The term vegetable is not an officially defined technical term. It is commonly based on usage in the culinary environment and on cultural traditions, rather than on morphology. The botanical classification on the other hand is based on the variability among plants with regard to flower type, morphology, and sexual compatibility. For us to make the distinction among them, they are sub-divided into: algae and fungi; mosses and liverworts; ferns; and seed plants. Through usage, we add fungi and seed plants under the same term “vegetables” and it is on these latter two groups that our daily consumption within a plant-based diet is based.
A plant has two main components: the vegetative part and the reproductive part and both are edible. Parts such as leaves, stems, roots, etc. are considered vegetables and belong to the vegetative part. Parts such as pollinated flowers, which produce seeds for the next generation, are considered fruits and belong to the reproductive part.
Parts of vegetables
There are certain instances when fruits are referred to as vegetables, such as tomatoes, eggplants, cucumbers, bitter gourds, and okra, etc. These edible plant parts contain seeds and are therefore considered as fruits.
- Leaves and stems are low in carbs, and high in vitamins, minerals and fiber.
- Seeds are the structures containing embryos and stored food for the next generation of plants.
- Starchy roots and other underground plant parts are loaded with starch, and can contribute a lot of calories to a meal.
- Fruits are the structure that contain the seeds that plants produce.
Classification by edible part:
Note: The maximum steam cooking time is an approximation based on my own experience.
- Enlarged taproot: beets, carrots, radishes, celeriac, rutabaga, turnips, and salsify, among others.
(Maximum steam cooking time: 1-2 minutes, cut in thin slices or small cubes.)
- Enlarged lateral root: sweet potatoes and cassava.
(Maximum steam cooking time: 10-15 minutes, cut in thin slices or small cubes.)
- Above ground and not starchy: asparagus and kohlrabi.
(Maximum steam cooking time: 3 minutes; asparagus cut in small chunks and the kohlrabi either in thin slices or small cubes.)
- Below ground and starchy: yams, taro, white and Irish potatoes, Andean tubers, and Jerusalem artichokes.
(Maximum steam cooking time: 10 minutes, cut in thin slices or small cubes.)
- Onion group and leaf bases (except chives): onions, garlic, leeks, chives, shallots, and broad-leaved plants.
(Maximum steam cooking time: 1-2 minutes; cut in small cubes.)
- Salad use: lettuce, celery, cabbage, chicory, and endives.
(Maximum steam cooking time: 1-2 minutes; cut in thin slices or small cubes.)
- Cooked (may include tender stems in some cases): chard, mustard, kale, dandelions, Chinese cabbage, spinach, vegetable amaranth, chicory, cardoon, and rhubarb.
(Maximum steam cooking time: 1 – 1.5 minutes; cut in small pieces.)
- Immature flowers: globe artichokes, broccoli raab, cauliflower, and broccoli.
(Maximum steam cooking time: 2 – 3 minutes, separated from the stem and in small branches.)
- Immature: okra, sweetcorn, lima beans, chayote, peas, summer squash, cucumber, snap beans, broad beans, and eggplant.
(Maximum steam cooking time: 1-2 minutes; cut in thin slices or small cubes.)
- Mature: pumpkin, muskmelons, watermelons, pepper, tomatoes, and husk tomatoes.
(Maximum steam cooking time: 1 minute; cut in thin slices or small cubes.)
Composition of vegetables
- Vegetables are mostly made of water. Depending on their classification by edible part, the content of water and dry matter varies from 60% to 95% in total water, with the rest being dry matter.
- After water, the next most important component in vegetables is carbohydrate. This is present in the form of starch, sugars and dietary fiber. Starch is mainly found in storage organs and it needs to be broken down into sugars in order to provide energy to cells.
- The main sugars that are present are glucose, sucrose and fructose although not every product contains all three. The speed at which carbohydrates are absorbed by the body is defined by the glycemic index.
- Dietary fiber compounds include cellulose, lignin, pectin and other substances. These may be soluble or insoluble and cannot be readily broken down by the digestive system. Therefore, most of them are simply excreted.
