The consumption of vegetables is essential because of their wealth in protective nutrients: vitamin C and B9, beta-carotene, polyphenols (antioxidants), fiber, potassium, calcium, magnesium and other minerals.

Vegetables: sensitive nutrient

Between harvest and consumption, some compounds of the vegetables can sometimes be altered. They need to be the best preserved precautions.

• Vegetables conserve vitamins C and B9, are generally susceptible to oxidation by contact with oxygen from the air (especially after peeling), and heat (mainly vitamin C), where conservation is at room temperature and during cooking. They are also water soluble and can therefore be lost in the water soaking or cooking. Beta-carotene and its congeners carotenoids, can be degraded by oxidation. Cooking improves contrast assimilation (this is the case, for example lycopene in tomatoes);
• Some polyphenols are oxidized. Further, soluble in water, are best preserved by a steam cooking;
• The fibers are generally not affected by the different stages of processing vegetables;
• Minerals such as calcium, phosphorus, iron, however, are quite stable and do not move much with the changes. However, there are water soluble and can be found in low proportion in the cooking water

Leafy vegetables like spinach or lettuce, the surface of contact with air or water is high, are most vulnerable to nutritional losses. Root vegetables (carrots, turnips …) are more stable. Fruit vegetables (tomato, green beans …) and flower vegetables (broccoli, cauliflower …) are intermediate.

Canned vegetables: nutritional qualities proved

Various studies, including a collective expertise of INRA, compared intakes of vitamins and other nutrients in vegetables and processed vegetables, canned or frozen at the consumption stage.
And the result is not necessarily the one thought: fresh vegetables, subject to the vagaries of storage at the wholesaler, retailer and consumer, may have lower levels of vegetables ready for use!
Packaged in 5 hours after harvesting, the vegetables to be canned or frozen have the advantage of being picked at maturity: this is when the fruit vegetables, tomatoes, peppers, green beans, peas, exhibit optimal intake of vitamin C, B9, beta-carotene, polyphenols, nutrients that accumulate throughout the development. Before being sterilized, these vegetables are stabilized by bleaching, a rapid heat treatment which inactivates the enzymes that could degrade vitamins. You can blanch the vegetables to steam, which limits the loss of soluble nutrients such as vitamin C.

While eating canned vegetables

Canned vegetables are packed in jars or airtight cans to protect them from air. They undergo sterilization, which destroys any possible microbe. This heat treatment affects the vitamin. C heat sensitive. Beware of water-soluble nutrients (including vitamins and minerals), they sometimes find themselves in more than 50% in the cooking liquid, it is advisable to consume.
Canned vegetables are generally retain 3 years from date of packing. To preserve their nutritional qualities, the ideal is to store in a cool, and eat before their deadline for optimal BBD.