Chemical composition, nutritional and biological value of vegetables and fruits. Chemical composition of fruits and vegetables Chemical composition and nutritional value of berries

Vegetables (this includes potatoes, although strictly speaking they are not vegetables, but root vegetables), fruits and berries are consumed both raw and after cooking. They are the most important source of carbohydrates, vitamins and minerals in the diet. To extend the season of their consumption, these products are stored in special conditions or canned in one way or another. Therefore, first we will consider the chemical composition of the raw materials and methods of preservation, and finally - methods of culinary processing.

Raw foods

Let's consider the chemical composition of natural vegetables, fruits and berries. Although, as mentioned above, the main role in the nutrition of this group of products is determined by the content of carbohydrates, vitamins and minerals, we will still briefly begin with a consideration of nitrogenous substances, since they are the basis for the growth and development of all plant products.

Nitrogenous substances. There are relatively few nitrogenous substances (in terms of protein) in vegetables (1.0-2.0%) and especially in fruits (0.5-1.0%) and berries (about 0.5%). At the same time, less than half of the proteins are found directly among nitrogenous substances (for example, in cabbage - 40%, potatoes - 30, and in grapes - 7%). The main part of the nitrogenous substances in this group of products are free amino acids and polypeptides.

In addition, the amino acid composition of these products is very unfavorable. Such important vegetables as potatoes, onions, carrots, cucumbers, cabbage, beets, and main fruits and berries are characterized by a low (50-70% of the norm, even less) content of essential sulfur-containing amino acids. Therefore, the importance of vegetables, fruits and berries as a source of protein in nutrition is insignificant. The only exception is potatoes. Although the total content of nitrogenous substances in it is only 2%, the consumption of potatoes in our country is quite significant: on average 330 g per day. Thus, on average, approximately 6-8% of a person’s total protein requirement is satisfied with potatoes, which, of course, is significant.

Nitrogenous substances in vegetables, fruits and berries are essential for the formation of the consumer properties of these products.

In this article we will look at enzymes related to nitrogenous substances, since they are all proteins. Although enzymes make up a tiny part of plant proteins, their role in ripening and storage is enormous. The preservation of vegetables and fruits mainly depends on the activity of enzymes involved in respiration, and measures that suppress this activity will be considered. It will also be explained that other enzymes, such as non-politic ones, on the contrary, contribute to the softening of some fruits, which improves their organoleptic properties. All this makes it necessary to consider some general concepts about plant enzymes,

Depending on the type of plant, the degree of maturation and external conditions, plant cells from the existing common “amino acid pool” synthesize those that it currently needs. They belong mainly to two classes: oxy-doreductases and hydrolases.

Anaerobic dehydrogenases. These dehydrogenases cannot react directly with oxygen, but transfer hydrogen or electron to other acceptors, such as aerobic dehydrogenases or oxidation substrates.

Plants contain active dehydrogenases of malic, succinic, citric and tartaric acids.

Oxygen-activating oxidoreductases. These oxidoreductases are capable of activating molecular oxygen: they are divided into electrical transfer oxidoreductases and oxygenases.

Electron transfer oxidoreductases (oxidases, aerobic dehydrogenases) catalyze the reduction of molecular oxygen either into water (by transferring four electrons) or into hydrogen peroxide (by transferring only two electrons).

The peculiarity of these enzymes is that they have iron or another metal in their active center. An example of dioxygenase is lipoxygenase. The chemistry of the process catalyzed by lipoxygenase is reduced to the formation of an enzyme-substrate-oxygen complex as a result of the interaction of the enzyme with each molecule of the oxidized substance.

The oxidized substrate formed as a result of the action of lipoxygenases has a high oxidizing ability. With their participation, phenols are divided in the cell, and the resulting quinones participate in the secondary oxidation of the breakdown products of proteins, carbohydrates, ascorbic acid and other compounds.

Monooxygenases (hydroxylases, mixed-function oxidases) activate molecular oxygen and introduce only one oxygen atom into the substrate. The second oxygen atom is reduced to water due to two electron donors.

The introduction of one atom into a substrate usually leads to the formation of a new hydroxyl group (OH).

Monooxygenases, unlike dioxygenases, can contain in the active center not only heavy metals, but also nucleotides. Monooxygenases include L-lactic acid oxidase, lysine oxygenase, etc.

Peroxidases include catalase, which oxidizes one molecule of hydrogen peroxide with another molecule of hydrogen peroxide to form two molecules of water and an oxygen molecule.

Ascarbate oxidase oxidizes ascorbic acid reversibly to dehydroascorbic acid to form water. Its prosthetic group includes copper in two forms: 75% Cu+ and 25% Cu2+.

