Radical (Free radical)
Radical
Japanese: ラジカル（フリーラジカル）
An extremely reactive molecule or atom with an unpaired electron. A type of ROS that directly causes oxidative cell damage.
A radical is a molecule or atom with an unpaired electron. The unpaired electron seeks stability by stealing electrons from surrounding molecules, triggering chain oxidation reactions. Among ROS, the hydroxyl radical (·OH) is the most reactive, oxidizing almost any molecule it encounters near-instantaneously.
In food contexts, lipid radical chain reactions (autoxidation) are a major cause of quality deterioration. The 'stale oil' flavor in miso occurs when its lipids undergo this reaction.
Antioxidants donate their own electrons to radicals, breaking the chain reaction—hence vitamin E and melanoidins are called 'radical scavengers.' The antioxidant power of fermented foods wages a quiet battle against radicals within the food itself.