Yeast nutrients, or yeast derivatives (YDs) as referred to in the referenced article, are widely used in winemaking to enhance fermentation, provide essential nutrients, and improve the sensory qualities of wine. These commercial products are derived from yeast colonies grown in bioreactors, inactivated, and dried. The compositional parameters of each product are highly influenced by the yeast strain used, the conditions in which the culture is grown and the manufacturing process itself. They serve multiple purposes in winemaking, including supplying nitrogen (N) to stimulate yeast growth and removing unwanted compounds. Since glucose is yeast’s primary carbon and energy source, agricultural byproducts such as molasses are often used to produce YDs.
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Atypical ageing (ATA) and its implications
Atypical ageing (ATA) is a notable defect in wine characterised by the rapid loss of desirable varietal aromas and the development of unpleasant odours, often described as naphthalene or dirty cloth. This defect is primarily caused by the oxidation of indole-3-acetic acid (IAA) to 2-aminoacetophenone (AAP), a compound responsible for the off-flavours associated with ATA. Since IAA is a plant hormone and YDs are often made from plant-derived materials, there is a concern that commercial YD formulations might contain precursors to AAP, potentially increasing the risk of ATA in wines.
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Study and findings
To investigate this hypothesis, a study was conducted to screen 28 different YD products for the presence of AAP-related compounds and their amino acid content. The study aimed to understand whether using YDs could increase AAP levels in wines.
Most of the samples under examination contained significant amounts of AAP-related compounds. Furthermore, great compositional variability was observed.
Fermentation experiments were carried out by adding varying amounts of two selected YD products (YD1 and YD2) to different grape musts, and the development of AAP was monitored. According to the specification sheet of the YDs, YD1 mainly constitutes yeast autolysate, and YD2 inactivated yeast. YD1 enhanced the AAP levels in wines dose-dependently, while YD2 diminished them. The yeast cell walls in YD2 might have contributed to the adsorption of some of the compounds involved in ATA formation.
The use of YD1 at different concentrations (200, 400 and 600 mg/L) was associated with a 16%, 36% and 44% higher AAP content in the final wines. The opposite was observed for YD2 where there was an 8% decrease in the AAP content of the wine. Zero % represents no YD added. Refer to the original article for exact experimental layout. This image is republished in its original form as permitted by the open access policy of Oeno One.
Additionally, the study explored the effects of supplementing grape must with diammonium phosphate (DAP), another common nitrogen source. It was found that increasing doses of DAP did not significantly affect the accumulation of AAP, suggesting that nitrogen supplementation alone does not influence ATA development.
Practical implications for winemakers
These findings have important implications for winemakers and YD producers. While YDs are beneficial for their role in fermentation and wine stabilisation, their use must be carefully managed to avoid the risk of ATA. Winemakers must consider the specific type and formulation of YDs, as some may contain higher levels of AAP precursors. Moreover, the presence of cell walls in YDs might offer a protective effect by adsorbing unwanted compounds, thus reducing the risk of ATA.
Further research is needed to understand better the relationship between the raw materials used in YD production and the presence of ATA precursors in the final products. By identifying the factors contributing to AAP formation, YD producers can potentially develop formulations that minimise the risk of ATA while still providing the desired benefits in winemaking.
Reference
Delaiti, S., Nardin, T., Pedò, S., Larcher, R., Gallo, A., Cappello, N., & Roman, T. (2024). Impact of using yeast derivatives on the development of atypical aging in wines. OENO One, 58(2). https://doi.org/10.20870/oeno-one.2024.58.2.7939
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