STATISTICAL COMPARISON OF GROWTH PARAMETERS OF NINE BIOPROTECTION STRAINS IMPLEMENTED ON ARTIFICIALLY CONTAMINATED SYNTHETIC MUST
In recent years, consumer demand for products without chemical additives increased, becoming a priority for the wine sector. SO₂ is widely used for its multiple properties including antiseptics, antioxidants and antioxidasics and the strategy of bioprotection in winemaking represents now an alternative to this chemical additive. In oenology, results have highlighted the interest of bioprotection to limit the development of microorganisms like Hanseniaspora uvarum and thus reduce the doses of sulphite. Indeed, this species is considered because of its acetic acid and methyl butyl acetate production, the latter can cover the varietal character of wines.
Previous data sled to the development of a bioprotection concept based more specifically on the principle of early yeasting (pre-fermentation phases). In recent years, non-Saccharomyces yeasts have seen a resurgence of interest. Today, some of these strains are commercialized, such as Torulaspora delbrueckii, Metschnikowia pulcherrima or Lachancea thermotolerans. The antimicrobial effect may be linked to interaction mechanisms between microorganisms, including competition for nutrients and the production of inhibitory compounds. Therefore, the mechanisms involved, their mode of action and their effectiveness according to the technical constraints of winemaking process, more particularly at pre-fermentation stage conducted at low temperature, have yet to be explored. The experiments presented here involve 9 bioprotection strains (3 T. delbrueckii, 3 Metschnikowia sp. and 3 L. thermotolerans) grown on synthetic must artificially contaminated at different population levels (5.104 or 5.106 UFC/mL) with a mix of Hanseniaspora sp. strains. The growth parameters of all the strains characterized at 20°C were compared to those obtained at 12°C. This comparison underlined a negative effect on some bioprotectants, independently of the genus and species tested. Growth monitoring in coculture at 12°C showed that when the rate of contamination of the medium is higher than the rate of inoculation of bioprotectants, none of the bioprotection strains reach a biomass equivalent to that of the Hanseniaspora mix. Nevertheless, for lower contamination, two strains of M. pulcherrima and M. fructicola had a negative impact on the development of Hanseniaspora. The analysis of the amino acid consumption of the different strains tested could explain the different behaviors observed.
Issue: OENO Macrowine 2023
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bioprotection, pre-fermentation maceration, non-Saccharomyces yeasts