Dioxyfumaric acid oxidase catalyzes the oxidation of dioxyfumaric acid to diketosuccinic acid.

Cytochrome oxidase is considered the main enzyme in cell respiration. The cytochrome oxidase system completes the respiratory process in animals, plants and yeast and is associated with the synthesis of adenosine triphosphate, due to which the living cell acquires energy. The cytochrome oxidase system is concentrated in mitochondria.

Along with the catalytic effect carried out by oxygen peroxide, peroxidase is able to function as an oxidase, catalyzing the oxidation of the substrate due to molecular oxygen in the absence of hydrogen peroxide. The oxidase action of peroxidase occurs under aerobic conditions; the cofactors of the reaction are Mn2+ ions and a number of enzymes.

1.2 mg%, since they consume quite a lot during the season. Of the berries (3-carotene is highest in sea buckthorn - up to 10 mg% and persimmon - about 1.2 mg%, which is generally quite significant.

Most vegetables (except leafy ones), fruits and berries are not rich in B vitamins. However, it should be noted that many vegetables, fruits and berries contain very important “vitamin-like” substances, which, although not true vitamins, exhibit a noticeable pharmacological effect. Thus, an antiulcer factor (promotes wound healing), sometimes called “vitamin O,” was found in cabbage. Bioflavonoids have been found in black currants, rose hips, apples and many other berries and fruits, which increase the effectiveness of vitamin C (“vitamin P”). Substances derived from naphthoquinone, which have the effectiveness of vitamin K (promotes blood clotting), were found in chokeberry and rosehip. By the way, this is not useful for everyone, and in some cases, with increased blood clotting, it is even harmful.

Minerals. Although the total content of minerals in vegetables, fruits and berries is small (0.5-1.0%), they are, as a rule, in an easily digestible form and therefore) play a significant role in nutrition.

Of the macroelements, potassium should be noted. There is a lot of it (in mg%’) in potatoes (570), peaches (360), black currants (350) and apricots (305). Therefore, these products are often used in the diets of patients suffering from hypertension, since potassium has the ability to normalize blood pressure. Of the trace elements (in mg%), iron should be mentioned in blackberries* (7.0), pear (3.2), quince (3.0), persimmon (2.5), and apples (2.2). Have; but these products are recommended in the diet of patients suffering from anemia caused by iron deficiency. Among other trace elements, we note rubidium, which accumulates in potatoes and red grapes, cobalt in pears, manganese in gooseberries and apricots, molybdenum in black currants.

In addition to the listed components, vegetables, fruits and berries contain a number of other physiologically active substances. These include phenolic substances, glycosides, essential oils and other compounds. Phenolic substances such as anthocyanins, catechins and their condensation products - tannins, flavonols, leukoanthocyanidins, etc., determine the varied colors of fruits and berries. Although their total amount is small - depending on the type of vegetable, fruit or berry and the degree of its ripening, it can be in the range of 0.3-1.5% (rarely higher, for example, sloe - 1.6%), they affect the organoleptic properties ( color and taste), safety (as they have some bactericidal effect) and physiological properties of the product. (The P-vitamin activity of bioflavonidids, which belong to phenolic substances, has already been noted above.)

Essential oils of most vegetables, fruits and berries have a bactericidal effect. Essential oils of garlic and onion are famous for their particularly strong effects. Before their composition was established, these substances were called “phytoncides.” Currently, the composition of phytoncides in many plant products has been established. Thus, a phytoncide of garlic and onions, allicin (allylthio-sulfinate), was identified. Despite the availability of medications, many prefer to carry out prevention during cold epidemics with garlic and onions. Of course, others don’t always like it, but your own health is also important. But you should also be careful about using excess onions and garlic in your diet. Alicin and its derivatives with systematic consumption of large quantities of onions and garlic (as well as cabbage, where these compounds are also found) can cause Graves' disease.

After considering the chemical composition of onions and garlic, we will focus on other herbs and spices. They have virtually no nutritional value, although these products contain a certain amount of proteins, fats, carbohydrates, vitamins and minerals, since they are consumed in small quantities. Therefore, we will not consider the composition of nutrients, herbs and spices. However, let us briefly consider the features of the chemical composition of some herbs and spices: horseradish, mustard and pepper.

Horseradish – responsible for the pungent taste is the same allicin found in garlic and onions, but in concentrations an order of magnitude higher. In addition, horseradish contains other substances that give it a special taste. Horseradish differs from other spices in its relatively high fiber content.

Mustard contains significant amounts of glycosides sinigrin and sinalbin, which, upon enzymatic hydrolysis, yield a number of allicin compounds (up to 1.1% of the so-called allylic oil), which give mustard powder a specific taste and antiseptic properties. The active principle is allyl isothiocyanate. (By the way, the powder is obtained from mustard seed cake after separating the oil. Mustard seeds are not used directly in food.)

