IL100496A - Process for modifying the crystalline structure of cocoa butter and its use in chocolate making - Google Patents

Abstract

Melted cocoa butter is seeded with a very large number of beta -SOS seeds and the mass is maintained in a temperature range in which only the beta -triglycerides crystallise. The cocoa butter thus modified makes it possible, on addition to chocolate issuing from the conche, to eliminate the operation of tempering of this chocolate. The latter, when moulded, is exceptionally resistant to blooming and to heat. <IMAGE> [EP0496310A1]

Description

«ηο*¾>ίη ικρρ ηκηη w 'κ ιηη mann >Ί Β>Ϊ> η ·>¾ηη Process for modifying the crystalline structure of cocoa butter and its use in chocolate making BATTELLE MEMORIAL INSTITUTE C. 85243 PROCESS FOR MODIFYING THE CRYSTALLINE STRUCTURE OF COCOA BUTTER AND ITS USE IN CHOCOLATE MAKING The present invention relates to a process for modifying the crystalline structure of cocoa butter, and more particularly to a process for raising the amount of the β crystalline form of the triglyceride 1, 3-distearoyl-2-oleoylglycerol (SOS) .

It is known that cocoa-butter, one of the main ingredients used in the chocolate industry, comprises principally (by weight) the following triglycerides: about 24 - 28% SOS; about 30 - 40% (l-palmitoyl-3-stearoyl-2-oleoylglycerol) POS; about 15 - 20% (dipalmitoyl-2-oleoylglycerol) POP; and about 10 to 20% of the remaining triglycerides, for example POO, OOO, etc. (see C. Giddey et al., Rev. Int. Choc. 10(1961), 548-554).

This mixture of triglycerides can exist in different polymorphic crystalline forms, that is to say as a, y, β', β, etc. forms, for which the physical properties (particularly the solid-liquid transition point Tc and the stability) are quite distinct. Thus, the melting temperature of the different forms can lie in the range of 15°C to more than 40°C. Furthermore, the overall physical properties of the mass of cocoa butter can vary substantially as a function of the type of heat treatment to which the latter is subjected during manufacture of the chocolate and during its use in chocolate making.

Thus, if molten cocoa butter is simply cooled down, it can remain liquid down to a temperature of 18 to 20°C. For this reason, it is common practice in the manufacture of chocolate to carry out a "tempering" of the molten mass, that is to temporarily cool it to about 25 to 27 °C while stirring, and then reheat it to between 29 and 31°C, still under agitation, so as to cause the appearance of seeds of crystallization of relatively more stable polymorphic forms of the triglycerides, the presence of these seeds tending to favour the preferential crystallization of these more stable forms with a higher melting point during subsequent cooling.

The "tempering" step, as generally practiced, gives the cocoa butter a solid structure suitable for chocolate industry applications. In fact, after tempering, the chocolate has a sufficient resistance to heat for current needs, that is to say a softening temperature of about 28 to 30°C. However, this heat resistance is not sufficient in tropical countries and, furthermore the prolonged storage of chocolate at temperatures not exceeding 30°C, for example, can lead to partial internal melting of the contained fats, which tend to diffuse to the surface and on cooling forms an unpleasant whitish rash (blooming) . It is therefore desirable to improve further the crystalline state of the fats in the chocolate and their tolerance to heat without adversely effecting their composition and the taste characteristics of the chocolate.

It is notable that among the stable forms of triglycerides of cocoa butter, it is the β form of SOS which has the highest melting point (M.P. = 40-43 °C) and which is most efficient at stabilizing the crystalline state of cocoa butter during its solidification by cooling, and thus at raising its overall melting point.

Thus, GIDDEY et al. (idib.) have shown that cocoa butter can be advantageously modified by dispersing seeds of β-SOS in the molten mass. For this purpose, the mass is raised to a temperature of 34 °C, and 1.5 to 5 percent by weight of purified B-SOS is dispersed therein. It is then homogenized by means of a piston homogenizer. The presence of the homogenized B-SOS in the molten mass brings about, during moderate cooling (10 to 15 °C) , the preferential partial crystallization of stable isomers of triglycerides of cocoa butter and a substantial improvement in its resistance to heat. Other similar techniques have been tried, notably the seeding of molten cocoa butter (and of chocolate) with very fine particles of B-SOS (20 to 70/xm) obtained by cryopulverisation (at -50°C) of SOS (see the articles of T. Koyana et al in J.A.O.C.S. 66(1989), 664-679 and 1757-1770) . In addition, the document EP 294 974 (FUJI OIL) describes a tempering accelerator, particularly for chocolate, comprising principally 1, 3-saturated-2-unsaturated triglycerides comprising residues of fatty acids with 50 to 56 carbon atoms in total. In one embodiment mentioned in this document, such an accelerator is obtained by pulverizing the cocoa butter and maintaining the obtained powder at temperatures less than 0°C for a certain time.

