On the impact of preformed α-dicarbonyls in the production of Strecker aldehydes. Exploring the addition of sacrificial amino acids as a tool to reduce Strecker aldehydes production

Abstract

The reaction between Strecker amino acids and α-dicarbonyls is a key pathway in the formation of Strecker aldehydes (SA), which are crucial oxidation-related odorants in wine [1]. While most α-dicarbonyls result from phenolic compound oxidation, others, such as diacetyl and methylglyoxal, are present in wine regardless oxidation and their role in SA production is not well understood. Additionally, the influence of specific metal ions on SA production via these preformed dicarbonyls remains unclear. Meanwhile, strategies to reduce SA formation based on the addition of naturally-occurring amino acids in wine that could deplete those α-dicarbonyls reacting in Strecker reaction would be promising which is particularly relevant in the context of the growing demand for minimal-intervention wines.

For this purpose, several accelerated oxidation procedures were applied in both synthetic and real wine matrices to analyse the reaction rates of diacetyl and methylglyoxal in anoxic conditions, evaluate the impact of Mn²⁺, Cu²⁺ and Fe²⁺ on their reactivity as well as to compare them with quinones formed from 4-methylcatechol and gallic acid. In the meanwhile, the reduction of SA by the addition of sacrificial amino acids was explored for alanine, tyrosine, aspartic acid, glutamic acid, serine, glycine, and threonine.

In synthetic wine under anoxic conditions, the reaction rates of diacetyl and methylglyoxal are significantly enhanced by Mn²⁺ (p<0.05), while Cu²⁺ has no effect. However, the production of SA from these compounds is still 2-3 orders of magnitude lower compared to phenolic-derived α-dicarbonyls, even when reactivity is higher in real wine. The addition of specific sacrificial amino acids to real wine results in small, but significant (p<0.05), changes in SA production.

Key findings of this research on SA production by preformed α-dicarbonyls include: first, these dicarbonyls are less reactive than those formed from phenolic compounds; secondly, their reactivity increases significantly in real wine, indicating substantial SA production even under anoxic conditions; finally, their reactivity can be influenced by metal ions in ways that differ from phenolic compounds.

References

[1] Bueno, M., Marrufo-Curtido, A., Carrascón, V., Fernández-Zurbano,P., Escudero, A. & Ferreira, V. (2018). Frontiers in Chemistry, 6(1).