During the processing of food products, sugars can undergo acid and enzymatic hydrolysis.
acid hydrolysis. Hydrolysis of disaccharides occurs in the preparation of sweet dishes (kissels, compotes, baking apples), as well as in the preparation of confectionery fudge. The hydrolysis of sucrose takes place in an acidified aqueous medium. Sucrose attaches a water molecule and breaks down into equal amounts of glucose and fructose:
C12 H22 O11 C6 H12 O6 + C6 H12 O6
hydrolysis glucose fructose
The process is called inversion, and the equimolecular mixture of monosaccharides is called invert sugar. Invert sugar has specific properties:
1. Enhances the sweetness of products in low concentration sugar solutions.
2.Prevents concentrated sucrose solutions from crystallization (saccharification). Responsible for this is fructose, which ranks first among sugars in terms of sweetness and is very hygroscopic.
The inversion ability of acids is not the same. The largest is in oxalic, the smallest is in acetic. The intermediate is occupied by lemon and apple (10-15 times less than that of oxalic). It should be noted that oxalic acid is a poison and is not used in culinary practice. But we are talking about it, because it is contained in the cell juice of vegetables and fruits.
along with citric and malic acids.
The reaction rate of sucrose hydrolysis is proportional to the concentration of hydrogen ions in the medium, and the degree of sucrose inversion depends on the type of acid, its concentration, and the duration of thermal exposure. In practice, this is important in the organization of the technological process. For example, cooking compote from summer varieties of apples. It is advisable to first boil the syrup with the addition of citric acid, and then put prepared apples into it, bring to a boil and cool.
Enzymatic hydrolysis sucrose and maltose occurs during the fermentation of yeast dough and at the beginning of baking products from it, the production of beer, kvass, wines, etc. Mapltose is formed by the action of amylolytic enzymes on starch. Being in the test sucrose and maltose under the action of yeast enzymes are hydrolyzed with the formation of invert saar. Glucose and fructose accumulating in the process are subjected to deep cleavage by the yeast enzymatic complex with the formation of ethyl alcohol and carbon dioxide. Lactic acid fermentation can also occur with the participation of lactic acid bacteria. The pH of the dough shifts to the acid side.
The hydrolysis reaction of sucrose proceeds with the formation of glucose and fructose:
C 12 H 22 O 11 + H 2 O C 6 H 12 O 6 + C 6 H 12 O 6 (124)
sucrose glucose fructose
glucose fructose
The reaction is bimolecular. Since the molar concentration of water in an aqueous solution is many times greater than that of sucrose, its change during the reaction will be insignificant compared to the change in the concentration of sucrose. Therefore, the rate of the sucrose hydrolysis reaction will be proportional practically only to the molar concentration of sucrose and the kinetic reaction equation will be the first order reaction equation.
Denote:
a is the molar concentration of sucrose in the reacting mixture at the time t \u003d 0, mol / dm 3;
X is the molar concentration of glucose or fructose at subsequent time points t, mol/dm 3 .
Then the kinetic equation of the reaction:
,
(125)
where k – reaction rate constant, s -1 ;
t – reaction time, s.
The reaction of hydrolysis of sucrose in an aqueous solution practically does not go. It is catalyzed by hydrogen ions by adding a solution of a strong mineral acid to the sucrose solution. The reaction is very convenient for studying, since sucrose itself and hydrolysis products have an asymmetric carbon atom and are optically active. Therefore, it is easy to monitor the course of this reaction using the instrument - polarimeter(or saccharimeter), the principle of which is based on the use of polarized light.
1 Radiation polarization
Radiation having a wavelength of 350 to 900 nm (visible region of the spectrum) is called light.
