Determination of reducing (reducing) sugars in plant material. Sugar. Reducing sugars A solution is used to oxidize reducing sugars

Introduction

Sugar. Reducing sugars

Invert syrup

Reducing sugar

The importance of sugars for the body

Methods for determining sugar in confectionery products

experimental part

Preparation of copper alkaline citrate solution (Benedict's reagent)

Carrying out analysis

Discussion of the research results

1. Determination of the content of reducing sugars in marmalade

2. Determination of the content of reducing sugars in marshmallows

3. Determination of the content of reducing sugars in caramel

conclusions

Bibliography

Annex 1

Introduction

Iodometry is a method of volumetric analysis, in which newer than which are the reactions: + 2e? 2I?

I? ?2 e? I2

The iodimetry method can be used to determine both oxides teli and reducing agents.

Determination of oxidizing agents. The iodimetry method can be used to determine those oxidizing agents that quantitatively oxidize I ?to free I2. Most often, permanganates, bichromates, copper (II) salts, and jelly salts are determined for (III), free halogens, etc. The indicator in the iodimetry method is a starch solution. This is a sensitive and specific indie cator that forms a blue adsorption compound with iodine.

Definition of reducing agents. From the number restored This method most often determines sulfites, sulfides, tin(II) chloride, etc. The working solution is a solution of iodine I2. The iodimetry method is widely used in chemical analysis. This method determines arsenic (III) compounds; copper (II) in salts, ores; many organic drugs - formaldehyde, analgin, ascorbic acid, etc.
Purpose of the work: determination of reducing sugars in various confectionery products. Tasks:

Development of a technique for the quantitative determination of reducing sugars in a working solution.

To establish compliance with the normal contents of reducing sugars in confectionery products contained in GOST

The main raw materials for the production of confectionery products are sugar, invert syrup, flour, fats, and milk. In addition, fruits and berries, nuts, cocoa beans, honey, spices and many other products are used in the production of confectionery products.

In shaping the consumer properties of confectionery products, a large role is given to products that give them structure, appearance, taste and color: gelling agents, emulsifiers, foaming agents, dyes, flavorings.

consumer confectionery reducing sugar

Sugar. Reducing sugars

The product is a pure carbohydrate - sucrose, characterized by a pleasant sweet taste and high digestibility. It has great physiological value, has a stimulating effect on the central nervous system, contributing to the aggravation of the organs of vision and hearing; is a nutrient for the gray matter of the brain; participates in the formation of fat, protein-carbohydrate compounds and glycogen. Excessive sugar consumption leads to obesity, diabetes, and caries. The daily norm is 100 g, per year - 36.5 kg, but it should be differentiated depending on age and lifestyle.

Invert syrup

Invert syrup serves as a substitute for molasses, as it has anti-crystallization properties. Invert syrup is obtained by heating an aqueous solution of sugar and acid, during which the inversion process occurs, which consists in the splitting of sucrose into fructose and glucose. Acids used for inversion are: hydrochloric, citric, lactic, acetic.

Reducing sugar

All monosaccharides, in the case of syrup glucose and fructose, and some disaccharides, including maltose and lactose, belong to the group of reducing (reducing) sugars, i.e. compounds that can enter into a reduction reaction.

Two common reactions for reducing sugars - the Benedict reaction and the Fehling reaction - are based on the ability of these sugars to reduce the divalent copper ion to monovalent. Both reactions use an alkaline solution of copper(II) sulfate (CuSO4), which is reduced to insoluble copper(I) oxide (Cu2O).

The Fehling reaction is most often used to prove the reducing properties of sugars; it involves the reduction of copper (II) hydroxide to copper (I) oxide by monosaccharides. When carrying out the reaction, Fehling's reagent is used, which is a mixture of copper sulfate with Rochelle salt (potassium, sodium tartrate) in an alkaline medium. When copper sulfate is mixed with alkali, copper hydroxide is formed.

CuSO4 + 2NaOH -> Cu(OH)2? + Na2SO4

In the presence of Rochelle salt, the released hydroxide does not precipitate, but forms a soluble copper(II) complex compound, which is reduced in the presence of monosaccharides to form copper(I) protoxide. In this case, the aldehyde or ketone group of the monosaccharide is oxidized to a carboxyl group. For example, the reaction of glucose with Fehling's reagent.

CH2OH - (CHOH) 4 - SON + Cu(OH) 2 ===>

The importance of sugars for the body

Fructose.

Fructose is less abundant than glucose and also oxidizes quickly. Some fructose is converted into glucose in the liver, but it does not require insulin for its absorption. This circumstance, as well as the significantly slower absorption of fructose compared to glucose in the intestine, explains its better tolerance in patients with diabetes.

