Special methods of analysis. 1 application.

There are many publications on food analysis, and some of them provide detailed information about the methods that can be applied in confectionery. All chocolate and pastry manufacturers should be familiar with organizations such as The International Office of Cocoa and Chocolate (IOCC), 172, Avenue de Cortenbergh, 1040 Bruxelles, Belgium and The International Sugar Confectionery Manufacturers' Association (ISCMA), 194, rue de Rivoli, 75001 Paris, France. Both of these organizations collect all its members every five years, and monitor all aspects of the industry.
IOCC publishes “official” analysis methods that are regularly updated and accepted as standard in the world. Periodic bulletins describing the activities of these organizations are also published.
Industry-specific analytical techniques are described in the manufacturers brochures. Industry journals often contain articles on the application of these techniques and the meaning of the results obtained.
Analytical procedures, when necessary, have been mentioned in previous chapters. Some of the methods given below are taken from the second edition of this book and supplemented, where it turned out to be necessary, with materials corresponding to the modern level.
Particle size
The size of the particles of cocoa, chocolate and confectionery products - this is a very important characteristic. It is important for sensory perception, and for industrial processes.
The smoothness of the feeling of chocolate on the palate is associated with the absence of large particles of sugar and cocoa. Similarly in the case of lipstick. In cocoa powder, the particle size determines the properties of their suspension in a liquid, for example, in milk and water. The distribution of particle size (that is, the proportion of particles of different sizes) is important from an economic point of view.
In chocolate, the use of cocoa butter to obtain a given fluidity is associated with the proportion of very small particles. Due to the larger total surface area, they require more cocoa butter for their “wetting”.
Differences particles
The particles in various chocolate and other confectionery products differ significantly in appearance, shape and size.
When examined under a microscope, it can be seen that, in cocoa liquor, the particles have an irregular shape, but do not have sharp edges and differ in color from transparent light brown to reddish-brown and opaque dark brown.
In dark chocolate, cocoa particles are similar, but less noticeable due to the presence of sugar. Sugar crystals are easily visible as light plates are usually irregular in shape, as they are crushed during grinding.
Milk chocolate contains cocoa particles, sugar crystals and milk solids, but if milk chocolate is made from crumbs, only one kind of particles is visible. These are aggregates of milk solids, sugar, and grated cocoa, which were formed during the crumbling process during final crystallization and drying. These conglomerates are destroyed in the process of fine grinding, but not divided into their constituent particles.
These aggregates have a light brown color, and in some of them you can see the combined sugar crystals and cocoa particles.
In the production of milk chips, it is important to make sure that the sugar crystals formed during the crystallization stage are small and when examined under a microscope, the aggregates are separated with a fixing chemical solution so that the sugar crystals can be measured independently. In milk chocolate, made from milk chips, powdered milk particles are clearly visible as separate pale yellow spots of irregular shape.
In the fondant, only sugar crystals are visible particles, and since most of them grew out of syrup without any interference, they mostly have a cubic shape and under the microscope have a very regular shape.
There is a difference between freshly made basic lipstick and lipstick that has been re-melted and cast into molding starch. In the re-melted lipstick, some of the crystals are large due to the growth in the melting and casting stages, while the rest of the crystals are small, as in the “base lipstick”. “Basic lipstick” can also contain large crystals due to poor whipping and cooling during production, and this is discussed in the “Lipstick production” section. The size distribution of sugar crystals in lipstick strongly influences the feeling of homogeneity in the mouth.
Approximate sizes of particles which can be in these products are given in tab. P1. The values ​​given are “average for large particles”.
Basic product The finished productParticle size, microns
grated cocoa
The size of the cocoa particlesSuperfine cocoa or chocolate production100
Cocoa powder for making beverages200
chocolate temnы
The size of the cocoa particlesHigh-quality chocolate for direct consumption or high-quality glaze30-50
Chocolate for the average quality of the glaze75-100
The size of sugar crystalsHigh-quality chocolate for direct consumption or high-quality glaze25-35
Chocolate for the average quality of the glaze50
milk chocolate
Size crumbs unitsHigh-quality chocolate for direct consumption.35
Chocolate for the average quality of the glaze50
fondant
"Basic lipstick" of the car10-15
Lipstick cast (Assorted)25-30
It should be understood that these data cannot be compared with the readings of a micrometer (see below).
Methods for determination
Methods for determination of particle sizes can be divided into the following groups:
  1. Using a micrometer, and modifications.
  2. Microscopic, including computer scan.
  3. Wet sieve analysis, water or oil solvent.
  4. Precipitation.
  5. Electronic counting, using a Coulter Counter and laser beam.
MIKROMETR
For many years, the standard micrometer has been used more than any other devices for determining the particle size of chocolate paste after a rolling machine.
The method uses a small amount of the finished paste, mixed with an equal amount of liquid oil. A drop of the mixture is placed on the bottom gauge.tion surface mic, sponges pull together using a spring-loaded knob until the movement is stopped. Next, read the testimony of a micrometer scale.
The resulting number is not the size of the particles and does not take into account their shape. It is most likely that individual large sugar crystals will collapse during this measurement. The result obtained in the hands of a qualified specialist is indicative, but in fact represents the thickness of a layer of particles compressed between micrometer jaws with a standard force. The weakness of this method lies in the fact that the result is influenced by the variety of micrometers, the individual differences between the people who use them, the sample size and the fact that the method does not give accurate information about the actual particle sizes or the content of particles of different sizes.
The achievement of recent years is the creation of an electron micrometer in which the sponges are larger in area and shift with a certain exact pressure. The device gives digital readings, but the resulting number has the same meaning. The characteristics of the micrometric method as a means of controlling the grinding process required research to improve the results.
MetriScope
This device was created at 1958 in Lockwood of Cadbury Research Laboratories and is the original mechanical device for measuring the effectiveness of grinding chocolate or cocoa. The method is actually an improved micrometric method and a much larger sample is used for measurements. Additional information about this instrument can be obtained from Confectionery Division Research Laboratories, Cadbury / Schweppes Ltd., Boumville, Birmingham, England.
The principle of the method is based on the fact that a film of chocolate or suspensions, the particle size of which is to be measured, maintains a steel conical “cork” in the nest.
"Cork" and the nest have a bevel exactly one to ten. A film of particles of sugar and cocoa in the gap raises the cork to a height twenty times the thickness of the film due to the bevel. The protruding part of the tube is accurately measured with a micrometer and this value can be associated with the average size of large particles of chocolate or suspension.
Metriscope works automatically and gives several repetitions in a short time. The device uses 28,4 g of sample dispersed in 142 g of lecithinized cocoa butter, which gives a much more significant result than that obtained with a very small sample used for micrometric measurement.
Fig. P1 is a schematic representation of the sample and the socket, and Fig. P2 and PZ shows how the machine operates at different factories.
25.1
25.2 Fig. PNNUMX- Metriscope - Front View
25.3 Fig. PP. MetriScope - Back view
method for determination
Detectable materials. Pasta after fine grinding, the chocolate after conching machine, ready chocolate suspension.
Necessary equipment. Metstsore, electric vibratory mixer, measure 5 liquid ounces (0,15 l) for cocoa butter, dispenser per 1 ounce (28,35 g) (for paste after grinding), stainless steel vessel with a capacity of about 10 liquid ounces (0,3 l), spatula, oven supporting 45 ° C.
Cocoa oil dispersion. This cocoa butter in which dissolved 0,25% soy lecithin.
Preparation of samples for testing. One ounce of crushed paste is measured using a “dispenser”, the chocolate cylinder is placed on a perforated disk of a vibrating mixer (Vigo-tikheg) and mixed in 1 min. with 5 liquid ounces (150 ml) of cocoa butter containing 0,25% lecithin. After that, the sample is ready for immediate measurements.
Other materials are typically scanned in small cups are weighed, mixed with a small portion of 5 fluid ounces (150 ml) cocoa butter with a spatula and then transferred to a stainless steel container for mixing.
Working with MetriScope. The heater is turned on for 2 hours before use to ensure that the appliance will work with liquid cocoa butter. The operating temperature range is from 40 to 45 ° C, the temperature can be maintained automatically. When it is necessary to perform measurements with
boron, turn on the engine, cocoa butter is passed through a sieve from a wire mesh into a bunker, the handle is moved to the “Test” position, and the oil begins to fill the inner recess. Any excess oil entering the inner recess flows into the outer recess, from which it enters the storage tank at the bottom of the device.
