Chocolate processing

Refining. The next stage in chocolate processing is a fine grinding in which a coarse paste from the mixer is passed between steel rollers and converted to a drier powdery mass. Refining breaks up crystalline sugar, fibrous cocoa matter, and milk soflds. 

A number of continuous ZSK processes are of interest for chocolate processing, with plants... 

Using a Couette device, which consists of a pair of concentric cylinders, with the inner one rotating, it is possible to generate approximately uniform shear on chocolate. The temperature of the device can be controlled and varied this allows a controlled temperature-time-shear pattern to be provided. Figure 22.5 shows the DSC trace for milk chocolates processed at different shear rates (Stapley, Tewkesbury and Fryer 1999). The phase change temperatures are lower than those shown in Table... 

Due to the polymorphism of the fats, tempering has a critical role. The need to temper limits the types of chocolate process that can be designed. Better rmder-standing of the material science of chocolate, leading to ways of rapidly generating the right crystal forms would be useful. Experiments have been carried out to study the rate at which crystallisation affects the shape of the final material both the rate and extent of crystallisation vary with the temper of chocolate. 

The first operation of chocolate processing is to homogenize the cocoa mass, ground sugar, milk powder and part of the cocoa butter in a mixer which can be a kneading machine with a Z-shape mixing arm or a continuous screw mixer. 

Bbder, R.G. and Morgan, J.N. (1999) Cocao bean and chocolate processing. In I. Knight (ed.). Chocolate and Cocoa Flealth and Nutrition. Blackwells, Oxford, pp. 43-60. 

A more complex flavor development occurs in the production of chocolate. The chocolate beans are first fermented to develop fewer complex flavor precursors upon roasting, these give the chocolate aroma. The beans from unfermented cocoa do not develop the chocolate notes (84—88) (see Chocolate and cocoa). The flavor development process with vanilla beans also allows for the formation of flavor precursors. The green vanilla beans, which have Htfle aroma or flavor, are scalded, removed, and allowed to perspire, which lowers the moisture content and retards the enzymatic activity. This process results in the formation of the vanilla aroma and flavor, and the dark-colored beans that after drying are the product of commerce. 

The boric and sulfuric acids are recycled to a HBF solution by reaction with CaF2. As a strong acid, fluoroboric acid is frequently used as an acid catalyst, eg, in synthesizing mixed polyol esters (29). This process provides an inexpensive route to confectioner s hard-butter compositions which are substitutes for cocoa butter in chocolate candies (see Chocolate and cocoa). Epichlorohydrin is polymerized in the presence of HBF for eventual conversion to polyglycidyl ethers (30) (see Chlorohydrins). A more concentrated solution, 61—71% HBF, catalyzes the addition of CO and water to olefins under pressure to form neo acids (31) (see Carboxylic acids). 

Potassium Carbonate. Except for small amounts produced by obsolete processes, eg, the leaching of wood ashes and the Engel-Precht process, potassium carbonate is produced by the carbonation, ie, via reaction with carbon dioxide, of potassium hydroxide. Potassium carbonate is available commercially as a concentrated solution containing ca 47 wt % K CO or in granular crystalline form containing 99.5 wt % K CO. Impurities are small amounts of sodium and chloride plus trace amounts (<2 ppm) of heavy metals such as lead. Heavy metals are a concern because potassium carbonate is used in the production of chocolate intended for human consumption. 

Winnowing. Winnowing, often called cracking and fanning, is one of the most important operations in cocoa processing. It is a simple process that involves separating the nib, or kernel, from the inedible shell. Failure to remove shell results in lower quahty cocoa and chocolate products, more wear on nib grinding machines, and lower efficiency in all subsequent operations. 

Commercial cocoa powders are produced for various specific uses and many cocoas are alkaH treated, or Dutched, to produce distinctive colors and flavors. The alkaH process can involve the treatment of nibs, chocolate Hquor, or cocoa with a wide variety of alkalizing agents (9). 

The Codex Committee on Cocoa and Chocolate Products defines cocoa butter as the fat produced from one or more of the following cocoa beans, cocoa nibs, cocoa mass (chocolate Hquor), cocoa cake, expeUer cake, or cocoa dust (fines) by a mechanical process and/or with the aid of permissible solvents (10). It further states that cocoa butter shall not contain sheU fat or germ fat ia excess of the proportion ia which they occur ia the whole bean. 

Codex has also defined the various types of cocoa butter ia commercial trade (10). Press cocoa butter is defined as fat obtained by pressure from cocoa nib or chocolate Hquor. In the United States, this is often referred to as prime pure cocoa butter. ExpeUer cocoa butter is defined as the fat prepared by the expeUer process. In this process, cocoa butter is obtained direcdy from whole beans by pressing ia a cage press. ExpeUer butter usuaUy has a stronger flavor and darker color than prime cocoa butter and is filtered with carbon or otherwise treated prior to use. Solvent extracted cocoa butter is cocoa butter obtained from beans, nibs, Hquor, cake, or fines by solvent extraction (qv), usuaUy with hexane. Refined cocoa butter is any of the above cocoa butters that has been treated to remove impurities or undesirable odors and flavors. 