Glucose is the constituent unit from which all the most important polysaccharides are built - glycogen, starch, cellulose. It is part of sucrose, lactose, maltose. Glucose is quickly absorbed into the blood from the gastrointestinal tract, then enters the cells of organs, where it is involved in the processes of biological oxidation. Glucose metabolism is accompanied by the formation of significant amounts of adenosine triphosphoric acid (ATP), which is a source of a unique type of energy. ATP plays the role of a universal battery and energy carrier in all living organisms. In medicine, adenosine preparations are used for vascular spasms and muscular dystrophy, and this proves the importance of ATP and glucose for the body.

While the body is awake, glucose energy replenishes almost half of its energy costs. The remaining unclaimed portion of glucose is converted into glycogen, a polysaccharide that is stored in the liver.

Methods for determining sugar in confectionery products

Since monitoring the sugar level in the body is necessary, there are a number of different methods for determining the amount of both total and reducing (inverse) sugars in confectionery products,
which is an important part of quality control for the production of these products. Iodimetric method

The method is based on the reduction of an alkaline solution of copper with a certain amount of a solution of reducing sugars and determining the amount of copper oxide (1) formed or unreduced copper using an iodometric method.

The method is used for all types of confectionery products and semi-finished products, except flour confectionery products, semi-finished products for cakes and pastries and oriental sweets.

The method is used when disagreements arise in quality assessment.

Permanganate method

The method is based on the reduction of iron (III) salt with copper (I) oxide and subsequent titration reduction of reduced iron oxide (I) with permanganate.

Polarimetric method

The method is based on measuring the rotation of the plane of polarization of light by optically active substances.

The method is used to determine the mass fraction of total sugar in chocolate, pralines, cocoa drinks, chocolate spreads, sweet bars, chocolate semi-finished products without additives and with the addition of milk.

experimental part

Preparation and standardization of a solution C(Na2S2O3) = 0.1 mol/dm3

Reagents:

Weight of Na2S2O3×5H 2O

Sample of K2Cr2O7

M HCl solution

% Starch solution

Distilled water

Volumetric flask 100cm3;

Measuring cylinder with a capacity of 25 cm3;

Conical titration flask 250 cm3

Pipette 10 ml

25 ml burette

Progress:

A working solution of sodium thiosulfate is prepared by weighing, based on the given concentration of the solution and its volume. To prepare 200 ml of a 0.1 m sodium thiosulfate solution, weigh out 5 g of sodium thiosulfate in a weighing bottle on a technical scale. The sample taken is dissolved in 200 ml of distilled water and 0.02 g of soda is added. The solution is stored in a dark glass bottle.

Determination of the exact concentration of sodium thiosulfate solution is carried out using 2-3 precise portions of potassium dichromate using the semi-micro method (25 ml burette, 0.1 ml division). The weight of potassium dichromate is calculated taking into account the volume of the volumetric flask, pipette, burette and the concentration of the prepared sodium thiosulfate solution. Considering that the titration of an aliquot of a solution of potassium dichromate should use 10 ml of 0.1 M sodium thio sulfate and the ratio of the volumetric flask and pipette

: 10, calculate the mass of potassium dichromate: (K2Cr2O7) = C(Na2S2O3) × V(Na2S2O3) × M(1/6 K2Cr2O7) × 100/10 = 0,1× 10 49×10 = 490 mg = 0.49 g.

The exact weight of potassium dichromate is in the range of 0.47-0.51 g. The test tube with potassium dichromate is weighed on an analytical balance, the dichromate is poured through a funnel into a 100 ml volumetric flask and the test tube with potassium dichromate is weighed. Based on the difference in weighing, a portion of potassium dichromate is found. Wash the potassium dichromate from the funnel into the flask with distilled water, shake the contents of the flask until the potassium dichromate is completely dissolved

and only after that add water to the mark. The solution is mixed well. A 10 ml pipette is washed with potassium dichromate solution

and take 1/10 of it into a 250 ml titration flask, add 5 ml of a 10% KI solution and 5 ml of a 2 M HCl solution. The flask is covered with a watch glass and left for 5 minutes in a dark place. Then add 50 ml of water to the solution and titrate with sodium thiosulfate solution, adding it drop by drop and mixing the solution well. When the color of the solution turns from brown to pale yellow, add 50 drops of starch solution

(2-3 ml) and continue titration until the blue color of the solution turns pale green, almost colorless. In the second and subsequent titrations, starch is added as close to the end of the titration as possible. The volume of sodium thiosulfate solution is measured with an accuracy of ±0.005 ml. Titration of an aliquot of the potassium dichromate solution is carried out 3-4 times and the average value of the volume of sodium thiosulfate (Vavg) is calculated, the relative deviation from the average is not more than 0.5%. Based on experimental data, the titer of sodium thiosulfate is calculated from potassium dichromate.

