Heat treatment changes the composition of fruits and vegetables, but it's not always a bad thing. Several studies have shown that under the influence of temperature, some nutrients are destroyed, but others are released.
The thing is the type of beneficial agent
Many people believe that raw vegetables contain more nutrients than cooked, but it depends on the type of substances.
When heat-treated fat cell walls of many plants are destroyed, releasing the stored nutrients in them.
A German studyLong-term strict raw food diet is associated with favourable plasma beta-carotene and low plasma lycopene concentrations in Germans. Spent on a group of 200 raw foodists, found that they had higher levels of beta-carotene in the plasma, but the lycopene content was below average. One of the factors influencing the result, it was minimal lycopene content in the raw tomatoes as compared to thermally processed.
What happens with vitamin C and other water-soluble substances
According to the report researchers from the University of California at Davis
Review Nutritional comparison of fresh, frozen and canned fruits and vegetables. Part 1. Vitamins C and B and phenolic compounds. , The loss of vitamin C, depending on the method of preparation may be from 15% to 55%. Fresh spinach in the cooking process loses about ⅔, as peas and carrots - 85-95% of vitamin C.Water-soluble nutrients such as vitamin C, vitamin B and polyphenols, are most susceptible to degradation during processing and cooking.
Interestingly, the level of vitamin C often higher in frozen products compared to fresh due to the fact that it reduces the storage and transportation of crude harvest.
Another study found that after six months of frozen cherries have lost 50% anthocyanins - nutrients found in dark pigments of fruits and vegetables. So that in the frozen foods are not always preserved vitamins.
What happens with the vitamin A and other fat-soluble substances
According to the report published in The Journal of Agriculture and Food ChemistryEffects of Different Cooking Methods on Nutritional and Physicochemical Characteristics of Selected Vegetables. To preserve vitamins in carrots, zucchini and broccoli to cook them better than steamed, cook or eat raw. Roasting proved the worst way to preserve nutrients.
The fat-soluble compounds such as vitamins A, D, E and K, and antioxidant compounds called carotenoids, better preserved during cooking and processing temperature.
But when it comes to cooking vegetablesAlways have to compromise. The same method can increase the availability of certain nutrients, but decompose other. For example, in the boiled carrot higher level of carotenoids as compared with the crude. However, raw carrots much more polyphenols, which disappear as soon as you start to cook it.
What happens to the vitamins in the microwave
Although many people thought that cooking in a microwave oven harmful vegetables cooked therein may have a higher concentration of certain vitamins.
In March 2007, the experiment was conducted, during which the scientists watched as boiling, cooking steam, cooking in a microwave oven and cooking food under pressure affect the nutrients in broccoli. Steaming and boiling resulted in the loss of 22 to 34% vitamin C. Cooked in a microwave oven under pressure and vegetables retained 90% of vitamin C.
conclusions
1. Neither method of preparation, filing and storage of food will not retain all the nutrients in vegetables.
2. If scientists have decided that boiled zucchini useful, yet the fact that it is right for you. If he will not go down your throat, it will not bring any good. Therefore, choosing a way of cooking, and more rely on your taste.
3. The best way to get the most out of vegetables - enjoy them in different variations: raw, stewed, boiled, baked and grilled.
4. If you regularly eat a variety of fruits and vegetables, you can not worry about the method of cooking.