There are two types of pepper: black and red. In black pepper, the taste is determined by essential oils and piperine (up to 7%), and in red pepper (paprika) by capsaicin.

All of the listed spices are not used in dietary nutrition, as they irritate the gastric mucosa and liver. The so-called spicy leafy vegetables - dill, parsley, coriander (cilantro), lemon balm, etc., as well as bay leaves, have become more widespread in general and dietary nutrition. They give food an attractive aroma and taste, thereby improving appetite, promoting the secretion of gastric juice and stimulating digestion. The use of such spices in dietary nutrition is especially necessary. After all, dietary food is mostly tasteless, as it contains few extractives and table salt.

Vegetables and fruits are of great importance in national nutrition. They are food and flavor products. In addition, fruits and many vegetables can serve as medicinal agents.

The nutritional value of potatoes, vegetables and fruits is determined by their content of carbohydrates (starch, sugar), proteins and other nitrogenous substances, mineral or ash substances and vitamins. Carbohydrates and proteins in the body serve as a source of vital energy. Protein is also necessary for building and repairing body tissue. Minerals are needed for proper blood circulation, regulation of intracellular pressure, building the skeleton, various organs and nervous tissue.

Fruits and vegetables are used as flavoring agents because they contain various fruit acids, tannins or astringents (in fruits) and essential or aromatic substances on which the smell of fruits and many vegetables depends - dill, parsley, celery, parsnips, tarragon, horseradish , onions, garlic, etc.

Aromatic substances and fruit acids, tannins and coloring substances of fruits and vegetables stimulate appetite, improve digestion, and increase the digestibility of meat and bread foods. Enzymes found in fresh fruits and vegetables also help improve digestion.

Many fruits and vegetables are used as medicinal products because they are rich in vitamins and contain minerals, some of which - iron, phosphorus, iodine, potassium, calcium, etc. play a large role in the body's metabolism.

Onions, garlic, radish, horseradish contain phytoncides - substances that kill infectious bacteria.

In the treatment of a number of diseases, grapes, lemons, oranges, apples, pears, plums, strawberries, raspberries, blueberries, cranberries, rose hips, black currants, beets, carrots, radishes, garlic, onions, spinach, tomatoes, etc. are used.

Fruits and vegetables are widely used in therapeutic nutrition for patients suffering from nervous system disorders, circulatory disorders, metabolic disorders, heart disease, liver disease, gout, and vitamin deficiencies.

Vitamin deficiency is a disease caused by the lack of a vitamin in the body.

A person's need for vitamins is insignificant - a few milligrams (thousandths of a gram) per day, but despite this, the role of vitamins for health and life is enormous.

About 20 vitamins are known. Some of them have not yet been sufficiently studied. Vitamins are designated by letters, since their chemical nature was not previously precisely established. Currently, most vitamins are not only isolated in their pure form from plants or animal organs (liver), rich in vitamins, but also obtained artificially and chemically.

Enzymes, which fresh fruits and vegetables are rich in, play an extremely important role in the body's metabolism.

Chemical composition of vegetables and fruits

Fruits and vegetables contain a variety of substances, most of which are soluble in water. The sugars contained in fruits and vegetables, some of the proteins, minerals and vitamins, as well as all fruit acids, tannins, coloring substances of black currants, cherries, etc. are in a dissolved state in the cell juice. Other substances - starch, fiber, most proteins, some mineral salts, a number of vitamins, fats, aromatic and coloring substances of tomatoes, apricots, carrots, etc. are insoluble in water. They are found in the cells of fruits and vegetables in undissolved form.

Water. Vegetables and fruits contain a lot of water - from 75% (in potatoes and green peas of waxy maturity) to 95% (in cucumbers, tomatoes, lettuce, etc.). This water contains various nutrients in the form of weak solutions. As a result, fresh fruits and vegetables are relatively easily affected by microorganisms - molds, yeasts and bacteria - tiny animal creatures invisible to the naked eye. Due to the content of a large amount of water and rapid damage by microorganisms, fresh fruits and vegetables are perishable and poorly transportable products.

Sahara. Fruits and vegetables contain beet sugar, or sucrose, fruit sugar (fructose), and grape sugar (glucose). Fruit sugar is much sweeter than beet sugar, and the latter is sweeter than grape sugar, or glucose. Grape and fruit sugars are easily absorbed by the human body, which uses them as a source of energy (thermal, mechanical - during work) and for the formation of fat reserves in the body.

In pome fruits, fructose predominates from sugars, in apricots and peaches - sucrose. Berries contain almost no sucrose; they contain (almost equal amounts) glucose and fructose. In watermelons, fructose predominates from sugars, and in beets, carrots and melons - sucrose.

