Relation of fat bloom in chocolate to polymorphic transition of cocoa butter

A special chocolate with spray-dried sugar (50:50 w/w sucrose/20 Dextrose Equivalent corn syrup solids) was made to study the polymorphic changes in cocoa butter crystals using X-ray diffraction. Anhydrous milk fat (AMF) and high-, middle-, and low-melting milk fat fractions were used to replace 2% (w/w) of cocoa butter. Chocolates were tempered, and the consistency of temper among chocolate samples was verified by a temper meter. Chocolates were cycled between 19 and 29°C at 6-h intervals to induce fat bloom. The special chocolates were analyzed by X-ray spectroscopy and colormeter. X-ray analysis on the special chocolates showed polymorphic transition from the βV to the βVI form of cocoa butter. After a lag phase, the percentage of the βVI form rapidly increased. However, the sample made with the high-melting milk fat fraction transformed slowly to βVI. Visual bloom appeared rapidly on the special chocolates made with AMF, middle- and low-melting fractions, whereas visual bloom was very slow to appear on the special chocolates made with high-melting milk fat fraction and on the cocoa butter control. The commercial chocolate responded consistently; the control bloomed rapidly, the AMF exhibited some bloom resistance, and the high-melting fraction inhibited bloom. Despite the βV to βVI transition, the control chocolates with amorphous sugar did not bloom. Since the only difference in the chocolates was sugar microstructure, differences in bloom formation were caused by the microstructure, not the polymorphic transition.     

Impact of Limonene on the Physical Properties of Reduced Fat Chocolate

The addition of limonene, a low molecular weight hydrophobic compound, to chocolate was reported to decrease the hardness and the viscosity of chocolate, facilitating the production and improving the eating quality of reduced fat chocolate. The objective of this study is to understand the functionality of limonene in decreasing the viscosity and the hardness of chocolate, a fat (cocoa butter)-based particulate suspension. This study shows that chocolate hardness was decreased because limonene mixes with cocoa butter, affects its crystallization pattern and decreases its solid fat content. After checking that limonene does not significantly affect the continuous phase volume fraction, we show that limonene decreases chocolate viscosity by decreasing the viscosity of the continuous phase, cocoa butter. The addition of low quantities of limonene in cocoa butter leads to a great decrease in the liquid fat viscosity. The dependence of the viscosity on the ratio of cocoa butter to limonene analyzed using Kay’s equation seems to indicate that limonene mixes with and within the cocoa butter triglycerides, diluting the fat and leading to a decrease in the overall fat viscosity.     

Bloom Formation on Poorly-Tempered Chocolate and Effects of Seed Addition

Bloom on chocolate with different levels of cocoa butter seed addition was investigated. When insufficient cocoa butter seed crystals were added to give proper temper, the chocolate developed bloom as dark brown spheres in lighter color areas, similar to that seen in bloom on untempered chocolate. These dark colored spheres overlapped and the lighter color areas disappeared with increasing seed amount added. The relationship between seed amount and lighter color area (bloom), as quantified by image analysis, showed that over 270 ppm seeds (fat basis) were needed to accomplish good tempering. The cocoa butter crystallization behavior with various amounts of seed was observed by light microscopy. Too few seeds caused sparse β crystallization and massive β′ crystallization, which explains the appearance of poorly tempered chocolate bloom. As seed amount increased, β crystallization of cocoa butter took less time to reach the upper level of solid fat content and the size became smaller. In addition, DSC analysis was carried out to study crystallization and melting behavior of cocoa butter with different seed amounts. Higher levels of added seeds resulted in greater amounts of β crystal formation and the crystallization temperature increased, which meant crystallization occurred earlier. These results showed that the mechanism of bloom formation on poorly tempered chocolate (insufficient seeds) is due to sufficient time and space for phase (particles and fat) separation as the stable polymorphs grow.     

Seeding effects on solidification behavior of cocoa butter and dark chocolate. I. Kinetics of solidification

Effects of seeding of fat crystals on the crystallization kinetics of cocoa butter and dark chocolate were examined with a rotational viscometer. The seed crystals employed were cocoa butter, 1,3-distearoyl-2-oleoylglycerol (SOS), 1,3-dibehenoyl-2-oleoylglycerol (BOB) and 1,2,3-tristearoylglycerol (SSS). The seed powders were prepared by pulverization below —50°C, the dimensions being in a range from 20–70 μm. Particular attention was paid to the influence of polymorphism of the seed crystal. We found that all of the above seed materials accelerated the crystallization, the degree of acceleration being in a following order; SOS (β ₁) > cocoa butter (Form V) > SOS (a mixture ofβ’ andβ ₂) > BOB (β ₂) > BOB (pseudo-β’) > SSS (β). Precise measurements of the crystallization kinetics showed that the most influential factors in the seeding effects are the physical properties of the seed materials—above all, thermodynamic stability, and similarity in the crystal structure to cocoa butter are the most determinative.     