Fig. 2. Process flow diagram for milk chocolate, chocolate symp, and cocoa powder.

At this stage of manufacture, chocolate may be stored for future use in bulk Hquid form if usage is expected to be within one to two weeks, or at 43—50°C in a hot water jacketed agitated tank or in soHd block form where it can be stored for as long as 6 to 12 months. Blocks typically weigh between 3 and 30 kg. Storage conditions for block chocolate should be cool and dry, ie, 7 to 18°C and 40 to 45% relative humidity. If chocolate has been stored in block form, it can be remelted to temperatures up to 50°C and then processed in the same manner as freshly made Hquid chocolate. 

Tempering. The state, or physical stmcture, of the fat base in which sugar, cocoa, and milk soHds are suspended is critical to the overall quaHty and stabiHty of chocolate. Production of a stable fat base is compHcated because the cocoa butter in soHdified chocolate exists in several polymorphic forms. Tempering is the process of inducing satisfactory crystal nucleation of the Hquid fat in chocolate. 

A stable crystalline form for chocolate depends primarily on the method used to cool the fat present in the Hquid chocolate. To avoid the grainy texture and poor color and appearance of improperly cooled chocolate, the chocolate must be tempered or cooled down so as to form cocoa butter seed crystals (31). This is usually accompHshed by cooling the warm (44—50°C) Hquid chocolate in a water jacketed tank, which has a slowly rotating scraper or mixer. As the chocolate cools, the fat begins to soHdify and form seed crystals. Cooling is continued to around 26—29°C, during which time the chocolate becomes more viscous. If not further processed quickly, the chocolate will become too thick to process. 

In another method of tempering, soHd chocolate shavings are added as seed crystals to Hquid chocolate at 32—33°C. This is a particularly good technique for a small confectionery manufacturer, who does not produce his own chocolate. However, the shavings are sometimes difficult to disperse and may cause lumps in the finished product (20). Most companies use continuous thin-film heat exchangers for the tempering process. 

The system shown is heavily used in food processing applications such as milk or chocolate crumb production, sugar substitutes, modified starch, and alginates. In addition to food processing applications, such a system is used in the processing of heat-sensitive pharmaceuticals, polymer suspensions like latex, in processing pigments and dyestuffs, and pesticides. 

A commercial advantage was present in many industrial processes. Uncontrolled heat and humidity impacted some products such as chocolate, pasta, textiles, and tobacco. Air conditioning allowed for unifonn and continuous production despite weather conditions, reduced spoilage and waste, and thus saved money—enough in many cases to easily justify the installed and operating costs. 

Mg2+ 21 g 0.35 g Activates enzymes for body processes Chocolate, nuts, instant coffee, wheat bran... 

This chapter defines the methylxanthine composition of raw and processed cocoa, as well as various chocolate foods and beverages. Patterns of consumption for cocoa and chocolate products are discussed and dietary intakes of caffeine from chocolate products are reported. 

The first important technical development in the chocolate manufacturing process occurred when water-powered mills superseded the use of manual labor to grind cocoa beans. This led to the establishment of many chocolate factories from 1804 to 1840. Early production consisted entirely of a type of chocolate beverage that was somewhat indigestible since none of the cocoa butter was removed during processing. In 1828, the Dutch firm of Van Houten invented the cocoa press, which facilitated the production of cocoa powder by partial removal of the cocoa butter from beans. 

The second major technical development occurred in 1876, when milk chocolate was invented in Switzerland by M. D. Peter. This process provided a new stimulus to the cacao trade. Milk chocolate powder and cocoa butter were later combined to make an eating chocolate that formed the backbone of the chocolate industry today. 

Bunker and McWilliams found that two beverages prepared from instant cocoa (with Dutch process cocoa) contained 10 to 17 mg caffeine per cup.37 Table 7 lists the theobromine and caffeine concentration of hot cocoa and chocolate milk prepared from instant mixes. Zoumas et al. analyzed five commercial hot cocoa mixes and reported an average of 65 mg per serving of theobromine and 4 mg per serving of caffeine.28 Similar results were reported by Blauch and Tarka.36... 

This chapter has compiled and evaluated information on the methylxanthine composition of cocoa and various chocolate foods and beverages, as well as the consumption pattern for these commodities. Cacao is the major natural source of the xanthine base theobromine. Small amounts of caffeine are present in the bean along with trace amounts of theophylline. Numerous factors, including varietal type and fermentation process, influence the methylxanthine content of beans. 

In 1990, 74% of all cocoa produced was exported.21 This figure does not include semi-processed cocoa products, including cocoa paste, cocoa butter, cocoa powder, and chocolate. However, it demonstrates that cocoa is not a crop of domestic consumption within the major producing nations. Similarly to coffee, cocoa contributes to the economy of several large producing nations. 

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