As far as the preferential stabilization of SOS of cocoa butter in its B crystalline form is concerned, the present inventor has now discovered that the results of the prior art techniques can be substantially improved (see the claims) by taking account of the following observations: in effect, when a mass of cocoa butter is seeded in the liquid state by a large number (by unit weight or volume) of seeds of very fine B-SOS particles (in the order of 0.1 to 100 ιη) , and when during this treatment the molten mass is maintained in a range of temperatures less than the melting point of β-SOS but at which other triglycerides remain in the molten state, a significant proportion of SOS triglyceride contained in the mass (in the order of at least 50 percent) crystallizes in the B form. This technique contrasts with the technique mentioned above where after seeding the mass with B-SOS and homogenizing it with a piston homogenizer, it is immediately left to cool.

Furthermore, to create a suspension of very fine particles for which the initial quantity is high (in the order of 10s to 1012 particles per gram of cocoa butter) , it is desirable to carry out the dispersion in conditions that give the medium sufficient energy to ensure that the dimensions of the added β-SOS particles are greatly reduced and do not exceed on average a size of approximately 100 μτα. Such energy can be provided to the medium by violent agitation or pounding. It is thus evident that this value of 100 μπι is only given by way of general preferred example: particles of a size exceeding this limit, for example reaching or even exceeding 500 μταε, can occasionally be present without affecting the properties of the modified cocoa butter (MCB) . In fact, the important factor to take into account in this process is the kinetic energy (shearing effect) produced by the agitation or pounding; this energy should be sufficient to reduce as much as possible the size of the seed crystals and simultaneously increase their number per unit weight (or volume) in the suspension resulting from the seeding. After seeding and dispersion, the thickening phase can be carried out with or without agitation, given that the agitation prevents the newly formed crystals from growing unduly after they have been started provided that the mass is maintained in the said temperature range.

To practice the present invention from the practical point-of-view, the cocoa butter is liquified so that it is completely melted, and then B SOS (preferably purified by recrystallization) is added to the liquid mass under mechanical conditions such that, initially, a very fine suspension of B-SOS is obtained in the completely liquified mass. Such a suspension contains approximately 108 or 1012 seeds of B-SOS in the form of particles having a size preferably between 0.1 and 100 m. The concentration and size of these particles can be estimated by microscopic observation or by using a particle counter employing conventional means. The liquid can then be left to rest or the agitation continued for a time sufficient for a significant portion of SOS present to crystallize in the form of fine particles of the B isomer of crystallization; this gives an opalescent or milky appearance to the mass.

Little by little, during the agitation this milky appearance intensifies until the mass becomes completely opaque and it thickens to a pasty consistency, which allows the degree of advancement of the operation to be assessed. The temperature at which the molten mass is maintained during the crystallization of B-SOS is 31 to 36°C, preferably 32.5 to 34 °C, more preferably 33 °C, and the time necessary to crystallize at this temperature at least 50% by weight of the SOS present in the β form is 1 to 6 hours, preferably 2 to 3 hours. Periods of less duration, for example 50 to 60 minutes, are equally possible, although less desirable, the degree of modification conferred on the cocoa butter thus treated depending to a certain extent on the amount of B-SOS formed. Thickening periods exceeding six hours, and as much as 20 hours, are also possible but less economic. The molten coated cocoa butter can also be seeded with quantities of B-SOS exceeding 5% but without any particular advantage .

The nature of construction of the homogenizer-agitator used in the present invention is of importance in that the agitation must be sufficiently effective to cause a mechanical reduction effect (attrition, pulverization, pounding) on the particles of the B-SOS seeds. The agitation must thus be very violent for the liquid mass to be well stirred and for the particles in suspension preferably to be given a turbulent motion. The agitation should not, however, heat the medium and the temperature should not exceed, even locally, the values indicated. It can thus be preferable to agitate in an intermittent manner. Good results have been obtained using a homogenizer-pounder apparatus with a cylindrical head having on its periphery longitudinal slits through which the liquid is radially expelled by the effect of rotation of a helical blade placed axially inside the head. However, from the practical point-of-view, the pounding function of the homogenizer apparatus can easily be replaced by the use of a pestle and mortar. Industrially, a roller-type pounder-mixer is preferably used. It should be noted as well that if the agitation is carried out beyond the initial dispersion and pounding phase, the newly forming particles of β-SOS are prevented from coalescing during the thickening phase or from forming large crystals.