Starch found in large quantities in potatoes (from 14 to 22% and more). There is a lot of starch in sweet potatoes, overripe green peas and sweet corn, beans and beans. Other vegetables and fruits have little starch, for example, carrots have about 1%. In unripe fruits its content reaches 1.5%.

Fiber found in potatoes and all vegetables and fruits in amounts from 0.5 to 3%, depending on the type, variety and place of cultivation. The coarser the fruits and vegetables, the more fiber they contain. Cell walls consist mainly of fiber and other water-insoluble substances. Fiber is not absorbed by the human body, but it gives a feeling of fullness and promotes digestion (improves intestinal motility).

Fruit or organic acids(apple, lemon and wine) are found in fruits in varying quantities - from 0.10% in pears and up to 3.5% in currants. Lemons contain the most acids - up to 8%. In vegetables, fruit acids - citric and malic - are found in large quantities only in tomatoes (from 0.22 to 1.39%).

Sorrel, rhubarb and spinach contain oxalic acid. Lingonberries and cranberries contain benzoic acid, which has a detrimental effect on bacteria. Therefore, these berries are well preserved fresh.

Raspberries and strawberries contain salicylic acid (along with malic acid) in negligible quantities. Salicylic acid is a diaphoretic. Therefore, raspberries are used to treat colds. For fruits and vegetables, acids are reserve substances and can be used during respiration.

Mineral salts or ash substances are present in fruits and vegetables in small quantities - from 0.3 to 1.8%.

Squirrels and other nitrogenous substances close to them are found in fruits and vegetables in small quantities. But green peas, beans and beans, i.e. legume vegetables, are rich in proteins. Cabbage, especially cauliflower, as well as spinach and lettuce contain a lot of protein and nitrogenous substances (1.43-3.28%). Proteins are the most important component of food.

Vitamins. Potatoes, vegetables and fruits are products through which a person meets his need for vitamin C. Meat, bread, cereals, and fish do not contain this vitamin. If there is no vitamin C in food, a person gets scurvy. Vitamin C is rich in: rose hips, green unripe walnuts, black currants, strawberries, etc., and vegetables include sweet peppers, cabbage, horseradish, spinach, lettuce, sorrel, parsley, etc. Cucumbers, beets, onions, garlic contain vitamin C is not enough.

In the absence of vitamin A, or carotene, in food, a person develops night blindness (eye disease - xerophthalmia); growth is stunted in young people. With a lack of this vitamin, the body's resistance to diseases decreases. Fruits and vegetables do not contain vitamin A, but in the body this vitamin is formed from carotene. Carrots, sea buckthorn, peaches with yellow flesh, apricots, turnips, and all greens are rich in carotene. Carotene is close in structure to chlorophyll and therefore is always found together with it.

Fruits and vegetables contain vitamins: B 1, B 2, PP, K, etc., which also prevent various disorders of the body and its diseases.

The daily requirement of an adult for vitamin C is on average 50 mg, for vitamin A - 1 mg. Vitamin A can be replaced with carotene (2 mg per day).

Tannins give the fruits a tart taste. Their content in fruits ranges from 0.02% (in pears) to 1.31% (in blueberries). Due to the high content of tannins, blueberries are used in the treatment of gastric diseases.

Dyes determine the color of fruits and vegetables. They are found in very small quantities in colored apples and pears, apricots and peaches, rowan berries, carrots, beets, tomatoes, etc. The green color of vegetables and fruits depends on the presence of chlorophyll in them, red and yellow - from carotene (the coloring matter of carrots). , apricots, sea buckthorn, etc.), lycopene (the coloring matter of tomatoes and rose hips), xanthophyll (the coloring matter of the skin of colored apples) and anthocyanins (the coloring matter of beets, cherries, plums, currants, red gooseberries, etc.).

Essential or aromatic substances found in small quantities in fruits and many vegetables (spicy root vegetables, dill, etc.). The skin of the fruit is especially rich in aromatic substances.

Vegetables and fruits also contain other substances: enzymes, phytoncides, etc. With the help enzymes In the cells of living organisms, including vegetables and fruits, life processes take place - respiration, growth and development. Phytoncides- special substances that have a detrimental effect on bacteria. These substances are released by the cells of vegetables and fruits, for example, when they are damaged. Consequently, phytoncides in vegetables and fruits play a protective role. The phytoncides of onions, garlic, carrots, mustard, radishes, horseradish, bird cherry, rowan, black currant, and oranges are very active.

If you chew garlic or onion for 5 minutes, all microbes in the oral cavity will be killed.

