Introduction

In consequence of systematic study of discipline «Processing productions safety» students solve following objectives: safety of food products and their production from the point of view of health and reliability for the people and environment, estimation methods and safety criteria for food production, microbiological safety quotient of food production, risk of disadvantage or superfluity nutrient materials, danger of xenobiotics from ambient medium, main criterion of safety food additive, mainstream industry article development of food in ХХI century, definition methods of content toxic elements in food products.

Laboratory workshops are connected with theory. On practicum students fortify obtained theoretical skills, get hand-on experience by definition of process specifications of preparation and delivery of ready-to-eat meal in accordance with applicable standards, norms and other scientific and technical documentation.

It is essential that students learn to economize chemical reagents, carefully refer to laboratory apparatus and facility, and follow regulations of personal hygiene and prophylaxis, safety procedures.

Laboratory work #1

Definition of butter fat oxidation level.

Purpose of the work: experimental determination of butter fat oxidation level

1.1. The task

1. Define oxidation level of dairy butter.

2. Calculate real optical density by formula.

3. Draw up report about the effort.

Theoretic part

Method is founded on formation of colored compounds of 2-thiobarbituric acid with some of secondary products of oxidation fat. Color grade depend upon oxidation rate of fat, as a result of which aldehydes form. Main of last is molon aldehyde. In absorption spectra of colored compounds there are two maximums, where the first (450 nm) corresponds yellow colored condensate of 2- thiobarbituric acid with monoaldehydes, but the second (535 nm) - red colored union 2- thiobarbituric acid with dialdehydes.

The given reaction is widely used for degree evaluation of vegetable and animal fats oxidation, owing to high sensitivity, reproducibility and correlation of this index with organoleptic estimation of fat freshness. Due to the fact that mechanism of this reaction is unknown fully, analysis results are expressed by per unit of absorbance. Analysis of fat oxidation degree of various products with 2-thiobarbituric acid differs by distinction of sample preparation for measurement of absorbance by spectophotometer Especially it concerns the method for discriminating of fat.

Technique definition.

Chemical reagents: 1n spirit of salt; petroleum ether; reagent of 2-thiobarbituric acid; extraction mixture (isoamyl alcohol and 99% pyridine in balance of volumes 1:1).

Weighed portion of dairy butter (10g) is settled in centrifugal test-tube with stoppered and is hold in hot water with temperature 70-80 gr C during 3 min for complete fusion of milk fat. Next 2 ml of distil water,1 ml of 1n spirit of salt are added in test-tube, then it is shacked up strenuously, reheated 1 min and centrifugated 3 min (about 5000 rounds per min). Layer of milk fat is pipetted off. Water fraction is cleaned by several portions of petroleum-ether until disappearance of visible slosh. The ether every time is deleted by pipette with pumping out rubber bulb. In the end of flushing out contents test tube is centrifugated 2-3 min for more complete dissection of ether. 1,5 ml reagent of 2-thiobarbituric acid adds in caught-on of water fraction and then it is hold on boiling-water bath 15 min. Test tube is quenched to 18-20 gr C,

5 ml extraction mixture is added, then strenuously shaken and centrifugated 10 min by 5000 rounds per minute.

Clear color solution is carried over by pipette in cuvette 1cm ,then optical density is measured under λ =490Nm, 535 Nm and 580 Nm. Control experiment is prepared in simulated conditions, but without butter, and 3,6 ml water instead 2 ml is added taking into account humidity of dairy butter.

Calculation of real optical density of colored compounds is carried by formula:

D=D535- D490+ D580,

where D535 - maximum absorption of colored compounds under λ =535Nm,

D490 и D580 - minimal absorption in spectrum of determined colored compounds under λ =490Nm, 580 Nm, their optical density is minused for liberation from phone.

A report on task performance.

Student designs activity report. Accounting results are filled in table1.

Product under investigation	Optical density λ= (nm), where
Dairy butter	Д535	Д490	Д580	Д

Quiz:

1. Wherein does oxidation level of dairy butter consist?.

2. By what formula do you calculate real optical density of colored compounds?

3. By what does analysis of fat oxidation degree of various products with 2-thiobarbituric acid differ?

4. Why weighed portion of dairy butter is hold in hot water with temperature 70-80 gr C?

Laboratory work #2

Theme: an estimation of quality of bread and bakery products

The purpose of job: To carry out an estimation of quality of the offered samples of bread and bakery products by organoleptical, physical and chemical parameters.