Calculation part

V1=9, 6 ml=10, 3 ml=9, 8 mlsr=9.9 ml

M(1/6 K2Cr2O7)=49 g/mol

M(Na2S2O3 × 5H2O)=248 g/mol(Na2S2O3)=158.11 g/ml(K2Cr2O7)= C(Na2S2O3) × V(Na2S2O3) × M(1/6 K2Cr2O7) × 100/10=0.1 ×10 ×49 ×10=490 mg =0.49 g

T (Na2S2O3/ K2Cr2O7) = , g/ml(Na2S2O3) = , mol/l(Na2S2O3) = , g/ml(Na2S2O3/ K2Cr2O7) = =0.005050 g/ml(Na2S2O3)= =0.1030 mol/ l(Na2S2O3) = = 0.01629 g/ml

Preparation of copper alkaline citrate solution (Benedict's reagent)

Reagents:×5H20

Citric acid C6H8O7CO3

Distilled water

Equipment

Volumetric flask 250 cm3

Beaker

Progress.

77 g of copper sulfate is dissolved in 25 cm3 dist. water.

5 g of citric acid are dissolved separately in 13 cm3 dist. water.

9 g of anhydrous sodium carbonate are also separately dissolved in 125 cm3 of hot dist. water.

The citric acid solution is carefully poured into the sodium carbonate solution. After the release of carbon dioxide ceases, the mixture of solutions is transferred to a volumetric flask with a capacity of 250 cm3, a solution of copper sulfate is poured into the flask and the contents of the flask are adjusted to dist. water to the mark, mix

During the experiment, aldehyde groups are oxidized, and copper cations are reduced. Benedict's reagent tends to form hydrated oxides, so the reaction product is not always red in color: it can also be yellow or green. If the sugar content is low, then a precipitate forms only upon cooling. If there are no reducing sugars, the solution remains clear. Solutions with a sugar content of 0.08% give a noticeable positive result, while for Fehling's reagent this value is 0.12%

Preparation of the working test solution.

A weighed portion of the crushed test product is taken so that the amount of reducing sugars in 1 cm3 of solution is about 0.005 g

The weight of the sample is calculated using the formula

where b is the optimal concentration of reducing sugars g/cm3 capacity of the volumetric flask, cm3 is the expected mass fraction of reducing sugars in the product under study, %

According to GOST 6442-89 Marmalade can contain no more than 20% reducing sugars by weight of the product.

According to GOST 6441-96 Pastille confectionery products can contain from 10% to 25% of reducing sugars by weight of the product.

According to GOST 6477-88, caramel can contain no more than 20% reducing sugars by weight of the product.

The sample in a glass is dissolved in distilled water heated to 60?-70?C

If the product dissolves without a residue, then the resulting solution is cooled and transferred to a 250 cm3 volumetric flask, adjusted to the mark with the same water and mixed well.

If the product contains substances that are insoluble in water, then after transferring the sample into a volumetric flask, place it in a water bath for 10-15 minutes, then filter, cool and adjust with distilled water to the mark.

Carrying out analysis

25 cm3 of an alkaline copper citrate solution, 10 cm3 of the test solution and 15 cm3 of distilled water are pipetted into a conical flask with a capacity of 250 cm3. The flask is connected to a reflux refrigerator and brought to a boil for 3-4 minutes and boiled for 10 minutes. During boiling, we observe a qualitative reaction of glucose with copper hydroxide: since glucose contains five hydroxyl groups and one aldehyde group, it is classified as an aldehyde alcohol. Its chemical properties are similar to those of polyhydric alcohols and aldehydes. The reaction with copper(II) hydroxide demonstrates the reducing properties of glucose. Add a few drops of Benedict's solution to the glucose solution. No copper hydroxide precipitate is formed. The solution turns bright blue. In this case, glucose dissolves copper (II) hydroxide and behaves like a polyhydric alcohol. Let's heat the solution. The color of the solution begins to change. First, a yellow Cu2O precipitate forms, which over time forms larger red Cu2O crystals. Glucose is oxidized to gluconic acid.

CH2OH - (CHOH) 4 - SON + Cu(OH) 2 ===> CH2OH - (CHOH) 4 - COOH + Cu2O?+ H2O

The flask is quickly cooled to room temperature.

Add 10 cm3 of KI solution 30% and 25 cm3 of H2SO4 solution with a concentration of 4 mol/dm3 to the cooled liquid. Sulfuric acid is poured in carefully to prevent it from splashing out of the flask due to the released carbon dioxide. After this, the released iodine is immediately titrated with a solution of sodium thiosulfate until the liquid turns light yellow.