Vegetables and fruits occupy an extremely important place in human nutrition, as they represent the main and often irreplaceable source of various vitamins, mineral salts, easily digestible carbohydrates, organic acids, phytoncides and other substances.

The composition of vegetables and fruits depends on their type, variety, maturity, harvesting time, storage methods and other factors. The chemical composition is also an important identification feature during examination.

Water is the main component of fresh vegetables and fruits: its content ranges from 70 to 95% (except nuts - 5–8%). It gives plant tissue juiciness, elasticity (turgor), organic and mineral substances are dissolved in it. Water is a medium and an active participant in various enzymatic processes occurring in the tissues of fruits and vegetables. A significant part of the water is in a free state, contained mainly in cell sap and is easily removed during dehydration of fresh vegetables and fruits. Part of the water (about 20%) is in a bound state and is difficult to evaporate.

Due to their high water content, vegetables and fruits provide a favorable environment for the development of microorganisms, which is why they are often classified as perishable goods. During storage, vegetables and fruits lose some water due to evaporation. When water loss exceeds acceptable limits (mostly 5–7%), fresh fruits and vegetables wither, lose freshness and their quality decreases sharply.

Minerals are found in vegetables and fruits in the form of well-digestible salts of organic and mineral acids (phosphoric, sulfuric, tartaric, etc.), and can also be an integral part of some high-molecular compounds - vitamins, proteins, pigments, etc.

Carbohydrates are substances whose content and variability determine the taste, consistency, and shelf life of fruits and vegetables. Among the dry matter of vegetables and fruits, carbohydrates account for up to 90%.

Organic acids affect the degree of sweetness and taste of fruits and vegetables. Fruits usually have more acids than vegetables (except sorrel, rhubarb and tomatoes). On average, they are found in vegetables about 0.1%. The most common acids in vegetables and fruits are malic, citric and tartaric. Less common and in small quantities are oxalic acid, benzoic acid, salicylic acid, succinic acid, etc.

Nitrogenous substances in the composition of fruits and vegetables they are presented mainly in the form of proteins, as well as amino acids, enzymes, nucleic acids, etc.

In general, vegetables are richer in protein than fruits. The amount of protein in vegetables and fruits is small, but they are well absorbed. Most of all (up to 7%) is found in olives, in legumes (4–5%), nuts, spinach and cabbage vegetables, and garlic are relatively rich in protein.

Vitamins. Fruits and vegetables are sources of vitamins C, P, B1, B2, PP, K, E, pantothenic (B3) and folic (B9) acids, as well as provitamin A (β-carotene). The content of vitamins depends on the type of fruits and vegetables, growing and storage conditions, degree of ripeness and other factors.

Dyes (pigments) are found in cell plastids (chloroplasts, chromoplasts, etc.), are highly diverse and usually accompany each other. They are divided into the following groups: chlorophylls, carotenoids, flavone pigments and anthocyanins.

Lipids. The fat content in the pulp of vegetables and most fruits does not exceed 1%. Fats are unsaturated in nature; oleic, linoleic and linolenic acids predominate. Nuts (60–69%), olive pulp (up to 50%) and sea buckthorn (up to 8.0%) contain a lot of fat.

The appearance, color, smell and taste of individual varieties of fruit depend on the chemical composition, degree of ripeness, climatic conditions of growth, etc. The characteristic chemical composition of fruit determines their main characteristics, methods of consumption, storage, and, consequently, appropriate preservation methods. Therefore, in order to better understand some of the processes occurring in raw fruits during their storage, transportation, and canning, it is necessary to know the main groups of elements that make up their composition.

Fruits are composed of various inorganic and organic substances. Most of the mass in fruits is water, which accounts for 75 to 90% of their volume. The main portion of water, which is relatively easily removed by squeezing, pressing, drying, etc., is called free water. The rest of the water is tightly bound to other substances that make up the fruit, so that it cannot be completely removed either by pressing or even by drying. Bound water, or water in a bound state, makes up 10-20% of the total moisture.

After removing the water by intensive drying, what remains is dry product, where the chemicals present in a given fruit variety are concentrated. The dry product makes up 16% of the fresh fruit. If, for example, a dry product is burned (that is, when all organic substances are completely oxidized), ash remains, constituting approximately 0.5% of the fresh weight of the fruit. Mineral substances such as sulfur, phosphorus, potassium, calcium, sodium, magnesium, iron, silicon, and chlorine are preserved in the ash. And although all of the listed minerals are important for the development of the body, the leading role still belongs to calcium, phosphorus and iron.

The chemical composition and content of vitamins in fruits are given in table. 1.

* (ME - international unit corresponds to 0.025 microgram (μ).)