When a light wave propagates, the electromagnetic field strength vector usually oscillates in all possible directions perpendicular to the line of propagation of the light beam. However, under certain conditions, the directions of these oscillations become parallel to each other - in this case, we say that the light is plane polarized. According to the electromagnetic theory of light propagation, magnetic perturbation occurs in the plane of polarization, and electrical perturbation occurs at right angles to the magnetic one. To simplify the scheme for considering oscillations in a polarized beam, we combine all parallel planes into one. If a beam of natural (unpolarized) light is passed through a crystal of Iceland spar in the direction of its crystallographic axis, then it splits into two beams, both of which become plane polarized, and their planes of polarization are mutually perpendicular. Each of these rays can be bifurcated again as it passes through an Icelandic spar crystal, and so on.
When determining the refractive index of this crystal, we studied the passage of radiation from an excited sodium atom through it (sodium line D). For each of the two rays, it was found that for one of them (called ordinary beam) the refractive index has a constant value of 1.658 , and for another (called extraordinary beam) the refractive index varies in the range from 1.486 to 1.658 depending on the direction in which the beam propagates in the crystal.
Both beams (ordinary and extraordinary) can be separated from each other using Nicolas prisms. This prism, simply called a nicol for short, is made as follows: a rhombic crystal of Iceland spar is sawn along a plane passing through the tops of its obtuse angles and dividing the crystal into two symmetrical parts; then the planes are polished and glued together again with Canadian balsam.
Figure 10.1 shows the cross-sectional plane of the crystal ABCD. Straight line AO shows the direction of the optical axis of the crystal; Ray PQ when entering the crystal near the surface AD refracted; the refracted beam turns out to be inclined to the optical axis at an angle of about 75 , and the extraordinary beam experiences less deviation due to the lower refractive index and passes in the direction PQRS. Since an ordinary beam has a higher refractive index, it deviates in the direction QX and meets the plane AC at a greater angle than the extraordinary beam.
Figure 10.1 - Scheme of the passage of light through a Nicol prism.
Thus, the nicole divides the light falling on it into two parts, and the light that comes out through the face BC the beam is plane polarized. If this ray falls on the second nicol, placed in the same way as the first, then the polarized ray will pass through it. If the second nicole is rotated by 90 , then the polarized light undergoes total internal reflection and exits through the side face; as a result, the indicated ray will not pass through the second nicole. When the second nicol is rotated through an angle less than 90 , a plane polarized beam is divided by the second nicol into two beams, and only one of them will pass through the prism. Thus, when the second nicol is rotated in any direction by 180 , the intensity of light transmitted through this prism decreases from the maximum value to zero, and then increases again from zero to the previous value.
If the nicols are crossed, that is, they are mutually oriented so that light does not pass through the second nicol, then when certain substances are introduced between the two nicols, part of the radiation passes through the second nicol. Substances that have this property are called optically active and they are said to rotate the plane of polarization. In such cases, the first nicol from which the polarized beam emerges is called polarizer, and the second nicol, which allows you to determine whether the light incident on it is polarized - analyzer.
When an optically active substance is introduced between the crossed nicols, the light can be extinguished again by turning the analyzer through a small angle. In some cases, this turn has to be made to the right, and in others to the left. Accordingly, these rotations are called right or left rotation of the polarization plane. If the light goes out when the analyzer is rotated to the right by 15°, then the same effect can be observed by rotating the analyzer to the left by 165°; however, when determining the direction of rotation, the smaller of the two angles of rotation is always taken into account.
The value of the angle of rotation of the polarization plane depends on the nature of the substance, on the thickness of the layer taken, on the wavelength of the applied light, on the temperature, and in the case of solutions, additionally on the concentration of the solute and on the nature of the solvent.
Scientists have proven that sucrose is part of all plants, it is found in large quantities in such consumer products as sugar beet and cane. In the nutrition of any person, the role of sucrose is large enough.
Sucrose is a disaccharide (belongs to the class of oligosaccharides), which, under the action of the enzyme sucrose or under the action of an acid, is hydrolyzed into glucose (all the main polysaccharides are composed of it) and fructose (fruit sugar), more precisely, the sucrose molecule consists of residues of D-fructose and D- glucose. The main and accessible to all product that serves as a source of sucrose is ordinary sugar.
