The test solution is poured into a burette with a capacity of 10 cm3. In two flat-bottomed flasks of 50 cm 3, pipet 5 cm 3 of a 1% solution of copper sulfate (solution 1) and an alkaline solution of potassium-sodium tartrate (solution 2). One of the flasks is placed on a hotplate, the copper-alkaline solution in the flask is brought to a boil and titrated from a burette with the test solution at a rate of 3...5 drops per second, making sure that the boiling in the flask did not stop (! ). The blue color of the copper-alkaline solution changes to yellow. The volume in cm 3 of the test solution used for titration is noted on the burette. Then a control titration is carried out. The second flask with a copper-alkaline solution is placed on a heated hotplate, the solution in the flask is brought to a boil and (85±5)% of the volume of the test solution used for preliminary titration is poured into it from a burette, making sure that the boiling in the flask does not stop. In this case, the blue color of the copper-alkaline solution changes to a light purple color. Titration of the copper-alkaline solution with the test solution is carried out at a rate of 1 drop per second until a yellow color appears.

The mass fraction of sugar in the product under study X, % in terms of dry matter is calculated using the formula:

where T is the titer of the copper-alkaline solution for sucrose;

V 1 – capacity of the volumetric flask taken for preparing the aqueous extract, cm 3;

m – mass of a sample of the product under study, g;

V 2 – volume of the test solution consumed for titration, cm 3;

W – mass fraction of moisture in the product under study, %.

2 – double dilution of the extract during hydrolysis of sucrose.

The final result is taken as the arithmetic mean of the results of two parallel determinations, the permissible differences between which should not exceed 0.5%.

5. Organoleptic assessment of the quality of bakery products

Organoleptic evaluation of bakery products in assessing their quality is very important. A description of methods for organoleptic analysis of bakery products is given in the regulatory document (ND) for the product. Below is a brief description of individual indicators of bread quality determined organoleptically, which in our country is subjective in nature and does not provide a quantitative assessment of indicators of organoleptic properties. The quality of bread is assessed no earlier than 4 hours after baking, but no later than 24 hours. Organoleptic assessment of bread quality is carried out according to table 2.7.

Table 2.7

Indicators of organoleptic assessment of bread quality

*Cracks The breaks passing through the upper surface of the crust in one direction are considered.

**Breaks are considered to be gaps between the side and top crust of pan bread or along the circumference of the bottom crust of hearth bread: small tears up to 0.5 cm; large – over 0.5 cm.

The elasticity of the crumb is determined by lightly pressing on the cut surface with two or three fingers to a depth of 1 cm, quickly tearing them off from the cut surface and observing the speed of restoration of its surface to its original position. In the complete absence of residual deformation, the elasticity of the crumb is characterized by good; in the case of insignificant, that is, with almost complete recovery, it is average; if the crumb is crushed and there is significant residual deformation, it is bad.

The taste and crunch of bread is determined by chewing the crumb of the product.

Organoleptic assessment of the quality of bakery products

Organoleptic the assessment of food products, including bakery products, in assessing their quality is very important. The results of organoleptic analysis should be decisive in determining the quality of new products and in the development of new technologies for obtaining basic food products for the population.

Organoleptically determined indicators of the quality of bakery products include appearance (surface condition, color and condition of the crust, the absence or presence of peeling of the crust from the crumb and the shape of the product), the condition of the crumb (freshness, bakedness). When assessing the porosity of a product, pay attention to the size of the pores (small, medium, large), the uniformity of their distribution throughout the entire space of the crumb cut (uniform, fairly uniform, not uniform enough, uneven) and the thickness of the pore walls (thin-walled, medium-thick, thick-walled), the presence voids and seals.

When assessing the smell, attention is paid to the presence or absence of foreign, unusual and especially unpleasant odors in the product.

The taste is determined by chewing the crumb of the product. Attention is drawn to the presence of a taste that is not characteristic of the bakery product. The taste can be normal, sweet, sour, insipid, bitter, etc. Sometimes the product has foreign odors that affect its taste.

