WINETECH Technical Yearbook 2020

AIM OF THE STUDY The study investigated the preferences and order of uptake of nitrogen sources for various commercially available non- Saccharomyces yeasts. The influence on growth and fermentation kinetics, as well as aroma formation, was also investigated. The study was, however, restricted to major secondary aromas only (i.e. those arising from the metabolism of sugar and certain amino acids). It is important to note that for some of the yeasts mentioned in the study, the aim of their selection for commercialisation was not their fermentative performance, but rather their specific enzymatic activities or metabol isms. The study resul ts provide winemakers with insights into the nutritional dynamics of multi-yeast fermentations. EXPERIMENTAL LAYOUT Five commercial yeasts were used in the study: • EC 1118 – Saccharomyces cerevisiae (Lallemand). • Viniflora Frootzen – Pichia kluyveri (Chr. Hansen). • Biodi va TD291 – Torulaspora delbrueckii (Lallemand). • Flavia MP346 – Metschnikowia pulcherrima (Lallemand).

• Viniflora Concerto – Lachancea ther- motolerans (Chr. Hansen). Fermentations were performed in three different synthetic grape musts with a total YAN of 200 mg/L: • Treatment 1 – Amino acids in equal amounts of assimilable nitrogen levels plus ammonium. • Treatment 2 – Amino acids in equal amounts of assimilable nitrogen levels without ammonium. • Treatment 3 – Grape must-like nitro- gen concentrations. Pure culture fermentations of all five yeasts were conducted, as well as co-inoculation treatments, where EC 1118 was inoculated 48 hours after non-Sacch inoculation. An additional treatment included filtering out the non-Sacch yeasts before EC 1118 inoculation. MAIN RESULTS • In the pure culture fermentations, only EC 1118 fermented to dryness. • Nitrogen source uptake started before the onset of active growth for all strains. • EC 1118 had the highest CO 2 release (most active fermentation), followed by Concerto and Biodiva. • Ammonia did not affect CO 2 release. There were also no significant differ -

The utilisation of nitrogenous compounds by commercial non- Saccharomyces yeasts

NOVEMBER 2020

KARIEN O’KENNEDY: Winetech, Paarl KEYWORDS: non- Saccharomyces yeasts, nitrogen utilisation

WINETECH TECHNICAL YEARBOOK 2020 121