In addition, fruits are rich in microelements, such as copper (about 0.1 μg%), boron, iodine, zinc, tin, etc. Among organic substances, fruits contain mainly saccharides, vitamins, coloring and tannins, organic acids, proteins, fats, etc.

Sugar carbohydrates make up the bulk of the dry fruit product and are the main carrier of energy materials and the taste sensation of sweetness. Fresh fruits contain about 15% carbohydrates. These are easily soluble simple types of various sugars: glucose (grape sugar), fructose (fruit sugar) - from 3 to 12% and sucrose (beet sugar). In addition, the fruit contains small amounts of sugar alcohols, especially sorbitol. Other carbohydrates (types of complex sugars) are relatively abundant in fruits: they mainly make up the cell walls of fruits and vegetables. Along with a very small amount of starch, fruits contain many other carbohydrates, in particular pectin (about 1%), hemicellulose and cellulose (from 1 to 1.5%), on which, although they are not absorbed by the body, the body largely depends on regulation of the digestive tract.

Fruits contain a sufficient amount of substances genetically related to carbohydrates, primarily organic acids, or glycosides, coloring and tannins. They are called substances of secondary origin, because they are formed in plants from primary products, that is, from sugars during photosynthesis through the oxidation of carbon dioxide. These substances are highly soluble, easily absorbed into tissue and, like carbohydrates, participate in the metabolic process in our body.

Fruits contain malic, citric, tartaric and other acids. The amount of acid in almost all fruits does not exceed 1%; Lemons (up to 6%) and currants (up to 2.5%) contain the most acid. Organic acids, which give the fruit a sour taste, promote digestion. Organic acids play an important role when processing fruits using the canning method, since their ability to suppress the vital activity of microorganisms is used.

Vitamins belong to one of the main components of fruits. These are mainly various organic substances found naturally in living nature in extremely small quantities. In plants that synthesize them, they participate in various biochemical processes, being, as is well known, a necessary component of nutrition for both animals and humans. Vitamins are divided into groups according to their solubility in water and fat; depending on this, their role and function for the human body and its proper nutrition are determined. The functional significance of fat-soluble vitamins is limited, while water-soluble vitamins are involved in the metabolism of the entire body.

Fat-soluble vitamins include vitamins A, D, E and K.

Vitamin A (retinol) is found in fruits in the form of provitamin - carotene. For some varieties, the presence of carotene is determined by the orange color of the fruit (apricots, rose hips), sometimes this color is hidden by chlorophyll.

In the liver, enzymatic breakdown of carotene into active vitamin A occurs. The amount of vitamin A obtained from carotene depends on its chemical characteristics and enzymatic activity, which is not too high in humans. Despite the low percentage of vitamin A in free form in fruits, taking into account the high level of carotene, it plays an important role in ensuring normal growth of the body.

Vitamin D (calciferol) is not found in fruits either in free form or in the form of provitamins (sterols).

Vitamin E (tocopherol) is most often found in green leaves of plants: its concentration in fruits has not yet been precisely established.

Vitamin K (an antihemorrhagic vitamin) forms some naphthoquinone derivatives. A person replenishes this vitamin with products of the microflora of the digestive tract, partly with food. Fruits, compared to vegetables, contain significantly less of this vitamin (strawberries and rose hips only 0.1 mcg%).

The second group of vitamins that dissolve in water includes B vitamins, vitamin C, and more recently vitamin P has also been included here.

Among the B vitamins there are substances that differ in their chemical composition: B 1 (thiamine), B 2 (riboflavin), PP (niacin), B 6 (pyridoxine), H (biotin), Vs (leaf acid), B 12 ( cobalamin) and Bx (pantothenic acid), of which thiamine and riboflavin should be distinguished first of all. And although the content of these last two vitamins in fruits is small (see Table 1), their importance cannot be underestimated. By consuming vegetables and fruits, our body provides about 10% of these very necessary vitamins.

Vitamin C is the most important active substance in fruits. In terms of its chemical composition, it is ascorbic acid; it is easily oxidized, and at the very first reaction it turns into dehydroascorbic acid, which is even more biologically active. With further oxidation, substances that are slightly active are formed. The ability of vitamin C to quickly oxidize leads to significant losses of this valuable substance due to improper processing of fruits and vegetables at home and canning.

Vitamin C is found in almost all types of fruit (see Table 1). The greatest amount of it is found in rose hips, black currants and citrus fruits.

Vitamin P in fruits is usually inextricably linked with ascorbic acid, since it promotes its active participation in metabolism.

Squirrels with amino acids in free form make up the bulk of the nitrogenous substances of fruits. Their content is relatively small; for example, protein in raw fruits amounts to barely 0.5% of the mass. Garden and hazelnuts are richest in proteins (about 15%).