Then add 2-3 cm3 of 1% starch solution and continue to titrate the dirty blue liquid until a milky white color appears. Record the amount of thiosulfate that was used for titration. The experiment is repeated 3 times.

The control experiment is carried out under the same conditions, for which 25 cm3 of an alkaline copper citrate solution and 25 cm3 of distilled water are taken.

The difference between the volume of sodium thiosulfate in cm3 spent in the control experiment and in the determination, multiplied by the correction factor K = 1.2, gives the amount of copper expressed in cm3 of 0.1 mol/dm3 sodium thiosulfate solution, from which the number of milligrams of inverse sugar is found in 10 cm3 of solution of a sample of the test product according to Table 1, provided in GOST 5903-89

The mass fraction of reducing sugars (X) as a percentage is calculated using the formula

Where m is the sample of the product, g is the mass of inverse sugar determined from Table 1, mg is the capacity of the volumetric flask, cm3 is the volume of the test solution taken for analysis, cm3

Discussion of the research results

Determination of the content of reducing sugars in marmalade.

Titration 123 Volume, ml 1716.616 Average value, ml 16.5 The volume of sodium thiosulfate in the control experiment was 31 cm3isk1 = (31-17)1.21= 16.9 cm3isk2 = (31-16.6)1.21= 17.4 cm3isk3 = (31-16)1.21= 18.2 cm3inv1 = 46.14 mg (in accordance with the table in Appendix 1) inv2 = 47.34 mg (in accordance with the table in Appendix 1) inv3 = 49.74 mg (in accordance with the table in Appendix 1) = 6, 25 g = 250 cm3 = 10 cm3

Average = 19.1%

Determination of the content of reducing sugars in marshmallows.

Volume of sodium thiosulfate used for titration

Titration 123 Volume 17.817.717.5 Average value, ml 17.7 isk1 = (31-17.8)1.21= 16 cm3isk2 = (31-17.7)1.21= 16.1 cm3isk3 = (31-17.5)1.21= 16.3 cm3inv1 =43, 53 mg (according to the table in Appendix 1) inv2 = 43.82 mg (according to the table in Appendix 1) inv3 = 44.11 mg (according to the table in Appendix 1) = 5, 25 g = 250 cm3 = 10 cm3

Average = 20.86%

Determination of the content of reducing sugars in caramel

Volume of sodium thiosulfate used for titration

Titration 123 Volume 18,318,518.1 Average value, ml 18.3 isk1 = (31-18.3)1.21= 15.4 cm3isk2 = (31-18.5)1.21= 15.1 cm3isk3 = (31-18.1)1.21= 15.6 cm3inv1 = 41.79 mg (in accordance with the table in Appendix 1) inv2 = 40.92 mg (in accordance with the table in Appendix 1) inv3 = 42.37 mg (in accordance with the table in Appendix 1) = 5, 25 g = 250 cm3=10 cm3

Average = 19.9%

Objects of research Established contents ed. sugars, % Normal content ed. sugars according to GOST,% Marmalade 19.1 No more than 20 Pastille 20.86 From 10 to 25 Caramel 19.9 No more than 20

As a result of the study, it was possible to establish the mass fraction of reducing sugars in various types of confectionery products using the method of iodometric titration. According to the results, the content of reducing sugars in all products provided for analysis corresponds to the state standard, and therefore can be approved for sale.

Bibliography

GOST 6477-88 Caramel. General technical conditions.

GOST 6441-96 Pastille confectionery products.

GOST 6442-89 Marmalade. Technical conditions.

V.P. Vasiliev Analytical Chemistry - M.: Bustard 2004

Skoog D., West D. Fundamentals of analytical chemistry. - M.: Mir, 1979. T. 1,2.

Fundamentals of Analytical Chemistry / Ed. Academician Yu. A. Zolotov. - M.: Higher School, 2002. Book. 12.

Alekseev V.I. Quantitative analysis. - M.: Chemistry, 1972.

Confectionery [Electronic resource]: #"justify">Confectionery [Electronic resource]: #"justify">Appendix 1

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Introduction

Sugar. Reducing sugars

Invert syrup

Reducing sugar

experimental part

Carrying out analysis

1. Determination of the content of reducing sugars in marmalade

2. Determination of the content of reducing sugars in marshmallows

conclusions

Bibliography

Annex 1

Introduction

Iodometry is a method of volumetric analysis, in which newer than which lie the reactions: + 2e → 2I ―

I ― ―2e → I2

The iodimetry method can be used to determine both oxides teli and reducing agents.

Determination of oxidizing agents. The iodimetry method can be used to determine those oxidizing agents that quantitatively oxidize I ―to free I2. Most often, permanganates, bichromates, copper (II) salts, and jelly salts are determined for (III), free halogens, etc. The indicator in the iodimetry method is a starch solution. This is a sensitive and specific indie cator that forms a blue adsorption compound with iodine.

