How does heat treatment of vegetables affect vitamin content?
Recently, one of my readers asked a question about how baked bell peppers are rich in vitamin C or is it completely resolved by heat treatment. This question prompted me to prepare a more detailed answer to the question about the preservation of vitamins and other nutrients during the heat treatment of vegetables in the form of this article.
Indeed, various cooking methods alter the nutrient composition of fruits and vegetables, but this is not always bad. Some studies show that although the thermal processing of foods may lead to the degradation of some nutrients, the availability of others may increase.
Therefore, to say that there is a “best” form of plant consumption, for example, raw, is impossible.
Many people think that raw vegetables contain more nutrients than cooked vegetables, but again, it depends on the type of nutrients. In a study in Germany with 200 people who had a raw food diet, they found that beta-carotene levels were elevated in their bodies, but plasma levels of lycopene were significantly lower than average. It is likely due to the fact that fresh, raw tomatoes are indeed characterized by a lower lycopene content than cooked or processed tomatoes. Heat treatment destroys the thick cell walls of many plants, releasing the nutrients stored in them.
Water-soluble vitamins, such as vitamin C and B vitamins, as well as a group of nutrients called polyphenols, are most vulnerable to processing and cooking. Canned peas and carrots lose 85 to 95 percent of their natural vitamin C. Another study found that frozen cherries lose up to 50 percent of anthocyanins, the nutrients found in the dark pigment of fruits and vegetables. About two-thirds of vitamin C is removed from fresh spinach during cooking.
Depending on the cooking method used, the loss of vitamin C in home cooking can vary from 15 to 55 percent, according to a review by researchers from the University of California, Davis. Interestingly, vitamin C levels are often higher in frozen foods compared to fresh foods — probably because Vitamin C dies during storage and transportation of fresh foods.
Fat-soluble vitamins such as A, D, E, and K, and antioxidant compounds called carotenoids become more available after preparation and processing. An article in The Journal of Agriculture and Food Chemistry concluded that carrots, zucchini, and broccoli are better than steamed, steamed, fried, or served raw. Least of all nutrients is stored during frying.
But when it comes to cooking vegetables, you always need to look for compromises. You can increase the availability of one nutrient, while destroying another. For example, boiled carrots have significantly more carotenoids compared to raw carrots. However, raw carrots contain much more polyphenols, which disappear as soon as you start cooking it.
Summarizing all this, it is fashionable to say that no cooking method is ideal in terms of preserving 100% of the nutrients in vegetables. And since the best vegetables are the ones that you really will eat, the taste should also be taken into account when deciding on the cooking method.
The best way to get the most out of your vegetables is to enjoy them in a variety of ways – raw, steamed, boiled, baked, and fried. If you regularly eat a variety of fruits and vegetables, you do not need to worry about how to prepare them.