For the first time, researchers have successfully developed and commercialised yeast strains that overproduce "floral" and "rose" aroma compounds at concentrations that can shape wine styles.
The research is exciting because it means winemakers can "dial up" desirable floral and rose aromas as-needed and create consumer-driven floral characteristics in newer wine styles.
Winemakers have access to a wide range of commercial yeast strains with substantial variation in their capacity to influence wine style. Most of that variation is due to a complex interplay between many compounds. There are a few examples where a single compound underpins a flavour attribute. Rose aroma is one of those. Its intensity in wine is predominantly associated with the concentration of the yeast-derived compounds 2-phenylethanol (2-PE) and 2-phenylethyl acetate (2-PEA).
As a part of ongoing yeast strain development project funded by Wine Australias at the Australian Wine Research Institute (AWRI), Research Scientist Dr Toni Cordente has generated more than 40 non-genetically modified (non-GM) yeasts that produce high concentrations of these "rose" aroma compounds.
Three of these "rose" yeasts were trialled over four vintages to assess varietal wines compatible with enhanced "rose" aroma characteristics, including white, rosé, red and sparkling wines. By selecting "rose" yeasts that produced different amounts of 2-PE and 2-PEA (moderate and high), it was possible to fine-tune concentrations for specific wine styles.
“We found that regardless of the style of wine, the ‘rose’ yeast produced significantly higher concentrations of 2-PE than prevailing commercially available strains,” said chief investigator Dr Simon Schmidt, Research Manager at AWRI.
The "rose" yeasts produced between 2 and 15 times more 2-PE than the control strain, depending on the grape variety assessed and well above its sensory threshold (10 mg/L). Similar increases were also observed for 2-PEA, which has an even lower sensory threshold (0.25 mg/L).
“The good news is that one of these strains is now commercially available under the name ‘AWRI Rosa’. The yeast is mainly suited to white varieties such as Pinot Gris, Riesling, Chardonnay, Colombard and Semillon, and makes floral and rose aroma compounds at concentrations that can significantly affect wine style,” said Simon.
“This provides winemakers with another tool to help them shape wine style and to find the balance of flavours their consumers are seeking.”
