Microbiological Impact of Different Inoculation Timings of a Dry Yeast during Winemaking; E2U Direct Pitching
Arnaud Delaherche,* Anne Flesch, and Etienne Dorignac *Fermentis, division of SI Lesaffre, 137 Rue Gabriel Péri, 59700 Marcq-en-Baroeul, France (i.vanmierlo@fermentis.lesaffre.com)
Modern industrial winemaking is based on the use of wine specialized Saccharomyces cerevisiae starter cultures. Commercial wine strains guarantee stability and reproducibility. In this work, two modes of yeast inoculation were studied: bioprotection mode on grapes or during prefermentation operations and conventional modes, including direct pitching after settling. Regarding the times of pitching, four times were tested: (i) directly on the grapes in the reception buckets, (ii) in the juice after crushing, (iii) pressing, or (iv) into the juice after crushing and settling. For the conventional modes, four timings were studied: (v) direct inoculation into the juice just after settling and temperature rise, and (vi) rehydrated in room temperature water and with gradual acclimatization after settling and temperature rise. In bioprotection modes, HD A54 could be inoculated onto grapes and during prefermentation phases only if the temperature was cool controlled (<10°C) to slow down the onset of alcoholic fermentation and avoid settling issues. HD A54 yeast also inhibited development of non-Saccharomyces and S. cerevisiae yeasts when inoculated at 20 g/hL before pressing. It then develops best and starts alcoholic fermentation faster when inoculated after pressing. In conventional modes and highly indigenous microflora-loaded must, we showed that E2U-processed HD A54 yeast could be inoculated immediately after cold settling into the must or after temperature rise-up without any implantation and fermentation issues. It also fully showed its particular aromatic and organoleptic profile (especially extreme amylic notes). When inoculated with prior rehydration or acclimatization, implantation issues have been encountered, leading to deviant profiles. This study showed that for certain yeast strains, E2U technology combined with early inoculation timing could guarantee the achievement of the targeted wine type.
Funding Support: Fermentis, division of SI Lesaffre