Development of a technique for the quantitative determination of reducing sugars in a working solution.

To establish compliance with the normal contents of reducing sugars in confectionery products contained in GOST

consumer confectionery reducing sugar

Sugar. Reducing sugars

Invert syrup

Reducing sugar

CuSO4 + 2NaOH -> Cu(OH)2↓ + Na2SO4

CH2OH - (CHOH) 4 - SON + Cu(OH) 2 ===>

The importance of sugars for the body

Fructose.

Fructose is less abundant than glucose and also oxidizes quickly. Some fructose is converted into glucose in the liver, but it does not require insulin for its absorption. This circumstance, as well as the much slower absorption of fructose compared to glucose in the intestine, explains its better tolerance in patients with diabetes.

Methods for determining sugar in confectionery products

The method is used for all types of confectionery products and semi-finished products, except flour confectionery products, semi-finished products for cakes and pastries and oriental sweets.

The method is used when disagreements arise in quality assessment.

Permanganate method

The method is based on the reduction of iron (III) salt with copper (I) oxide and subsequent titration reduction of reduced iron oxide (I) with permanganate.

Polarimetric method

The method is based on measuring the rotation of the plane of polarization of light by optically active lenses. creatures.

experimental part

Preparation and standardization of a solution C(Na2S2O3) = 0.1 mol/dm3

Reagents:

Weight of Na2S2O3 ×5H 2O

Sample of K2Cr2O7

M HCl solution

% Starch solution

Distilled water

Volumetric flask 100cm3;

Measuring cylinder with a capacity of 25 cm3;

Conical titration flask 250 cm3

25 ml burette

Progress:

: 10, calculate the mass of potassium dichromate: (K2Cr2O7) = C(Na2S2O3) × V(Na2S2O3) × M(1/6 K2Cr2O7) × 100/10 = 0,1× 10 49× 10 = 490 mg = 0.49 g.

and only after that add water to the mark. The solution is mixed well. A 10 ml pipette is washed with potassium dichromate solution

Calculation part

V1=9, 6 ml=10, 3 ml=9, 8 mlsr=9.9 ml

M(1/6 K2Cr2O7)=49 g/mol

M(Na2S2O3 × 5H2O)=248 g/mol(Na2S2O3)=158.11 g/ml(K2Cr2O7)= C(Na2S2O3) × V(Na2S2O3) × M(1/6 K2Cr2O7) × 100/10=0.1 ×10 ×49 ×10=490 mg =0.49 g

T (Na2S2O3/ K2Cr2O7) = , g/ml(Na2S2O3) = , mol/l(Na2S2O3) = , g/ml(Na2S2O3/ K2Cr2O7) = =0.005050 g/ml(Na2S2O3)= =0.1030 mol/ l(Na2S2O3) = = 0.01629 g/ml

Preparation of copper alkaline citrate solution (Benedict's reagent)

Reagents:×5H20

Citric acid C6H8O7CO3

Distilled water

Equipment

Volumetric flask 250 cm3

Beaker

Progress.

77 g of copper sulfate is dissolved in 25 cm3 dist. water.

5 g of citric acid are dissolved separately in 13 cm3 dist. water.

9 g of anhydrous sodium carbonate are also separately dissolved in 125 cm3 of hot dist. water.

Preparation of the working test solution.

A weighed portion of the crushed test product is taken so that the amount of reducing sugars in 1 cm3 of solution is about 0.005 g

The weight of the sample is calculated using the formula

m= b×V×100/P

where b is the optimal concentration of reducing sugars g/cm3 capacity of the volumetric flask, cm3 is the expected mass fraction of reducing sugars in the product under study, %

According to GOST 6442-89 Marmalade can contain no more than 20% reducing sugars by weight of the product.

According to GOST 6441-96 Pastille confectionery products can contain from 10% to 25% of reducing sugars by weight of the product.

According to GOST 6477-88, caramel can contain no more than 20% reducing sugars by weight of the product.

The sample in a glass is dissolved in distilled water heated to 60˚-70˚С

If the product dissolves without a residue, then the resulting solution is cooled and transferred to a 250 cm3 volumetric flask, adjusted to the mark with the same water and mixed well.

Carrying out analysis

CH2OH - (CHOH) 4 - SON + Cu(OH) 2 ===> CH2OH - (CHOH) 4 - COOH + Cu2O↓+ H2O

The flask is quickly cooled to room temperature.

The control experiment is carried out under the same conditions, for which 25 cm3 of an alkaline copper citrate solution and 25 cm3 of distilled water are taken.

The mass fraction of reducing sugars (X) as a percentage is calculated using the formula

Discussion of the research results

Determination of the content of reducing sugars in marmalade.