Once the thickening phase has ended, that is to say when the quantity of β-SOS in suspension in the moving mass is sufficient, the agitation is stopped and the mass cooled. This operation is not very critical and is carried out, preferably by simply leaving the mass to rest at ambient temperature for several hours. If necessary, the process can be accelerated by blowing with air at between 10 and 25°C.

To purify the B-SOS added as crystallization seed in the present process, known techniques can be used, that is to say fractional crystallization of cocoa butter by means of organic solvents such as acetone or hexane. These techniques are described in the above-mentioned references as well as in the documents GB-A-2 177 715 and 2 177 170. It should be noted that in the present process the purified β-SOS can be replaced by modified cocoa butter (MCB) made during a previous implementation of the present process.

Once solidified, the cocoa butter modified according to the invention has a texture quite distinct from that of ordinary cocoa butter. In particular, it is more brittle, breaks more easily under bending stress, and the broken zone has an irregular and heterogeneous surface with very shiny facets. Besides, when the MCB is heated, it softens at a temperature well above 30°C, and at 37°C it is still not completely molten, a portion of the triglycerides which constitute it (probably B-SOS) being entirely solid.

Figure 1 shows the X-ray diffraction spectrum of ordinary cocoa butter; Figure 2 shows the X-ray diffraction spectrum of the B-SOS isomer; Figure 3 shows the X-ray diffraction spectrum of modified cocoa butter (MCB) in accordance with the present invention.

It can be seen by comparing Figure 3 with Figure 1 how much the process enriches the cocoa butter with the B-SOS isomer of crystallization.

The use of thus modified cocoa butter (MCB) is very interesting for the chocolate industry because incorporated in chocolate in small amounts, it allows the tempering step to be omitted, and furthermore it can confer on the treated chocolate an unusual resistance to heat as well as an excellent stability against blooming during storage.

From the practical point-of-view, an amount of about 0.5 to 5% by weight of MCB powder, for example grated, can be added to a conched chocolate mass, that is to say slightly kneaded at a temperature between 32 and 38 °C; then the kneading can be continued between 32 and 36 °C to distribute the MCB in the liquid mass and cause the formation of B-SOS (a few hours of kneading is sufficient) . The mass is then cooled to about 30°C and molded in a conventional manner, the necessity for tempering being completely eliminated, which has undeniable energy and practical advantages. Once molded, the chocolate is cooled to solidification, this process being advantageously speeded by an air current at 10 to 15 °C. It is important to note incidentally that in the framework of the present invention, the chocolate mass can be maintained in the fluid state, for example at 35 °C, for an indeterminate time. As a result, this mass can be continually available at such a temperature for any subsequent applications, which is obviously not possible with conventional tempering techniques.

The chocolate thus obtained has very desirable properties, and in particular it softens less quickly on exposure to heat than non treated chocolate; for example, it is still firm at 30°C, which is not the case for ordinary chocolate, and in the best conditions it does not become really soft until 34 °C. Besides, it is perfectly resistant when stored and subjected to successive cycles of heating to 30°C and subsequent cooling. It has in particular much less tendency to bloom when exposed in summer to such conditions on the shelves of a store. It should be noted however that the advantageous properties disappear after prolonged heating to temperatures exceeding 38 °C, probably because in such conditions the triglycerides in the β crystalline form dissolve slowly in the molten mass of other triglycerides.

The following examples illustrate the invention.

Example 1 To 100 grams of cocoa butter (X-ray diffraction spectrum shown in Figure l) , brought to 33 °C, were added 2 grams of β-SOS (M.P. = 40-42°C) and this mixture was pounded for two minutes in a mortar maintained at 33 °C. The mixture was left for one hour at 33 °C and then allowed to cool to ambient temperature.

The X-ray diffraction spectrum of the obtained MCB powder has (see Figure 3) four characteristic peaks of the stable forms of the triglycerides of cocoa butter.

Example 2 To one kilogram of molten cocoa butter at 32 °C were added 10 grams of pulverized B-SOS, and then the mixture was agitated for one hour by means of a homogenizer head (1.5 mm Schweizer type) operating intermittently, that is to say in periods of 10 to 15 seconds approximately every three minutes so that the temperature was maintained at 33 to 34 °C. During this period, the mass thickened and took on a milky appearance, the dimension of the crystalline particles formed lying principally in the range of 30 to 100 μια.

The MCB mass was then cooled in a cold chamber where it was reduced to powder by means of a grater or pounder. It should be noted that the process of the invention does not only apply to cocoa butter in the pure state, but also to mixtures with other solids, particularly cocoa solids.

