Features of solidification of cocoa butter and its influence on the molding process
Chocolate mass after treatment in a finishing machine puts an almost finished product; it should be a mold and let it solidify. However, the operation for casting chocolate requires special attention because of the presence of cocoa butter, which is even sensitive to the slightest changes in temperature.
According to the literature, the main cocoa butter following figures.
The melting temperature (initial) 31-34 °
The melting point (final) 33-36 °
Pour 23-28 °
Caption 45-51 °
Iodine number 34-36
Rodanovoe number 32-35
The number of Reichert-Meislle 0,1-0,4
Number Polensky 0,5-1,0
Saponification number 192-200
Acid number 1,0-1,5
Data on glyceride composition of cocoa-butter glycerides and the melting point are given in the tables.
These data show that cocoa butter is mainly composed of glycerides raznokislotnyh.
The predominant triglyceride in cocoa butter is β-olepalmitostearin with the so-called "plastil." 34,5 ° symmetric oleodipalmitin with c, melting, 29 °, oleodistearin with melting point. 43,5 ° have one unsaturated bond. In addition, cocoa butter contains a fully saturated triglyceride, dipalmitostearin, m.p. 68 ° (for a symmetrical shape). Finally, cocoa butter contains four more mixed acidic triglycerides, each of which has two or three unsaturated bonds; The total amount of the last group of glycerides is 17,5%; At room temperature these glycerides are in the liquid state.
Thus, the melting temperature of the whole complex triglycerides constituting cocoa butter, is very close to the melting temperature of β-oleopalmitostearina located therein, and the greatest quantity. Remaining triglycerides - liquid and triglycerides with the highest melting point - apparently slightly affect or cocoa butter melting point generally have vzaimnokompensiruyuschee or impact.
Hence, the small gap between the initial and final cocoa butter melting points (determined in a capillary tube), so that it has a surface nemazhuschey.
Low iodine number indicates a large resistance-cocoa butter against rancidity.
The molten cocoa butter is a true state, viscous liquid with a constant coefficient of internal friction. At temperatures below 20 ° crystallized cocoa butter (the crystal size does not exceed a few microns) and becomes hard and brittle; These properties are typical for chocolate due to its high content of oils-cocoa.
The inherent cocoa butter is hard and durable structure is determined (predominance of solid fractions (about 84%).
By separating the cocoa butter into four similar in physical properties of fractions were obtained the data by which you can judge the amount of solid (Ti and T2) and liquid (ZH1 and ZH2) at room temperature groups of triglycerides.
Fractional composition of cocoa butter is given in Table. 27,
|Name of oil fractions, cocoa||Output in%||The melting point in ° C||The pour point in ° C|
|T1||73,17-74,71||34,7 35,2||25,8 27,5|
|T2||8,06 9,43||30,1 31,0||20,8 20,9|
If carefully, without stirring cooled cocoa butter, which is free of crystallization centers, it can easily be brought to a temperature that is at 10 ° below freezing temperature, and being alone, long oil will retain its amorphous structure. Only after a long period of time it becomes cloudy due to the formation of crystals in it, which are often not distributed uniformly throughout the mass and concentrated in certain areas.
The ability of cocoa butter supercool, move to solid state without crystallizing, it is one of the main challenges that must be overcome in the molding of chocolate as features specific to cocoa butter, also apply to the solidification of chocolate, which includes about 30-35 % cocoa butter.
If the warm chocolate mass unloaded from the finishing machine at a temperature of about 50 ° is poured into chocolate molds and allowed to cool at the usual temperature of about 20-25 °, then in a fracture such a chocolate will have a coarse structure that reflects unpleasantly on taste: instead of a gentle and melting "Such chocolate acquires a crude taste resulting from the fact that the solid particles contained in the warm chocolate mass at rest are collected in large oil-cemented aggregates (visible to the naked eye) and in this form E freeze,
Flowering (posedenie) chocolate
Another disadvantage, making chocolate molded mentioned above (the method unusable, is that after some time the tile is covered with the original gray surface coating.
There are two types of bloom: fat bloom that occurs due to changes in the structure of the fat contained in chocolate and sugar bloom - due to the transition of crystals contained in chocolate icing sugar crystals in a larger size. Both of these drawbacks significantly reduce the quality of the chocolate.
Molded in shape and left for a slow and quiescent cooling, the chocolate mass is in conditions favorable for the transition of the cocoa butter contained in it to the supercooling state. After a more or less scorching period of time, the oil will nevertheless begin to crystallize, but large clusters of large crystals will be obtained. These crystals and will cause a gray plaque, or chocolate graying. A lot of work has been devoted to the study of the reasons for the graying of chocolate, but until recently there have been conflicting interpretations of this phenomenon in the literature. Many researchers have argued that graying is caused by the release of crystals of high melting cocoa butter triglycerides; Other authors did not share this opinion.
To find out the causes of the graying of chocolate contributed to the study of the polymorphism of butter-cocoa, carried out in recent years.
Four polymorphic forms of γ, α, β1 and β are established in cocoa butter, three of which are metastable, that is, they are unstable, and one is stable, stable and retains its state for a long time.
Daylight-one polymorphic forms of cocoa butter in the other, or so-called phase transformation to occur under the influence of certain temperature conditions, and there is a temperature to effect conversion of each form.
With a sharp cooling of the molten oil obtained amorphous solid fusible γ-phase, transparent in the solid state; γ-phase metastable rapidly into the metastable crystalline α-phase
having a higher temperature n l a g e m e n s.
Further conversion conditional on receipt of a metastable phase a hot-β1, also
Most high melting, crystalline β-phase - the only stable of all the above.
Temperatures polymorphic transformations cocoa butter following.
Name phase transformation temperature in ° C
Polymorphism of cocoa butter gives grounds to assume that the cocoa butter triglycerides form a solid
homogeneous solution and therefore cocoa butter, like an individual substance capable of phase transformations.
Studies have shown that chocolate mainly stored temperature phase transformations inherent maslu- cocoa.
Cocoa butter substitutes
The production of chocolate is greatly complicated by the fact that the oil in cocoa beans is not enough for making chocolate, glaze and other products. Of the 800 kg of cocoa beans required to produce 1 t chocolate, about 500 kg is required to produce cocoa butter. These circumstances confronted the confectionery industry with the question of replacing the natural cocoa butter with another fat with the properties of cocoa butter.
a process for preparing fat chocolate was developed by modifying
glyceride composition of beef fat as fat is closest in composition to natural cocoa butter.
Cocoa butter contains about 78% dvunasyschennyh triglycerides, and beef fat, about 62%; odnonasyschennyh triglycerides in cocoa butter contains 17,5%, and beef zhire- about 14%. According to the content of triglycerides trisaturated there is a significant difference: trisaturated triglycerides in cocoa butter-2,5%, beef fat to 44%.
A method of manufacturing a substitute for cocoa butter, developed VKNII, is hydrogenated tallow at which partial transition dvunasyschennyh and odnonasyschennyh trisaturated triglycerides.
Subsequent dissolution of fat in gasoline and fractionation of the hydrogenated product trinasyshcheniya part of it (the most highly melting) is removed; The low melting part, which is a heterogeneous acid fraction of hydrogenated beef fat, is a substitute for cocoa butter. The obtained substitute is very similar in its characteristics to cacao butter:
melting point 35,2 °
solidification temperature 28,7e
titer 42,7 °
iodine number 39,9
saponification 195 factor