From this moment on, the device works fully automatically, the cork rises and falls so that a certain amount of cocoa butter remains between the surfaces of the cork and the nest. The vertical bar is released, and the reading on the dial indicates the film thickness. This operation is repeated every 20 s, and after the 3-4 complete cycles, the internal recess must be empty. For cocoa butter, the reading on the scale should be 25 or less, and when this value is reached, the test suspension is fed through a sieve from a wire mesh. When the inner well is filled, the control knob is turned to “Waste” (“Reset”) and the rest of the sample enters the storage tank. The first reading on the dial is discarded, and the average of the next three measurements is recorded as the measurement result of the instrument. Measurements are carried out in tens of microns.
instrument calibration. To make sure that all devices give the same readings in the working range (30-150), standard chocolate comes from the central laboratory with a known value in terms of metriscope. Standard chocolate is made, as mentioned above, and the scale of the device is set to the desired position. To do this, release the bolt from behind and move the scale higher or lower along the rack until they reach the required reading, then tighten the bolt. A small final adjustment can be made by turning the scale in front, but this setting should not exceed the 2-3 division. This operation is performed with the zero adjustment removed. The device is then started, and the rod should set the scale to a negative reading near the 10 units. The zero adjuster is then installed in place so that the prism fixes the outer ring of the dial and the adjustment screw is set so that the scale pointer returns to zero after each measurement. The accuracy of the instrument readings is checked daily by scientific personnel (metrologists) and adjustment by factory workers is not required.
A standard mixture of chocolate and cocoa butter. Two ounces of chocolate are weighed into a glass, melted and mixed with 0,3 l of cocoa butter, and the mixture is poured into a closed bottle with a label. This mixture is stored in the instrument, ready for testing on a standard sample. This check is performed by carefully shaking the contents of the bottle and pouring approximately 1 fluid ounces (30 ml) into the inner well of the device.
MICROSCOPES
At the initial stage of grinding control, measurements of sugar crystals and cocoa particles were carried out using standard microscopes equipped with transparent scales in the eyepiece and a mechanical table for fixing the slide with the preparation. The mechanical table made it possible to methodically examine the material on a glass slide, and the particles were measured using a scale in the eyepiece.
The microscopic method was very tedious and caused eye strain during long periods of work, but despite this, it was used for many years. Hand-held microscopes have basically changed the projection microscopes, the design of which is also greatly improved, especially in terms of the brightness of the lighting and the size of the viewing screen.
The projection microscope is shown in fig. P4. This device is not available now, but the figure illustrates the principle of operation that can be applied. The illumination is carried out by a powerful xenon lamp, and the image of particles is projected through a prism onto a mirror, from which it is reflected onto a ten-inch screen.
The primary lens of the microscope has low power, but with the help of a lever an additional lens is inserted and an enlarged image appears in the middle of the screen. The image given by this device turns out bright enough that allows you to take measurements in muffled daylight. A grid is created on the screen, which is calibrated for simple particle measurement.
Microscopic measurements are empirical, and their value depends to some extent on the exact method of preparation of the drug and the systematic method of measuring particles. Using the described system, only large particles (10-50 μm) are measured. This is usually acceptable for the control of grinding equipment and the production of lipstick.
25.4Fig. P.4. projection microscope
a. Look-ekrand. g. Fine tuning
b. Casing h. The lamp and the condenser
c. Doublet lens to. Fan
d. Subject stolikt. m. Mirror (swing projection on the screen)
e. Condenser
f. Preset n. Wall screen
Company Elcometer Instruments Ltd., Manchester, England
Other methods used to measure the very small particles and size distribution (see. below).
It is often said that one of the advantages of the microscopic method is that the particles are “visible”, while in other methods they are not. For many products, this quality aspect is a great advantage.
Microscopic measurement techniques. The following are simple practical methods. Specific details can be changed as convenient for the user.
grated cocoa. Preparation of the sample. Get a representative sample from the refining rollers and mix well. In the case of grated cocoa, larger particles often settle after exposure, and if measurements are not taken immediately the product should be brought to the desired state (temper) and molded.
Preparation of microscopic sample. The amount of product used on a glass slide is determined using a stainless steel 5 x 2,5 cm and 1,2 mm plate. The plate has a hole in the center with a diameter of 3 mm.
The plate is placed on a glass slide and the hole in it is filled with a solid or pasty product using a scalpel blade. Excess product is removed by swiping the blade over the hole. The product is pushed out with a blunt metal rod that fits tightly into the hole. The pellet from the product is placed in the center of the slide.
To the ground product is added one drop of liquid oil from a micropipette, which indicates the required amount. A coarse grinding product requires a little more oil. A glass slide is heated and the oil and the product are mixed with the tip of a scalpel so that the mixture remains within a circumference of less than 2,5 cm in diameter. A small amount of the oily mixture at the end of the scalpel is neglected, so it should be minimal. After thorough mixing in a spot with a diameter of 2,2, the cover glass is placed on top, and it is allowed to sink under its own weight. The pressure should not be applied, and the amount of oil used should be sufficient to cover the cover glass without extending beyond its edges.
It is important that the material remains on the slide. The instructions should be strictly followed so that the preparations have a standard density.
Measurement using a projection microscope. A glass slide is placed on the table of the microscope and the image is focused on the screen. First, the drug was investigated methodically to determine the uniformity of the distribution of particles and to estimate approximately the size of large particles. Then the drug is examined a second time, the size of large particles is measured and recorded.
After performing 10-15 measurements, it is easy to determine if the results are representative of most large particles on the slide. Then the average of the ten first results is taken.
The size of the particles of chocolate, pasta after the refining rolls and cocoa in the milk crumb. To determine the size of cocoa particles in dark and milk chocolate, paste after refining rollers or in milk crumb, it is necessary to make preparations so that the density of cocoa particles on slides is the same as in measurements of grated cocoa. If this is not done, the results, strictly speaking, cannot be compared. Stainless steel plates with larger holes and rods will be required to account for the content of grated cocoa in chocolate.
The composition of chocolate and crumbs varies somewhat, but examples of the content of cocoa liquor in them are given below (in%):
dark chocolate for eating 30
milk chocolate for eating 11
Milk paste after grinding in the mill 13
milk crumb 14
The calculation of the size of the hole and the rod should be carried out in accordance with the recipe.
In the case of breast crumb best necessary quantity weighed (approximately 15 mg) at predmetnoesteklo, then the product must be mitigated in order to make it possible to manufacture the drug. This can be done using a medium consisting of ethylene glycol saturated with ammonia or dichlorohydrin.
Measurement of particles on a microscope slide is performed by the same procedure as that for cocoa liquor.
Crystals sugar lumps and crumbs
The method of making preparations is similar to that used to measure cocoa particles, except that the oil is reddened with a fat-soluble dye. The density of the crystals and aggregates on the slide is such that it is usually not necessary to make an adjustment that takes into account the sugar content of the chocolate.
The first study of the drug may show the presence of a small number of "wrong" crystals, the size of which is significantly higher than the average size of large crystals. Usually they are not taken into account when measuring.
In dark chocolate, sugar crystals have a clearly defined contour and are easy to measure, but in milk chocolate and in pastes it is necessary to measure aggregates of ground crumbs, which are more difficult to distinguish. Sometimes when grinding, some sugar crystals are separated from the aggregates, and they are smaller in size than the aggregates.
If the production of crumb, crystallization occurred too slowly, sugar crystals grow too large, and aggregates containing these large crystals are formed. They make grinding difficult and yield is reduced.
The sugar crystals in the crumb are measured using a medium of glycol or dichlorohydrin, but this measurement is rarely required when chocolate manufacturers make their own crumb, so they have to check the size of the sugar crystals at the kneading stage (see “Dairy Crumb Production”).
In milk chocolate, made with powdered milk, sugar crystals are visible as in dark chocolate. Particles of powdered milk are light yellow and have an irregular shape.
fondant. It has already been noted that in the fondant there may be crystals whose sizes lie in two ranges, due to the bad conditions of whipping in the machine to obtain lipstick or poor melting. Large crystals may also appear due to the inclusions of waste for reuse, but now this is rarely done. The inclusion of waste is best done by processing it into syrup and discoloration (see “Regeneration”).
Preparation of the drug. The hole in the plate, similar to that used for grated cocoa, is filled with lipstick. Then the lipstick from the hole is placed on a glass slide, where it is mixed with a glycerin medium and colored red or green. The slide is then necessary to investigate immediately, it can not be heated, as the formation of a certain amount of solution from the crystals may occur.
A well-prepared basic lipstick should have a size distribution similar to the following: a very large number of 10 μm and 15 μm crystals; 20 μm crystals should be missing. The average crystal size should be 12,5 μm.
Measurements fondant chocolates molded casting. This is a difficult task if the inspection of several areas shows that there are two different size ranges.
