Zygotorulaspora florentina and Starmerella bacillaris in multistarter fermentation with Saccharomyces cerevisiae to reduce volatile acidity of high sugar musts L. LENCIONI 1 , M. TACCARI 1,2 , M. CIANI 2 and P. DOMIZIO 1 1 Dipartimento di Gestione dei Sistemi Agrari, Alimentari e Forestali, Università degli Studi di Firenze, 50144 Florence, Italy 2 Dipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, 60131 Ancona, Italy Corresponding author: Dr Paola Domizio, email paola.domizio@unifi.it Abstract Background and Aims: The possibility to decrease wine volatile acidity (VA) is an important aspect in wine production. This applies in particular to wines that are produced from musts with high sugar concentration, where the osmotic pressure promotes an increase in acetic acid production by Saccharomyces cerevisiae. This study aimed to identify suitable yeast strains and fermentation temperature to undertake the alcoholic fermentation of high sugar musts. Methods and Results: To lower VA during fermentation of high sugar musts, two non-Saccharomyces yeast strains, Zygotor- ulaspora florentina and Starmerella bacillaris, were used in multistarter fermentations with S. cerevisiae at a fermentation tem- perature of 14 and 20  C. The fermentation temperature influenced the yeast behaviour and the composition of the two mixed fermentations. Conclusions: Independent of fermentation temperature, the mixed fermentations with Z. florentina performed best to reduce VA. Significance of the Study: Mixed fermentations with the non-Saccharomyces yeast strains Z. florentina and S. bacillaris may represent a valuable approach for the fermentation of high sugar musts. Keywords: high sugar must, mixed fermentation, non-Saccharomyces yeast, Starmerella bacillaris, Zygotorulaspora florentina Introduction Alcoholic fermentation of high sugar must by Saccharomyces cerevisiae is often associated with the production of a high concentration of acetic acid (Erasmus et al. 2003, 2004). Indeed, up-regulation of the genes encoding aldehyde dehy- drogenases and the subsequent increase in acetic acid pro- duction have been reported for Saccharomyces yeast in response to osmotic stress conditions (Hohmann 2002, Eras- mus et al. 2004). High acetic acid concentration can have a considerable impact on the quality of a wine, as this imparts a vinegar-like character. Thus, depending on the type of wine, the concentration of volatile acidity (VA) might exceed the European Economic Community legal limit that is spe- cific for each type of wine. In this context, mixed fermenta- tion with Saccharomyces and Starmerella bacillaris (synonym Candida zemplinina) (Rantsiou et al. 2012) or Torulaspora del- brueckii (Bely et al. 2008) has been proposed for the fermen- tation of high sugar musts, to reduce the VA of the resulting wines. Such reduction in VA has been explained mainly as a consequence of the osmophilic characters of these non-Sac- charomyces yeasts. Therefore, they might be suitable for the initial stages of multistarter fermentation, to lower the sugar concentration of the must, to make it more suitable for sub- sequent fermentation by S. cerevisiae. Several authors have highlighted that non-Saccharomyces yeasts in mixed fermentation can strongly impact the sen- sory features of the wines. Most of the non-Saccharomyces yeasts are able to produce a wide range of hydrolytic enzymes, involved in the release of aromatic compounds from grape precursors, to produce a high concentration of interesting esters, such as isoamyl acetate (banana-like aroma) and 2-phenyl-ethyl acetate (rose-like aroma), and to release a high quantity of mannoproteins, which have many positive oenological properties (Viana et al. 2008, Ciani et al. 2010, Andorrà et al. 2012, Sadoudi et al. 2012, Domi- zio et al. 2014, 2017). Strains belonging to S. bacillaris have been shown to have a strong fructophilic character, and to be characterised by the production of a low concentration of ethanol and acetic acid and a high concentration of glycerol (Sipiczki 2003, Magyar and Tóth 2011, Tofalo et al. 2012, Englezos et al. 2015). In contrast, there have been few studies on Zygotorulaspora florentina yeast. In recent studies, Domizio et al. (2011) and Lencioni et al. (2016) used the Z. florentina #42 strain (formerly known as Zygosaccharomyces florentinus) in pure and mixed fermentations with S. cerevisiae of must with a standard level of sugar; they reported not only a reduction in VA but also an enhancement of the concentra- tion of polysaccharides, phenyl-ethyl acetate and 2-phenyl ethanol in wine. In the present study, the effect of temperature on the oenological performance of Z. florentina and S. bacillaris was evaluated during mixed fermentations with S. cerevisiae in high sugar musts, to assess their potential use for the pro- duction of some types of dessert wines, such as Vinsanto wine and similar wine styles that are not fortified. doi: 10.1111/ajgw.12327 © 2017 Australian Society of Viticulture and Oenology Inc. Lencioni et al. Multistarter fermentation of high sugar musts 1