PLANT COOKING PRACTICE
We described earlier what happens to the vegetables color and texture when they are cooked. Now, we will cover the essential techniques of cooking and provide advice on how to become more successful with vegetables.
Water is the main medium in which we cook vegetables. Boiling water, either when we immerse the veggies in it, or if we use it to steam the vegetables, has a high temperature and strikes quickly through the plants. This is desirable to avoid prolonged exposure to the lower temperatures that have a negative effect on color and texture. So, simply use boiling water to cook vegetables. However, you need to make some adjustments - first of all, add enough salt to the water (around 30 g/1 oz per liter/quart) so the veggies cook faster and don't lose too much of their own minerals. You should also avoid any acidic ingredient in the water. Make sure that the water is neutral or slightly alkaline. All these points in mind, the vegetables will be cooked in a few minutes. And once they are cooked, either serve them immediately or plunge them into ice water for a short moment to stop short the cooking process that will make them too soft.
Cooking with boiling water is good for most vegetables, but not for all. Veggies that have a lot of starch in them (e.g. potatoes) fare much better when cooked in lower temperatures, that is when they are simmered in hot water. The reason is that too hot a water will quickly cook the outer part of the vegetable and make it very soft and disrupted, while the inner part is still about to be cooked. Maybe you know the feeling when you stick a fork into a potato that has boiled in water for a while? First you feel that the potato is soft and "cooked" but as you get deeper into the potato you notice how hard the inner core is. That's why you should cook them in simmering water, starting from the cold water that is, and raise the temperature gently. Also, omit the salt so they don't cook too quickly. Cooking at 80 C/180 F or so is enough, and even though it takes longer time the result will be very satisfactory.
Another popular way of cooking vegetables is by baking them in the oven. This process takes longer time because the hot air is much less efficient heat conductor, and the evaporation of the water from the veggies further cools them down. This water evaporation is also a good thing if you want to concentrate the flavor of the vegetable. Another nice thing about ovens is that you can heat them up more than water, and trigger chemical reactions between flavor molecules, which will create additional flavors in the veggies. To speed up the cooking process and creation of brown crispy surfaces you can not only raise the heat but also coat the vegetables in oil. Oil will provide a barrier against escape of water molecules from the veggies, and also get hot and add to the browning effect and flavor.
Oil or fat can also be used on a hot pan. We're talking about sweating, sautéing, and stir-frying vegetables. These three forms of cooking reflect the different oil temperatures used, from bottom to top. Sweating is slow and low temperature cooking which extracts the juices from the vegetables into oil, without browning them. This is a basic technique for making many dishes where veggies are meant to provide flavor for the liquid or other ingredients. sautéing is done at moderate heat and makes the vegetables lightly browned after a while. A substantial flavor extraction also occurs prior to browning. Stir-frying is quick cooking at high heat, with quick browning, which necessiates smaller cuts of vegetables just to let them cook through before the browning effect gets too advanced (read: burns!).