This method involves counting crystals in large ranges and recording sizes, as shown in Table. P2. The average size of “larger crystals” should then be evaluated as follows:
Example 1 28 microns
Example 2 20 microns
Example 3 40 microns
P2 Table. Lipstick candy molded casting (Assorted)
Size, mm
Less than 202530 354045
Example 1
Number of crystals Example 2
Number of crystals Example 3
A large number of

A large number of

XXX

XXXX

XXX XXX XXXXXXX
Number of crystalsA large number ofXXXXX
XXX
XXX
XXX
XXX
Examples of 1 and 2 can be viewed as an average size distribution, and in the 3 example, two clearly distinguishable size ranges are clearly visible, indicating poor melting and casting methods or poor basic lipstick, but if 1,2 and 3 examples are obtained on the same lipstick , the reason for the appearance of the data given in the 3 example seems to be bad tempering.
screening methods for the determination of particle size
Dry sieve analysis is rarely used to determine particle sizes, only occasionally for low-fat cocoa powder and finely ground sugar.
To do this, sets of sieves with different hole sizes are subjected to automatic vibration, then the material collected on each sieve and the material passed through the smallest sieve are weighed. In this way, some understanding of the particle size distribution is obtained. Dry sieve analysis is more suitable for powders that do not clog the sieve - fatty powders often clog the sieve.
"Wet" sieve analysis
The principle of the method consists in preparing a suspension of a powder or solution in a solvent and rinsing it (with a pure solvent) through a thin sieve. The technique described below uses an 325 mesh woven wire screen, which is suitable for most practical purposes; in practice, 200 mesh is more commonly used for cocoa powder [UK aperture size: 200 mesh — 0,0030 inches (75 µm); 325 mesh - 0,0018 inches (45 µm)].
Now there are fine-meshed sieve, and can be measured by a particle size of up to 8 microns.
"Wet" sieve analysis (solvent)
The sieve consists of a hollow cylinder of tinned copper with a diameter of 3 inch and a height of 2 1 / 2 inch, to which is attached a handle in the form of a long arc. The base of the sieve has a flange and is covered with standard 325 mesh wire mesh, soldered along the edge of the cylinder. A metal ring is soldered to the underside of the mesh to protect the sieve when it is placed on the laboratory bench.
25 g[1] Cocoa is placed in a sieve and slowly lowered into a vessel containing petroleum ether at a temperature of 60-90 ° C. During testing, the sieve is rotated, holding the mesh at an angle of 30 ° to the horizon. When the sieve is filled less than a quarter, it is slightly raised so that about half of the mesh is below the surface of petroleum ether in the vessel. When the volume in the sieve is significantly reduced, the sieve is lowered until it is again less than a quarter full, and the solution is allowed to drain. The process continues for as long as necessary, usually around 5 minutes, without ceasing to rotate the sieve gently. After this time, the residue in the sieve will look noticeably larger than the original cocoa.
Then the sieve is transferred to another vessel containing pure petroleum ether. Cocoa, sticks to the side of the sieve, washed using the wash bottle with petroleum ether. Sieve dipped several times in ether, then raised and allowed to drain. After this screening is completed.
The sieve is dried in an oven 10 min. Cocoa tails are transferred to a tared cup with a small brush, weighed and calculated in percent.
In the method described below, desiccators with an internal diameter of approximately 20 cm with well-ground covers can be used as washing vessels.
After a series of definitions, the screen will have a noticeable number of clogged holes. It is washed in a large beaker with a layer of boiling Sgc-solution of sodium hydroxide with a thickness of about 12,5 mm. The sieve is boiled for about 2 min, after which the holes should be free, and it is immediately washed thoroughly with water, then with alcohol and dried in a drying cabinet.
"Wet" sieve analysis (with water)
In this method 200 mesh sieve residue was determined as described below. Full description is given in [11].
The technique. Weigh out approximately 5 g of cocoa powder in an 400-ml beaker with an accuracy of 10 mg. Add 20 ml of distilled water and mix thoroughly with a glass rod until the lumps completely disappear. Then add 280 ml of hot distilled water (75 ± 5 ° C) and vigorously mix 2 minutes with a mechanical stirrer so that no funnel forms (at a speed of around 300 rpm). Pass the suspension through a 200 mesh screen, while simultaneously rotating the screen in a horizontal plane.
Rinse the beaker and sieve with hot distilled water (75 ± 5 ° C). If the slurry does not evenly pass through the sieve, tap it lightly. Attach the Buchner funnel (diameter about 7 cm) to the 500-ml suction flask.
The fiberglass filter, pre-dried for 30 min at 103-105 ° C, cool and immediately weigh to the nearest 1 mg. Then moisten the filter with water and press firmly against the perforated base of the Buchner funnel. Wash the residue from the sieve onto the filter and turn on the vacuum. First rinse the top of the sieve and then the bottom. Rinse the filter using approximately 15 ml of acetone and dry the 60 min at 103-05 ° C. Cool and immediately weigh the filter with sediment to the nearest 1 mg.
Calculate the percentage of sludge as a "sieve mesh 200 tails."
mikroproseivaniya method. We have already mentioned mikroproseivanie to a particle size of 8-10 microns.
[13] showed that adjustable sieve vibration is required to obtain satisfactory results. For information on smaller
particles (4 microns or less) using an electron microscope, and the [17] discloses a method using a sputtering system to obtain a uniform distribution on a microscopic specimen.
sedimentation method
For information on the distribution of particle size, there are many methods based on standing. If the powder is suspended in water or other liquid, the rate at which the particles settle depends on the particle size and density of the liquid.
When settling the suspension part of the sample can be separated after a while and weighed. It can also be used volumetric method - measuring the volume of sediment after a specified time.
Standard equipment for measuring with settling is the Andreasena pipette. In the first edition of this book, a method was described for determining the degree of grinding of cocoa powder on the sedimentation of particles on the bottom. This method has been used for many years to determine the chosen particle size range in milk chocolate. A useful water precipitation method for cocoa powder research is described below. Cocoa containing particles of husk and germ quickly form precipitation. In chocolate drinks this is undesirable.
Test Imgoffa. Tube Imgoffa designed to monitor effluent and sediment control, but to control the precipitation of cocoa it narrowed more than to be able to receive indications to 0,05 ml (Fig. P5).
25.5
The controlled powder must be free of pressed flakes that may appear during packing and transportation, the powder is passed through a 100 mesh sieve to remove them. Weigh the cocoa 2,5 g and transfer to a beaker with a volume of 1 l. Rinse the 500-ml cylinder with hot distilled water. Then fill the cylinder to the 500 ml mark with hot distilled water. Allow the water in the cylinder to cool to 82 ° C.
While the water is cooling, fill the Imhoff tube to the 500 ml mark with hot distilled water (82 ° C).
Make a liquid cocoa paste with a small amount of water at a temperature of 82 ° C from a measuring cylinder, rotating the glass to give the movement of water around the circumference. Slowly add about 200 ml of water, rotating contents. Add the remaining water from 500 ml at 82 ° C, without rotating the contents.
Stir the mixture with an electric stirrer exactly 30 with, and during this time completely drain the Imgoff tube, turning it over and tapping on the tapered end to remove any residual water.
Place the tube in a rack Imgoffa and immediately transfer the cocoa suspension in a tube and let stand exactly 5 minutes.
The deposition can be observed by placing a weak light source on the side of the Imgoff tube. To make it easier to measure the amount of sediment, you can use a magnifying glass.
The sediment line should be well delineated, but if it is uneven or oblique, the test is repeated.
Good cocoa, suitable for making beverages, should give less 0,25 ml of sediment when measured by this method.
Methods based on precipitation, are empirical, and some of them are very long. In addition, they say nothing about the shape of the particles.
Determination of particle size distribution by laser
This method has been used successfully to determine the size and distribution of particles in chocolate pastes and powders.
Operating principle. A low-power laser beam illuminates a cell containing a suspension of particles that can be dispersed in various organic or aqueous fluids in cells of small or large volume. Light is made diffused and focused using a collecting optical system on a multi-element ring detector. The position of the detector ring is selected for each particle size distribution and measurement.
The degree of light scattering depends on the size of the particles — the smaller the particles, the wider the scattering angle. The detector operates continuously, the output signal is amplified, control is carried out using a microprocessor.
The results of determining the distribution of particle sizes in the form of a table and a histogram are displayed on the display of the device and can be output to a printer. The principle of operation of the detector is schematically shown in Fig. P6 and P7.
25.7
Fig. P6- principle of diffraction scattering. The company Malvern Instruments Ltd., Malvern, England
25.6Fig. A.7. 3600E detector. The intensity on each detector is the sum of the intensities from all the particles of a given size. Malvern Instruments Ltd., Molvern, AngLeah
Coulter Counter
This method, developed at the end of 1950's, is used to determine the particle size distribution. The device, known as the Coulter Counter (Coulter Countei <©), was first used to count blood cells, but was later used for a wide range of materials containing particles — powders, pastes, suspensions, and emulsions.
