Cocoa powder comes from the beans (seeds) of cacao tress, a tropical plant grown in Africa, southeast Asia, Hawaii, Brazil, Colombia and other countries where rainforest conditions exist.

Cocoa powder is an organic material that is derived from the extraction of fat (cocoa butter) from cocoa beans. Roasted cocoa bean material is pressed at high intensity (6,000 to 12,000 psi or 413.7 to 827.4 bar) to extract most of the cocoa butter. The residual material typically contains about 10% fat and may then be ground with no further modification to yield natural cocoa powder, or may be treated with a mild alkali solution (a process called "Dutching") to improve certain characteristics for food and beverage applications.

Natural cocoa powder has a light brown color and a pH level of 5.1 to 5.4. The processed (alkalized) cocoa powder is darker in color, ranging from brownish red to nearly black, with a pH from 6.8 to 8.1. The alkalization process reduces bitterness and improves solubility, which is important for beverage product applications. All of these pH values are considered safe for food use.1

Cocoa powder should be stored in a cool, dry place to preserve flavor and shelf life. Storage temperatures below 86°F (30°C) are necessary to maintain overall quality. Cocoa powder should be kept away from direct ultraviolet light or natural sunlight at all times and should be stored in tightly sealed bags or bulk bags to avoid contamination from other aromatic material or odors.2

Characteristics and Challenges:

Difficult to handle, cocoa powder cakes and packs easily and tends to fluidize, meaning the fine cocoa powder particles may take on characteristics of a liquid. As a result, cocoa powder has a tendency to form deposits in the conveying line. Cocoa powder is hygroscopic, which makes moisture control a crucial element during handling. Preventing spills is important when handling cocoa powder primarily due to the expense of wasted product and clean-up; a dry vacuuming process is usually the best method for a complete clean up. Experienced handlers of cocoa powder have observed that bulk densities tend to change without notice as shipments may arrive at the processing facility from a multitude of suppliers. Some of these grades of cocoa powder will be free flowing and while others are far less so.

Most grades of cocoa powder have an average bulk density of 35 lb/cu ft.3 Cocoa powder is aeratable, meaning air movement may cause the cocoa powder to take flight and settle as dust, if not properly contained.

Cocoa Powder

If the cocoa powder arrives at the processing facility in bulk bags, the frames used to discharge the bags should ideally be equipped with additional accessories to completely empty the cocoa powder from the bag. This includes features such as spring-loaded frames that will stretch the bags as they empty and lighten, removing any residual accumulations of cocoa powder in the bags. Bag activating devices are usually effective in loosening agglomerations of cocoa powder, promoting a better flow. Some of these bag activating devices also serve as a dust tight seal between the bulk bag and the receiving hopper.

After the bulk bag has been connected to the receiving hopper and the cocoa powder begins to flow, the air inside the hopper is forced out. Unless this displaced air passes through a filter, airborne dust particles can escape into the surrounding atmosphere. A dust collector mounted on the discharger frame will contain the cocoa powder inside the conveyance system. Cocoa powder dust trapped in the filter media can be returned to the receiving hopper by a pneumatic pulse through the filter. This reduces waste and the time necessary to perform the routine cleaning and sanitation typically required in most food processing environments.

If the cocoa powder is being added into the processing stream from smaller bags, a bag-breaking station with a dust hood, filtration devices and a pneumatic pulse cleaner is the recommended solution to support the manual unloading of the material. If empty bag disposal is an issue, a dust-tight bag compacting system may be necessary.

With its poor flow characteristics, cocoa powder will tend to "rat hole" or bridge in hoppers, completely blocking the flow of the material. Because of this, feed hoppers should be designed with proper geometry and may need to incorporate devices such as mechanical agitators, vibrators or air fluidizers to promote flow. A hopper grate above the receiving vessel will help to prevent the introduction of foreign objects and protects the operators from any moving equipment inside the hoppers.

If a flexible screw is being used to convey the cocoa powder, it is important to use a screw that matches the material's characteristics and other application requirements. Generally a screw with a wider, flatter surface than the standard-sized screw is necessary for this type of material.

Should your cocoa powder application feature the loading the material into bulk bags, the bag capacity will be maximized by use of a vibratory densification deck to level the cocoa powder as it fills the bag and by the application of load cells to attain the desired weight. Seals and other dust containment devices will ensure a dust-tight operation.

Flexicon Applications:

Flexicon's automated bulk powder discharge system increased blending speeds by 25% for an Ohio USA chocolate processor.

Flexicon's expert design and engineering staff will weigh each parameter and recommend the best solution for you. Upon request, Flexicon's test lab will simulate your cocoa powder handling applications before the system is installed in your plant.

Flexicon's Dust Suppression and Collection Systems ensure proper containment of cocoa powder throughout the conveyance process. Flexicon's BLOCK-BUSTER® Bulk Bag Conditioner loosens bulk solid materials that have solidified during storage and shipment, enabling bulk bag unloaders to discharge the material through bag spouts. Flexicon's bag compacting stations will allow you dispose of empty bags safely and efficiently.

Flexicon's product line of advanced flow promotion conveyors, high flow hoppers, deaeration/densification decks and a host of other components and accessories are proven performers that promote flow while reducing degradation, dusting and/or the separation of blends comprised of disparate particles.

Related Articles on Cocoa Powder:

1 The Hershey Company
2 The Kissner Group, Cocoa Powder
3 Source: Powder and Bulk. Com - Bulk Density Chart

Sources: Where noted. All other information courtesy of Flexicon Corporation.