Conclusion: Sample 1 fully meets the requirements of GOST 27844-88. Sample 2 does not comply with GOST 27844-88 in terms of “mesh” and “porosity” indicators

Determination of the quality of bakery products by physical and chemical indicators

In accordance with the requirements of the standards, the main physical and chemical indicators of the quality of bakery products are: humidity; acidity; porosity; mass fraction of fat; mass fraction of sugar; mass fraction of table salt; for fortified products - the mass fraction of vitamins B, (thiamine), B2 (riboflavin), PP (nicotinic acid).

In this work, the moisture content, acidity and porosity of Capital loaves will be determined.

Moisture content of baked goods

The moisture content of a bakery product is determined: to calculate the yield; to check compliance with the technological process and recipe; to take into account energy value. As the humidity of the product increases, its yield increases, the energy value decreases, and such indicators of product quality as shape, appearance (hearth products can blur, and for molded products the upper crust can be flat, less convex), and color of the crust may also change. crumb structure, etc.

You can get an accurate idea of ​​the moisture content of bread by drying a sample of the product to a constant weight at 100-105°C. The standard for bakery products provides an accelerated method for determining the moisture content (GOST 21094-75) not of whole bread, but only of its crumb.

Method for determining humidity.

When preparing for analysis, a laboratory sample is cut approximately in half and a piece 1-3 cm thick is cut from one part. The crumb is separated from the crusts at a distance of 1 cm. The mass of the isolated sample must be at least 20 g.

The prepared sample is quickly and thoroughly crushed with a knife, grater or mechanical chopper, mixed and two samples are immediately taken. If the sample consists of a piece of bread, then the windy part about 0.5 cm thick is first cut off from it.

Determination of the mass fraction of moisture in bread crumb is carried out in electric drying ovens with thermostats. Drying is carried out in metal bottles with a height of 2.0 cm and a diameter of 4.5 cm.

In pre-dried and weighed bottles with a lid, weigh 5 g of bread crumb with an accuracy of ±0.01 g. The cabinet must be heated to a temperature of 140--145 ° C. Prepared samples in open bottles (the lids must be placed under the bottom of the bottles) are placed in a drying cabinet , while the temperature in the cabinet quickly drops, usually below 130 °C. Within 10 minutes it is brought to 130 °C and drying is continued at this temperature for 40 minutes. (the deviation should not exceed ±2 °C).

If the required temperature (130 °C) in the drying cabinet is established in 1-2 minutes, it is recommended to dry it within 50 minutes from the moment the samples are placed in the cabinet.

After drying, the bottles are covered with lids, cooled in a desiccator for 15-20 minutes and weighed. You cannot leave the bottles in the desiccator for more than 2 hours, because the samples will absorb moisture.

From the difference in the sample before and after drying, the mass of evaporated moisture is determined and the mass fraction of moisture (%) is calculated with an accuracy of ± 0.5%.

Humidity is calculated using the formula:

W = 100 (m1- m2) / m,

where m1 is the weight of the weighing bottle with the sample before drying, g;

m2 - weight of the weighing bottle with a sample after drying, g;

m is the mass of the sample, g.

Porosity of baked goods

The porosity of a bakery product is understood as the ratio of the pore volume of the crumb to the total volume of the bread crumb, expressed as a percentage. The porosity of the product, taking into account its structure (pore size, uniformity, wall thickness) characterizes such an important property of the product as digestibility. Low porosity is usually inherent in products made from poorly fermented dough, with low humidity, etc.

The standard specifies what the porosity should be (a lower limit is given). So the porosity of rye, rye-wheat and wheat-rye bread should be at least 45-65%; products made from wheat flour - 54-74% depending on the type of product and baking method.

The porosity of bread is determined by the Zhuravlev method.

Method of determination

A piece with a width of at least 7-8 cm is cut out from the middle of the product. Recesses are made from a piece of crumb at a distance of at least 1 cm from the crusts using the cylinder of a Zhuravlev device. The sharp edge of the cylinder is pre-lubricated with vegetable oil. The cylinder is inserted into the bread crumb with rotational movements.

The cylinder filled with crumb is placed on the tray so that the rim fits tightly into the slot in the tray. Then the bread crumb is pushed out of the cylinder by about 1 cm with a wooden sleeve and cut off at the edge of the cylinder with a sharp knife. The cut piece of crumb is removed. The crumb remaining in the cylinder is pushed out with a sleeve to the wall of the tray and is also cut off at the edge of the cylinder.

