Bioprotective non-Saccharomyces yeast as an alternative to sulfites for the winemaking process

Abstract

Sulfur dioxide (SO2) is used in winemaking due of its antioxidant, antioxydasic and antiseptic properties. Excessive amount of SO2 can negatively impact wine sensory perception and be detrimental for health. Agri-food industries are more transparent towards consumers concerning addition of sulfites, and oenology is no exception in this clairvoyance. As a consequence, the increase of consumers preference for wine with low or absent of sulfites addition is notorious. In this context, the impact of low/zero sulfites winemaking process on the microbial community should be evaluated. Moreover, microbial agents corresponding to bioprotective cultures represent a growing interest as an alternative to sulfites preservation in the early stages of vinification. However, scientific studies conducted to demonstrate their real effect are almost rare. 

The aim of this study was to evaluate the bioprotection efficiency of non-Saccharomyces yeasts as an alternative to the antimicrobial effect of SO2. Experiments at different scales (winery, semi-industrial and laboratory) were implemented during two consecutive vintages. Three different treatments: without SO2, with SO2 and bioprotection (mix of Torulaspora delbrueckii (Td) and Metchnikowia pulcherrima (Mp)) were compared. Population dynamics of targeted microorganisms (Td, Mp, acetic acid and lactic acid bacteria and Hanseniaspora spp.) were monitored by qPCR throughout the pre-fermentary stages and the alcoholic fermentation. In a second step, biodiversity of the fungi community was evaluated by high-throughput 18S sequencing using the Illumina MiSeq. qPCR data confirmed that the implantation of the bioprotection non-Saccharomyces was effective in all treatments and no significant effect on Hanseniaspora spp. population was found. However, a negative effect on the population levels of acetic acid bacteria was showned during the prefermentary stages, higher than sulfiting. Regarding the diversity indices, lower values were obtained for the bioprotection modalities compared with the others, which correlates well with the population dynamics observed previously. Bioprotective cultures seem to represent a promising alternative to SO2 for niche occupation during the early stage of the winemaking process.