The study had two aims: 1 - To evaluate hybrid yeast strains from the Nietvoorbij culture collection for their ability to enhance volatile thiols and produce low volatile acidity, and 2 - To investigate the expression of wine yeast proteins and to determine if regulated proteins correlate with metabolites released. This article summary will focus on the first objective of the study.
Basic project layout:
- Fifteen hybrid strains (Saccharomyces intra-genus) were compared with six commercial wine yeast strains: Anchor VIN 7, Anchor VIN 13, Anchor N96, Zymaflore X5, Zymaflore VL3 and Fermicru 4F9.
- Fermentations were conducted in 21.9°Balling S. blanc juice in stainless steel canisters.
- Samples were taken every 48 hours during fermentation for basic chemical analysis.
- Volatile aroma compounds were identified and measured by GC and GC-MS/MS.
- Wines were sensorially evaluated by a 14 member expert panel.
The project delivered many results but only some are highlighted here:
- In this trial all 21 yeast strains produced VA levels that comply with legislation.
- None of the strains produced undesirable characteristics in sensory evaluation.
- Several of the hybrids produced 3MH and 3MHA concentrations higher than the commercial yeasts.
- Finally six new hybrid strains were identified as high tropical fruit aroma (thiol enhancing) and low VA producing strains.
- Hybrid NH 56 was identified as the most promising strain for commercialisation as it produced the second highest concentration of volatile thiols of all strains tested, but the lowest volatile acidity of experimental hybrids tested.
Significance of the study:
Six new strains have been identified for possible commercialisation for the production of aromatic white wines.
Hart, R.S., Ndimba, B.K., Jolly, N.P. (2017) Characterisation of thiol-releasing and lower volatile acidity-forming intra-genus hybrid yeast strains for Sauvignon blanc wine. S. Afr. Enol. Vitic., Vol. 38, No. 2