Interactions between caffeic and caftaric acids, furan-derived aroma compounds, and chitosan during base wine ageing

Abstract

During sparkling wine ageing, chemical changes take place that alter the composition of the wine, creating nutty, roasted, and caramel aromas and flavours not previously detected in young wines. Furan-derived aroma compounds, a group of odor-active chemicals formed during the long-term storage of wine, contribute to these empyreumatic aroma changes. Hydroxycinnamic acids (HCAs) such as caffeic and caftaric acid, known to be responsible for oxidative browning in wine, also influence the formation of furan-derivative aroma compounds in model wine solutions. Additionally, sparkling wine research using chitosan has been shown to influence the formation of furfural, a furan-derivative thought to contribute a caramel aroma to aged wine. This project had three aims: To determine (1) the impact caffeic and caftaric acid have on furan-derived compound formation during base wine storage, (2) the ability of mushroom-derived chitosan to reduce caffeic and caftaric acid concentrations in Pinot noir juice, and (3) to establish whether chitosan added to base wine influences the generation of furan-derived aroma compounds during storage. For Aim 1, Chardonnay (2019) base wine was stored at 15 and 30 °C for 90 days with additions of fructose, caffeic acid, and caftaric acid independently, or in combinations. Results showed that at 15 and 30 °C, furfural increased slightly with 5 mg/L additions of caffeic and caftaric acid. For Aim 2, Pinot noir juice (2021) was stored at 10 °C for 18 hours with 1 g/L additions of < 3 kDa, 250 kDa, and 422 kDa molecular weight (MW) chitosan, before being racked off prior to fermentation. In the finished wine, < 3 kDa chitosan treatment decreased caftaric acid and increased the amino acids, while the 250 kDa chitosan decreased total HCA estimation, turbidity, and brown pigmentation compared to the control. For Aim 3, Pinot noir (2021) base wine was stored at 15 and 30 °C for 90 days with the aforementioned chitosan treatments. All three MW chitosan treatments at 30 °C substantially increased furfural, homofuraneol, and 5-methylfurfural generation relative to the control. At 15 °C, furfural and homofuraneol were also found at greater concentrations in the chitosan-treated wine. Overall results show (1) Slight modulation of furan-derived compounds due to increased caffeic and caftaric acid concentrations, (2) The reduction of caftaric acid by a low MW chitosan prior to fermentation, and (3) An increase in furan-derived compounds in base wine treated with chitosan during short-term storage. The findings of this thesis determined for the first time the influence of HCAs and chitosan on the concentrations of aroma and flavour compounds, with real applications into the acceleration of ageing in sparkling wines.