Fats, like proteins, are found most in nuts (approximately 50%). Fruits are not rich in fat - only 0.2 to 0.3%.

Tannins They give fruits a tartness, bitterish and astringent taste, in appropriate proportions, in particular apples, they harmoniously complement the sweet and sour taste. In the presence of oxidative enzymes, tannins quickly oxidize, changing color - fruits darken (green peel of nuts, cut apple), which negatively affects the quality of the finished product (change in color of syrup, compote, etc.).

The pleasant and characteristic smell inherent in many types and varieties of fruits is the result of the presence in them of the so-called aromatics, which have recently become the subject of careful study. These substances consist mainly of alcohols, aldehydes, various essential oils and other specific compounds.

Fruits containing large amounts pectin substances, are used primarily for making marmalade, jams and jellies. Pectin substances are found in large excess in unripe fruits, as well as in gooseberries, currants and apples. To make up for the missing amount of natural pectin, various seasonings (petose) are usually added during processing, as well as, if necessary, less ripe fruits.

Federal Agency for Education

State Educational Institution of Higher Professional Education "Samara State Economic University"

Department of Service

Coursework

by discipline

Commodity research and examination of food products

on the topic

2nd year students

Full-time education

Specialty "Service"

Yakovishena Evgenia Valerievna

Samara 2008

Introduction

I.I Chemical composition of vegetables and fruits

I.II Group characteristics of vegetables and fruits

II.Benefits of vegetables and fruits

II.II Harm to vegetables and fruits

III.I Harm and benefits of watermelons

Conclusion

Applications

Sources used

Introduction

Relevance of the selected topic

In the 20th century, significant changes occurred in human nutrition. Refined foods began to dominate the diet, consumption of animal products increased sharply, and the share of vegetables and fruits decreased. The added physical inactivity completed the picture: from overeating and lack of exercise, the person began to get sick seriously and often.

Vegetables are the most important suppliers of vitamins C, P, some B vitamins, provitamin A - carotene, mineral salts (especially potassium salts), a number of microelements, carbohydrates - sugars, phytoncides that help destroy pathogenic microbes, and, finally, ballast substances necessary for normal functioning of the intestines.

A remarkable property of vegetables is their ability to significantly increase the secretion of digestive juices and enhance their enzymatic activity.

Meat and fish dishes are better absorbed by the body if they are consumed with vegetables. Vegetable dishes enhance the secretion of the digestive glands and thereby prepare the digestive tract for the digestion of protein and fatty foods. Therefore, it is useful to start lunch with vegetable appetizers: vinaigrettes and salads, and then move on to soups, borscht, etc.

Vegetables are not only suppliers of important nutrients and vitamins, they are also dynamic regulators of digestion, increasing the ability to absorb nutrients, and therefore the nutritional value of most products. Vegetables are very valuable and necessary for the body every day at all times of the year.

In most regions of the Russian Federation, the consumption of vegetables and fruits fluctuates sharply and depends on the time of year. As a rule, they are sufficient in the second half of summer and autumn and somewhat lacking in late winter and early spring. In addition, the nutritional value of vegetables and fruits from the previous year's harvest is significantly reduced in the spring months. Lack of vegetable nutrition in winter and early spring is one of the reasons for the decrease in the body’s overall resistance to colds and infectious diseases. The daily intake of vegetables, except potatoes, should be from 300 to 400 grams for an adult at all times of the year. This amount should under no circumstances be reduced during the winter and spring months.

Growing early vegetables, developing suburban greenhouse farming, as well as improving storage and canning methods make it possible to consume them all year round. The best way to preserve vegetables and fruits, the most perfect way to preserve their nutritional value and taste, is freezing. Quick-frozen fruits and tomatoes are very healthy. It’s gratifying that lately more and more of them are appearing on the shelves of our stores. Unfortunately, we still do not make enough use of the huge variety of vegetables and fruits that nature gives us. Suffice it to say that of the many varieties of cabbage, white cabbage is the most common in our country. But it is not at all the healthiest: cauliflower, Brussels sprouts, kohlrabi and other types of cabbage are much richer in vitamin C. In the spring, a variety of vegetables are undeservedly little used in our diet: green onions, lettuce, spinach, rhubarb, etc. Green onions are especially useful at this time of year, 100 grams of which contain about 30 milligrams of vitamin C and 2 milligrams of carotene - provitamin A, which significantly helps to satisfy the daily requirement of an adult for vitamin C.

Chapter I

I . I Chemical composition of vegetables and fruits

Considering the wide variety of vegetables and fruits, let's get acquainted with their classification.

