why does vegetables change color after cooking?

Answer 1

Some veggies will "fade" in color when boiled or roasted. The boiling process contrubutes several factors that could effect color such as ph of the water and oxidation of certain acids in foods. The methods of cooking which are performed at a higher temperature will change the level of pH more drastically, because the denaturization of the proteins will be increased. Most likely, as the temperature rises, the pH will lower, and the lower the level of pH, or the higher the acidity, the more the pigment will lose its natural color.

The best way to cook fresh veggies so as not to effect color would be to steam them. I do it in the microwave which used the least amount of water possible. I always have brightly colored veggies with this method.

Answer 2

The purple vegetables (red onions and purple cabbage) tend to change and become lighter almost a blue color as they cook. Although the skin of an eggplant tends to stay that deep aubergine color.

The reason they cange is that the compound (anthocyanin) that gives the cabbage the red / purple color reacts with alkaline substances. Tap water is often full of alkaline minerals such as lime. Sometimes adding about 1 teaspoon of acidic agent, such as lemon juice, vinegar, or wine, to the pot when using tap water to cook your red / purple cabbage may bring back the original color.

Answer 3

What vegetables are you talking about specifically? I've never seen it happen. All the veggies I've cooked stay the same color after cooking as they were before. Carrots stay orange, corn stays yellow, broccoli, spinach, green beans, Brussels sprouts, cabbage all stay green, cauliflower stays white. Zucchini stays green or yellow, depending on the type. I've never seen a vegetable change color, so I'm interested in what you're cooking and how you're cooking it.

Please expand on your question with more info.

Answer 4

The main reason is that they are over cooked.