According to culinary expert Vu Nhat Thong, director of Eric Vu Cooking Class, the initial water temperature when cooking produce directly affects the final dish quality. This critical decision hinges on the unique chemical properties and cellular structure of each food type.
Greens require boiling water
Green vegetables, such as water spinach, green beans, and broccoli, are rich in chlorophyll. Their cells naturally contain chlorophyllase, an enzyme that breaks down chlorophyll, causing the vegetables to lose their vibrant color.
This enzyme is most active between 60-75°C. If greens are placed in cold water and gradually heated, chlorophyllase has 3 to 5 minutes to degrade the chlorophyll, resulting in dull, yellowed vegetables. Submerging greens directly into 100°C boiling water immediately deactivates this enzyme, preserving their color.
For crisp, vibrant greens, plunge them immediately into an ice bath for 30-60 seconds after boiling. This rapid temperature drop halts the cooking process and causes the vegetable cells to contract quickly, maintaining their texture and color.
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Greens should be boiled in hot water, while tubers should be boiled in cold water. *Photo: AI* |
Starchy tubers cooked from cold water
For large, dense tubers such as potatoes, carrots, or white radish, cooking should always begin in cold water.
Cooking these tubers requires starch gelatinization, a process where starch absorbs water and swells with heat. Starting in cold water allows heat to penetrate gradually from the exterior to the core, ensuring even cooking. Conversely, adding them to boiling water causes the outer layer to cook and harden rapidly, impeding heat transfer to the center and leaving the interior undercooked.
Furthermore, a gradual increase in temperature helps carrots maintain their texture. This slow heating activates pectin methylesterase, an enzyme that reinforces cell walls, allowing carrots to become tender without turning mushy.
Sweet corn presents an exception. Unlike starchy tubers, corn on the cob should be cooked in boiling water to preserve its sweetness. The natural sugars in corn begin converting to starch soon after harvest. Rapid boiling minimizes heat exposure, maximizing the retention of these natural sugars.
Bao Nhien
