Quinones as Strecker degradation reagents in wine oxidation processes

Area of Science:

• Food Chemistry
• Wine Chemistry
• Organic Chemistry

Background:

• Strecker aldehydes are key aroma compounds in wine.
• Polyphenols, such as gallic acid, caffeic acid, and (+)-catechin, are abundant in wine.
• Ortho-quinones derived from polyphenols can react with amino acids.

Purpose of the Study:

• To investigate the formation of Strecker aldehydes from the reaction of α-amino acids with gallic acid, caffeic acid, and (+)-catechin ortho-quinones.
• To quantify the amount of phenylacetaldehyde formed in a wine-model system.
• To elucidate the intermediate structures formed during these reactions.

Main Methods:

• Wine-model systems were used to simulate wine conditions.
• Reactions involved α-amino acids (phenylalanine or methionine) and ortho-quinones of gallic acid, caffeic acid, or (+)-catechin.
• Phenylacetaldehyde quantification was performed over 10 days.
• Mass spectrometry (MSn) was used to identify intermediate structures.

Main Results:

• Phenylacetaldehyde was formed via quinone intermediates at wine pH.
• (+)-Catechin yielded the highest amounts of phenylacetaldehyde (69±5µg/L/day), followed by gallic acid (61±4µg/L/day) and caffeic acid (41±4µg/L/day).
• Intermediate structures were successfully identified using MSn.

Conclusions:

• Polyphenols in wine can contribute to Strecker aldehyde formation through reactions with amino acids.
• The type of polyphenol significantly influences the amount of phenylacetaldehyde produced.
• Understanding these reactions provides insight into wine aroma development and potential off-flavors.