In this method, a suspension of the studied particles is prepared in a suitable electrolyte solution, and passed through a narrow opening in which there is an electrode on each side. When a particle passes through an orifice, it displaces a volume of electrolyte solution equal to its volume, changing the impedance (electrical impedance) between the two electrodes for a short time and modulating the flowing current (similar to changing the resistance) and forming a pulse. The pulse amplitude is almost proportional to the volume of the particle. A series of pulses arising from the passage of a stream of particles is amplified by an electronic circuit and is scaled, allowing you to count particles and / or determine the volume (mass) of particles or series of particles between known sizes.
For chocolate, a special electrolyte solution is needed. It is shown that the most acceptable is 5% (w / v) ammonium thiocyanate solution in technical or isopropyl alcohol, and chocolate particles are dispersed in a solution of fractionated (alcohol-soluble) lecithin or Span 80 (sorbitan oleate, Honeywill Atlas). For the analysis of dark chocolate, the electrolyte solution is pre-saturated with sucrose, and for the analysis of milk chocolate, the electrolyte is pre-saturated with non-fat solids of milk chocolate. Using these solutions of electrolytes and various openings, particle size distributions in chocolate, cocoa and cocoa liquor were obtained in terms of number and weight (mass or volume) in percent to the size 0,5 μm. You can analyze the chocolate obtained using different processes, and determine the ratio of small and large particles. It is not intended to describe the operation of various models of the device or the methods used, as they are described in detail elsewhere, but the technologist will be interested to get acquainted with the particle size distributions in popular varieties of milk chocolate, determined using the Coulter Counter (Fig. П8 and П9).
Determination of fat in chocolate and cocoa products
The analytical methods described in standard textbooks in detail as follows:
  • Continuous extraction with petroleum ether in a Soxhlet extractor and extractor Bolton; •
  • Werner-Schmidt method, which is used when the protein interferes with extraction; the product is heated with hydrochloric (hydrochloric) acid before extraction;
  • methods Mozhonier and Rose-Gottlieb (the product is treated with ammonium hydroxide and alcohol to dissolve the protein; suitable for dairy products and caramel);
25.8Fig. P8. The particle size distribution, popular varieties of chocolate, the differential and total volume (mass or weight). The percentage depends on the size (m) Firma Coulter Electronics Ltd., Luton, England.
25.9Fig. The particle size distribution P9- popular varieties of chocolate, the differential size and the total number of excess relative size (microns). Company Coulter
Electronics Ltd., г. Лутон, Англия.
Gerber method (volumetric method used for monitoring milk; product is treated with sulfuric acid and then centrifuged).
Express - methods using trichlorethylene extraction
These are simple, fast and cheap methods that can be used with routine monitoring.
sample preparation. If possible, samples of chocolate and cocoa liquor should be homogenized and molded accordingly. Other
ant to obtain a homogeneous sample - finely rub a large sample and mix.
Except as indicated below, 10 g is taken for measurements. Samples containing a large amount of husk, for example, whole beans and trend products, should be analyzed by the Soxhlet method, since full extraction is not achieved in the express method.
Peeled husks of cocoa are products of trend: use the Soxhlet method.
Cocoa liquor. Take measurement 5 g fine shavings. If the weighing takes place in a fluid state, mix well.
Chocolate. Take 10 g. Finely rub. If weighing occurs in a fluid state, mix well.
Cocoa cake. Take 10 was milled until yet not pass through a screen mesh 30.
Cocoa powder. Take 10 of Mix sample.
Milk crumb. Take the 10 d. Grind and sift as in the case of cocoa cake. Periodically check should be carried out by the Soxhlet method. In some types of milk crumb, part of the fat may be “blocked” in the agglomerates of protein or sugar.
Weighing samples. Samples 5 or 10 g, depending on the conditions of determination, weighed in balanced metal cups. Accuracy of ± 0,01 g is sufficient when weighing 10 g, but when weighing 5 g accuracy of ± 0,005 is required. The weighted sample is carefully placed in a narrow bottle with a ground-in 6 cc ounce stopper (—180 ml), the remnants of the sample are removed from the metal cups by tapping on them or using a brush from a camel's hair. Then 100 ml of pure distilled trichlorethylene is added from an automatic pipette into which the solvent flows from the reservoir. Two pipettes are used so that one can be emptied, while the other can be filled at this time. The bottle is sealed with a glass stopper, its contents are well shaken and allowed to stand for at least 30 minutes. During this time, the contents are periodically shaken.
Filtration. The filter paper Whatman №5 (18,5 cm) is pleated, folding on the tube (sealed with a rubber stopper), get out of her "cup", and insert it into the bottle so that the filter is below the "coat hanger"
(Fig. П10). Filter paper tends to straighten up and therefore easily held in place. The cork is closed again.
Ten minutes is usually enough to give a sufficient amount of leachate accumulated by filtering into the "cup."
25.10
Introduction pipette. Twenty milliliters are pipetted from a filter cup into a weighted 100-ml wide-necked flask. Rinse the pipette with a small amount of filtrate.
With the current control, when a large number of samples are examined, rinsing after the first time can be avoided. 20-ml pipettes must be calibrated using automatic 100-ml pipettes to get them to give exactly one-fifth of the volume.
Note: Always use the "safe" pipettes to avoid inhalation of trichlorethylene vapor.
Distillation. Excess solvent in the flask is removed by distillation in a special apparatus containing 8 flasks (Fig. П11). This unit consists of a water-cooled condenser, a tile and connecting tubes. Care should be taken to ensure that distillation does not go too far, otherwise there is a risk of fat decomposition. After distillation of a large part of the solvent, the flask is removed, hot air is fed inside to remove as much of the remaining traces as possible. The flask is then placed in an oven at 90 ° C in 2 hours. After cooling to room temperature, the flask is weighed again to obtain the weight of the extracted fat.
If it is necessary to perform an analysis urgently, the solvent can only be removed by blowing hot air, which takes 20-30 minutes, and then cooled and weighed. It is advisable then to continue purging for a short time to make sure that the weight is constant.
Fat (%) = Weight of the extracted fat x coeff. x 100 / sample weight.
Coefficient. The coefficient takes into account the increase in volume due to the fat extracted from the sample, and is calculated by the equation
Fat (%) = x (4,988 + 0,28h) 100 / W, where x = the weight (mass) in fat 20 ml; W = weight (mass) of the sample.
25.11
For the current analysis, tables are usually prepared based on this equation in accordance with the sample weight (mass) (5 or 10 g). These tables can be “coefficients” or long lists of fat content corresponding to the weight (mass) of the fat obtained from the 20 ml of solution.
Temperature correction, taking into account the expansion of the solvent. If there is a noticeable change in the room temperature between the measurement of the solvent and the introduction of an 20 ml pipette, it is necessary to introduce a temperature correction to compensate for the increase or decrease in solvent volume.
Adjusted coefficient. If an aliquot is measured at a temperature of T ° C and the temperature of the initially added solvent was T1 ° С, then the true coefficient = coefficient + 0,0055 (ТТ1).
Removing solvent residues. After the determination of fat, the residues are filtered and distilled into an anhydrous potassium carbonate bottle.
The dried distilled solvent is filtered and stored in a bottle of yellow (dark) glasses. The residue is defined in 50 ml should not exceed 0,0010 of
Conservation of trichlorethylene. Trichlorethylene is subject to some destruction by repeated use and distillation. Adding 2% technical alcohol (ethanol) to each new portion of the solvent prevents this destruction and does not affect the definition.
Refractometric methods
These methods are based on determining the refractive cocoa butter solution coefficient in nonvolatile chloronaphthalene solvent.
The procedure is to weigh 2,5 g of cocoa powder (or cocoa liquor) into a small glass and add 5,0 g of solvent, chloronaphthalene. The mixture is heated to 70 ° C with stirring, and then filtered. The refractive index of the filtrate is measured using a precision refractometer with accurate temperature control and compared with the refractive index of pure solvent [11].
Determination of fat by means of nuclear magnetic resonance
The method of nuclear magnetic resonance with low resolution (NMR) has been very successfully developed in recent years. Using this method, you can measure the ratio of solids to fluids in fats and determine the fat content of chocolate products, nuts, seeds, etc. The method can also be used to determine moisture.
The method is now widely used for quality control. Monitoring (control) of the fat content in chocolate during production is used in many large factories. Working with the device is simple, and therefore it can be performed by non-trained personnel. The method requires very little sample preparation.
The initial cost of the device is high compared with the analytical methods described above. However, where frequent measurements are required, the savings from staff and time are significant when using NMR.
Further information can be obtained from the company Newport Instruments Ltd., Milton Keynes, England.
