Bakery products methods for determining acidity. Bakery products methods for determining acidity The procedure for preparing for analysis

1 area of ​​use

1.1 This standard applies to bakery products, as well as low-moisture bakery products, and establishes methods for determining acidity.

1.2 The degree of acidity is understood as the volume in cubic centimeters of a solution of the exact molar concentration of 1 sodium hydroxide or potassium hydroxide necessary to neutralize the acids contained in 100 g of products.

Conical flasks and glasses with a capacity of 50, 100, 150, 250 - according to GOST 25336.

Pipettes of the 4th accuracy class with a capacity of 25, 50 - according to GOST 29227.

Burettes of the 4th accuracy class - according to GOST 29251.

Wooden spatula or glass stick with a rubber tip.

Medical gauze - according to GOST 9412.

Sodium hydroxide - according to GOST 4328, a solution of a molar concentration of 0.1.

It is allowed to use similar equipment, glassware and reagents that are not inferior in technical and metrological characteristics to those listed above.

4 How to prepare for analysis

4.2 The procedure for preparing for the analysis of weight and piece bakery products weighing more than 0.5 kg.

Samples consisting of a whole product are cut in half in width and a piece (chunk) weighing about 70 g is cut from one half, from which the crusts and subcrustal layer are cut off with a total thickness of about 1 cm.

For a sample consisting of a part of the product, the windward part is cut off on one side, making a continuous cut about 0.5 cm thick. Then a piece weighing about 70 g is cut off, from which the crusts and subcrustal layer are cut off with a total thickness of about 1 cm.

4.3 The procedure for preparing for the analysis of piece bakery products weighing 0.5-0.2 kg.

The products are cut in half in width and a piece weighing about 70 g is cut off from one half, from which the crusts and the subcrustal layer are cut off about 1 cm thick.

4.4 The procedure for preparing for the analysis of piece bakery products weighing less than 0.2 kg

Whole products are taken, from which the crusts are cut off with a layer of about 1 cm.

The procedure for preparing for the analysis of baked piece bakery products of a specific form is established in the regulatory documentation for these products.

4.6 The procedure for preparing for the analysis of low-moisture bakery products (lamb products, crackers, etc.).

The selection of samples of bakery products of low humidity to determine the acidity is carried out in accordance with the requirements set forth in GOST 7128 (for lamb products); in GOST 8494 (for crackers); in GOST 9846 (for crispbread); in GOST 11270 (for straws, bread sticks).

In low-moisture bakery products, inclusions and finishes are removed, except for products with poppy seeds and nuts, and ground on a grater, in a mortar or on a mechanical grinder such as an electric coffee grinder, crumbs are obtained. The crumbs are mixed and immediately take the sample.

5 Analysis procedure

5.1 How to analyze bakery products

5.1.1 Verification (arbitration) method

Weigh out 25.0 g of the crumb obtained according to 4.5. The sample is placed in a dry bottle (such as milk) with a capacity of 500 with a well-fitting cork.

A volumetric flask with a capacity of 250 is filled to the mark with distilled water at a temperature of 18-25°C. About 1/4 of the distilled water taken is poured into a bottle with crumbs, quickly rubbed with a wooden spatula or a glass rod with a rubber tip until a homogeneous mass is obtained, without noticeable lumps of unrubbed crumbs.

To the resulting mixture is poured from a volumetric flask all the remaining distilled water. The bottle is stoppered, the mixture is shaken vigorously for 2 minutes and left alone at room temperature for 10 minutes. The mixture is then shaken again vigorously for 2 minutes and left alone for 8 minutes.

After 8 minutes, the settled liquid layer is carefully poured through a fine sieve or gauze into a dry glass. From a beaker, 50 solutions are taken with a pipette into two conical flasks with a capacity of 100-150 each and titrated with a solution of a molar concentration of 0.1 potassium hydroxide or sodium hydroxide with 2-3 drops of phenolphthalein until a faint pink color is obtained, which does not disappear when the flask is at rest in within 1 min.

5.1.2 Fast method

Weigh out 25.0 g of the crumb obtained according to 4.5. The sample is placed in a dry bottle (such as milk) with a capacity of 500, with a well-fitting cork.

