Bioprotection in the early stages of fermentation

One of the alternatives to SO₂ as an antimicrobial is the use of bioprotection yeasts, which colonise the medium preventing the proliferation of undesirable microorganisms. In this work, the bioprotective effect of a mixed inoculum formed by Torulaspora delbrueckii/Lachancea thermotolerans during fermentation was evaluated. The results showed a bioprotective effect of the non-Saccharomyces (NS) mixed inoculum comparable to that of SO₂ in the control of populations of lactic acid bacteria and acetic acid bacteria in the early stages of fermentation. In the case of yeasts, the addition of the NS inoculum allowed the control of the proliferation of indigenous apiculate yeasts such as Hanseniaspora uvarum, which can lead to defects in wine. In previous studies, this inoculum had shown the ability to improve certain parameters related to the quality of red wine. With this study, it was shown that it can also exert an antimicrobial activity similar to that of SO₂ in non-sulphite vinifications.

Figure: Proportion of yeast species at 24 h after vatting in the in the different inoculation strategies (SS: spontaneous sulfite, S: spontaneous without SO₂, TL: inoculation with T. delbrueckii/L. thermotolerans at vatting without SO₂). The main species found in the TL samples was L. thermotolerans, one of the yeasts present in the inoculum, followed by those present in the spontaneous fermentations, H. uvarum and Candida zemplinina, and finally, T. delbrueckii, the other species that was part of the mixed inoculum. In wines made with the non-Saccharomyces-mixed inoculum, a significant reduction in the proportion of H. uvarum was observed. Some studies have shown the production of high levels of ethyl acetate and acetic acid by indigenous apiculate yeasts during the early stages of fermentation, therefore, the reduction of the population achieved with the inoculation would be positive in terms of its bioprotective effect.

REFERENCE
Escribano-Viana, R.; González-Arenzana, L.; Garijo, P.; Fernández, L.; López, R.; Santamaría, P.; Gutiérrez, A.R. Bioprotective Effect of a Torulaspora delbrueckii/Lachancea thermotolerans-Mixed Inoculum in Red Winemaking. Fermentation 2022, 8, 337. https://doi.org/10.3390/fermentation8070337