1.1. The task

1. Define an estimation of quality of bread and bakery products.

2. Learning of bakery products defects.

3. Draw up report about the effort

Theoretic part.

Potato bacillus, molding of bread and other diseases, called by wrong keeping and processing of charge stock, can induce diseases of man. In aid of food safety in the manufacture of bread it is necessary to use quality products, passed off microbiological and physicochemical check-out. End products also must compliant with standards.

The order of performance of job.

Necessary reagents and materials:

1.Counter balance, knives, apparatus of Juravlev, sample bottles, desiccator;

2.Solution of alkali of concentration 0,1 n; phenolphthalein.

Organoleptical estimation of quality. Organoleptical estimation is made under the standard on the appropriate kind of products. The researched sample attentively looks round. Pay attention to the form of a product, colouring of crust, their thickness, absence of cracks on a surface. Check uniformity of distribution of pores, their figure, establish presence or absence cores (закала) in crumb (мякише), it adhesiveness, estimate freshness of bread. Crumb of baked fresh bread well restores the form at easy pressing and not crumble at cutting.

At degustation estimation establish conformity of taste and smell to a grade of bread. At mouth feeling (разжевывании) of bread should not be felt crunch (хруста) on teeth.

The received supervision compare to the requirements of the standard and judge conformity of the examinee of a sample to standard norms.

Definition of humidity of bread crumb. Crust and crumb of bread have various humidity. Humidity of crumb in different layers of a product is not identical. In the standard on bread only humidity of crumb is normed. To receive comparable results of humidity, it is necessary correctly to select a sample.

The order of performance of job

Weigh on technical weights with accuracy 0,01g two metal sample bottles. A sample cut across on two approximately equal parts and from one part cut a slice by thickness 1-3sm, separate crumb from crust on distance 1sm,delete all inclusions (raisin, jam, nuts and others, except for poppy seed). Weight of the selected sample should be not less than 20.

The prepared sample carefully grind by a knife on a glass plate to avoid losses of a moisture from evaporation (испарение), and mix.

From crushed crumb take in weighed bottles samples on 5 g to within 0,01. The drying of samples is made in a desiccator СЭШ-ЗМ during 40 min.

Humidity of crumb in percentage (Wcr) define under the formula:

Wcr=( m₂- m₃)100/( m₂- m₁), where

m₁, - weight of bottle with a cover, g;

m₂ – weight of bottle with grain crumb before drying, g;

m₃ - weight of bottle with grain crumb after drying, g.

The conclusion about conformity of the examinee of a sample to the requirements of the standard.

Definition of porosity. Porosity is attitude of pores volume to total volume of bread crumb in %. The bread with thin-walled pores is the best because it expands easy by digestive juice, that’s good for organism. The method of definition of porosity is based at that nonporous mass of bread from certain sort of flour have constant density. When defined volume and mass of crumb it is able to calculate volume of pores.

The order of performance of job

To determine porosity apply an apparatus of Juravlev, which consists of metal body, cylinder and wooden plug(втулки). For sampling preparation from the middle of product grave a piece (slice of bread) by width at least 7-8 cm. From piece of crumb in the distance at least 1 cm to crust groove (делают выемки) by cylinder of apparatus.

The sharp end of cylinder prelube by plant oil. Cylinder entry into the crumb by round moving. Cylinder with the crumb put on the metal body so that ring fits snugly (плотно входил) into hole. Then crumb put out from cylinder by wooden plug at 1sm and cut by knife at the end of cylinder. Left in the cylinder crumb push by plug to the wall of body and cut at the end of cylinder. Volume of crumb’ cylinders ought to be 7 sm³, because internal diameter of cylinder equal to 3sm and distance from the wall of tray (лоток) to the hole -3,8sm.

