A food, depending on the conditions of conservation and cooking, can lose from 40% of vitamin A, up to 80% of vitamin B1 or practically all the vitamin C of origin. The nutritional composition of any fresh food varies from its collection to its consumption if several days pass. The passage of hours and days, the conditions of storage during the collection, distribution and sale, the conservation at home, the preparation prior to cooking (washing or soaking, cutting?) And the applied cooking technique, in addition to the time save once elaborated, they are determining factors of the final nutritional value of the food at the time of consumption. The vitamins are the most sensitive nutrients, while part of the minerals they pass to the soaking or cooking water and can be used if that water is recovered for other culinary purposes.
Vitamins are essential nutrients and, as such, the body needs a daily and continuous contribution. The disadvantage is that these are nutrients sensitive to various factors such as temperature, light, oxygen, external acidity or own food, in addition to other natural components that could contain food. This is the case of the so-called antinutrients, which limit the use of certain vitamins, minerals or trace elements.
The Professor of Nutrition and Bromatology at the University of Murcia, Gaspar Ros Berruezo and coordinator of the Spanish Database Network of Food Composition (RedBDECA) , warns that “losses and / or changes in the structure suffered by vitamins during the technological and culinary processes determine a lower availability and / or a loss of nutritional value that affects them directly or the food as a whole “.
This is the case of the processes inherent in the preparation of vegetables before they are tasted. In this way, when selecting the parts to consume the external green leaves of lettuce, endive or endive, they have a higher content of calcium, iron and carotenoids than the whiter internal ones. The moment of chopping is also decisive, so that more nutrients are preserved with large and uniform cuts. In the next phase, cooking, the nutrient content of food can be altered in three ways: the absorption of nutrients from the outside (fried foods absorb some of the nutrients from the frying oil),
The vitamin losses that occur as a result of the different preparation, cooking and storage processes, two terms are used: Apparent Retention (RA) and Real Retention (RR).
In general, if this criterion is met, the most unstable vitamins during the culinary processes are the water-soluble vitamins, specifically, vitamin C, folates B9, thiamine or B1 and riboflavin or B2, in addition to the fat-soluble vitamin A or retinol. Therefore, it is useful to follow the advice of eating raw vegetables and fresh fruit freshly washed and unpeeled daily.
Real retention values ??(RR) in percentage of food vitamins subjected to different culinary treatments.
- Baked fruits: 80% RR of vitamin C, 60% of folates and 85% of retinoids and carotenoids.
- Fruits in compote: 70% RR of vitamin C, 50% of folates and 75% of retinoids.
- Legumes, cooked 15/20 minutes (boiled): 70% RR of vitamin C, 65% of folates, 90% of retinoids.
- Legumes, cooked 45/75 minutes (boiled): 70% RR of vitamin C, 50% of folates, 90% of retinoids.
- Legumes, cooked 2 / 2,5 hours (boiled): 70% RR of vitamin C, 35% of folates, 90% of retinoids.
- Vegetables (leaves and stems), boiled, covered with water, drained: 55% RR of vitamin C, 60% of folates, 95% of retinoids.
- Vegetables (leaves and stems), boiled, little water, drained: 60% RR of vitamin C, 65% of folates, 95% of retinoids.
- Vegetables (leaves and stems), sautéed: 85% RR of vitamin C, 85% of folates, 90% of retinoids.
The loss of vitamins from processed foods at home can be significantly reduced if you follow some simple practical advice. It is necessary to take into account the conditions of storage of the vegetables, always in a cool place (it does not have to be the refrigerator, although this increases its useful life thanks to the temperature of refrigeration), without humidity and preserved from direct sunlight . If your consumption is made as close to the collection as the nutritional concentration will be higher, which forces you to buy vegetables and fresh fruits more regularly.
The whole vegetables will be thoroughly cleaned and chopped whenever possible at the moment just before serving or cooking them. When cooking vegetables, it is best to do it with just the right amount of water, add them to the boiling water, not cold, and cook them in the shortest possible time. The steam cooking is the one that best preserves the vitamins of the vegetables. If boiling liquid is left over, it can be used to make other dishes such as stews, rice, pasta, pulses, etc.
VITAMINS IN NATURAL FOODS
Vegetables have always stood out in nutritional advice for their significant contribution of vitamins, minerals and trace elements. However, other foods such as nuts and dried fruits far exceed the content of some of these regulatory nutrients such as folates, vitamin E, magnesium, potassium and iron.
Therefore, the combination in the recipes of each other results in a more complete dish in said nutrients. This is the case of the salad with mixed nuts, the one that brings nuts and cheese or the rice with olives and pistachios, among hundreds of delicious suggestions. Something similar happens if the fresh fruit and nuts combined, either as beaten as roasted fruit or fruit salad of fresh fruit
The storage of natural orange juice within reach of light, makes it lose much of its vitamin content both by contact with light, as by the temperature at which it is.
Considering what is discarded and / or not consumed in many fruits and vegetables implies recognizing a great loss of vitamin potential in foods.
Peel a pear, removes part of the vitamins B2 ,B3 , folic acid (also called B9) and C , also discard the carrot tail, removes part of the vitamins B1 , B2 and B3 that are contained in it.
At the time of cooking, the loss of vitamins is inevitable. Water, heat and time reduce the vitamin level of any portion by an accelerated oxidation of the content. This is not going to make us stop boiling a vegetable, but it is useful to know it because its vitamin content will be notoriously lower than the natural one.
The vitamins sensitive to temperature, light and oxidation are:
|Vitamin C||Considerable||Considerable||Very sensible|
|Vitamin B1||Very sensible||Not very sensitive||Not very sensitive|
|Vitamin B2||Considerable||Very sensible||Not very sensitive|
|Vitamin B3||Not very sensitive||Not very sensitive||Not very sensitive|
|Vitamin B6||Considerable||Very sensible||Considerable|
|B12 vitamin||Considerable||Very sensible||Very sensible|
|Biotin||Not very sensitive||Not very sensitive||Not very sensitive|
|Calcium||Not very sensitive||Not very sensitive||Not very sensitive|
* Information extracted and adapted from: Nutrition and clinical dietetics. Jordi Salas-Salvadó, Anna Bonada, Roser Trallero, M. Engràcia Saló. Ed. Masson, 2002.