A volumetric flask with a capacity of 250 is filled to the mark with distilled water heated to a temperature of 60°C.

About 1/4 of the distilled water taken is poured into a bottle with crumbs, quickly rubbed with a wooden spatula until a homogeneous mass is obtained, without noticeable lumps of unrubbed crumbs.

All the remaining distilled water is added to the resulting mixture from a volumetric flask. The bottle is stoppered and shaken vigorously for 3 minutes.

After shaking, the mixture is allowed to settle for 1 min, and the settled liquid layer is carefully poured into a dry glass through a fine sieve or gauze. From a beaker, 50 solutions are taken with a pipette into two conical flasks with a capacity of 100-150 each and titrated with a solution of a molar concentration of 0.1 sodium hydroxide or potassium hydroxide with 2-3 drops of phenolphthalein until a faint pink color is obtained, which does not disappear when the flask is at rest in within 1 min.

Titration is continued if after 1 min the color disappears and does not appear from the addition of 2-3 drops of phenolphthalein.

5.2 How to analyze low moisture bakery products

Weigh out 10.0 g of the crumb obtained according to 4.6. The sample is placed in a dry conical flask with a capacity of 250.

Of the pre-measured 100 distilled water with a temperature of 18-25 ° C, about 30 distilled water is poured into a flask with a sample, mixed, shaken until a homogeneous mass is obtained. The rest of the water is added, shaken again, making sure that no crumb particles stick to the walls of the flask. The mixture is allowed to stand for 15 minutes, and then the liquid is drained through a fine sieve or gauze into a dry flask. From the flask, 25% of the filtrate is pipetted into two conical flasks with a capacity of 100-150 each and titrated with a solution of a molar concentration of 0.1 sodium hydroxide or potassium hydroxide with phenolphthalein (5 drops) until a pink color is obtained that does not disappear within 1 min.

Titration is continued if after 1 min the color disappears and does not appear from the addition of 2-3 drops of phenolphthalein.

5.3 In case of use drinking water instead of distilled, its preliminary titration is mandatory.

6 Rules for processing analysis results

Acidity X, deg., is calculated by the formula

where V is the volume of a solution of a molar concentration of 0.1 sodium hydroxide or potassium hydroxide consumed during titration of the test solution, ;

The volume of distilled water taken to extract acids from the product under study, ;

Foreword

1 DEVELOPED by the State Research Institute of the Baking Industry

REPRESENTED by the Interstate Technical Committee for Standardization MTK 3 “Bread, bakery and pasta»

INTRODUCED by Gosstandart of Russia

2 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (Protocol No. 9 of April 12, 1996)

3 Decision of the Committee Russian Federation on standardization, metrology and certification dated September 10, 1996 No. 569, the interstate standard GOST 5670-96 was put into effect as state standard Russian Federation since August 1, 1997

INTERSTATE ST A N D A R T

BAKERY PRODUCTS Methods for determining acidity

Bread, rolls and buns.

Methods for determination of acidity

Introduction date 1997-08-01

1 AREA OF USE

1.1 This standard applies to bakery products, as well as bakery products of reduced tartar, and establishes methods for determining acidity.

1.2 The degree of acidity is understood as the volume in cubic centimeters of a solution of the exact molar concentration I mother / dm "sodium hydroxide or potassium hydroxide, necessary for the neutralization of acids contained in 100 g of products.

GOST 1770--74 Measuring laboratory glassware. Cylinders, beakers, flasks, test tubes. Are common specifications

Official edition

3 CONTROLS AND ACCESSORIES

Scales laboratory general purpose 4th accuracy class, not more than 1.0 kg, with an allowable error of ± 75 mg according to GOST 24104.

Grater, mortar or mechanical grinder.

Thermometer.

Bottles (such as milk) with a capacity of 500 cm.

Plugs according to GOSG 5541 or TU 38 1051835.

Volumetric flasks of the 4th accuracy class with a capacity of 100.250 cm 5 according to GOST 1770.

Conical flasks and glasses with a capacity of 50, 100. 150. 250 cm 1 according to GOST 25336.

Pipettes of the 4th accuracy class with a capacity of 25.50 cm3 according to GOST 29227.

Burettes of the 4th accuracy class according to GOST 29251.

