Enzymatic vs non-enzymatic oxidation in wine is best described by which statement?

• A. Enzymatic oxidation involves oxidative enzymes from damaged tissue
• B. Non-enzymatic oxidation occurs via microbial action
• C. Enzymatic oxidation occurs only in red wines
• D. Non-enzymatic oxidation is a chemical reaction with oxygen

Answer: (D)

Oxidation in wine can occur through two routes: enzymatic and non-enzymatic. The non-enzymatic path is simply a chemical reaction with dissolved oxygen. Oxygen reacts with compounds in the wine, such as phenolics and ethanol, often with trace metal catalysts, leading to changes like browning, acetaldehyde formation, and off-flavors. This description captures the core way oxidation happens in the wine matrix without invoking enzymes.

Enzymatic oxidation would require active oxidative enzymes (for example, from grape tissue) to catalyze the reaction, which is less representative of what dominates oxidation in finished wine. Microbial action involves living organisms metabolizing compounds, not just a direct chemical reaction with oxygen. And enzymatic oxidation is not limited to red wines; white wines can oxidize through the same non-enzymatic chemical pathways, while enzymatic routes, if present, depend on tissue damage and enzyme release.