To determine the porosity of the rye bread crumb, four cylindrical recesses with a volume of 27 ± (0.5) cm3 each are made from the flour mixture and weighed at the same time.

Processing the results:

P = 100 (V - m / p) / V,

where P is porosity, %;

V is the total volume of bread recesses, cm3;

m is the mass of the recesses, g;

p is the density of the non-porous crumb mass.

Acidity of bread

The acidity index of a bakery product characterizes its quality in terms of taste. This indicator can also be used to judge compliance with the rules for conducting the technological process of preparing the product.

The sourness of bread is mainly due to the products resulting from the fermentation of the dough. Acidity is expressed in degrees acidity.

The degree of acidity (according to GOST 5670-96) 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.

The standard specifies what the acidity of the product should be. So, for rye, rye-wheat, wheat-rye bread (the upper limit is indicated), the acidity should be no more than 7.0--11.0 degrees, bakery products made from wheat flour - 2.5--4.0 degrees per depending on the type of product.

Method of determination

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

For a sample consisting of a part of the product, the ventral 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 subcortical layer about 1 cm thick are cut off.

The prepared pieces are quickly crushed and mixed.

Weigh 25 g of crushed bread crumb with an accuracy of +0.01 g and place it in a jar with a capacity of 500 cm 3. A 250 cm volumetric flask is filled to the mark with water at room temperature, about 1/4 of the taken water is poured into a jar of bread and rubbed well with a wooden spatula. Then add the remaining water, stir the contents of the jar vigorously for 2 minutes and leave alone at room temperature for 10 minutes. Then the contents are mixed again for 2 minutes and again left alone for 8 minutes. During this time, acid-reacting substances from the bread crumb pass into the extract.

Then the settled layer of liquid is poured through a fine sieve or gauze into a dry glass. Pipette 50 cm of filtrate from the glass into two conical flasks with a capacity of 100-150 cm3 each and titrate with a 0.1 N solution of sodium or potassium hydroxide with the addition of 2-3 drops of phenolphthalein until a faint pink color appears that does not disappear within 1 min.

The acidity of the crumb X (degrees) is calculated with an accuracy of 0.5 degrees. according to the formula:

where X is acidity, degrees;

V is the volume of sodium hydroxide solution with a molar concentration of 0.1;

mol/dm 3 spent on titration of the test solution, cm 3;

K - correction factor for bringing the solution used

sodium hydroxide to a solution with a concentration of 0.1 mol/dm 3.

organoleptic chemical bread fruit

The quality of bread, like any food product, is a complex concept, covering a number of its characteristics. The consumer first of all pays attention to the organoleptic properties - appearance, taste and aroma, freshness. A commodity expert should evaluate quality much more broadly; he also needs to know the nutritional value and safety, shelf life, conditions and shelf life. The quality of bread, as well as the main methods for assessing quality, are regulated by relevant standards.

The quality of bread is assessed by organoleptic and physico-chemical indicators.

Organoleptic indicators determined by inspection and tasting of bread and bakery products.

Appearance is primarily determined by the shape of the product. It must be correct, corresponding to the given type of bread. Hearth products should not be blurred or have side bulges. For most hearth products, pressings are not allowed, which can easily lead to molding of the crumb. Molded products have a slightly convex upper crust without side sagging. Products that are wrinkled or deformed due to careless handling of bread are not allowed to be sold.

Product surface should be smooth, shiny, without large cracks or tears, and not dirty.

Coloring of crusts should be uniform, not pale or burnt.

For many types of products, the thickness of the crusts is also standardized (for rye and rye-wheat - up to 3-4 mm, for wheat - up to 1.5-3 mm).

Crumb condition - an important indicator of bread quality. Good quality bread has uniform fine thin-walled porosity, without voids and signs of hardening (unloosed areas of crumb). There are no foreign inclusions in it in the form of unmixed lumps of flour or accidentally fallen objects (chips, pieces of twine, etc.). The crumb of fresh bread is soft, well baked, not sticky or wet to the touch, elastic, and after light pressure with a finger it returns to its original shape. Stale bread becomes hard and crumbly.

Taste and aroma bread should be pleasant, appropriate for this type of product.