ω1 = = = 18.5%

ω2 = = = 18.9%

ω3 = = = 19.9%

ωaverage = 19.1%

Determination of the content of reducing sugars in marshmallows.

Volume of sodium thiosulfate used for titration

ωaverage = 20.86%

Determination of the content of reducing sugars in caramel

Volume of sodium thiosulfate used for titration

ωaverage = 19.9%

Objects of research Established contents ed. sugars, % Normal content ed. sugars according to GOST,% Marmalade 19.1 No more than 20 Pastille 20.86 From 10 to 25 Caramel 19.9 No more than 20

conclusions

Bibliography

GOST 6477-88 Caramel. General technical conditions.

GOST 6441-96 Pastille confectionery products.

GOST 6442-89 Marmalade. Technical conditions.

V.P. Vasiliev Analytical Chemistry - M.: Bustard 2004

Skoog D., West D. Fundamentals of analytical chemistry. - M.: Mir, 1979. T. 1,2.

Fundamentals of Analytical Chemistry / Ed. Academician Yu. A. Zolotov. - M.: Higher School, 2002. Book. 12.

Alekseev V.I. Quantitative analysis. - M.: Chemistry, 1972.

Confectionery [Electronic resource]: #"justify">Confectionery [Electronic resource]: #"justify">Appendix 1

At one time in medicine, we used the methodology of detecting glucose in urine or blood according to Fehling or Benedict. She taught me so-so, like “leave me alone.” Having acquired a new profession, I had to delve even deeper into the chemistry of reduction. She got me. In the food industry, the analysis of reducing sugars is very common and allows one to quantify the simple sugars present (electron donors in the redox reaction) and their concentration.
This reaction occurs in thermal processes: in the so-called Maillard or caramelization reactions. For example, in the case of chocolate, reducing sugars are naturally present in the cocoa bean and, during roasting, produce characteristic variations in color and aroma. Reducing and non-reducing substances give an idea of the stages of operation of all sugar syrups, help in the field of wine, juice, sugar cane and much more.
Thus, this term "reducing agent" allows the classification of certain sugars between them based on their chemical property.
Confectioners and culinary specialists, let's remember Chemistry! It turns out that all this is necessary! Very much!

Reducing sugars.

Monosaccharides and most disaccharides have reducing properties, all of which are due to the (aldehyde) carboxyl group they have in their own molecule. The free end of an atom is used by donating electrons to another free molecule. Their open chemical structure (with two chemical rings) allows them to break down at twice the rate of disaccharides.
This reducing nature can be demonstrated by the redox reaction carried out between them and copper(II) sulfate. Solutions of this salt are blue. After reaction with the reducing carbohydrate copper(I) oxide, a brick-red color is formed. Thus, a change in color indicates that the specified reaction has occurred and that, therefore, the carbohydrate is reducing. Scientists use several common chemical compounds to determine reducing sugar: the most common are the Benedict reaction and the Fehling reaction.

Sugars that test positive are known as reducing sugars. Sugars with a hemiacetal or hemiketal group give a positive result. But I will not consider them (this is for a general concept).

The most common sugars in food are glucose and fructose (monosaccharides), and to a lesser extent lactose and galactose (disaccharides). A number of sugars or sucrose are not reducing sugars, but if the sugar solution is heated or acidified, hydrolysis occurs: sucrose is broken down into glucose and fructose, and these are monosaccharides. And they are being reduced.

Non-reducing sugars.

These are carbohydrates - polysaccharides. The most common is sucrose. It has a closed (closed) chemical structure. It has several chemical rings (three), where open atoms are used to bind the structure as a whole and, therefore, do not have free electrons to donate to the connecting molecule. Because of this, there is no oxidation during the reaction. It will take much longer to cause decomposition.

Non-reducing sugar has no reactivity and no aldehyde group, so the Benedict test gives a negative result.

You can see the practical results in the photo:

1. Sucrose solution + 2 drops of Benedict's reagent (negative result, non-reducing agent)
2. Fructose solution + 2 drops of Benedict's reagent
3. Glucose solution + 2 drops of Benedict's reagent
4. Lactose solution + 2 drops of Benedict's reagent

Reduce (the word itself) - literally, if translated, then in biology: to become reduced in size, in the technical sense - a decrease (about gas pressure)

For those who don’t understand anything, watch the video, albeit in English.