Prepared 3 samples weight with accuracy 0,01g and then calculate the porosity by formula:

X=(V-(m/p)100/V, where

V- common volume of the bread grooves, sm³;

m- mass of grooves, g ;

p- density of nonporous mass of bread, g/ sm³;

(1,25- for black and wheaten bread)

Definition of acidity. During processing of the dough beside of alcohol fermentation formation of acids flows in chief lactic acid and a few acetic acid. The great amount of acids forms in rye bread, which is made at sourdough. A few acids accumulate in wheaten bread, which is made at yeast.

The order of performance of job. For definition of acidity cut a slice of bread (mass about 70g), cut off crust and subcrustal layer from it. Prepared crumb carefully grind up by knife on the glass leaf and take 25g of the sample, which put in the 500sm³ bottle with well gauged tube plug.

Previously measure 250 sm³ of distil water. 1/4 part of it add into the bottle, where the bread is ground up prior receipt of indiscrete mass without nubbles.

To gotten mixture add residual water. The bottle close by tube plug, shake mixture strenuously 2min and leave for 10min. Then again shake mixture strenuously 2min and leave for 8min.

As time passes settled liquid layer carefully pour through sieve into dry bowl. Carry out two 50 sm³’ samples of solution by pipette into cone flasks (of 100-150 sm³) and titrate by alkali of 0,1n concentration at the presence of the indicator - phenolphtalein before occurrence of weak - pink colouring which is not disappearing during 1 min.

Acidity count by formula:

X=(25·50·4VK)/250·10=2VK, where

V- amount of a solution of alkali of concentration 0,1 n, used by titration, sm³;

K- amendment to a titer of a solution of alkali of concentration 0,1 n;

10-coefficient of alkali concentration’ change;

25- mass of sample,g;

4- re-count of sample to 100g;

250-volume of water taken for extraction of acids, sm³;

50- volume of titrated solution, sm³.

The form of record:

The name of a grade of bread _______________________________________ _

Weight of a product ___________ g, deviation(отклонение) __________ g, ___________ of %

Results of an estimation:

1. Appearance of bread _______________________________________ _____

Condition of a surface _______________________________________ ___

Colouring and thickness of crust_______________________________________ __

2. Condition of crumb _______________________________________ ______

Transition from crust to crumb _______________________________________

Distribution of pores (porosity)__________________________ ______________

Elasticity _______________________________________ ____________

Degree of baked _______________________________________ ___

Freshness of crumb _______________________________________ ______

3. Taste _______________________________________ __________________

4. Smell _______________________________________ _________________

5. Crunch at mouth feeling _______________________________________

6. Humidity of crumb_________________________________________

7. Porosity of crumb_________________________________________

8. Acidity of crumb___________________________________________

Questions:

1. What diseases of bread do you know and why do they appear?

2. By what indexes is organoleptical estimation of quality carried?

3. What apparatus is used by definition of humidity of bread crumb?

4. Why is the bread with thin-walled pores the best?

5. What acids form during processing of the dough?

Laboratory work # 3

Definition of physicochemical parameters of sugar-beet.

Purpose of the work: experimental determination of physicochemical parameters of fruits and vegetables.

1.1. The task

1. Define physicochemical parameters of fruits and vegetables.

2. Calculate content of ascorbic acid by formula.

3. Draw up report about the effort.

Definition of titrable acidity.

Theoretic part

Titrable acidity of fruits and vegetables characterize taste and food value of product. Fruits and vegetables content several acids, but only one of them predominates. So, apple acid predominates in seed-bearing fruit, beet, and carrot. Citric acid predominates in citrus plants, grape, potatoes, raspberry, cranberry and others. Definition of titrable acidity is based at ability of alkali to neutralize quantitatively as free acids as their salts in researched solution. According to quantity of alkali it is necessary to re-count it according predominated acid.

Technique definition.

Necessary materials and facility:

1.Fruits and vegetables. 2.Porcelain cup. 3. Measuring flask. 4. Counter balance. 5.Litmus- paper.