- Protein is also found in vegetables in smaller amounts.
Vegetables: the best combination is to eat them steamed and raw
The importance of vegetables to the human body is determined by their complex chemical content, which includes organic substances (carbohydrates, lipids, proteins, and organic acids). Among these, the high content of vitamins (A, B complex, C, E, F, K, P, and PP) and the high content of minerals (Ca, Cl, Cu, Fe, K, Mg, P, S, and Zn) highlight their importance. Substances like phytoncides (essential aromatic, volatile oils that are excreted by plants and trees and have anti-bacterial and anti-fungal qualities for humans), anti-microbial and antioxidant properties, as well as fiber content complete the circle of reasons for having a high daily consumption of vegetables. To top these facts, steamed vegetables tend to retain more color and texture than through other types of cooking and it is easier to avoid overcooking.
The steaming process
Steaming helps us digest food without having to expend great amounts of energy in the process. It softens the cellulose fiber allowing us to chew it better and also breaks down the outer layers and cellular structures of many vegetables. Not only does this process increase the number of certain nutrients available to us within many vegetables, like carotenoids, antioxidants and lycopene (which are better digested if they have been heated), it also increases digestibility and improves the net-energy value of foods in those that contain fat-soluble vitamins such as A, E and K, which are more stable and fare better during steaming. After steaming such vegetables, serve them with a small amount of fat, otherwise, you won’t be able to absorb the fat-soluble vitamins in them.
It is true that steaming kills some vitamins and minerals in food, and denatures enzymes that aid digestion. For example, water-soluble vitamins such as B vitamins and vitamin C are often lost during many cooking processes because they leach out of vegetables into the cooking water. With steaming they are only lost up to 25%. Minerals like potassium, phosphorus, calcium, magnesium, iron, and zinc may be reduced by up to 60%. With steaming they are only reduced by half this amount, to 30%. However, steaming vegetables increases the body’s ability to absorb minerals and provides us with more antioxidants from many vegetables than when they are raw.
Tips to get the most benefits from steamed cruciferous vegetables and garlic
- Pre-chop them first and let them sit for 40 minutes before steaming. Add some mustard seeds or horseradish (both optional) for taste, and nutritional benefits, or a small amount of fresh, raw ones to the steamed ones.
- With garlic, crush or chop it and then wait 10 minutes before cooking. This creates a series of chemical reactions, first in the garlic and then in the body when we ingest it, that help the body fight bacteria and viruses.
- When steaming, leave skins on whenever possible. Many fruits and vegetables hold most of their antioxidants in their skins. Simply wash well before steaming or eating raw, and I recommend always eating organic.
How to steam vegetables correctly
Get the water up to the boil first when you want to steam vegetables, then add them. Steaming times will vary depending on the size and texture of the vegetable. Usually, the most convenient way to get a crunchy texture and lose the least amount of nutrients is to cut them in thin slices or small cubes. We can consume the water that boiled them with its rich supply of antioxidants, vitamin C and beneficial polyphenols. Therefore, use the liquid as a base for stock or sauces to recover the nutrients easily. The only exception to this method is when we make stewed vegetables or soups.
Best time to consume vegetables
Once picked, raw vegetables begin to lose nutrients, therefore, purchase the amount of food you can use in a few days. Try to buy what is local and in season to obtain the most nutrients.
The most relevant aspect of eating vegetables
On one hand, no cooking method will preserve 100% of the nutrients and protective phytochemicals in vegetables. So, enjoy variety and incorporate boiling, roasting, baking, grilling, sautéing, and stewing when preparing dishes! But regardless of the cooking method, I personally always recommend eating a variety of vegetables and as often as you can. Also, enjoy them fresh, locally grown and organic. On the other hand, comparing the healthiness of raw and steamed food is complicated, and there are still many mysteries surrounding how the different molecules in plants interact with the human body. In the end, it also depends on the nutrients involved and the cooking methods used.
The whole point of eating vegetables is to make them the biggest portion in each meal and to enjoy them with different kinds of spices, herbs, oils, vinegars, some drops of lemon juice, and homemade sauces.