Or a schematic analysis, the Benedict test:

Used additional source:
Pratt, Charlotte W.; Cornely, Kathleen (2013). Essential Biochemistry

Introduction

Sugar. Reducing sugars

Invert syrup

Reducing sugar

The importance of sugars for the body

Methods for determining sugar in confectionery products

experimental part

Preparation of copper alkaline citrate solution (Benedict's reagent)

Carrying out analysis

Discussion of the research results

1. Determination of the content of reducing sugars in marmalade

2. Determination of the content of reducing sugars in marshmallows

3. Determination of the content of reducing sugars in caramel

conclusions

Bibliography

Annex 1

Introduction

Iodometry is a method of volumetric analysis, which is based on the following reactions:

The iodimetry method can be used to determine both oxidizing agents and reducing agents.

Determination of oxidizing agents. The iodimetry method can be used to determine those oxidizing agents that quantitatively oxidize IЇ into free I2. Most often, permanganates, dichromates, copper (II) salts, iron (III) salts, free halogens, etc. are determined. The indicator in the iodimetry method is a starch solution. This is a sensitive and specific indicator that forms a blue adsorption compound with iodine.

Definition of reducing agents. Among the reducing agents, this method most often determines sulfites, sulfides, tin (II) chloride, etc. The working solution is a solution of iodine I2. The iodimetry method is widely used in chemical analysis. This method determines arsenic (III) compounds; copper (II) in salts, ores; many organic drugs - formaldehyde, analgin, ascorbic acid, etc.
Purpose of the work: determination of reducing sugars in various confectionery products.

Development of a technique for the quantitative determination of reducing sugars in a working solution.

To establish compliance with the normal contents of reducing sugars in confectionery products contained in GOST

consumer confectionery reducing sugar

Sugar. Reducing sugars

Invert syrup

Reducing sugar

Two common reactions to reducing sugars - the Benedict reaction and the Fehling reaction - are based on the ability of these sugars to reduce the divalent copper ion to monovalent. Both reactions use an alkaline solution of copper(II) sulfate (CuSO4), which is reduced to insoluble copper(I) oxide (Cu2O).

CuSO4 + 2NaOH -> Cu(OH)2v + Na2SO4

CH2OH - (CHOH) 4 - SON + Cu(OH) 2 ===>

The importance of sugars for the body

Fructose.

Methods for determining sugar in confectionery products

Iodimetric method

The method is used for all types of confectionery products and semi-finished products, except flour confectionery products, semi-finished products for cakes and pastries and oriental sweets.

The method is used when disagreements arise in quality assessment.

Permanganate method

The method is based on the reduction of iron (III) salt with copper (I) oxide and subsequent titration of the reduced iron (I) oxide with permanganate.

Polarimetric method

The method is based on measuring the rotation of the plane of polarization of light by optically active substances.

experimental part

Preparation and standardization of a solution C(Na2S2O3) = 0.1 mol/dm3

Reagents:

Weighed portion of Na2S2O3Х5pO

Sample of K2Cr2O7

2M HCl solution

1% Starch solution

Distilled water

1. Volumetric flask 100cm3;

2. Measuring cylinder with a capacity of 25 cm3;

3. Conical titration flask 250 cm3

4. Pipette 10 ml

4. 25 ml burette

Progress:

100:10, calculate the mass of potassium dichromate:

m(K2Cr2O7) = C(Na2S2O3) ChV(Na2S2O3) ChM(1/6 K2Cr2O7) Ch100/10 = 0.1H 10 49H10 = 490 mg = 0.49 g.

and only after that add water to the mark. The solution is mixed well. A 10 ml pipette is washed with potassium dichromate solution

(2--3 ml) and continue titration until the blue color of the solution turns pale green, almost colorless. In the second and subsequent titrations, starch is added as close to the end of the titration as possible. The volume of sodium thiosulfate solution is measured with an accuracy of ±0.005 ml. Titration of an aliquot of the potassium dichromate solution is carried out 3-4 times and the average value of the volume of sodium thiosulfate (Vavg) is calculated, the relative deviation from the average is not more than 0.5%. Based on experimental data, the titer of sodium thiosulfate is calculated from potassium dichromate.

Calculation part

M(1/6 K2Cr2O7)=49 g/mol

М(Na2S2O3Ч 5pO)=248 g/mol

M (Na2S2O3)=158.11 g/ml

m(K2Cr2O7)= C(Na2S2O3) P V(Na2S2O3) P M(1/6 K2Cr2O7) P 100/10=0.1 P10 P49 P10=490 mg =0.49 g

T (Na2S2O3/ K2Cr2O7) = , g/ml

C (Na2S2O3) = , mol/l

T (Na2S2O3) = , g/ml

T (Na2S2O3/ K2Cr2O7) = =0.005050 g/ml

C (Na2S2O3)= =0.1030 mol/l

T (Na2S2O3) = = 0.01629 g/ml

Preparation of copper alkaline citrate solution (Benedict's reagent)

Reagents:

Citric acid C6H8O7

Distilled water

Equipment

Volumetric flask 250 cm3

Beaker

Progress.