In chemistry, the sucrose molecule is written by the following formula - C 12 H 22 O 11 and is an isomer.
Hydrolysis of sucrose
C 12 H 22 O 11 + H 2 O → C 6 H 12 O 6 + C 6 H 12 O 6
Sucrose is the most important of the disaccharides. As seen from sucrose leads to the formation of elements such as glucose and fructose. Their molecular formulas are the same, but their structural formulas are completely different:
CH 2 (OH) -(CHOH) 4 -SON - glucose.
CH 2 - CH - CH - CH -C - CH 2 - fructose
Physical properties of sucrose
- Sucrose is colorless in taste and readily soluble in water.
- 160 °C is the temperature characteristic for the melting of sucrose.
- Caramel is an amorphous transparent mass that is formed when molten sucrose solidifies.
Chemical properties of sucrose
- Sucrose is not an aldehyde.
- Sucrose is the most important disaccharide.
- When heated with an ammonia solution, Ag 2 O does not give the so-called "silver mirror", just as when heated with Cu (OH) 2 does not form red copper oxide.
- If you boil a solution of sucrose with 2-3 drops of sulfuric acid or then neutralize it with any alkali, then heat the resulting solution with Cu (OH) 2, then a red precipitate will form.
Composition of sucrose
The sucrose molecule, as you know, consists of fructose and glucose residues, which are closely linked. Among the isomers that have the molecular formula C 12 H 22 O 11, the following are distinguished: and, of course,
Foods rich in sucrose
The effect of sucrose on the human body
Sucrose provides the human body with the energy necessary for its full functioning. It also improves the brain activity of a person and stimulates the protective functions of his liver from the effects of toxic substances. Supports the life support of striated muscles and nerve cells. That is why sucrose is one of the most important substances contained in almost all human consumption products.
With a lack of sucrose in a person, the following conditions are observed: depression, irritability, apathy, lack of energy, lack of strength. This condition can constantly worsen if the sucrose content in the body is not normalized in time. Excess sucrose leads to the following: caries, excessive fullness, periodontal disease, inflammatory diseases of the oral cavity, the development of candidiasis and itching of the genital organs, there is a risk of developing diabetes.
The need for sucrose increases in cases where the human brain is overloaded as a result of vigorous activity, and (or) when the human body is exposed to severe toxic effects. The need for sucrose consumption is sharply reduced if a person has diabetes or is overweight.
The effect of fructose and glucose on the human body
As it turned out earlier, as a result of the interaction "sucrose - water", elements such as fructose and glucose are formed. Consider the main characteristics of these substances and how these elements affect human life.
Fructose, a type of sugar molecule found in fresh fruits, gives them their sweetness. As a result, many believe that fructose is the healthiest. is a natural component. Also, fructose has a minimal effect on glucose levels (because it has a low glycemic index).
By itself, fructose is very sweet, however, fruits known to man contain relatively small amounts of it. As a result of this, a small amount of sugar enters our body, which is processed very quickly. However, you should not introduce a large amount of fructose into the body, because. excessive use of it can lead to such consequences as obesity, cirrhosis (scarring of the liver), gout and heart disease (increased levels of uric acid), fatty liver and, of course, premature aging of the skin, resulting in wrinkles.
As a result of research, scientists came to the conclusion that fructose, unlike glucose, accumulates signs of aging much faster. What can we say about fructose substitutes.
Based on the material previously proposed, it can be concluded that eating a reasonable amount of fruits is good for human health, since they contain a minimum amount of fructose. Concentrated fructose, on the other hand, should be avoided as it can lead to real illness.
Glucose - just like fructose, is one of and is a form of carbohydrate - the most common form. from starches, it quickly raises the level of sugar in the blood and supplies energy to our body for a fairly long period of time.