Wooden spatula or glass stick with a rubber tip.

Medical gauze according to GOST 9412.

Sodium hydroxide according to GOST 4328. solution of molar concentration 0.1 mother/dm 1 .

Potassium pyroxide according to GOST 24363, solution of molar concentration 0.1 mol/dm".

Phenolphthalein according to TU 6-09-5360, alcohol solution with a mass ratio of 1%.

Distilled water according to GOST 6709.

Drinking water according to GOST 2874.

It is allowed to use similar equipment, laboratory glassware and reagents that are not inferior in technical and metrological characteristics to those listed above.

4 PROCEDURE TO PREPARE FOR THE ANALYSIS

4.1 Sampling - according to GOST 5667.

4.2 How to prepare for the analysis of weight and piece bakery products weighing more than 0.5 kg

Samples consisting of a whole product are cut in half in width and a piece (chunk) weighing about 70 g is cut from one half, from which the crusts and the subcrustal layer are cut off with a total thickness of about 1 cm.

For a sample consisting of a part of the product, the windward part is cut off on one side, making a continuous cut about 0.5 cm thick. Then a piece weighing about 70 g is cut off, from which the crusts and subcrustal layer are cut off with a total thickness of about 1 cm.

4.3 Procedure for preparing for the analysis of piece

bakery products weighing 0.5-0.2 kg

The products are cut in half in width and a piece weighing about 70 g is cut off from one half, from which the crusts and the subcrustal layer are cut off about 1 cm thick.

4.4 The procedure for preparing for the analysis of piece

bakery products weighing less than 0.2 kg

Whole products are taken, from which the crusts are cut off with a layer of about 1 cm.

The procedure for preparing for the analysis of baked piece bakery products of a specific form is established in the regulatory documentation for these products.

4.5 From pieces of products prepared according to 4.2. 4.3. 4.4. all inclusions are removed (jam, jam, raisins, etc.), then they are quickly crushed into crumbs, mixed and immediately taken in portions.

4.6 The procedure for preparing for the analysis of low-moisture bakery products (lamb products, crackers, etc.).

The selection of samples of bakery products of reduced size to determine the acidity is carried out in accordance with the requirements set forth in GOST 7128 (for lamb products); in GOST 8494 (for crackers): in GOST 9846 (for crispbread); in GOST 11270 (for straws, bread sticks).

In low-moisture bakery products, inclusions and finishes are removed, except for products with poppy seeds and nuts, and ground on a grater, in a mortar or on a mechanical grinder such as an electric coffee grinder, crumbs are obtained. The crumbs are mixed and immediately take the sample.

5 ORDER II14) ANALYSIS

5.1 How to analyze bakery products

5.1.1 Verification (arbitration) method

Weigh out 25.0 g of the crumb obtained according to 4.5. The sample is placed in a dry bottle (such as milk) with a capacity of 500 cm 3 with a well-fitting cork.

A volumetric flask with a capacity of 250 cm * is filled to the mark with distilled water at a temperature of 18-25 "C. About '/ 4 of the taken distilled water is poured into a bottle with crumbs, quickly rubbed with a wooden spatula or a glass rod with a rubber tip until a homogeneous mass is obtained, without noticeable lumps of unrubbed crumbs.

All the remaining distilled water is poured from the measured kaaba to the resulting mixture. The bottle is stoppered, the mixture is shaken vigorously for 2 minutes and left alone at room temperature for 10 minutes. The mixture is then shaken vigorously again for 2 minutes and left to rest for 8 minutes.

After 8 minutes, the settled liquid layer is carefully poured through a fine sieve or gauze into a dry glass. From a glass, 50 cm 3 of a solution is pipetted into two conical flasks with a capacity of 100-150 cm "each and titrated with a solution of a molar concentration of 0.1 mol / dm 3 of potassium hydroxide or sodium hydroxide with 2-3 drops of phenolphthalein until a faint pink color is obtained. not disappearing at a calm state of the flask for 1 min.

5.1.2 Fast method

Weigh out 25.0 g of the crumb obtained according to 4.5. The sample is placed in a dry bottle (such as milk) with a capacity of 500 cm 3 with a well-fitting cork.