6. Glass rod. 7.Boiling-water bath. 8. Chemical reagents for titrating.

At Counter balance weigh 25gr of pulp in porcelain cup and put it into 250 ml’ measuring flask through feeder with the help of glass rod, adding some water in order the volume of it was 2/3 of flask volume. Then content of the flask heat on boiling-water bath to 80⁰C and hold it 10-15 min. After quenching of flask’ content add water till mark and filter. 50ml of gotten filtrate carry over by pipette into cone flask, add 3 drops of phenolphthalein and titrate by 0,1n alkali until pink color. If filtrate is colored, litmus- paper as indicator can used. Titrating ends, if the drop of liquid doesn’t color litmus- paper to red.

Calculation of titrable acidity of fruits and vegetables (X_t) is carried by formula:

X_t=V·K·K₁·V₁·100/m·V₂ , where

V-consumed at titration quantity of 0,1n alkali, ml;

K-correction coefficient of alkali concentration;

K₁ - correction coefficient of corresponding acid; for apple acid - 0,0067; for lemon acid-0,0064; for tartaric acid-0,0075;

V₁- volume of extract, prepared from weighed amount of being investigated product, ml;

100-correction coefficient of 100g of product;

V₂- volume of filtrate of being investigated product, taken for titration, ml;

m-weighed amount of product, g.

Definition of solids content in plant fruits and vegetables with the help of refractometer.

Before launching the labor check correctness of refractometer evidence on distilled water. Evidenceof refractometer at 20 ^оС must be next: refraction coefficient - 1,333, solids content-0.

Technique definition.

Definition of solids content in plant fruits and vegetables conduct as follows: take some drops from pushed up juice and infiltrate it. Then on center of refractometer bed knife lay on a drop of juice by glass rod, but set aside a knife edge. For every sample conduct at least three measurements and output average from obtained rate.

Processing of results.

After account by scale register evidence of thermometer, incorporated in refractometer, in order to correct temperature. Temperature correction is included in case when there is difference between temperature at the moment of definition and temperature, wherein is graduated scale of refractometer.

For correction of received data use table 1.

Temperature, оС	Solids content, %
	5	10	15	20	30	40	50
15 16 17 18 19	Take off evidence
	0,25 0,21 0,16 0,11 0,06	0,27 0,28 0,18 0,12 0,07	0,31 0,26 0,20 0,14 0,08	0,34 0,29 0,22 0,14 0,08	0,35 0,31 0,23 0,15 0,09	0,36 0,31 0,23 0,16 0,07	0,36 0,32 0,23 0,16 0,07
Add to evidence
21 22 23 24 25 26 27 28 29 30	0,06 0,12 0,18 0,24 0,30 0,36 0,43 0,50 0,57 0,64	0,07 0,14 0,20 0,26 0,32 0,39 0,46 0,53 0,60 0,67	0,07 0,14 0,20 0,26 0,32 0,39 0,46 0,53 0,61 0,70	0,77 0,14 0,21 0,27 0,34 0,41 0,48 0,55 0,62 0,71	0,07 0,14 0,21 0,28 0,36 0,43 0,50 0,58 0,66 0,74	0,07 0,14 0,21 0,28 0,36 0,43 0,51 0,59 0,67 0,75	0,07 0,15 0,22 0,30 0,38 0,46 0,52 0,63 0,71 0,80

Definition of sugar content. For determining of sugar prepare water extract from gritted masses of fruits and vegetables. Extract must be prepared with such account, that after attenuating- разбавление, connected with clearing of solution, they contain from 0,25 to 1% of sugar.

Technique definition.