Determination of the cooling curve of the cocoa butter or similar fats
The meaning of the term “cooling curve” is explained in the chapter on cocoa butter and other fats. The method described below requires precise control of all operations.
In most large companies that produce fat, this method is fully mechanized, and a number of devices operating in parallel are used. They are used in product control and quality control.
In a modification Shukoff-De Zaan used tube with a vacuum jacketed thermometer registering and printing. Driving Shukoff tube is shown in Fig. P12.
25.13

25.12Fig. P13. Apparatus for determining the cooling curve
Equipment for the analysis (Fig. P13)
  1. Test tube for test: 15 tube x cm 2,5 cm, thin-walled, with a rim of pyrex, corresponding to the British standard WB 3218: 1960, and closed with a stopper, through which the thermometer and agitator. The hole with the thermometer must have a gap.
  2. Thermometer: from up to 0,5 50 ° C, with divisions 0,1 ° C Immersion 6 cm total length cm 35.
  3. Stirrer: Pyrex core 4 mm in diameter with a loop at the lower end having such a diameter as to be approximately halfway between the thermometer bulb and the wall of the tube when the stirrer is installed. The total height of the mixer 190 mm ± 10 mm. A suitable glass liner for the agitator must be inserted into the plug of the sample tube.
  4. Air jacket: a high beaker 1 l, approximately 190 mm high and 88 mm in diameter, weighted with lead shot and equipped with a lid of five layers of cardboard (felt) ~ 6 mm. Three layers of such diameter that they fit tightly into the glass, and two - so that they lay on top of the glass. These five layers must be glued together and drilled to firmly hold the tube in the center of the air jacket. Placing the dried silica gel in an air jacket prevents mist formation during measurements. The prepared air jacket is immersed in a water bath so that 2 cm remains on top, the temperature is maintained at 17 ± 0,2 ° С and the system is allowed to reach equilibrium;
  5. holding her 30 min, before taking measurements. The water bath is made of glass or a glass window is made in it so that you can observe the contents of the test tube.
analysis
Preparation of fat for seeding. Melt the representative part of the sample in a drying oven at 55-60 ° C and filter at this temperature through dry filter paper. Cool the filtered fat, stirring occasionally until the temperature drops to 32-34 ° C, and then continuously mix it manually or mechanically until the fat has the consistency of the paste. Immediately transfer it to the vessel, previously brought to the temperature of 15-22 ° and allow it to stand at this temperature for at least 24 hours before being used as a seed in the determination.
Determination of the cooling curve. Transfer the 15 ± 0,1 g of the representative sample of pre-filtered fat to the tube, close it with a stopper and completely melt the contents in a separate water bath at 50 ° С. Replace the stopper with another (with a stirrer and a thermometer) and keep in a water bath at 50 ° С no less than 15 minutes, stirring from time to time. Remove the tube with stirrer and thermometer from the water bath, wipe the tube dry and hold it in the air. Stir the sample gently until reaching 40 ° C, transfer the tube to the air jacket. Clamp the thermometer so that its ball is in the center of the fat, and adjust the stopper so that it can slide up the thermometer and raised enough to introduce a seed at a later stage without disturbing the position of the thermometer. If appropriate equipment is available, the agitator can be connected at this stage with any suitable mechanical device, the speed of which is set in accordance with the required mixing speed.
Stir the fat periodically until reaching 35 ° C. From this point on, measure and record the temperature at intervals of 1 minutes and mix the fat with two gentle movements of the stirrer every 15 with so as not to destroy the surface of the fat with the stirrer loop. At 28 ° C (see note below), quickly add 0,03-0,04 to finely grated flakes, which are obtained by easily scraping off a well-crystallized sample of fat prepared as described in the 1 procedure. Continue to record the temperature and stir at the same rate as before, but additionally fix the temperature at which the first clear signs of crystallization appear. Finally, stop stirring immediately after the temperature increase within a minute has passed its maximum, but continue to record the temperature until five identical consecutive results are obtained. Apply a time / temperature curve to the graph paper, setting aside time along the horizontal axis, and temperature along the vertical. At least two measurements must be made on each sample.
Note. If the fat under study has solidification properties that are very different from those of cocoa butter, some modification of the method may be desirable. So, if crystallization occurs at temperatures above 28 ° C, the seed should be added to 2-3 ° C above the crystallization temperature; in addition, the temperature at which periodic stirring and reading begin periodically may require changes.
The melting point of fats
Methods for determining the melting point are numerous and varied. The results obtained depend on the exact adherence to the instructions of the methodology used. In various countries, there are recognized standard techniques - for example, the Wylie melting point in the United States. When comparison is required, it is always necessary to specify the method used.
The capillary method described below is widespread. Sample preparation is very important for obtaining fat in a stable state before determining the melting point.
Determination of melting point, strength and transparency (haze)
Sample preparation. Transfer 30-50 g of a representative sample of fat to a small, clean, dry beaker. Melt the fat by heating it in an oven to 55-60 ° C. Filter the fat through dry cotton paper No. 41, maintaining the temperature when filtering 55-60 ° C. Cool the fat, stirring occasionally, until the temperature is equal to 32-34 ° C, and then continuously stir until the first signs of turbidity appear. When a pasty consistency is reached, quickly transfer the fat into a form that has previously been adjusted to 15-22 ° C. Prior to measurement, soak the fat at 15-22 ° C for at least one day.
Analysis.
Machinery and Accessories. Glass 400 ml. Thermometer divisions to 0,1 ° C (calibrated on a standard thermometer). The capillary tube length 5-6 cm internal diameter 1,1-1,3 mm and external - 1,4-1,7 mm, chromic acid rinsed with distilled water and then dried. Mechanical stirrer. Vata. Rubber rings.
Conduct analysis. Roll some cotton between your thumb and forefinger and insert it into the capillary. Push it inside with a piece of wire until it is at a distance 2 cm from the end. Squeeze it slightly in this position while simultaneously pressing a piece of wire on the other side. The cotton plug serves to keep the fat (after it has “swelled”) below the level of the water bath so that the point of transparency can be determined on the same sample.
Press the capillary (end with cotton) into the fat to get a cap of 1 fat in length in the capillary. Attach the capillary to the thermometer with two small rubber rings so that the fat tube is aligned with the bulb of the thermometer.
In a beaker, pour pre-boiled and cooled distilled water to a depth of at least 6 cm and hold the thermometer in the center of the glass so that the lower end of the capillary was on 4 cm below the surface
water. Install a mechanical stirrer and heat the water so as to obtain a heating rate of about 0,5 ° C per minute when approaching the yield point, ie approximately 5 ° to the yield point. Determine and record:
  1. The point in which the observed softening = melting point.
  2. The point at which fat begins to rise through the capillary = point of fluidity.
  3. The point at which the fat is made transparent = the point of transparency (cloud).
Softening point fats
Barnikota Method (Varnicoat) *
Principle. A technique based on the ring and ball method used to control bitumen is to determine the temperature at which the 3-mm steel ball penetrates half the fat column, the temperature of which is raised at a rate of 0,5 ° C per minute.
Tools and equipment. Glass - 2 l, low and wide. A metal plate with a circular cut corresponding to the top of the glass, a hole in the center for the thermometer, and a row of symmetrically drilled holes in which tubes of fat hang on their edges. A special hole is drilled for the shaft of the mechanical agitator. Test tubes with edges (nozzles) - thin-walled, 5 cm long, with an external diameter 1 cm, 3 mm (0,1 inch) steel balls (bearing). Standard thermometer titration. Mercury. Mechanical agitator.
[1] Apalyst, 69, 176. - Note. author
Assembly apparatus. Place the beaker on a wire mesh on a tripod, fill it with distilled water at a temperature of 20 ° C and place the thermometer, plate and stirrer in place (see fig. П14).
25.14Fig. P14. apparatus Barnikota
Conduct analysis. Place 0,5 ml of mercury in a 5 cm tube length and 1 cm diameter, cool the tube with content for 5 min in crushed ice and water, pour the 1 ml of melted fat into the mercury, leave the tube in 15 min ice with water.
At the same time it is possible to carry out several determinations, i.e. as many as the test tubes can be placed in the lid of the apparatus. Place a 3 mm ball from the bearing into each tube in the groove on the surface of the grease that forms when the grease cools. Place the tubes in the plate orifices and adjust the height of the thermometer bulb so that it is flush with the fat columns in each tube. Start the determination with the bath temperature 20 ° С. Maintain this temperature 15 min. (The time is reduced to 15 min compared to the original 30 min.) Then raise the bath temperature at a rate of 0,5 ° C per minute, stirring vigorously. Record the temperature at which the steel ball fell half the height of the grease column. This is the softening point.