9.77 g of copper sulfate is dissolved in 25 cm3 dist. water.

12.5 g of citric acid are dissolved separately in 13 cm3 dist. water.

35.9 g of anhydrous sodium carbonate are also separately dissolved in 125 cm3 of hot dist. water.

Preparation of the working test solution.

A weighed portion of the crushed test product is taken so that the amount of reducing sugars in 1 cm3 of solution is about 0.005 g

The weight of the sample is calculated using the formula

where b is the optimal concentration of reducing sugars g/cm3

P - estimated mass fraction of reducing sugars in the product under study, %

According to GOST 6442-89 Marmalade can contain no more than 20% reducing sugars by weight of the product.

According to GOST 6441-96 Pastille confectionery products can contain from 10% to 25% of reducing sugars by weight of the product.

According to GOST 6477-88, caramel can contain no more than 20% reducing sugars by weight of the product.

The sample in a glass is dissolved in distilled water heated to 60?-70?C

If the product dissolves without a residue, then the resulting solution is cooled and transferred to a 250 cm3 volumetric flask, adjusted to the mark with the same water and mixed well.

Carrying out analysis

CH2OH - (CHOH) 4 - SON + Cu(OH) 2 ===> CH2OH - (CHOH) 4 - COOH + Cu2Ov+ H2O

The flask is quickly cooled to room temperature.

Add 10 cm3 of KI solution 30% and 25 cm3 of pSO4 solution with a concentration of 4 mol/dm3 to the cooled liquid. Sulfuric acid is poured in carefully to prevent it from splashing out of the flask due to the released carbon dioxide. After this, the released iodine is immediately titrated with a solution of sodium thiosulfate until the liquid turns light yellow.

The control experiment is carried out under the same conditions, for which 25 cm3 of an alkaline copper citrate solution and 25 cm3 of distilled water are taken.

The mass fraction of reducing sugars (X) as a percentage is calculated using the formula

Where m-weight of the product, g

m1 - mass of inverse sugar determined from Table 1, mg

V-capacity of the volumetric flask, cm3

V1 is the volume of the test solution taken for analysis, cm3

Discussion of the research results

Determination of the content of reducing sugars in marmalade.

The volume of sodium thiosulfate in the control experiment is 31 cm3

Visk1 = (31-17)1.21= 16.9 cm3

Visk2 = (31-16.6)1.21= 17.4 cm3

Visk3 = (31-16)1.21= 18.2 cm3

minv1 =46.14 mg (according to the table in Appendix 1)

minv2 =47.34 mg (according to the table in Appendix 1)

minv3 =49.74 mg (according to the table in Appendix 1)

sch1 = = = 18.5%

u2 = = = 18.9%

u3 = = = 19.9%

waverage = 19.1%

Determination of the content of reducing sugars in marshmallows.

Volume of sodium thiosulfate used for titration

Visk1 = (31-17.8)1.21= 16 cm3

Visk2 = (31-17.7)1.21= 16.1 cm3

Visk3 = (31-17.5)1.21= 16.3 cm3

minv1 =43.53 mg (according to the table in Appendix 1)

minv2 =43.82 mg (according to the table in Appendix 1)

minv3 =44.11 mg (according to the table in Appendix 1)

wav = 20.86%

Determination of the content of reducing sugars in caramel

Volume of sodium thiosulfate used for titration

Visk1 = (31-18.3)1.21= 15.4 cm3

Visk2 = (31-18.5)1.21= 15.1 cm3

Visk3 = (31-18.1)1.21= 15.6 cm3

minv1 =41.79 mg (according to the table in Appendix 1)

minv2 =40.92 mg (according to the table in Appendix 1)

minv3 =42.37 mg (according to the table in Appendix 1)

waverage = 19.9%

Bibliography

GOST 6477-88 Caramel. General technical conditions.

GOST 6441-96 Pastille confectionery products.

GOST 6442-89 Marmalade. Technical conditions.

V.P. Vasiliev Analytical Chemistry - M.: Bustard 2004

Skoog D., West D. Fundamentals of analytical chemistry. - M.: Mir, 1979. T. 1,2.

Fundamentals of Analytical Chemistry / Ed. Academician Yu. A. Zolotov. - M.: Higher School, 2002. Book. 12.

Alekseev V.I. Quantitative analysis. - M.: Chemistry, 1972.

Confectionery products [Electronic resource]: http://ru.wikipedia.org/wiki/Confectionery_products

Confectionery products [Electronic resource]: http://www.amaras.biz/publ/1-1-0-1

Annex 1

Determination of reducing (reducing) sugars in plant material. Sugar. Reducing sugars A solution is used to oxidize reducing sugars

Tutoring

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