Consistently eating foods that are highly processed, or simple starches such as white rice or white flour, will cause your blood sugar levels to rise significantly. And the result of this will be certain problems, such as a decrease in the level of the body's defenses, which, as a result, leads to poor wound healing, kidney failure, nerve damage, increased blood lipids, the risk of nerve disease (peripheral), obesity, as well as the occurrence of a heart attack and (or) stroke.
Artificial sweeteners - harm or benefit
Many people who are afraid to consume glucose or fructose turn to artificial sweeteners such as aspart or sucrapose. However, they also have their drawbacks. Due to the fact that these substances are artificial chemical neurotoxic substances, substitutes can cause headaches, and there is also a high risk of developing cancer. Therefore, this option, like the previous ones, is not 100%.
The whole world around us affects the human body, and none of us can protect ourselves from all diseases. However, based on some knowledge, we can control the processes of occurrence of certain ailments. It is the same with the use of sucrose: do not neglect it, exactly the same as constantly using it. You should find a "golden" mean and stick to the best options. Options in which your body will feel great and tell you a huge "thank you"! So choose which type of sugar you should use and glow with energy all day long.
sucrose C 12 H 22 O 11, or beet sugar, cane sugar, in everyday life just sugar - a disaccharide from the group of oligosaccharides, consisting of two monosaccharides - α-glucose and β-fructose.
Chemical properties of sucrose
An important chemical property of sucrose is the ability to undergo hydrolysis (when heated in the presence of hydrogen ions).
Since the bond between monosaccharide residues in sucrose is formed by both glycosidic hydroxyls, it does not have restorative properties and does not give a "silver mirror" reaction. Sucrose retains the properties of polyhydric alcohols: it forms water-soluble sugars with metal hydroxides, in particular, with calcium hydroxide. This reaction is used to isolate and purify sucrose in sugar refineries, which we will talk about a little later.
When an aqueous solution of sucrose is heated in the presence of strong acids or under the action of an enzyme invertases going on hydrolysis of this disaccharide to form a mixture of equal amounts of glucose and fructose. This reaction is the reverse of the formation of sucrose from monosaccharides:
The resulting mixture is called invert sugar and is used for the production of caramel, sweetening food products, to prevent the crystallization of sucrose, obtaining artificial honey, and the production of polyhydric alcohols.
Relation to hydrolysis
The hydrolysis of sucrose is easy to follow with a polarimeter, since the sucrose solution has right-hand rotation, and the resulting mixture D- glucose and D- fructose has a left rotation, due to the prevailing value of the left rotation of D-fructose. Consequently, as sucrose is hydrolyzed, the angle of right rotation gradually decreases, passes through zero, and at the end of hydrolysis, a solution containing equal amounts of glucose and fructose acquires a stable left rotation. In this regard, hydrolyzed sucrose (a mixture of glucose and fructose) is called invert sugar, and the hydrolysis process itself is called inversion (from Latin inversia - turning, rearranging).
The structure of maltose and celobiose. Relation to hydrolysis
Maltose and starch. Composition, structure and properties. Relation to hydrolysis
Physical Properties
Maltose is easily soluble in water and has a sweet taste. The molecular weight of maltose is 342.32. The melting point of maltose is 108 (anhydrous).
Chemical properties
Maltose is a reducing sugar because it has an unsubstituted hemiacetal hydroxyl group.
By boiling maltose with dilute acid and by the action of an enzyme maltose hydrolyzes (two molecules of glucose C 6 H 12 O 6 are formed).
Starch (C 6 H 10 O 5) n polysaccharides of amylose and amylopectin, the monomer of which is alpha-glucose. Starch, synthesized by different plants in chloroplasts, under the action of light during photosynthesis, differs somewhat in the structure of grains, the degree of polymerization of molecules, the structure of polymer chains, and physicochemical properties.