A volumetric flask with a capacity of 250 cm 3 is filled up to the mark with distilled water, heated to a temperature of 60 * C.

Near "/< взятой дистиллированной воды переливают в бутылку с крошкой, быстро растирают деревянной лопаточкой до получения однородной массы, без заметных комочков нерастертой крошки.

To the resulting mixture, add all the remaining distilled water from a volumetric flask. The bottle is stoppered and shaken vigorously for 3 minutes.

After shaking, the mixture is allowed to settle for 1 min, and the settled liquid layer is carefully poured into a dry glass through a fine sieve or gauze. 50 cm 3 of the solution are pipetted from the glass into two conical flasks with a capacity of 100-150 cm 3 each and titrated with a solution of a molar concentration of 0.1 mol / dm 3 sodium hydroxide or potassium hydroxide with 2-3 drops of phenolphthalein until a faint pink color is obtained , which does not disappear when the flask stands still for 1 min.

Titration is continued if after 1 min the color disappears and does not appear after the addition of 2-3 drops of phenolphthalein.

5.2 The procedure for carrying out a and a l and a bakery products of low humidity

Weigh out 10.0 g of the crumb obtained according to 4.6. The sample is placed in a dry conical flask with a capacity of 250 cm 3 .

From pre-measured 100 cm 'of distilled water with a temperature of 18-25 "C, about 30 cm" of distilled water is poured into a flask with a sample, mixed, shaken until a homogeneous mass is obtained. They add the rest of the water, shake it again, keeping an eye on it. so that the axis of the adhered crumb particles does not remain on the walls of the flask. The mixture is allowed to stand for 15 minutes, and then the liquid is drained through a fine sieve or gauze into a dry flask. From the flask, 25 cm3 of the filtrate are pipetted into two conical flasks with a capacity of 100-150 cm3 each and titrated with a solution of a molar concentration of 0.1 mol / dm 3 sodium hydroxide or potassium hydroxide with phenolphthalein (5 drops) until a pink color is obtained, not disappearing within I min.

Titration is continued if after 1 min the color disappears and does not appear from the addition of 2-3 drops of phenolphthalein.

5.3 If drinking water is used instead of distilled water, it must be pre-titrated.

6 RULES FOR PROCESSING ANALYSIS RESULTS

Acidity X. deg, calculated by the formula

V v -v ( .a „

pG^TG * (I)

where K is the volume of a solution of a molar concentration of 0.1 mol / dm 1 of sodium hydroxide or potassium hydroxide consumed during titration of the test solution, cm ";

K - the volume of distilled water taken to extract acids from the product under study. cm*;

a - conversion factor per 100 g sample;

K - correction factor for bringing the used solution of sodium hydroxide or potassium hydroxide to a solution of an exact molar concentration of 0.1 mol / dm ';

yjj - reduction coefficient of a solution of sodium hydroxide or potassium pyroxide molar

concentrations of 0.1 mol/dm 1 to 1.0 mol/dm"; t is the sample weight, g;

V ) - the volume of the test solution taken for titration, cm '.

For bakery products, formula (1) can be represented

y y ■ 250 100 „

X \u003d 7V K. (3)

For bakery products of low moisture, formula (1) can be represented

X \u003d 4Y K. (5)

The calculation is carried out to the second decimal place.

7 RULES FOR RECORDING THE RESULTS OF THE ANALYSIS

7.1 Determination of acidity is considered correct if the results of two parallel titrations for one filtrate completely coincide or differ for bread and bakery products by no more than 0.30 deg, for bakery products of low moisture - by no more than 0.40 deg.

7.2 The arithmetic mean of the results of two parallel determinations is taken as the final result of the analysis.

7.3 The result of the analysis is recorded with an accuracy of 0.5 deg, and fractions up to 0.25 deg

discarded inclusive; shares over 0.25 and up to 0.75 degrees inclusive equate to 0.5 degrees;

fractions over 0.75 degrees are equated to 1.0 degrees.

8 PERMISSIBLE ANALYSIS ERROR

The discrepancies between the results of determining the acidity of a laboratory sample of one batch of products in different laboratories should not exceed 0.5 deg.