The hardness of fats
Measurement method with penetrometer. A penetrometer is used (Fig. PNNUMX), used to determine the measurements of bitumen and solid hydrocarbons. It can be applied to fats, chocolate and glazes. The degree of penetration of the needle or cone is measured at different temperatures, and the results are considered in combination with the melting point, expansion point and NMR measurements.
25.15
[1] In the original method Barnnicot tube was kept in water with ice 30 min, and then placed in the refrigerator overnight. This procedure made the test too long for routine monitoring, and it was found that it can be modified as described here. - Note. auth.
Testing of the foam - a modified method Bikerman
The foaming test is useful for checking the foaming properties of syrups made from sugar, glucose syrup and invert sugar when used for hard caramel, and is especially useful if a foaming agent such as sodium bicarbonate is added to the syrup for candy caramel.
Excessive foaming indicates the presence of foaming agents such as protein, mucus and saponins. They may be present in poorly purified beet sugar and some low-grade glucose syrups. High sugar content promotes foaming. The strong foaming properties of the ingredients lead to the formation of dense aeration with small bubbles and low bulk density of the aerated product.
Low levels of foam may be due to the presence of traces of fat or fatty acids, usually any contamination of equipment or containers. Cane sugar, if it is poorly cleaned, may contain traces of cane wax {wax wax).
These "antifoams" are very harmful for the production of aerated confectionery, they cause either complete destruction of aeration, or give a "rough" aeration with large bubbles (see "Beater confectionery").
Equipment and accessories. The apparatus for the formation of foam (Fig. PNNUMX) includes 16-ml glasses, watch glasses, mixing rods and a refractometer.
25.16 Fig. P16. The device for the foam test
Disconnect tube A, empty it, and rinse with hot water before performing the next test. According to Ind. Eng. Chem. (32), p. Xnumx
Washing machine. Glasses, hour glass, glass rods and tubes for foaming sintered glass is washed by immersing in chromic acid solid is not less than 20 minutes and then rinsed with distilled water and allowed to drain on clean absorbent paper.
Conduct analysis. Weigh the 20-5 g of glucose or sugar (or 35 g of sugar / glucose syrup) into a beaker and add 85 ml of distilled water. Add a few clean glass beads, warm slightly and stir until the sample is dissolved. Then close the glass with a watch glass and boil the solution at exactly 3 minutes. Quickly cool the solution to 20 ° C and bring the concentration to 20 ± 0,5% using freshly boiled and cooled distilled water.
Rinse the tube (A) a small amount of the solution, and re-insert the tube into its support clips.
Set the gauge level to zero by adjusting the moving scale (B), and then slowly open the valve (C) controlling the vacuum until you reach the height of the vacuum 8 cm on the gauge.
Remove the foaming tube and pour the sample up to the (E) mark, keeping the lower tube exit closed with a finger.
Replace the tube tightly on the rubber ring and adjust the pressure to the correct height using a pressure gauge (12,5 cm for glucose and 30 cm for sugars), then start the countdown. The injection of the sample into the foaming tube and the pressure regulation must be completed within 1 min.
Maintain the 12,5 cm pressure (or 30 cm for sugar) for the duration of the test, and record the maximum foam head every minute.
The foam level is the foam height in centimeters after 10 minutes (recording readings at one minute intervals is used only to show the stability of readings).
After testing, turn off the valve to adjust the vacuum, and when the bubbles in the tube for foam formation calm down, remove the rubber ring.
Water activity, the equilibrium relative humidity
Equilibrium relative humidity (DOM) has been mentioned in several places in this book. DOM or specific vapor pressure is moisture at which the food product does not gain and does not lose moisture, and is expressed as a percentage.
"Water activity" (αω) Is now being used more frequently, but the meaning is not changed. It is measured as the proportion of the unit rather than as a percentage; eg, αω, = 0,65 - is the same as DOM 65%.
αω food products, including pastry, significantly affects the shelf life and hygroscopicity. Take, for example, two products at opposite ends of the range. αω- Hard Candy at αω = 0,25-0,30 and fondant cream with αω = 0,65-0,75. In a temperate climate, hard candy will almost always absorb moisture, and the fondant will most likely dry out. Pastry with αω= 0,75 and above become vulnerable to the action of microorganisms and molds. In fig. P17 is a graph of the approximate relationship between αω and microbial activity, but differences in pastry recipes lead to some deviations.
The moisture content of the syrup and the concentration of phase (referred to in the book) has no connection with the certain αω For example, in cereal flakes with a moisture content of 12-14% αω is about 0,65, while in oilseeds with the same αω Moisture content is about 8%. Some syrups and jams with 25-30% moisture content also have αω equal to 0,65.
25.17

As in the case of the saturated salt solutions mentioned below, the vapor pressure (and hence aw) of the sugar solution depends both on the specific substances in the solution and on the concentration.
Definition αω
In a simple practical method of determining αω (fig. П18) saturated solutions of various salts are used, which have different pressures of saturated steam (Table PZ).
A modern apparatus consists of thermohygrometers and cells containing the product under test.
An example of such a device is described below Protimeter.
Calculation αw /ALL
For relatively simple formulations in which the syrup phase contains only sugar, glucose syrup and invert sugar, DOM can be calculated using the Money and Born equation. These researchers showed that if the concentrations of solutes are related to the 100 parts of water by weight, the equation takes the form
% DOM = 100 / (1 + 0,27N),
where N - is the total number of moles of solute (mol - a unit weight of the substance is equal to its molecular weight in grams).
A nomogram [14] was subsequently created, and a series of articles [3] gave further explanations of the principles underlying the calculations. For complex formulations, it is usually better to evaluate DOV by one of the methods described.
Definition αω c using salt solutions
This is a simple way to determine the cheapest aw confectionery.
Equipment. An apparatus is used (Fig. П18), consisting of a glass jar with a lid containing a saturated solution of the selected salt. A small hole is drilled in the lid, and thin wire is passed through it, ending in a small stainless steel base. The upper end of the wire is provided with a loop and a small metal disk, so that the platform can be suspended close to the surface of the salt solution when the hole in the lid is closed by the disk. The loop at the top end of the wire is attached to the hook.

present salt0 ° c5 ° C10° C15° C20° C25° C30° C35° C40° C45° C50° C
* Lithium chlorideLiSlN2014,714,013,312,812,412,011,811,711,611,511,4
potassium acetateSN3С00К * 1.5Н2023,022,922,7
* Hexahydrate magnesium chlorideMgCI2-6H2035,034,634,233,933,633,232,832,532,131,831,4
* Chromic acid (chromium trioxide)Sg0z (N2sg207)38,739,5
PotashК2С03-2Н2044,344,043,7
potassium nitriteKNO250,049,148,2
* Magnesium nitrateMg(N03)2-6H2060,659,257,856,354,953,452,050,649,247,746,3
* Sodium dichromate dihydrateNa2Cr207-2H2060,659,357,956,655,253,852,551,249,848,547,1
Sodium bromide dihydrateNaBr2H2060,559,357,8
sodium nitriteNaN0266,265,264,2
ammonium AzotnokïslıyNH4DO NOT377,174,071,068,064,961,858,855,953,250,547,8
* Sodium chlorideNaCl74,975,175,275,375,575,875,675,575,475,174,7
* Ammonium sulphate(NH4)2S0483,782,681,781,180,680,380,079,879,679,379,1
* Potassium chromateK2Cr0486,886,686,5
* Potassium NitrateKN0397,696,695,594,493,292,090,789,387,986,585,0
Monoammonium phosphate, PKFANH4H2PO493,793,292,6
* Potassium SulphateK2S0499,198,497,997,597,296,996,696,496,296,095,8
* Данные взяты из работы Wexler, А., & Saburo, Н. (1954). Relative humidity temperature relationships of some saturated salt solutions. J. Res., National Bureau of Standards. Непосредствен но перед тестированием готовят пробу, чтобы равновесие установилось как можно быстрее, например, фадж должен быть наструган, а твердая карамель быстро размолота до крупного порошка.
pan, the bottom of the sample thus hangs freely in the pot, and the wire on which it is suspended, without regard to the holes in the cover edge.
Conduct analysis. For the test requires a number of bottles; saturated salt solutions are prepared in accordance with the table. PZ depending on the tested samples. Prepare the bottles required for the test, which should be completely clean.
Each sample should be tested at four different values ​​of atm, two higher and two below the expected level, and the difference between two consecutive values ​​should not exceed 5%.
Each bottle enter 50 mL brine with a known value and adjust ahyu wire, holding the foundation so that it was approximately 19 mm above the liquid level when a small disc is on the cover. Based on the watch glass is a small sample.
Allow the machine to reach a stable state at 18 ° C (or another test temperature) for at least one day.
Weigh the empty watch glass, wire holder and base in each can. This can be done by placing the jar on the “bridge” above the cup of the single-plate scale and attaching the upper end of the wire holder to the hook on the balance beam.