From gritted average sample take and weigh on counter balance 25 g of(cabbage, tomato, potatoes) in previous measured porcelain cup. Carry over a weighed amount through funnel into 250 cm³’ measuring flask. Float out adherent particles. Pour over sample by distilled water with such account, that total volume of sample and water does not exceed 150 cm³. Then put down a bit of litmus paper into flask and neutralize liquid carefully by 15-percentage soda solution until litmus paper become dark blue (deacidification is carried out for warning of sucrose splitting). After neutralization of liquid heat flask, which is continuously shaken, on boiling-water bath by temperature 80^оС during 30 min for the more full and fast transition of sugar into solution. After quenching contents of flask add 10-15 cm³ 30-percentage solution of lead tetraagetate, carefully shaking up contents of flask and give to defecate, but then bring in yet 1-2 drops of reagent.If at that dreg forms in free liquids, it is necessary to continue addition of lead tetraagetate in solution. It is carried out for removal protein, pectic, tannic and some other matters, which block definition of sugar and distort analytical results. When reached full clearing of solution (at the bottom of flask must be dense deposit, but over it must be transparent liquid) flask contents put across mark and filter through fold filter. Obtained filtrate contains abundance of lead, which is deleted by fat solution of sodium sulphate. For this purpose transfer 100 cm³of filtrate in flask of 200 ^оС volume, add 10-20 cm³ of saturated solution of sodium sulphate and shake up. After 5 min carefully stick by wall of flask precipitation agent- natrium sulfurous (Na₂SO₄), then check fullness of lead precipitation. If sludge doesn't form, contents of flask put across mark, shake, give sludge to go down and filter it through paper filter, if it is possible don’t carry there sludge. This light filtrate, called solution "A", answers for determining of reducing sugar, but after sucrose splitting-of saccharose.

A report on task performance

Questions:

1. What does titrable acidity of fruits and vegetables characterize?

2. On what is definition of titrable acidity based?

3. What acid predominates in seed-bearing fruit, beet, and carrot?

4. What acid predominates in citrus plants, grape, potatoes, raspberry, cranberry and others?

5. What reagents are used for definition of sugar content?

Laboratory work #4 Definition of mayonnaise quality.

The purpose of job: At performance of this job in mayonnaise define parameters established by the requirements of standards: a mass share of a moisture, mass share of fat, acidity and stability of emulsion.

1.1. The task

1. Define physicochemical parameters of mayonnaise.

2. Write down in the worker copy-book parameters of safety of mayonnaise.

3. Draw up report about the effort

Theoretic part

Except for physical-chemical parameters at realization of examination of quality of mayonnaise define parameters of safety. The list of these parameters according to the hygienic requirements of safety is given in tab. 33.1 of a theme 33.

Definition of a mass share of a moisture. There are two methods of definition of a moisture in mayonnaise: arbitration and accelerated.

Necessary materials and facility:

1.Samples of mayonnaise. 2.Oleometre. 3. Boiling-water bath, centrifuge,balance and desiccator.

4. a sulfuric acid (density 1,5 g/sm³); isoamyl spirit, caustic alkali, phenolphthalein, the sand which has been washed out and calcined.

Technique definition of a mass share of a moisture.

Arbitration method. In clean weighing bottle (бюксу) with a glass stick fill 3-4 g of calcined (прокаленного) sand and dry up up to constant weight (weight). After cooling in it give 2-3 g of mayonnaise to within 0,0002.

Weighing bottle with sample place in a drying case with temperature 102-105⁰С on 2 h, periodically mixing sample by a glass stick.

Upon termination of drying weighing bottle with mayonnaise cool in exsiccator during 30 min and weigh. After repeated drying sample of mayonnaise make the subsequent weighings up to constant weight.

Constant weight consider achieved, if the difference between two subsequent weighings will not exceed 0,001.

Moisture content in mayonnaise in percentage (W) expect under the formula:

where

m₁ — mass of weighing bottle with mayonnaise before drying, g

m₂, — mass of weighing bottle with mayonnaise after drying, g

X_у.к — acidity of mayonnaise in equivalent to acetic or citric acid, %;

m — sample of examined mayonnaise, g.

Discordance between two parallel definitions should be not above 0,2%.

The order of performance of a mass share of fat.

In oleometer give on technical weights 1,7-1,9 g previously of hashed mayonnaise and place it in boiling water on 10 mines. Then in oleometer pour 18 см³ of a sulfuric acid (density 1,5 g/sm³) and 1 sm³ isoamyl spirit. Close by a dry fuse, well stir up, heat up on water bath, with temperature 65-70⁰С, periodically stirring up up to complete dissolution of protein substances of mayonnaise, and during 5 mines make centrifugation with speed 1500 об./mines.

Then oleomtre immerse by a fuse downwards on 5 min in water bath with temperature 65-70⁰С and make readout of fat, holding oleometre vertically so that the border of fat was at a level of an eye. By movement of a fuse upwards and downwards establish the bottom border level of fat on the whole division of a scale oleometre and from it count number of divisions up to bottom meniscus of fat level.

