Why Does Matcha Powder Oxidize and Change Color Easily?

Matcha powder is prone to oxidation and color change primarily due to the following reasons:

• Instability of Chlorophyll: Matcha is rich in chlorophyll (the green pigment), which readily undergoes oxidation when exposed to oxygen, light, or high temperatures. This causes the molecule to degrade, turning the color from vibrant green to brown or yellow.

• Oxidation of Catechins: Although catechins in matcha (such as EGCG) possess antioxidant properties, they themselves are easily oxidized. This forms quinone compounds, which appear yellow or brown, altering the overall color.

• Enzymatic Reactions: If enzymes (like polyphenol oxidase) are not sufficiently inactivated by heat during processing, residual enzymes can catalyze the oxidation of tea polyphenols, accelerating the discoloration process.

• High Surface Area Exposure: Matcha powder is a fine powder with a large surface area, allowing greater exposure to air. This facilitates oxygen penetration and promotes oxidation reactions.

• Accelerating Environmental Factors: Light (particularly UV rays), high temperatures, and high humidity significantly increase the oxidation rate. For example, UV light directly breaks down chlorophyll, while elevated humidity and temperature accelerate chemical reactions.

To slow oxidation, it is recommended to store matcha powder sealed in a cool, dry, dark place and minimize exposure time.