Place about 1 g of the prepared sample on the watch glass and immediately weigh it again.
Let the machine stand for two days at 18 ° C (or other temperature), and then weigh the sample, watch glass, wire holder and base in each can again, and then record the change in weight (mass).
Weigh again again after a day of stabilization until significant changes in weight cease to occur.
Calculate the change in weight as a percentage for each value of at and build a graph of the percentage change in weight (mass) depending on at. According to the schedule, count am, corresponding to zero weight / mass change. This value corresponds to the sample.
If many measurements have to be done, you can use small cabinets with salt solutions and small dishes with the tested confectionery. They must be equipped with a lid for weighing. When using cabinets, it is recommended to have a small internal fan for air circulation above the solution.
Definition αω using protimetra (Rgotimeter)
This device is an electronic hygrometer (Prtimeter Ltd, Marlow, England) with a digital display. The device allows to determine the water activity, in percent relative humidity, dew point, and moisture content.
To determine the A / W (DOM), a special-design sensor is placed in the cell, as shown in Fig. P19 and P20.
25.19 Fig. P.19. Standard probe
25.20 Fig. P.20. Sensor device in DOM to determine cell aw
The use of DOM-cell. You can use the device to measure the DOM through sample space in the DOM-cell or other suitable container.
With liquid, viscous or lumpy materials
or
With clean granular materials to achieveof the early results.
Protimeter Ltd., Meter House, Марлоу, Бакс, Англия
Machinery used in the production of
When it is necessary to quickly receive results in order to control technological processes, devices are installed in production departments.
At first, instruments were developed that gave readings, which were then used to manually adjust the equipment. Then devices were developed that gave signals to controllers that made the necessary changes. Now many enterprises are fully computerized, monitoring and management of all operations and parameters, such as temperature, vapor pressure, temporal parameters, recipes, chocolate tempering and viscosity, are provided.
Viscosimeters
The rheological properties of chocolate have been extensively studied in recent years. The need for economic reasons to work with chocolate, which has a low cocoa butter content, has led to studies of plastic viscosity and yield strengths.
Simple viscometers suitable for liquid chocolate forms do not provide the information needed when working with more viscous products.
Viscometers are described in detail in Chapter 4; below is a brief summary.
Instruments of the Redwood viscometer type. These are flow-through instruments with aperture sizes similar to Redwood's Viscometer No. XXUMX. The method is empirical and standards are prepared in accordance with the chocolate recipes used at a particular factory. These devices are used only for liquid chocolate. The Horn <2 Cyr Viscometer (Ford's Funnel) used in the paint industry is also used for chocolate.
Viscometer to determine the viscosity of the solution according to the falling ball method. This device is useful for determining the consistency of thick chocolate used for casting into molds, feeding through pipes and making pills. The instrument is less accurate than the Redwood's viscometer, but more accurate results can be obtained using a falling cone with ring marks as well as using a ball (see also “Mobile meter”).
Rotational Viscometer. In the United States for many years it was decided to use the rotational viscometer Mac-Michael. It was accepted by the National American Confectioners Association as a simple, relatively cheap device, but in recent years it has been seriously criticized for not providing all the necessary rheological data.
Brookfield viscometer and Haake (Naake) are increasingly being used in many countries.
Refraktometrы
Refractometers are now indispensable for control at a confectionery factory. They replaced thermometers to determine the end point of cooking syrups, jellies and jams, and in combination with a syrup press (see “Confectionery Technologies”) to determine the concentration of the syrup phase in lipsticks, pastes and marzipan. Below is a brief description of the various types of devices.
"Pocket" refractometer. This is a relatively cheap sliding portable device with turning prisms at one end (weight - 241 g, length - 17 cm).
The device is available for several ranges and can be applied to a wide range of products and syrups. For example, it is used to check the sugar content and, consequently, the ripeness of apples, beets and potatoes. It is especially useful for determining changes in sugar penetration during fruit canning.
Abbe's refractometer Usually regarded as laboratory instruments, they are now produced very durable and can be used in production with certain accuracy. The refractive index range is 1,300-1,740 or on the 0-95% sugar scale. A flow model is also available. In this model, a compartment with a water jacket, replacing the traditional folding prism, is equipped with a funnel and an exhaust drain pipe. The funnel and the drain pipe can be replaced by fittings to turn on the flow cell in a laboratory experimental setup for measuring the refractive index of moving liquids. Water that maintains the temperature comes from a fixed box with prisms, and there is no need for connecting pipes.
Submersible refractometer. This device can be used for laboratory or industrial work in the confectionery and food industry.
Since the accuracy of measurements is high, it is necessary to limit the range of the instrument to a relatively small range of the refractive index, but by replacing one prism with another for another range, the instrument can be changed without loss of accuracy. Several prism ranges are available. In absolute measurements, the result depends on the accuracy for which the instrument was calibrated, and for this reason refractometers are mainly used for measurements by a differential method, including a comparison of the refractive indices of known and unknown solutions, in which the differences of the coefficient are small.
The housing of the device consists of a rigid tube covered with leather so that it can be held securely. In the upper part there is an eyepiece through which a uniformly divided scale is visible. The screw allows you to move the scale one division. The screw has ten divisions, which allows you to divide the scale into ten more parts. The scale of the critical angle appears on the scale due to the difference in the refractive index between the prism and the sample, which looks like the border dividing the circular field of view into a light and dark part (light and shade). The point at which the boundary of the light and shade crosses the scale gives an indication that allows to find the refractive index of the sample using the calibration table supplied with the prism.
The lower shell has a scattering range of which is rotated to remove the border color of light and shade, and below is a prism, which is to be immersed in the test solution. Lighting, which for this device must be external, may be provided by natural light from a window or a light bulb.
To protect the prism and as a sample container, the instrument is equipped with a metal cup, which is partially filled with the sample so that it is convenient to use the refractometer, holding it in your hand and directing it to the light source.
There are two modifications of the immersion refractometer. One has a box of prisms with a jacket, mounted at the bottom of the device, and a few drops of the sample are sufficient. In another modification, there is an attached cell through which the test fluid flows, and this fluid can therefore be continuously monitored.
Projection refractometer. This refractometer is widely used in the confectionery industry and works on the principle of internal reflection. This device is large and durable (length about 75 cm, width 15 cm, height 22,5 cm), it usually does not need cooling, as the weight of the device is enough to cool a small sample to ambient temperature. For special applications a cooling device can be supplied.
Measurement. The boundary of the critical angle, observed as the boundary of light and shade, crossing the scale, gives the result directly in percent sugar content. The illumination is provided by one of the two light bulbs with a voltage of 6 B. Light bulbs are mounted on a rod, which is mounted on a ledge located on the side of the device. Each bulb can be set to the lighting position and adjusted to provide (1) ambient light or (2) illumination with orange light through a filter; The second option serves to reduce the coloring of the border of light and shade.
Power to the lamp can be supplied from an external transformer or battery. The device thus uses only a safe low voltage and in wet conditions. Scale is inside the device and is visible through a window on its upper surface.
The concentration of sugar in lipstick, marzipan or lozenges (gums) can be determined regardless of color, optical density, the presence of grains (pips) or other solid particles. The sample is simply distributed on a horizontal glass surface, the lighting is regulated and the percentage of sugar is read directly on the scale, there is no need for magnification or an eyepiece. After measurement, the material is removed with a sponge from the surface, the surface is wiped with a soft cloth to dryness, and the next sample can be applied to it.
Technological refractometers. There are two types of such refractometers - for boilers and pipelines.
Refractometers for boilers. These refractometers are designed for direct attachment to the digester in which boiling or evaporation is performed. The refractive index, expressed as a percentage of solids, usually sugar, is continuously displayed on the display, which is located on the front surface of the instrument and which can be immediately seen. A cleaning mechanism (“janitor”) is provided, which periodically removes material that is in contact with the surface of the measuring prism, bringing a new layer into contact with it. The cleaning device is drilled to supply water so that, in addition to cleaning, you can flush the surface of the prism during boiler operation. The device uses the principle of internal reflection, so it can measure optically dense materials. The device has a built-in light source with external power supply 6 B, 0,5 A from the battery or from the mains through a transformer. The refractometer is therefore an electrical safety instrument, even in wet conditions.
Refractometers for pipelines. These refractometers are designed for direct installation in stainless steel pipelines and give readings continuously.
There is a device, which uses the same principle as in immersion refractometer, and its reading depends on the light transmitted through the material in the tube. In another device the reflection method, and it can be used in opaque liquids.
Automatic electronic refractometers. These instruments are designed to continuously record the refractive index and are used for special production processes. Compared with the described devices they are expensive.