The interpretation of GLC triglyceride data for the determination of cocoa butter equivalents in chocolate: A new approach

A new approach to interpret triglyceride data obtained by gas liquid chromatography (GLC) in order to determine cocoa butter equivalents (CBE) in chocolate is described. The approach is based on the known straight line relationship which exists between the C₅₀ and C₅₄ triglycerides of cocoa butter of different origins and the realization that, for currently available CBE conforming to CAOBISCO’s criteria, a similar band relationship exists. The technique described enables the quantity of unspecified CBE in a chocolate containing an unknown cocoa butter to be determined to an accuracy of ±1.5% when present in chocolate at the 5% level. Nut oils (almond, walnut or hazelnut) are sometimes present in mainland European chocolates and, should CBE also be present, it is possible to calculate the combined percentages of nut oil and CBE in the chocolate. The method of interpretation described is not dependent on a particular GLC technique for determining triglycerides. Interpretation of other laboratories’ results obtained using different GLC instruments and procedures has shown that the method enables any CBE present in the fat under examination to be determined accurately. The method compensates for variations in the composition of CBE and for the differences between cocoa butters of different origin. A detailed knowledge of CBE compositions is not required and only a few cocoa butter/CBE standards are necessary. The method described is graphical, enabling small laboratories not equipped with microcomputers to utilize the method. The calculation can, however, be programmed for a computer.     

Seeding effects on solidification behavior of cocoa butter and dark chocolate. II. Physical properties of dark chocolate

Demolding property just after solidification, we examined the polymorphism of cocoa butter in seed-solidified dark chocolate and fat-bloom stability through two thermocycle tests between 38 and 20°C (38/20) and between 32 and 20°C (32/20). The seed crystals employed are Form VI of cocoa butter,β ₁ of SOS (1,3-distearoyl-2-oleoyl-glycerol), pseudo-β’ andβ ₂ of BOB (1,3-dibehenoyl-2-oleoylglycerol) and β of SSS (1,2,3-tristearoylglycerol). The influence of the seed concentration was also examined. The seeding of cocoa butter (Form VI) and SOSβ ₁ caused the crystallization of Form V of cocoa butter and exhibited better demolding. As to the fat-bloom stability, the two, seed crystals were effective through the 32/20 cycle test, but the fat-bloom occurred through the 38/20 test. The seeding ofβ ₂ of BOB caused better demolding, crystallization of Form V of cocoa butter, and the most preferable fat-bloom stability; particularly, the seeding of 5 wt% concentration ofβ ₂ of BOB completely prevented the fat-bloom after the 38/20 test, although the seeding of all of the other materials and conditions caused the fat-bloom by this thermo-cycle test. The seeding of pseudo-β’ of BOB did not prevent the fat-bloom, although the demolding property was improved. In the case of the seed of β of SSS, both the demolding and fat-bloom stability were not improved. We concluded that the seeding ofβ ₂ of BOB revealed the most desirable, influences on the demolding and the fat-bloom stability of dark chocolate. This conclusion suggests the usage ofβ ₂ of BOB as the most preferable seed material in the solidification of dark chocolate, since the crystallization rate was also enhanced by this material as described in Paper I.     

Fats and processes used in manufacturing chocolate and confectionery coatings

The basic requirements of the confectioner for fats to be used in chocolate are briefly reviewed. The melting properties of the polymorphs of cocoa butter and variation in them are outlined together with methods of measuring them. These properties govern two important steps in the manufacture of chocolate—tempering and cooling. The tempering process and methods for determining the state of temper in a sample are noted. The main types of chocolate in common use are described along with two main processes used for their manufacture. The polymorphic forms commonly found in commercial operations are discussed. The discussion on chocolate and cocoa butter leads to reasons for the interest of confectioners in so-called coating fats or cocoa butter substitutes. The various classes of fat which have been tried so far for this use are briefly reviewed along with their limitations from the viewpoint of the confectioner and his consumers. Desirable specifications for a coating fat and possible future developments in their use in the candy industry are discussed briefly. One of seven papers presented in the symposium “Fats and Oils in the Food Industry,” Atlantic City, October 1971.     

