Abstract
In oenology, the utilization of mixed starter cultures composed by Saccharomyces and non-Saccharomyces yeasts is an approach of growing importance for winemakers in order to enhance sensory quality and complexity of the final product without compromising the general quality and safety of the oenological products. In fact, several non-Saccharomyces yeasts are already commercialized as oenological starter cultures to be used in combination with Saccharomyces cerevisiae, while several others are the subject of various studies to evaluate their application. Our aim, in this study was to assess, for the first time, the oenological potential of H. uvarum in mixed cultures (co-inoculation) and sequential inoculation with S. cerevisiae for industrial wine production. Three previously characterized H. uvarum strains were separately used as multi-starter together with an autochthonous S. cerevisiae starter culture in lab-scale micro-vinification trials. On the basis of microbial development, fermentation kinetics and secondary compounds formation, the strain H. uvarum ITEM8795 was further selected and it was co- and sequentially inoculated, jointly with the S. cerevisiae starter, in a pilot scale wine production. The fermentation course and the quality of final product indicated that the co-inoculation was the better performing modality of inoculum. The above results were finally validated by performing an industrial scale vinification The mixed starter was able to successfully dominate the different stages of the fermentation process and the H. uvarum strain ITEM8795 contributed to increasing the wine organoleptic quality and to simultaneously reduce the volatile acidity. At the best of our knowledge, the present report is the first study regarding the utilization of a selected H. uvarum strain in multi-starter inoculation with S. cerevisiae for the industrial production of a wine. In addition, we demonstrated, at an industrial scale, the importance of non-Saccharomyces in the design of tailored starter cultures for typical wines.
Highlights
Fermentation associated with wine production represents complex biological processes denoted by several biochemical interactions between grape must and different micro-organisms such as fungi, yeasts and bacteria (Fleet, 2003)
The growth dynamics of the H. uvarum strains were comparable in the tests when the inoculum ratio were equivalent to 100:1 and 10.000:1, i.e., the S. cerevisiae starter inoculated at 105 and 103 CFU/mL, which reached a concentration of 107 CFU/mL respectively after 7 and 15 days
When the S. cerevisiae strain was inoculated at 107 CFU/mL the non-Saccharomyces cell concentration declined after 5 days
Summary
Fermentation associated with wine production represents complex biological processes denoted by several biochemical interactions between grape must and different micro-organisms such as fungi, yeasts and bacteria (Fleet, 2003). The AF is initially promoted by the action of a heterogeneous consortium of yeasts belonging to different non-Saccharomyces species usually characterized by a low fermentative power (Heard and Fleet, 1985), while its final step is under the control of alcohol-tolerant Saccharomyces cerevisiae strains (Fleet and Heard, 1993). Autochthonous yeasts provide distinctive regional features to wines (Romano et al, 2003; Fleet, 2008; Ciani et al, 2010; Medina et al, 2013; Garofalo et al, 2015) advising their use as commercial starter cultures in order to differentiate wine productions. Some non-Saccharomyces yeasts are already commercialized as oenological starter cultures (e.g., Torulaspora delbrueckii, Metschnikowia pulcherrima, Pichia kluyveri, Lachancea thermotolerans) to be used in combination with Saccharomyces cerevisiae (Lu et al, 2015), while several others are the subject of various studies (e.g., Hanseniaspora uvarum, Starmerella bacillaris) (Masneuf-Pomarede et al, 2016)
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