The X-ray diffraction spectrum was similar to that of the powder resulting from Example 1.

Example 3 400 grams of black chocolate comprising, by weight, 50% cocoa powder, 30% sugar, 17% cocoa butter and 2% proteins were heated for one hour at 50 to 55 °C so as to liquify the mixture .

The temperature was allowed to fall to 38 °C, and then 12 grams of MCB prepared according to Example 1 were added while agitating gently. The agitation was carried out for three hours at 35°C, and then the mixture was cooled to 30°C in about 15 minutes. The liquid mass was molded by conventional molding processes into plates or bars of chocolate. After cooling to 7°C (in 20 to 30 minutes) the plates were removed from the mold and subjected to a blooming test which consisted of heating the chocolate to 30°c, letting it cool to 20 to 25°C and repeating the cycle about 10 times.

No blooming of the above chocolate was observed as compared with a test sample (the same chocolate which had not been treated with MCB) which became quite whitish.

Example 4 To 150 grams of melted cocoa butter, for which the diffraction spectrum is shown in Figure 1, were added 50 grams of grated MCB according to Example 2. The two phases were intermittently mixed and allowed to rest for three hours at 33 °C. After cooling and solidifying, it was observed that the spectrum of the solidified product corresponded to that shown in Figure 3.

Example 5 Commercial chocolate was used for which the principal composition is approximately the following: Cocoa solids 15 % Cocoa butter 15 % Sugar 54 % Whole milk powder 12 % Skim milk powder 3 % Lecithin 0.5 % Vanillin 0.02 % grams of this chocolate were liquified at .50 °C and after lowering the temperature to 3 °C, 6.9 grams (1.5 % by weight) of MCB prepared in accordance with Example 2 were added. Agitation was maintained for three hours at 33 °C and then the mixture was cooled to 30°C and the molding step carried out. After cooling of the molten plates at 10 °C (in approximately 15 minutes) , the obtained chocolate was subjected to a blooming test consisting of heating it to 30°C, then cooling it to 17°C, the cycle being repeated several times (5 to 10 times) . No blooming of the treated chocolate was observed whereas the test sample (the same chocolate, but not treated with MCB) showed blooming.

Example 6 A mass of pure cocoa having the following principal composition was employed: Cocoa solids 47 % Cocoa butter 52 % H20 1 % 500 grams of this mass of cocoa were liquified at 50°C, and after lowering the temperature to 32 °C, 10 grams of pulverized β-SOS were added; then the mixture was agitated for one and a quarter hours by means of a homogenizer head (1.5 mm Schweizer type) operating intermittently, that is to say in periods of 20 to 25 seconds every four minutes so that the temperature was maintained at 33 to 34°C. During this period, the mass thickened strongly. After cooling in a cold chamber and reduction to powder of the solidified mass by means of a grater, it was observed that the X-ray diffraction spectrum was similar to that of the cocoa butter powder modified in accordance with Example 1.

Claims (6)

1. A process for modifying the crystalline structure of cocoa butter and raising the temperature at which it is completely molten by increasing, in the mass of triglycerides which constitute it, the β monotropic form of the triglyceride SOS, the process comprising, in a first operational phase, heating the cocoa butter to complete liquefaction, seeding it above 30°C with crystallization seeds, the seeding taking place by addition and dispersion in the liquid mass of 0.1 to 5% by weight of purified β-SOS, then leaving the mass, still in the liquid state, to thicken by partial crystallization, and in a second phase, leaving the mass to solidify by cooling, characterized in that the dispersion of purified β-SOS is carried out by pounding and/or homogenizing the latter in the fluid mass of molten cocoa butter so as to create a suspension containing approximately 108 to 1012 solid particles per gram of cocoa butter, and that the seeded fluid mass is left to thicken at a temperature where only the β form of triglycerides can crystallize.

2. A process according to Claim 1, characterized in that the temperature at which the dispersion and thickening phase is carried out is from 31 to 36°C, preferably 32 to 35°C.

3. A process according to Claim 1, characterized in that the duration of the thickening phase is from one to three hours.

4. A process according to Claim 4, characterized in that the proportion of SOS which crystallizes in the β form during the thickening phase relative to the total amount of SOS present in the mass of cocoa butter is at least 50% by weight. 100496/3

5. A process according to Claim 1, characterized in that the pounding and homogenization are carried out with a homogenizer-pounder apparatus functioning intermittently or a roller pounder.

6. Use of modified cocoa butter obtained by the process of Claim 1 in the preparation of conched molten chocolate for manufacturing chocolate, substantially as described in the specification.