Physical Chemical Properties of Shea/Cocoa Butter Blends and their Potential for Chocolate Manufacture

Cocoa butter (CB) is the preferred fat for chocolates and confections. However, for technological and economic reasons, there have been strong efforts for partially replacing it. As shea butter (SB) has become an important natural source of symmetrical stearic-rich triacylglycerols (TAG), the aim of this work was to study physical chemical behavior of blends of CB and SB and the dynamic mechanical and polymorphic behaviors of chocolates prepared with these systems as added fat. The compatibility of SB and CB blends was studied using the isosolid diagram. Data showed that softening occurred due to both dilution effects and a slight eutectic formation. Chocolates formulated with a fat phase consisting in CB, or SB, or blends with 10, 20, or 30 wt.% SB in CB showed different polymorphic behaviors during storage. The polymorphic transition from β₂ to β₁ occurred to a greater extent with increasing content of SB in formulation. Dynamic mechanical analysis (DMA) results agree with X-ray findings. E′ modulus significantly increased during storage most likely due to formation of β₁ form. As shown by Grazing incidence wide-angle X-ray scattering (GIWAXS) studies, crystals preferred growing on the chocolate surface than on bulk chocolate. However, even after a year at 18°C, chocolates had good appearance indicating that SB was a good CB extender.     

The analysis of sterol degradation products to detect vegetable fats in chocolate

A method for the detection of hydrocarbon sterol degradation products (sterenes) has been adapted for the analysis of noncocoa butter vegetable fats in chocolate. The method involves solvent extraction of the fat separation of the sterene fraction, and analysis of individual sterenes with mass spectrometric detection. The sterene composition of refined noncocoa vegetable fats was determined in samples of cocoa butter, and retail chocolates. The presence of known sterenes was confirmed for all of the refined vegetable fats and for a single sample of cocoa butter, the processing history of which was not known. Detection of vegetable fat added to chocolate at the 5% level was demonstrated. Sterenes were detected only in chocolates labeled as containing vegetable fats. This technique has potential use as a screening method for the detection, but not quantification, of refined vegetable fat in chocolate.     

The determination of cocoa butter equivalents in chocolate

A method of determining cocoa butter equivalents in chocolate and cocoa butter is described. The method relies on a new approach for interpreting data obtained by triglyceride gas liquid chromatography (GLC). This technique provides information on the composition of a fat according to the carbon number of the triglycerides (C_n). Examination of the data for a wide range of cocoa butters shows that a straight line relationship between the C₅₀ and C₅₄ contents exists. This relationship has been used as the basis for a quantitative method determining the amount and type of cocoa butter equivalent added to chocolate. The application of the method to both plain and milk chocolate is described. The method is also used to determine the amount of milk fat in chocolate.     

Crystallization Kinetics of Cocoa Fat Systems: Experiments and Modeling

Isothermal crystallization kinetics of unseeded and seeded cocoa butter and milk chocolate is experimentally investigated under quiescent conditions at different temperatures in terms of the temporal increase in the solid fat content. The theoretical equations of Avrami based on one-, two- and three-dimensional crystal growth are tested with the experimental data. The equation for one-dimensional crystal growth represents well the kinetics of unseeded cocoa butter crystallization of form α and β′. This is also true for cocoa butter crystal seeded milk chocolate. The sterical hindrance due to high solids content in chocolate restricts crystallization to lineal growth. In contrast, the equation for two-dimensional crystal growth fits best the seeded cocoa butter crystallization kinetics. However, a transition from three- to one-dimensional growth kinetics seems to occur. Published data on crystallization of a single component involving spherulite crystals are represented well by Avrami’s three-dimensional theoretical equation. The theoretical equations enable the determination of the fundamental crystallization parameters such as the probability of nucleation and the number density of nuclei based on the measured crystal growth rate. This is not possible with Avrami’s approximate equation although it fits the experimental data well. The crystallization can be reasonably well defined for single component systems. However, there is no model which fits the multicomponent crystallization processes as observed in fat systems.     

Fat Bloom Caused by Partial De-Oiling on Chocolate Surfaces after High-Temperature Exposure

Fat bloom in chocolate is a substantial problem that affects its sensory properties, such as texture and appearance. This phenomenon is because of diffuse light reflection on a roughened surface of chocolate, caused by structural changes of fat crystals subjected to various temperature conditions. The purpose of this study is to characterize the fat bloom formed through gradual two-step cooling after exposure to temperatures (35–37 °C) slightly above the cocoa butter Form βV melting point (33.8 °C). To clarify the fat bloom formation process, the structural changes in cocoa butter and on the chocolate surface, at the dynamic thermal condition for bloom formation, was investigated using X-ray diffraction (XRD), fluorescence light microscopy, and scanning electron microscopy (SEM). The results revealed that an entirely light brown fat bloom occurred, even in the absence of the Form βVI or other polymorphic transformation. Microscopic observation showed that the light brown appearance was because of the porous structure on the chocolate surface. This porous structure was formed by liquid oil moving inside of chocolate from the surface. The formation of a coarse network and the subsequent de-oiling, because of movement of unsolidified liquid fat into the chocolate, appeared to be the main causes of bloom formation. Therefore, a coarsened fat network and oil movement besides the conventional principles of polymorphic transformation of cocoa butter should be considered.     