Physico-chemical quality indicators characterize strict adherence to the recipe and technological process by bakery enterprises. For most. Products such indicators are humidity, acidity and porosity. In improved and rich products, the fat and sugar content is additionally determined.

Humidity established by standards at a certain, optimal level for a given product, depends on the strength of flour and bread recipe and is to a certain extent related to nutritional value, since with increasing humidity the proportion of nutrients

substances decreases. The moisture content of bread is (in%): for plain and improved wheat bread - 42-48, for butter products - 34-42; for bread made from rye flour - 45-51.

Acidity to some extent characterizes the taste qualities of bread. Insufficiently and overly sour bread tastes unpleasant. The acidity of bread (like flour) is expressed in degrees Neumann (°N) and is (in °N): for products made from high-quality wheat flour - 2-5; from rye - 6-12.

Bread porosity shows the percentage of pore volume to the total volume of the crumb. The porosity of bread is related to its digestibility. Well-loose bread with uniform fine thin-walled porosity is easily chewed and soaked in digestive juices and is therefore more fully digestible. Wheat bread made from high-quality flour has a porosity of 60-75%, and from rye flour - 46-60%.

In improved and rich products, the content is standardized fat and sugar Compliance with standards is guaranteed by the supplier. In controversial cases, these indicators are determined by appropriate methods. Downward deviations are allowed for fat by no more than 0.5-1%, for sugar - by 1-2%.

The hygienic assessment of bread is given on the basis of organoleptic examination and determination of moisture, porosity and acidity. If necessary, a microbiological analysis of bread is carried out and the determination of toxic and foreign inclusions in it.

Organoleptic characteristics of bread

The surface of the bread should be smooth, without cracks or tears, swelling, burnt areas, or foreign inclusions. It is not allowed for the top crust to lag behind the crumb. The thickness of the crusts should be no more than 0.5 cm. If the top crust is very thin and lags behind the crumb, then the oven temperature was too high, the crust formed quickly, and gases (carbon dioxide, water vapor and alcohol) expanded in the heated space, trying to escape out, lift the top crust. On the contrary, a thick crust and the presence of hardening (a layer of unbaked dough at the bottom crust) are signs of insufficient oven temperature. The color of the crust should be uniform, brownish-brown for rye bread, light or dark yellow for wheat bread. The cut crumb should be homogeneous (there should be no lumps of unkneaded dough or old bread), finely porous and, with light pressure with a finger, should quickly return to its original shape. The taste should be pleasant, without bitterness or foreign aftertaste. When chewing, there should be no crunching on the teeth or mineral impurities.

The smell of bread should be pleasant, aromatic, characteristic of this type of bread. A musty smell is a sign of poor quality flour from which the bread is baked.

Porosity Definitions

The porosity of bread is an indicator of the quality of the bread and the good quality of the flour from which it is baked. The porosity of bread improves the organoleptic properties of bread and promotes better absorption of nutrients. Porosity is understood as the ratio of the pore volume of the crumb to the total volume of the bread crumb, expressed as a percentage.

To determine the porosity of bread, a Zhuravlev device is used, which consists of the following parts: a metal cylinder with a pointed end on one side; wooden sleeve; wooden or metal tray with a cross wall.

A piece 7-8 cm long is cut out of the middle of the bread, and a recess is made from its crumb using the cylinder of the device (with a rotational movement, having previously lubricated its sharp edge with vegetable oil). The cylinder filled with crumb is placed on the tray so that its rim fits into the slot in the tray. Then the bread crumb is pushed out of the cylinder by about 1 cm and cut off at the edge of the cylinder with a sharp knife. The cut piece is removed, and the remaining cylinder is pushed out with a sleeve to the wall of the tray and cut off at the very rim of the cylinder. The volume of the cylinder crumb is 27 cm3.

To determine the porosity of wheat bread, 3 are made, and for rye bread and bread made from a mixture of flour - 4 cylindrical recesses. The prepared excavations are simultaneously weighed and the porosity is calculated using the formula:

X is the desired percentage of porosity,

B is the total volume of bread removals,

a is the weight of the recesses in grams,

b - density of the non-porous mass.

The density of the non-porous mass (b) is taken for rye bread, wheat bread made from wallpaper flour and rye wheat bread - 1.21; wheat of the second grade - 1.26, wheat of the highest and first grade - 1.31.