Legumes: what they are and how they are eaten
Legumes (legumes, Fabaceae or Papilionaceae ) are foods of vegetable origin; more precisely, they are seeds enclosed in a pod ; they belong to the order of the Fabales, so it is neither cereal nor berries or other vegetables.
Legumes are marketed under different forms of conservation; the fresh ones can be easily found on the fruit and vegetable stalls at the harvest time. Each species stands on its own: beans and peas are available at the end of spring, while beans (based on variety), lentils and chickpeas in summer. There are also legumes stored in cans, inside which they are immersed in the corresponding cooking and cooking liquid. Finally, legumes can be stored at room temperature in an optimal manner after drying; the latter method allows not to use large quantities of salt (NaCl) and maintains a certain nutritional integrity.
NB . Dried legumes, except for lentils, need to be soaked in COLD water before cooking, which is essential for the rehydration of the seed.
The functions of legumes in the kitchen are many. Having a good starchy composition they can replace (and frequently it would be desirable to do so!) Cereal and potato products (with the exception of bread that requires gluten, absent from legumes). At the same time, thanks to the typical protein abundance, legumes can reach a biological value (VB) such as to replace foods of animal origin if properly associated with other foods. To learn more, see the article: Legume proteins.
On a practical level, legumes can be used stews instead of pasta or rice, boiled, drained and cooled to accompany dishes, and cooked together with cereals to achieve a VB similar to that of egg proteins.
Functions
Legumes have both nutritional and extra-nutritional functions.
Nutritional properties
The nutritional aspects of legumes can be differentiated into 1. Energy and macronutrients, 2. Minerals and vitamins.
- Energy and macronutrients
- Energy function and carbohydrate intake: fresh legumes provide a rather heterogeneous amount of energy; ranges from 40kcal / 100g of the beans, notoriously low-calorie, to 115kcal / 100g of lupins. Evaluating the energy introduced with legumes we must remember that, while for fresh and canned ones it is not necessary to change the values of the food composition tables, for dry legumes it is necessary to correct all the nutrients for a hydration coefficient equal to 3 A dry legume to be soaked (for example dried beans ) which provides 300kcal / 100g, once rehydrated it will weigh 3 times as much, but with the same mass it brings 300/3 = 100kcal / 100g. Ultimately, all the values of dried vegetables in the table must be divided by 3.
Most of the energy introduced comes from carbohydrates; these, even after cooking and the relative increase in digestibility, still have a moderate glycemic index (also thanks to the abundance of dietary fiber ).
- Protein and lipid intake: the proteins they contain represent about 1/3 of the total kcal. These, although having a modest VB, are lacking only in methionine and cysteine; it follows that, associating them with other proteins rich in these two amino acids (such as those of cereals), can reach a VB similar to that of animal proteins.
The lipids contained are polyunsaturated, therefore of good quality, but quantitatively irrelevant (1/15 of the total calories).
- Energy function and carbohydrate intake: fresh legumes provide a rather heterogeneous amount of energy; ranges from 40kcal / 100g of the beans, notoriously low-calorie, to 115kcal / 100g of lupins. Evaluating the energy introduced with legumes we must remember that, while for fresh and canned ones it is not necessary to change the values of the food composition tables, for dry legumes it is necessary to correct all the nutrients for a hydration coefficient equal to 3 A dry legume to be soaked (for example dried beans ) which provides 300kcal / 100g, once rehydrated it will weigh 3 times as much, but with the same mass it brings 300/3 = 100kcal / 100g. Ultimately, all the values of dried vegetables in the table must be divided by 3.
- Minerals and vitamins
- Mineral salts: legumes provide excellent amounts of iron (Fe), potassium (K) and phosphorus (P). The bioavailability of these minerals is limited, but considering that (for example) almost no fertile woman reaches the recommended daily amount of iron (18mg / day) with nutrition (see anemia of women), supplementing the diet with legumes may favor the approach to these values.
- Vitamins: the typical vitamins of legumes are mainly thiamine (B1), niacin (PP), folic acid and biotin (vit. H).
The problem of meteorism and anti-nutritional factors
What generally curbs the population in the consumption of legumes are the so-called "side effects", namely meteorism and flatulence. This phenomenon is mainly due to the colonic bacterial fermentation (large intestine) towards some glucidic molecules, more precisely two oligosaccharides: raffinose and stachiosio . The result is a more or less abundant production of methane that is absorbed in a very small part, but mostly it is directly expelled. On the other hand, a similar mechanism seems to favor the significant reduction of carcinogenic compounds by lowering the risk of colon cancer. However, to limit the onset of meteorism and flatulence it is possible to sift well-cooked legumes to the vegetable mill (do not blend!), Excluding the peel.
It is however appropriate to specify that legumes also have some anti-nutritional functions; among these we mention in the first place the ANTITRIPTIC and ATIAMYLASE; in fact, during the digestion of legumes it is possible to observe a significant reduction in digestive efficacy towards proteins (up to 40% due to inhibition of trypsin and chymotrypsin ) and that of starch ( amylase inhibition); it is therefore inadvisable to consume excessively large portions (as with all foods, after all!), but above all to associate them with large quantities of protein foods. NB . These anti-nutritional elements can be inactivated through careful heat treatment.
There are also some chelating molecules that hinder the absorption of minerals; obviously this is an aspect that does not completely negate the contribution of calcium and iron ... but it is still good to remember its existence.
Additional problems may concern the specific consumption of fava beans and peas by subjects affected by favism.
Legumes against high cholesterol
From a lipid-digestive point of view, a significant reduction in cholesterol absorption is observed when eating legumes; this happens thanks to the chelating action of saponins ( glycosides ) and lecithin ( vegetable steroid ) both on exogenous fat molecules, and on endogenous molecules excreted in the intestine by means of bile. NB . Sapinins injected parenterally have also demonstrated a beneficial metabolic effect.
Ultimately, the consumption of legumes is particularly indicated in glycemic control, in the prevention and treatment of dyslipidemia, colon cancer and constipation.
Bibliography:
- Cereals and legumes in the diet for health - A. Formenti, C. Mazzi - Tecniche Nuove - pag 46-49