Effects of ultrasonic irradiation on crystallization behavior of tripalmitoylglycerol and cocoa butter

Effects of application of ultrasonic power (20 kHz, 100 W) on the crystallization behavior of tripalmitoylglycerol (PPP) and cocoa butter have been examined in terms of rate of nucleation and polymorphic control. High-purity PPP (>99%) and low-purity PPP (>80%) samples were employed to mimic real fat systems, which usually have higher concentrations of minor components in addition to the main component. For both the high-purity and low-purity PPP, the application of ultrasonic power accelerated the rate of nucleation as measured by induction time for the occurrence of crystals and by the number of crystals nucleated. As for the polymorphic influences, the nucleation of both the β′ and β forms was accelerated by the ultrasound, yet the β′ form nucleation was more accelerated when the low-purity PPP samples were employed. As for cocoa butter, sonication for a short period accelerated the crystallization of Form V. The present results indicate that ultrasound irradiation is an efficient tool for controlling polymorphic crystallization of fats.     

Polymorphism of cocoa butter

Largely by x-ray diffraction six crystalline states, I–VI, in order of increasing melting point, have been identified for cocoa butter. Of these states II, IV, V and VI are pure and identifiable with previously (or presently) identified polymorphs of 2-oleoylpalmitoyl stearin (POS), namelyα-2,β′-2,β-3 (“V”) andβ-3 (“VI”); V and VI representing distinct but very closely related crystalline structures. State I is a definite but fleeting and not readily characterized subα state and may be a phase mixture, as state III may be also. Melting points, heats of fusion and dilatometric data are reported for all states to the extent that their stability permits. The normal state of cocoa butter in chocolate is apparently V, certainlyβ-3. While it is true that “bloom” has not been observed for pure V nor observed to exist in the absence of VI, it is premature to say that VI is specifically the phase of chocolate “bloom”.     

Das physikalische Verhalten und die chemischen Zusammensetzung von Schokolade,Kakaobutter und einigen Kakaobutter-Austauschfetten

Physical Behaviour and Chemical Composition of Chocolate, Cocoa Butter and Some Cocoa Butter Substitutes Cocoa butter, which forms the continuous phase in the dispersed system of chocolate, is responsible for the most important properties of the latter. Such properties and methods for determining the same are treated exhaustively. Physical properties of cocoa butter and its substitutes, as well as the relationship between their physical behaviour and chemical composition are discussed. Fats that can replace cocoa butter satisfactorily, have a chemical composition which is similar to that of cocoa butter, Such substitutes are available and fairly good quality chocolates can be prepared from them. Determination of fatty acid composition and aniline point are adequate for ascertaining, whether a fat is suitable as cocoa butter substitute.     

Influence of Soft Cocoa Butter Equivalents on Color and Other Physical Attributes of Chocolate

The physical characteristics and color of chocolate depend on the physical properties and crystallization behavior of the fat phase. In this study, the fat phase of chocolate samples contains cocoa butter from Ghana and soft cocoa butter equivalent (CBE). The laboratory-made chocolate samples were tempered at three different precrystallization temperatures (25, 27 and 29 °C), using three different concentrations of CBE (3, 5 and 7%), calculated as percentage of the chocolate. Physical characteristics of chocolate, namely thermoreographic parameters and solid fat content (SFC), were measured. The color of the chocolate was determined instrumentally, before and after thermo-cycle testing at 32/20 °C. It was found that CBE changed the melting properties of chocolate produced with cocoa butter from Ghana, which is of moderate hardness. It was determined that the optimum precrystallization temperature for chocolate mass with addition of CBE in the given conditions of measurement was 27 °C, the temperature that resulted in the best fat bloom resistance.     