Relative density and density
Determining the density or relative density (specific gravity) of syrups has been the traditional test method for a pastry chef in the past and the scale hygrometer is too well known to describe it. Continuous methods for controlling and regulating density, which are based on changing the weight of a column of fluid in a flexible U-shaped tube, have been developed.
To control the density of whipped confectionery products, a simple cylindrical vessel with a bottom of a wire mesh with large cells turned out to be applicable. The vessel is filled with a whipped mass until it begins to exit the wire mesh, then the excess mass is removed with a knife from both ends, and the vessel is weighed. Since the mass of the vessel is known in advance, you can quickly determine the density of its contents. Such a vessel avoids the formation of voids that may occur in a cylinder with a solid bottom.
There are many physical methods for determining the density, which are described in the scientific literature.
temperature measurement
Thermometers. Temperature measurement is still a way to control the concentration of sugar syrups for caramel and other syrups that do not contain interfering ingredients such as gelatin, pectin, or solids.
Accurate temperature measurement and its regulation are very important in tempering and cooling chocolate. The following types of thermometers are used.
Glass mercury thermometers. These thermometers are reliable and usually maintain their accuracy well. For production needs, they are usually supplied with protective covers so that their tank (ball) does not break. As protection, an open safety net made of thick wire at the end with a ball should be used, since a thick metal casing greatly reduces sensitivity and leads to erroneous results.
Some cookers have built-in thermometers that can be inserted into heavy metal stirrers. Such protection can lead to very slow acquisition of testimony and significant inaccuracy in determining the end point.
In the UK, “standard” glass mercury thermometers are available, supplied with a certificate from the National Physical Laboratory. It is useful to have such thermometers available in the laboratory to test other thermometers used in the experimental setup and in production. They should not be used for other purposes.
Metallic mercury pointer thermometers. These thermometers use mercury expansion in a tank immersed in a liquid whose temperature is to be measured. Expansion is transmitted through a steel tube to the dial indicator. With careful handling, these thermometers are reliable, but their adjustment may be disturbed, and therefore they must be constantly checked.
Thermometers, working on the expansion of air. In these thermometers, the scale moves due to the expansion of air in the tank. They can be very unreliable and should not be used where constant accuracy is required.
Thermocouples and thermometers of resistance. The use of these devices has grown significantly, their special value lies in their high sensitivity, due to the small size of the sensor compared to the balls of the other thermometers described above. They are also very convenient for working with recorders.
There are many portable thermometers with thermocouples that are very sensitive and reliable when handled with care. Unfortunately, they are often mistreated, and they are no longer accurate. Such thermometers should be regularly checked with a glass mercury thermometer.
Telemetry methods. To measure the temperature in tunnels, cooling devices, etc., radiotelemetric devices are being produced. These devices emit signals that are transmitted to the receiver, and they do not require wires or pipe connections. Very useful for controlling temperature on moving conveyors in confined spaces.
Several companies specialize in the production of such thermometers, and they can provide all the information necessary for any particular process.
Thermometers for infrared part of the spectrum. These devices accurately measure the temperature without contact. They are especially useful for measuring the temperature of very viscous substances, which often clog thermometers. A telescopic system with a narrow directional lighting lamp ensures temperature measurement is always at one point.
Thermometer control. Despite assurances from manufacturers of thermometers, errors in thermometers are not uncommon. All thermometers entering the factory must be checked. For this, an oil bath with a stirrer and temperature control (thermostat) can be used. The bath should be large enough to check several thermometers at once. The thermostat is periodically set to different temperatures so that the thermometers can be checked at certain temperatures in the range.
Inspection of thermometers “in installation” is also very important, so the heads of production departments should conduct regular inspections. If errors are detected, thermometers should be replaced immediately. It is very bad when the installation operator must amend the measured temperature or attach a tag to the thermometer indicating the correction to be made.
To test should be used "certified" thermometers mentioned above.
Эlektronnыe vlagomerы
Electronic instrumentation is used in many industries to determine the moisture content of powders or granular products, such as flour and grain.
In the confectionery industry one of the most important applications - is to check the moisture content of the starch in the casting apparatus for casting and after dryers.
The principle of operation of most devices is based on electrical capacitance, and the material to be tested is in a cell of standard dimensions. To obtain reliable, stable results, it is important that the packing density is constant, and most measuring instruments are equipped with means to achieve a constant packing density.
However, periodic gravimetric (weighting) tests are necessary, and, if this is done, correct results can be obtained quickly for one type of material. To measure each type of product or raw material, instruments should be calibrated.
Other electronic methods are used to determine moisture during production.
moisture meters
It is often necessary to obtain data on the relative humidity in factory premises, such as warehouses, premises where starch is treated or crystallized. The simplest reliable device is a rotary hygrometer used in conjunction with the correct psychrometric tables.
Mason's psychrometer (in the form of a dry and wet thermometer) is notorious for its unreliability, unless means are provided to ensure proper air movement around the thermometer beads. These psychrometers, hung on a wall in still air, are completely useless.
Where continuous recordings are necessary, the best results are achieved by recording a hair hygrometer, but it requires regular checking and adjustment. A recording psychrometer with dry and wet thermometers, like Mason's psychrometer, is reliable only with good air movement. "Wet ball" consists of a bimetallic spiral coated with a damp cloth. The hair hygrometer is much more sensitive.
The device, which is considered a standard reference hygrometer - this diet graduate psychrometer (Assmann psychrometer). It consists of a sensing wet and dry thermometer in the cylinder are provided with a small fan which supplies ambient air to the beads at the standard speed.
Another type of device is a paper or bayonet hygrometer. It can be inserted between the layers of paper or containerboard, and then the equilibrium moisture content and, consequently, the moisture content of the paperboard can be determined from the recorded relative humidity.
Literature
  1. Apparatus for determinations of Isotherms for water vapour sorption in foods. Department of Food Science, Agriculture University, Wageningen, Holland.
  2. British Standard BS 3406: Part 5. 1983. British Standard Methods for Particle Size Distribution. Part 5. Recommendations for Electrical Sensing Zone Method (the Coulter Principle), 33 p.
  3. Cakebread, S. H. 1970. Mafg. Confect. 50(11), 36; 50(12) 42; 51(1) 25.
  4. Chemical analysis and its application to candy technology. Conf. Prod. 161. London.
  5. Coulter, W. H. 1956. Proc. Nat. Elect. Conf. 12,1034 (Coulter Counter® is a registered trademark of Coulter Electronics Inc.)
  6. Coulter Counter® Industrial Bibliography 1986, (1521 references) Coulter Electronics Ltd., Luton, England.
  7. Instruments for the Food Industry, British Food Research Association, LeathPOBead, Surrey, England. (Series of leaflets on special equipment.)
  8. Jacobson, A. Chocolate - Use of NMR in the Chocolate Industry. Cloetta, Sweden.
  9. Lockwood, H. C. 1958. A new method for assessing chocolate grinding. Chem. &Ind., 1506-1507, Nov. 15.
  10. Meursing, E. H. Cocoa Butter, Quality and Analysis. Cacaofabriek de Zaan, Holland.
  11. Meursing, E. H. 1976. Cocoa Powders for Industrial Processing. Cacaofabriek de Zaan, Holland.
  12. Money, R. W., and Born, R. 1951.]. Sci. Fd. & Agric. 2,180.
  13. Niediek, E. A. 1978. New equipment for determination of particle size. Chocolate, Confectionery, Bakery.
  14. Norrish, R. S. 1964. Conf. Prod. 30, 769.
  15. Reade, M G. 1971. Fat content by refractometer. Rev. Int. Choc. 26,334-342.
  16. Refractometers, electronic moisture meters. (From a series of 17 papers on Candy Analysis, B. W. Minifie.) Confectionery Production (1970 et seq) London.
  17. Sutjiadi, I., and Niediek, E. A. 1974. Preparation methods for control of fineness (in German). Gordian, 284-291.
  18. Van den Berg, C.1983. Description of Water Purposes. International Congress, Dublin, Ireland.
  19. Department of Food Science, Agriculture University, Wageningen, Holland.
  20. Wiggins, P. H., Ince, A. D., and Walker, E., Rapid determination of Fat in Chocolate and Related Products Using Low Resolution N.M.R. Cadbury Schweppes, Boumville, Birmingham, England.
Manufacturers
  • Baird and Tatlock, Romford, England (miscellaneous equipment)
  • Bellingham and Stanley, Ltd., London (рефрактометры)
  • Raytek Inc., Mountain View, Calif, (thermometers for the infrared part of the spectrum)

[1] For the current control can be used 10 g of cocoa. Note: Fine cocoa powder during this test is less than 2% «tails." This method can be tested and cocoa mass, cocoa liquor and small will be less than 1% «tails." - Note. aut.

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