UDC 664.66.001.4:006.354 MKS 67.060 N39 OKSTU 9109

Keywords: bread, bakery products, low moisture bakery products, acidity, titration

Editor L. V. Karetnikopa Technical editor O.N. Vlasova Proofreader A.S. Chsrppusgta Computer nutlet L. A. Krugovoi

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GOST 5670-96

Group H39

INTERSTATE STANDARD

BAKERY PRODUCTS

Methods for determining acidity

Bread, rolls and buns.
Methods for determination of acidity

OKS 67.060
OKSTU 9109

Introduction date 1997-08-01

Foreword

1 DEVELOPED by the State Research Institute of the Baking Industry

REPRESENTED by the Interstate Technical Committee MTK-3 "Bread, bakery and pasta"

INTRODUCED by Gosstandart of Russia

2 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (Minutes N 9-96 of April 12, 1996)

Voted to accept:

State name	Name of the national standardization body
The Republic of Azerbaijan	Azgosstandart
Republic of Armenia	Armstate standard
Republic of Belarus	Belstandard
The Republic of Kazakhstan	State Standard of the Republic of Kazakhstan
Kyrgyz Republic	Kyrgyzstandart
The Republic of Moldova	Moldovastandard
The Republic of Tajikistan	Tajik state center for standardization, metrology and certification
Turkmenistan	Turkmenglavstate inspection
The Republic of Uzbekistan	Uzgosstandart
Ukraine	State Standard of Ukraine

3 By Resolution of the Committee of the Russian Federation for Standardization, Metrology and Certification of September 10, 1996 N 569, the interstate standard GOST 5670-96 was put into effect directly as the state standard of the Russian Federation from August 1, 1997.

4 INSTEAD OF GOST 5670-51, GOST 7128-91 (in part 3.7)

1 AREA OF USE

1 AREA OF USE

1.1 This standard applies to bakery products, as well as low-moisture bakery products, and establishes methods for determining acidity.

1.2 The degree of acidity is understood as the volume in cubic centimeters of a solution of an exact molar concentration of 1 mol / dm3 of sodium hydroxide or potassium hydroxide, necessary to neutralize the acids contained in 100 g of products.

2 REGULATORY REFERENCES

2.1 This standard uses references to the following standards:

GOST 1770-74 Measuring laboratory glassware. Cylinders, beakers, flasks, test tubes. Specifications

GOST 2874-82 Drinking water. Hygiene requirements and quality control

GOST 4328-77 Sodium hydroxide. Specifications

GOST 5541-76 Cork closures. Specifications

GOST 5667-65 Bread and bakery products. Acceptance rules, sampling methods, methods for determining organoleptic indicators and mass of products

GOST 6709-72 Distilled water. Specifications

GOST 7128-91 Bagel bakery products. Specifications

GOST 8494-96 Wheat biscuits. Specifications

GOST 9412-93 Medical gauze. General specifications

GOST 9846-88 Crispy bread. General specifications

GOST 11270-88 Bakery products. Straw. General specifications

GOST 24104-88 Laboratory scales for general purposes and exemplary. General specifications

GOST 24363-80 Potassium hydroxide. Specifications

GOST 25336-82 Laboratory glassware and equipment. Types, basic parameters and dimensions

GOST 29227-91 Laboratory glassware. Pipettes graduated. Part 1. General requirements

GOST 29251-91 Laboratory glassware. Burettes. Part 1. General requirements

TU 6-09-5360-88 Phenolphthalein. Specifications

TU 38 1051835-88 Rubber cone plugs. Specifications

3 CONTROLS AND ACCESSORIES

3.1 General purpose laboratory scales of the 4th accuracy class, not more than 1.0 kg, with an allowable error of ± 75 mg - in accordance with GOST 24104.

Grater, mortar or mechanical grinder.

Sieve.

Watch.

Thermometer.

Bottles (such as milk) with a capacity of 500 cm.

Plugs - according to GOST 5541 or TU 38 1051835.

Volumetric flasks of the 4th accuracy class with a capacity of 100, 250 cm - according to GOST 1770.

Conical flasks and glasses with a capacity of 50, 100, 150, 250 cm - according to GOST 25336.

Pipettes of the 4th accuracy class with a capacity of 25.50 cm - according to GOST 29227.

Burettes of the 4th accuracy class - according to GOST 29251.