Permeability of some fat products to moisture

Summary Films of cocoa butter, highly hydrogenated cottonseed oil, mixtures of highly hydrogenated cottonseed oil and cottonseed oil, chocolate liquor, and sweet milk chocolate were prepared; and their permeability to water vapor was determined by the cup method. The permeability constant was calculated in terms of grams of water diffusing through a centimeter cube in one second under a vapor pressure gradient of one millimeter of mercury across the cube. Under the test conditions employed, the permeability constant for cocoa butter at room temperature was found to vary from 5.8×10⁻¹² to 81.6×10⁻¹². The permeability constants for the highly hydrogenated cottonseed oil and the cocoa butter, under comparable conditions at room temperature, was found to be approximately 1.3×10⁻¹² and 33×10⁻¹², respectively. From data obtained with cocoa butter it was concluded that the permeability constant increased with moderate increases in film thickness. Polymorphism was found to have a large effect on permeability, an approximately 15-fold difference was found between quickly chilled and tempered films of cocoa butter at 3°C. (37.4°F.). The percentage of liquid component in the fat was found to have a large effect on permeability. The increasing of the percentage of liquid cottonseed oil in highly hydrogenated cottonseed oil from 0 to 40% increased the permeability constant from 1.3×10⁻¹² to about 420×10⁻¹². The permeability of chocolate liquor and sweet milk chocolate at room temperature was increased greatly when the relative humidity on the wet side of the films was increased to 100%. The nonfat components absorbed enough moisture to impair the structure of the film. Presented at the 32nd Fall Meeting of the American Oil Chemists' Society, Chicago, Ill., October 20–22, 1958. Fellow, National Confectioners' Association. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Use of ethylcellulose polymers as stabilizer in fat-based food suspensions examined on the example of model reduced-fat chocolate

Surfactants are an important ingredient in the manufacture of chocolate. Their role is to coat the surfaces of the sugar and cocoa particles dispersed in fat, generally cocoa butter, to maintain or enhance the flowability of molten chocolate. Coating the surfaces of the dispersed particles with a surfactant reduces inter-particle interactions responsible for particle aggregation which leads to viscosity reduction of the mixture. Controlled flow behavior of molten chocolate is a requirement for successful processing and for optimal mouthfeel. This becomes in particular crucial in the formulation of fat-reduced chocolate. In fat-reduced chocolate, low molecular weight surfactants such as lecithin and polyglycerol polyricinoleate (PGPR) need to be applied at unacceptably high concentrations to maintain flowability of a chocolate with increased dispersed phase volume. This paper reports on an alternative approach, the use of the polymeric surfactant ethylcellulose. Shear viscosity measurements on model chocolates demonstrated a viscosity reducing effect. The effect of ethylcellulose polymer adsorbed at an oil/water interface was visualized in volume change experiments on macroscopic pendant drops revealing a difference in the nature of the interface compared to an interface covered with a low molecular weight surfactant.     

Tempering triglycerides by mechanical working

The tempering of fat products to convert their components to stable polymorphs is an important and a sometimes troublesome problem in the manufacture of these products, particularly chocolate and chocolate-type confections. It has been found that a solid-to-solid transformation to the stable polymorphs can be effected by mechanical working consisting of extrusion under pressure. With a fat of relatively few components, such as cocoa butter, evidence of the transformation can be obtained from X-ray diffraction patterns. For more complex fats, hardness and melting characteristics must be considered. There is evidence that mechanical working is also effective in the transformation of a cocoa butter-like fat made from hydrogenated cottonseed oil and olive oil, and in the transformation of highly hydrogenated cottonseed oil. Mechanical working to effect polymorphic transformation is also effective with products containing the fats mentioned. Presented at the 35th Fall Meeting of the American Oil Chemists' Society, Chicago, Illinois, October 30–November 1, 1961. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Effect of fat composition on texture and bloom of lauric compound chocolate

Cocoa butter (CB) and milk fat (MF) contents were varied and their effects on the textural property and bloom formation of lauric cocoa butter substitutes (CBS)‐based compound chocolates was investigated. Compositional parameters for CBS compound chocolates were two types of CBS (hydrogenated palm kernel olein (HPKO) and hydrogenated palm kernel sterin (HPKS)), CB (0, 5, 10, and 15%) and MF (0, 3, and 6%) contents. Addition of CB or MF significantly (p<0.001) influenced the hardness of compound chocolates but the effects were less pronounced at higher fat content. Addition of MF or CB accelerated the bloom formation compared with the control samples, but in combination they delayed the bloom formation, suggesting that the mechanisms of bloom formation were different in the CBS compound chocolate made with different fat mixtures. Practical applications This study deals with the effect of fat composition on both texture and bloom of lauric‐based compound chocolates. CB and MF can be used in lauric‐based compound chocolates to improve the flavor, but eutectic and dilution effects appear when these fats are added separately. However, there are few studies on the interactions of ternary mixtures and the physical properties such as hardness of corresponding compound chocolates. In order to be able to predict the bloom formation, it is important to study how these fats affect the physical properties of the compound chocolates.