The contents of fat (Хж), in percentage expect under the formula:

,where

a- indication of oleometre;

m – sample of mayonnaise, г;

К - factor of recalculation of the indications oleometre in percents (To = 5).

The divergence between two parallel definitions should be no more than 0,5 %.

Definition of acidity. In conic flask give about 2 gof mayonnaise on technical weights, add 50 sm³ of distilled water. Mix and titrate by a solution of caustic alkali of concentration 0,1n at the presence of the indicator - phenolphtalein before occurrence of weak - pink colouring which is not disappearing during 1 min.

For mayonnaise with sauce "Southern", with tomato - paste the quantity of distilled water is increased up to 100 sm³. For exacter establishment of the end of titration of these mayonnaises near to titrated sample it is necessary to put control flask with same or close to it a sample of mayonnaise in 100 sm³ of distilled water.

Acidity of mayonnaise (Xу.к) count on an acetic acid under the formula:

,where

V - amount of a solution of alkali of concentration 0,1 n, used by titration, sm³;

К - amendment to a titer of a solution of alkali of concentration 0,1 n;

0,0006 - factor of recalculation on an acetic acid;

m – sample of. mayonnaise,.

The divergence between two parallel definitions should not exceed 0,2 %.

Definition of emulsion stability. The parameter of emulsion stability of mayonnaise is served a quantityof fat allocated from mayonnaise as a result of strong mechanical and thermal influence.

The order of performance of job. Definition of emulsion stability of mayonnaise make in two steps: centrifugal test-tube with divisions by capacity 10 sm³ fill before the top division by mayonnaise, then place test-tube in a centrifuge and centrifugate with speed 1500 об./min, then observe destruction of emulsion. Further that test-tube place in boiling water on 3 min and again centrifugate during 5 min.

Stability of emulsion expect under the formula:

,where

Xэм – stability of emulsion, % about.,

Vж - quantityof the selected fat, sm³;

10 - reduction of volume taken for the analysis to 100 sm³.

The results of an estimation of quality of mayonnaise on physical-chemical parameters issue as tab. 34.5.

Physical-chemical parameters of quality of mayonnaise

Parameter	Norms	The fact
1. Moisture content, %, no more 2. Contents of fat, %, not less 3. Acidity in recalculation on an acetic acid, %, no more 4. Stability of emulsion of the allocated fat, %, no more

The conclusion about quality of mayonnaise __________________

Laboratory job № 5

Theme: Estimation of quality of cocoa powder and chocolate.

The purpose of work: make skills and attainments of identification of various kinds of chocolate and definition of quality of cocoa powder and chocolate.

1.1 The task

1. Definition of organoleptic indicator of cocoa powder and chocolate.

2. Definition of cocoa powder grinding degree.

3. Definition of fat’ mass fraction by refractometric method.

4.Draw up report on the work done.

1.2. Theoretical part

To get cocoa powder and chocolate the cocoa beans are cleaned and roasted. Then they go trough a machine which cracks them A current of air removes the shells, leaving the edible pieces of cocoa, called “nibs”.These nibs, containing about 54% fat (cocoa butter), are ground between rollers which free the fat and produce a brown liquor. This liquor is treated in presses which turn it into a hard cake after squeezing out some of the fat. This is next crushed and sifted to produce the familiar brown cocoa powder. In the manufacture of chocolate the roasted nibs are mixed with sugar and roughly ground to a paste.

The order of performance of job

Required materials and ware: 1. Cocoa powder and chocolate. 2. Sieve with wire-netting.

3. Crayon brush. 4. Pounder with pestle. 5. Refractometer. 6.Measuring glass or flask capacity 25,50 cm³, funnel, micropipette. 7. Picnometer on 25 cm³. 8. Paper filter, cotton, scalpel.

9. Technical balance. 10. Naphthalene monobromate or naphthalene monochloride.

1.Definition of organoleptic indicator cocoa powder and chocolate. At determining of organoleptic indicator of cocoa powder its taste and flavour are tested in drink, prepared in such a manner. Weigh out 4g of powder, add 6g ofgranulated sugar and 5cm³ of water or milk. After cooling it to 40⁰ C determine it taste and flavour. Definition of cocoa powder suspension’ firmness determine also in drink. Suspension is considered firm, if during 2 min after brew there is no noticeable sludge.