Wooden spatula or glass stick with a rubber tip.

Medical gauze - according to GOST 9412.

Sodium hydroxide - according to GOST 4328

Potassium hydroxide - according to GOST 24363, a solution of a molar concentration of 0.1 mol / dm.

Phenolphthalein - according to TU 6-09-5360-88, alcohol solution with mass fraction 1%.

Distilled water - according to GOST 6709.

Drinking water - according to GOST 2874.

It is allowed to use similar equipment, laboratory glassware and reagents that are not inferior in technical and metrological characteristics to those listed above.

4 PROCEDURE TO PREPARE FOR THE ANALYSIS

4.1 Sampling - according to GOST 5667.

4.2 The procedure for preparing for the analysis of weight and piece bakery products weighing more than 0.5 kg.

Samples consisting of a whole product are cut in half in width and a piece (chunk) weighing about 70 g is cut from one half, from which the crusts and subcrustal layer are cut off with a total thickness of about 1 cm.

For a sample consisting of a part of the product, the windward part is cut off on one side, making a continuous cut about 0.5 cm thick. Then a piece weighing about 70 g is cut off, from which the crusts and subcrustal layer are cut off with a total thickness of about 1 cm.

4.3 The procedure for preparing for the analysis of piece bakery products weighing 0.5-0.2 kg.

The products are cut in half in width and a piece weighing about 70 g is cut off from one half, from which the crusts and the subcrustal layer are cut off about 1 cm thick.

4.4 The procedure for preparing for the analysis of piece bakery products weighing less than 0.2 kg.

Whole products are taken, from which the crusts are cut off with a layer of about 1 cm.

The procedure for preparing for the analysis of baked piece bakery products of a specific form is established in the regulatory documentation for these products.

4.5 From the pieces of products prepared according to 4.2, 4.3, 4.4, remove all inclusions (jam, jam, raisins, etc.), then they are quickly crushed into crumbs, mixed and immediately take the sample.

4.6 The procedure for preparing for the analysis of low-moisture bakery products (lamb products, crackers, etc.).

The selection of samples of bakery products of low humidity to determine the acidity is carried out in accordance with the requirements set forth in GOST 7128 (for lamb products); in GOST 8494 (for crackers); in GOST 9846 (for crispbread); in GOST 11270 (for straws, bread sticks).

In low-moisture bakery products, inclusions and finishes are removed, except for products with poppy seeds and nuts, and ground on a grater, in a mortar or on a mechanical grinder such as an electric coffee grinder, crumbs are obtained. The crumbs are mixed and immediately take the sample.

5 PROCEDURE FOR THE ANALYSIS

5.1 How to analyze bakery products

5.1.1 Verification (arbitration) method

Weigh out 25.0 g of the crumb obtained according to 4.5. The sample is placed in a dry bottle (such as milk) with a capacity of 500 ml with a well-fitting cork.

A volumetric flask with a capacity of 250 ml is filled up to the mark with distilled water at a temperature of 18-25 °C. About the taken distilled water is poured into a bottle with crumbs, quickly rubbed with a wooden spatula or a glass rod with a rubber tip until a homogeneous mass is obtained, without noticeable lumps of unrubbed crumbs.

To the resulting mixture is poured from a volumetric flask all the remaining distilled water. The bottle is stoppered, the mixture is shaken vigorously for 2 minutes and left alone at room temperature for 10 minutes. The mixture is then shaken again vigorously for 2 minutes and left alone for 8 minutes.

After 8 minutes, the settled liquid layer is carefully poured through a fine sieve or gauze into a dry glass. From a beaker, 50 cm3 of a solution is taken with a pipette into two conical flasks with a capacity of 100-150 cm3 each and titrated with a solution of a molar concentration of 0.1 mol / dm3 of potassium hydroxide or sodium hydroxide with 2-3 drops of phenolphthalein until a faint pink color is obtained that does not disappear at a calm state of the flask for 1 min.

5.1.2 Fast method

Weigh out 25.0 g of the crumb obtained according to 4.5. The sample is placed in a dry bottle (such as milk) with a capacity of 500 ml, with a well-fitting cork.

A volumetric flask with a capacity of 250 ml is filled to the mark with distilled water heated to a temperature of 60 °C.