Vegetables are divided into:

tubers (potatoes, sweet potatoes),

root vegetables (radish, radish, rutabaga, carrots, beets, celery),

cabbages (white cabbage, red cabbage, savoy cabbage, Brussels sprouts, cauliflower, kohlrabi),

onions (onions, leeks, wild garlic, garlic),

salad-spinach (lettuce, spinach, sorrel),

pumpkin (pumpkin, zucchini, cucumber, squash, melon),

tomato (tomato, eggplant, pepper),

dessert (asparagus, rhubarb, artichoke),

spicy (basil, dill, parsley, tarragon, horseradish),

legumes (beans, peas, beans, lentils, soybeans).

Fruits are divided into stone fruits (apricots, cherries, dogwoods, peaches, plums, sweet cherries), pome fruits (quinces, pears, rowan berries, apples), subtropical and tropical crops (pineapples, bananas, pomegranates, etc.), real berries (grapes, gooseberries , currants, barberries, lingonberries, blueberries, blueberries, cranberries, raspberries, blackberries, sea buckthorn) and false (strawberries).

Vegetables, fruits, berries and other edible plants have a high ability to stimulate appetite, stimulate the secretory function of the digestive glands, improve bile formation and bile flow.

Plants rich in essential oils - tomatoes, cucumbers, radishes, onions, garlic, horseradish - have a pronounced juice effect. Of the pickled and pickled vegetables, cabbage has the strongest property of stimulating the appetite, then cucumbers, beets, and carrots least of all.

Vegetables increase the digestibility of proteins, fats, and minerals. Added to protein foods and cereals, they enhance the secretory effect of the latter, and when consumed together with fat, they remove its inhibitory effect on gastric secretion. It is important to note that undiluted juices of vegetables and fruits reduce the secretory function of the stomach, and diluted ones increase it.

Berries and fruits also have different effects on the secretory function of the stomach. Some (most) increase it (grapes, prunes, apples, strawberries), others (especially sweet varieties) decrease it (cherries, raspberries, apricots, etc.).

The beneficial effect of vegetables, fruits and berries is explained by the presence of mineral salts, vitamins, organic acids, essential oils, and fiber. Vegetables activate the bile-forming function of the liver: some are weaker (beetroot, cabbage, rutabaga juices), others are stronger (radish, turnip, carrot juice). When vegetables are combined with proteins or carbohydrates, less bile enters the duodenum than with purely protein or carbohydrate foods. And the combination of vegetables with oil increases the formation of bile and its flow into the duodenum; vegetables are stimulants of pancreatic secretion: undiluted vegetable juices inhibit secretion, and diluted juices stimulate it.

Water- an important factor ensuring the course of various processes in the body. It is an integral part of cells, tissues and body fluids and ensures the supply of nutrients and energy substances to the tissues, the removal of metabolic products, heat exchange, etc. A person can live without food for more than a month, without water - only a few days.

Plants contain water in free and bound form. Organic acids, minerals, and sugar are dissolved in freely circulating water (juice). Bound water entering plant tissues is released from them when their structure changes and is absorbed more slowly into the human body. Water from plants is quickly eliminated from the body, since plants are rich in potassium, which increases urination. Metabolic products and various toxic substances are excreted in the urine.l

Carbohydrates Plants are divided into monosaccharides (glucose and fructose), disaccharides (sucrose and maltose) and polysaccharides (starch, cellulose, hemicellulose, pectin substances). Monosaccharides and disaccharides

dissolve in water and provide the sweet taste of plants.

Glucose is part of sucrose, maltose, starch, and cellulose. It is easily absorbed in the gastrointestinal tract, enters the blood, and is absorbed by the cells of various tissues and organs. When it is oxidized, ATP is formed - adenosine triphosphoric acid, which is used by the body to carry out various physiological functions as a source of energy. When excess glucose enters the body, it turns into fats. The richest in glucose are cherries, sweet cherries, grapes, then raspberries, tangerines, plums, strawberries, carrots, pumpkin, watermelon, peaches, and apples. Fructose is also easily absorbed by the body and, to a greater extent than glucose, turns into fats. In the intestine, it is absorbed more slowly than glucose and does not require insulin for its absorption, therefore it is better tolerated by patients with diabetes. Grapes, apples, pears, cherries, cherries are rich in fructose, then watermelon, black currants, raspberries, and strawberries. The main source of sucrose is sugar. In the intestine, sucrose is broken down into glucose and fructose. Sucrose is found in beets, peaches, melon, plums, tangerines, carrots, pears, watermelons, apples, and strawberries.

Maltose is an intermediate product of starch breakdown and is broken down into glucose in the intestines. Maltose is found in honey, beer, baked goods and confectionery products.

Starch is the main source of carbohydrates. Flour, cereals, pasta and, to a lesser extent, potatoes are richest in it.