Аt determining of organoleptic indicator of chocolate its outward, form, consistence, structure, taste and flavour are defined. By inspection of outward regard must be paid to condition of front surface, form, presence of defects. Consistence of chocolate must be firm, structure- homogeneous, for porous- honeycomb. Taste and flavour must be peculiar for chocolate.

2.Definition of degree of cocoa powder grinding. Method is founded on sifting product and weighing residue on the sieve. Sample of cocoa powder in quantity 5g, taken with accuracy 0,01g, sift on sieve with wire-netting 016, slightly shake and help with brush. Sifting lead till on list can be seen black particulate solids. On the end of sifting sieve with remains and brush weight. Degree of grinding in percentage calculate by formula Х_изм=(m₁-m₂)·100%/m, where m₁- mass of sieve with remains of studied product and brush, g; m₂- mass of sieve with brush, g; m- sample of cocoa powder, g. Obtained data compare with norm.

3.Definition of fat mass fraction by refractometric method. Method is founded on pulling out fat from sample with the help of naphthalene monobromate and definition refraction index of solvent and solution of fat in solvent with the help of refractometer. Naphthalene monobromate well dissolves fat in the cold and have high rate of refraction, differ markedly from from refraction index of fat. On dissolving of fat by naphthalene monobromate refraction index decrease at amount, proportional amount of fat resolve.

Mass of solvent density is determined by picnometer and calculate by formula: p²⁰= (m₂-m)998,23/ m₁-m,where m₂-mass of picnometer with solvent, g; m₁-mass of picnometer with water, g; m- mass of empty picnometer, g; 998,23- value water-mass density by 20⁰C, kg/m³. Density of solvent is necessary to know in order to calculate exact volume of pipette.

Pipette by capacity 2cm³ is calibrated according to solvent, measuring by it corresponding volume of solvent and weighing it in measuring glass with an accuracy to 0,0015g. Discordance between parallel deliberations must be not above 0,005g. From three weighing take arithmetic average and calculate volume of pipette Vп by formula: Vп= m₃ ·100/ p²⁰,where m₃-mass of solvent, according to volume of given pipette, g; p²⁰ -density of solvent by 20⁰C, kg/m³ .

At first determine refraction coefficient of solvent, applying on prism of refractometer 1-2 drops of it by temperature 20⁰C. Then weigh out 0,5-1,5g well gritted product to the accuracy 0,001g . Mass of sample depends on content therein fat (tabla1).

The table1. Dependence mass sample from fat content

Fat content, %	Sample,g
Above 30	Not less than 0,5
From 20 to 30	0,75
From 10 to 20	1,00
Below 10	1,50

Sample place in pounder, grind by pestle 2 min, then add with calibrated pipette 2cm³ of solvent and once more grind during 3 min. Mixture filter in measuring glass or test tube through paper filter during 30min. Filtrate mix by glass rod, apply on prism of refractometer by temperature 20⁰C and count off refraction index.

Mass fraction of fat Хж in percentage terms calculate by formula:

Х_ж= V_р ·p²⁰_ж/1000· m·К_р/ К_рж·100%, where

V_р- volume of solvent, taken for fat recovery,cm³;

p²⁰_ж- density of fat by 20⁰С, kg/m³;

К_р- refraction coefficient of solvent;

К_рж- refraction coefficient of fat solution in solvent;

m- sample of product.

Report on the work done fix in table 2.

Table 2. Quality factors of cocoa powder

Factor	Norms	Factual evidence
Outward
Taste and flavour
Degree of grinding
Firmness of suspension
Fat content

Control questions:

1. What does organoleptic analysis of products consist of?

2. How does mass of sample depend of fat content?

3. How is mass fraction of fat in cocoa powder determined?

4. Describe the process of getting cocoa powder and chocolate.

Laboratory work # 6

Definition of phenol compounds in vegetable products

The purpose of job: At performance of this job define technologic store of phenol matters in grape or other vegetable products by permanganate method.