profile and the complexity of the wines produced with these new species, as well as the commercial success of the first non-Saccharomyces strains. This third issue of the ‘Enological Repercussions of Non-Saccharomyces Species’ Special Issue in Fermentation features research from scientists from Europe, the United States, Australia, South Africa, Uruguay, Argentina, and Peru. Currently, the fourth edition is being held. Thank you to all the researchers and professors participating in these successful SIs.

The impact of non-Saccharomyces yeasts is based on the possibilities that they offer to modulate wine aroma [3,4], acidity and freshness [5], mouth feel [4,6], color [4], stability and bioprotection/biocontrol [6]. Moreover, they even facilitate an improvement in wine stability, a reduction in SO₂, the control of off-flavors [7] and biological ageing [4]. About 42 commercial products based on non-Saccharomyces are currently available, the majority of which are dried yeasts, primarily from the species Torulaspora delbrueckii, Lachancea thermotolerans, and Metschnikowia pulcherrima [3]. The selection of new non-Saccharomyces strains is increasing in these traditional species, but also in others with new potential applications, opening new opportunities in winemaking [8]. Some of them are now in use for special products such as sparkling wines [9] or for wines made from hybrid varieties [10].

Several publications in this SI on the modulation of wine scent have concentrated on the formation and release of fermentative esters [4,5,10,11], the effect of yeast enzymes on varietal aroma [5,12] and the protection of varietal compounds [10]. Some interesting volatiles with a positive impact on wine aroma include ethoxy-1-propanol [5], 2-phenylethyl, tryptophol and tyrosol acetates [4,11]. Particularly, when Hanseniaspora spp. are utilized, the increased content of these fermentative volatiles, as well as free terpenes, has been correlated with fruitier and more flowery sensory profiles [4,10,11].

The use of L. thermotolerans is a trend in current enology, and this species’ generation of lactic acid from carbohydrates is a powerful tool for regulating pH during fermentation [13]. It has been proven as a powerful biotechnology to substitute the use of chemical acidification in warm areas, while also having a favorable effect on wine aroma [5].

Many non-Saccharomyces have an influence on mouthfeel, producing full-bodied wines, even with low-structure white varieties. The use of apiculate yeast from Hanseniaspora spp. frequently produces better roundness and density in the mouth, which can be clearly observed when tasting after fermentation [4]. Furthermore, it has been noted that sparkling wines with base wines made from Metschnikowia pulcherrima have greater foamability and foam stability [9]. Glycerol is another component whose viscosity has an impact on the volume and softness of wine. The concentration of this polyalcohol is increased when non-Saccharomyces such as Starmerella bacillaris are used, which enhances the structure and mouthfeel of the wine [6]. Furthermore, as the production of glycerol is performed with sugars, some reduction in alcoholic degree can be expected, which is advantageous for warm-climate wines. The effects of stress such as osmotic pressure, ethanol and pH conditions in non-Saccharomyces have also been studied [14]. The better prepared species to grow under stress conditions are Lachancea fermentati, L. thermotolerans, and S. pombe [14], opening new applications for overripe grapes in warm areas.

The use of metagenomic tools is also a powerful and interesting way to map the microbial community that can be found in a winery, identify areas with a higher concentration of spoilage microorganisms, and manage specific sanitization procedures to eradicate these threats and their associated issues, such as wine alteration and off flavors [15]. With regard to Brettanomyces—a typical spoilage yeast—a very low relative abundance has been detected. The populations of Brettanomyces and Zygosaccharomyces that can be persistent in cellars can be reduced and controlled with the aid of these procedures. Bioprotection is another way of controlling yeasts in grapes or must fermentations that is a trend in current enology. Because of their interesting abilities in bioprotection, Picchia kluyveri and Candida pyralidae are two non-Saccharomyces yeasts that are frequently utilized [16]. Biochemical and engineering parameters have been studied to build stoichiometric models that aid in understanding yeast’s biochemical conversion when we are working with specific growth media derived from grape bioproducts.

As a summary, non-Saccharomyces offer new ways to improve wine quality and manage enological problems. This SI contains numerous advantageous applications for a number of non-Saccharomyces species.