About the taken distilled water is poured into a bottle with crumbs, quickly rubbed with a wooden spatula until a homogeneous mass is obtained, without noticeable lumps of unrubbed crumbs.

All the remaining distilled water is added to the resulting mixture from a volumetric flask. The bottle is stoppered and shaken vigorously for 3 minutes.

After shaking, the mixture is allowed to settle for 1 min, and the settled liquid layer is carefully poured into a dry glass through a fine sieve or gauze. From a beaker, 50 ml of a solution is taken with a pipette into two conical flasks with a capacity of 100-150 ml each and titrated with a solution of a molar concentration of 0.1 mol / dm3 of sodium hydroxide or potassium hydroxide with 2-3 drops of phenolphthalein until a faint pink color is obtained that does not disappear with the flask standing still for 1 min.

Titration is continued if after 1 min the color disappears and does not appear from the addition of 2-3 drops of phenolphthalein.

5.2 How to analyze low moisture bakery products

Weigh out 10.0 g of the crumb obtained according to 4.6. The sample is placed in a dry conical flask with a capacity of 250 ml.

From pre-measured 100 cm3 of distilled water at a temperature of 18-25 ° C, about 30 cm3 of distilled water is poured into a flask with a sample, mixed, shaken until a homogeneous mass is obtained. The rest of the water is added, shaken again, making sure that no crumb particles stick to the walls of the flask. The mixture is allowed to stand for 15 minutes, and then the liquid is drained through a fine sieve or gauze into a dry flask. From the flask, 25 cm3 of the filtrate is taken with a pipette into two conical flasks with a capacity of 100-150 cm3 each and titrated with a solution of a molar concentration of 0.1 mol / dm3 of sodium hydroxide or potassium hydroxide with phenolphthalein (5 drops) until a pink color is obtained that does not disappear within 1 min.

Titration is continued if after 1 min the color disappears and does not appear from the addition of 2-3 drops of phenolphthalein.

This indicator is determined according to GOST 5670-96 by titration of the filtrate obtained from bread crumbs, by the arbitration or accelerated method and expressed in degrees of acidity.

GOST 5670-96 applies to bread and bakery products, low-moisture bakery products (drying, bagels, straws, bread sticks, crackers, crispbread) and establishes methods for determining the acidity of the crumb.

The degree of acidity is understood as the volume in (cm 3) of a solution of an exact molar concentration of 1 mol / dm 3 (1 N) sodium hydroxide or potassium hydroxide necessary to neutralize the acids contained in 100 g of products.

Preparation for analysis for weight and piece products weighing more than 0.5 kg includes the following: samples consisting of a whole product are cut in half in width and a piece (chunk) weighing about 70 g is cut from one half, from which the crusts and subcrustal layer are cut off with a total thickness of about 1 cm; the leeward part of the sample is cut off on one side, making a continuous cut about 0.5 cm thick. Then a piece weighing about 70 g is cut off, from which the crusts and subcrustal layer are cut off with a total thickness of about 1 cm.

Preparation for the analysis of piece products weighing 0.5-0.2 kg is carried out as follows: the products are cut in half in width and a piece weighing about 70 g is cut from one half, from which the crusts and the subcrustal layer are cut off about 1 cm thick.

Preparation for the analysis of piece products weighing less than 0.2 kg is carried out as follows: peels are cut off from whole products with a layer of about 1 cm, all inclusions (jam, jam, raisins, etc.) are removed from the prepared samples, then they are quickly crushed and mixed .

In low-moisture bakery products, inclusions and finishes are removed, except for products with poppy seeds and nuts, and crushed on a mechanical grinder until crumbs are obtained, which are used for analysis.

Determination of acidity is carried out by verification (arbitration) or accelerated methods.

Arbitration method is as follows: 25 g of prepared crumbs are placed in a dry bottle (such as milk) with a capacity of 500 cm 3 with a well-fitting cork. A volumetric flask with a capacity of 250 cm 3 is filled to the control mark with distilled water at a temperature of 18-25°C. About 1/4 of the distilled water taken is poured into a bottle with crumbs, quickly rubbed with a wooden spatula or a glass rod with a rubber tip until a homogeneous mass is obtained, without noticeable lumps of unrubbed crumbs.

