In an online lecture, food technologist Matthijs Dekker explains the difference between fresh vegetables and utensils and explains how to get the healthiest substances out of your veggies.
Vegetables contain important nutrients such as vitamins, minerals and fiber. But vegetables contain much more. “A whole bunch of other healthy substances that are also called bioactive substances,” Matisse explains.
Vegetables also contain a lot of water. “That’s why they have a large volume, compared to the number of calories they contain. This makes you feel full faster, so you eat less than other high-calorie products like pasta and potatoes.”
Matisse continues: “If you look under the microscope at the cell of a piece of vegetable, you will see that healthy substances are protected by the cell membrane and cell wall. If you cook, freeze or canned vegetables, it affects the membrane and cell wall.” The food technologist explains that these can break down, causing the good nutrients to leak out of the vegetables.
But not only the method of preparation, transportation also plays a role. “From the moment the vegetables are harvested, the nutritional value decreases,” Matisse says. “After harvesting, the cells try to survive and this comes at the cost of all kinds of substances that can no longer be produced. This can reduce vitamins. But exposure to oxygen can also lead to a decrease.”
Matisse explains that you get the most nutrients right after you harvest your vegetables. But not everyone has a vegetable garden with their own vegetables. As a result, the majority simply buy their vegetables from the supermarket in the fresh produce section. Decker: “Fresh sounds good, but it’s actually a marketing term. Vegetables can stay on the road for days.” It basically refers to vegetables that are not available here in the Netherlands every season and therefore must come from all over the world. After a long transportation, vegetables sometimes spend days in the distribution center. Vegetables also remain on the shelves for a few days and at home you can eat purchased vegetables only after three days. “For example, fresh red cabbage can sometimes be aged for up to five months.”
Pre-cut vegetables have a shorter shelf life because the cells in the smaller pieces have a harder time and bacteria grow faster on the cut surfaces. Many people associate vegetables from a jar with unhealthy preservatives, but preserving vegetables isn’t as bad as you might think. Heating the vegetables kills bacteria and because the pot draws a vacuum during cooling, the oxygen escapes. So it’s just a way to make fresh vegetables last longer.
During the freezing of vegetables, ice crystals are formed in the previously mentioned cells. They are sharp and easily burrow through cell walls, causing them to crack and deplete good nutrients. But it looks worse than it actually is. Because the nutrients are still in the package. Only if you wash frozen vegetables before using them or boil them in water, the substances that were still in the package immediately leak out.
What is the best option now? Fresh, frozen or from a jar? “If the vegetables come from the area, fresh greens are really best,” Mattis says. “You can compare that to 100%. Frozen and potted vegetables are equally good because they are packed right after harvest. In the process they provide some healthy stuff, but about 70% are left. But once the vegetables come from far away – eg because they are not Available in the Netherlands in a certain season – they’ve also been in a distribution center for a while, the healthy stuff goes down really fast.” Mattis says that about 60% of healthy subjects will survive after that. In addition, the storage time in the refrigerator and the preparation of vegetables also play a role. If you cook vegetables in a lot of water, you may lose up to 50% of the good nutrients.
source | Linda† Netherlands University
