How does blanching vegetables preserve their color and nutrients?

Blanching involves briefly submerging vegetables in boiling water then immediately cooling them in ice water. The heat deactivates enzymes, particularly peroxidase and catalase, that would otherwise break down chlorophyll and other pigments over time. By stopping these enzymes quickly, the bright green or vivid colors are locked in rather than fading to dull browns and yellows. For nutrients, the process is a tradeoff. The short cooking time minimizes leaching of water-soluble vitamins like vitamin C and B vitamins compared to prolonged cooking. The rapid cooling also halts any further heat degradation. However, some nutrient loss does occur, so the key is keeping blanching times brief, typically one to three minutes depending on the vegetable, to balance enzyme deactivation against nutrient preservation.