All the remaining distilled water is added to the resulting mixture from a volumetric flask. The bottle is stoppered, the mixture is shaken vigorously for 2 minutes and left alone at room temperature for 10 minutes. The mixture is then shaken again vigorously for 2 minutes and left alone for 8 minutes.

After 8 minutes, the settled liquid layer is carefully poured through a fine sieve or gauze into a dry glass. From a glass, 50 cm 3 of a solution is pipetted into 2 conical flasks with a capacity of 100-150 cm 3 each and titrated with a solution of a molar concentration of 0.1 mol / dm 3 of potassium hydroxide or sodium hydroxide with 2-3 drops of phenolphthalein until a faint pink color is obtained , which does not disappear when the flask is at rest for 1 min. Titration is continued if after 1 min the color disappears and does not appear from the addition of 2-3 drops of phenolphthalein.

accelerated method is as follows: 25 g of crumbs are weighed and placed in a dry bottle (such as milk) with a capacity of 500 cm 3 with a well-fitting cork. A volumetric flask with a capacity of 250 cm 3 is filled to the control mark with distilled water heated to a temperature of 60 ° C. About 1/4 of the distilled water taken is poured into a bottle with crumbs, quickly rubbed with a wooden spatula until a homogeneous mass is obtained, without noticeable pieces of unrubbed crumbs.

All the remaining distilled water is added to the resulting mixture from a volumetric flask. The bottle is stoppered and shaken vigorously for 3 minutes.

After shaking, the mixture is allowed to settle for 1 min, and the settled liquid layer is carefully poured into a dry glass through a fine sieve or gauze. Further, the determination is carried out as in the first case.

Determination of acidity of bakery products of low humidity carried out as follows: 10 g of crumbs are weighed and placed in a dry conical flask with a capacity of 250 cm 3 .

From pre-measured 100 cm3 of distilled water at a temperature of 18-25°C, add about 30 cm3 of distilled water to a flask with a sample, mix, shake until a homogeneous mass is obtained. The rest of the water is added, shaken again, making sure that no crumb particles stick to the walls of the flask. The mixture is left to stand for 15 minutes, and then the liquid is drained through a fine sieve or gauze into a dry flask. 25 cm 3 of the filtrate are taken from the flask with a pipette into 2 conical flasks with a capacity of 100-150 cm 3 each, and then the acidity determination process is carried out, as in the first case.

When drinking water is used instead of distilled water, it must be pre-titrated.

The acidity of the product (X) in degrees is calculated by the formula

where V is the volume of a solution of a molar concentration of 0.1 mol / dm 3 sodium hydroxide or potassium hydroxide consumed during titration of the test solution, cm3;

V1 - the volume of distilled water taken to extract acids from the product under study, cm 3;

a - conversion factor per 100 g sample;

K - correction factor for bringing the used solution of sodium hydroxide or potassium hydroxide to a solution of an exact molar concentration of 0.1 mol / dm 3;

1/10 is the coefficient of reduction of a solution of sodium hydroxide or potassium hydroxide of a molar concentration of 0.1 mol/dm 3 to 1 mol/dm 3;

m - sample weight, g;

V2 is the volume of the test solution taken for titration, cm3.

For the final test result, the arithmetic mean of two parallel titrations for one filtrate is taken, the allowable discrepancies between which should not exceed 0.3 deg.

For bakery products, the formula for determining acidity can be represented as:

For products of low humidity, the formula for determining acidity can be represented:

The calculation is carried out to the second decimal place.

The determination of acidity is considered correct if the results of two parallel titrations for one filtrate completely coincide or differ for bread and bakery products by no more than 0.30 degrees, for bakery products with low moisture - by no more than 0.40 degrees.

The arithmetic mean of the results of two parallel determinations is taken as the final result of the analysis.

The result of the analysis is recorded with an accuracy of 0.5 degrees, with fractions up to 0.25 degrees. discarded inclusive; shares over 0.25 and up to 0.75 deg. inclusive equate to 0.5 degrees; shares over 0.75 deg. equate to 1.0 deg.

The discrepancies between the results of determining the acidity of a laboratory sample of one batch of products in different laboratories should not exceed 0.5 deg.