Modern Cocoa Processing

Chocolate now has a healthy market image as there are well documented studies on the health benefits of poliphenols contained in cocoa-derived products, especially chocolates with high cocoa content. The value-chain from cocoa farmers to chocolate manufacturers enjoy the benefits of these trends, as the cocoa processing sector adapts its capabilities continuously to meet changing market demands.

While some cocoa processors produce cocoa products such as cocoa butter, cocoa powder and cocoa liquor, others are making headway into vertical integration: they are processing cocoa for their own chocolate production. Traditional cocoa processors are also expanding their business into industrial chocolate production. Process equipment manufacturers should therefore deliver customized solutions for different applications and capacities.

Challenges in the cocoa industry

As cocoa is a valuable commodity, modern cocoa processing plants should enable capabilities for reproducible product quality and maximum yield. The debacterization process is necessary to ensure high hygienic standards in chocolate and related processing industries. Safety is to be considered in detail due to the thermal processes used in cocoa processing. Innovative solutions are also needed to minimize energy consumption.

The industry has some basic preferred plant concepts when it comes to processing cocoa for different product requirements. When producing produce cocoa powder, it is important to achieve desired hues (cocoa path). Flavor characteristics are crucial when the focus is on mass production of cocoa for chocolate manufacturing (chocolate path). On the cocoa path, a standard system enables the optimal selection of value-determining features of the semi-finished cocoa products – color, flavor and yield. Here, cocoa beans are first ruptured and then roasted. On the chocolate path, standard solutions might present a roasting step before crushing the cocoa beans.

Into the processes
Quality assurance starts with the cleaning of the cocoa beans. This prevents impairment of the downstream processes and thereby contributes considerably to a high production system uptime. The standard cleaning system involves four operations to remove the impurities:

1) Mechanical classifi cation and separation to reject large and small impurities through screens,
2) Aspiration of light particles (dust, shells and fibers) in an aspiration channel,
3) Separation of metal materials by a rotary magnet, and
4) Separation by destoner of heavy materials such as stones, glass and metal parts.

• Cocoa path

On the cocoa path, process steps after cleaning are pretreatment,cocoa bean winnowing, cocoa nibs alkalizing, cocoa nibs roasting and sterilizing, grinding, cocoa liquor storage and block off, cocoa liquor pressing, cocoa butter storage and blocking off, cocoa powder production and bagging off.

A cost effective, successful cocoa production is mainly influenced by the achieved yield of cocoa nibs – the kernels of the cocoa bean. The decisive criterion is the separation of worthless shells from valuable cocoa nibs.

To minimize the fraction of shell in the nibs and the nib fractions in the shell, raw and cleaned cocoa beans are thermally pre-treated. This intensive shell treatment with infra-red radiation causes a “puffing effect” through the quick evaporation of the water between the shell and the bean. This makes it possible to remove the beans from the shells easily and completely in the winnower that follows after. At the same time, the extremely fast heating of the shells prevents the migration of fat from the nibs to the shells and the elastic structure of the hot beans reduces the formation of fines fractions during crushing.

The winnowing process is performed in two recommended crushing steps. This enables the impact crushers with different velocities to be optimally adjusted to avoid the formation of dust. The first is to have a sequence of different sieves that allows the cocoa nibs to be sorted to size. This makes it easier for ascending sifters to separate the shells from the nibs. The oscillating rakes on the screens enable an equal product distribution and, therefore, achieving the highest efficiency of the screen facility.

Next, the alkalizing process provides the basis for producing cocoa powder of excellent quality. The simple adjustment of the pH value and the determination of the pressure-temperature-time process profile enable the color intensity of the finished cocoa powder to be varied from natural hues to deep brown, red or black shades. Generating alkalization reaction typically requires a batch operating system – in a vessel with a gentle mixing spiral – as the process parameters could be optimally adapted to the raw nibs and achieving the required quality.

Roasting comes next. This process is considered the heart of the cocoa process as the quality of cocoa liquor, butter and powder is primarily defined here. More than 500 aroma components in the cocoa are submitted to a thermal reaction that demands a precise process control.

Using a batch type roaster is preferred as it enables the control of a combination of parameters such as time, temperature, as well as having the possibility of adding sugar solutions (thereby allowing the optimal flavor development of different qualities of cocoa during the desiccation and subsequent roasting processes). Steam can be injected for an additional sterilizing effect for a finished product with germ counts of less than 100 per gram.

After the roasting process, the cocoa nibs are discharged from the roasting drum and fed into the cooler. The objective of the subsequent grinding process is to produce cocoa liquor with a low particle size. High shear forces are applied in a two-stage grinding process to ensure an effi cient grinding. The high release of fat results in a cocoa liquor with very low viscosity, which increases the throughput rate of the downstream hydraulic presses.

In the pressing step, the cocoa butter obtained is molded in blocks and the kibbled cake produced goes towards the pulverizing plant. In the pulverizing process, the goal is to produce a glossy cocoa powder with a deep and an attractive color. Optimal coloring of the cocoa powder is only possible if a completely stabilized coco butter rate is guaranteed. This process can only be reached with a precise temperature-time cooling program for the individual particles.

Before the stabilizing process, the kibbled cake is fed into a cocoa powder mill (a classifier mill). The finesse and particle size distribution of the powder could then be adjusted by varying speeds of grinding disk and classifi er wheel. It is important to control the residual oxygen level (by adding nitrogen) in the cocoa powder processes to avoid any risk of fire or explosion.

• Chocolate path

On the chocolate path, the beans go through following steps: cleaning, debacterization, roasting, winnowing and grinding. Debacterization of the cocoa beans effi ciently reduces the germ count without affecting the flavor. The beans are treated in batches in a vertical reactor with a gentle agitator to ensure a reproducible result. The use of superheated steam allows short cycle time. Debacterization could be done either before or after the roasting process depending on the set up. Flavor development of the beans is done selectively by gentle drying and roasting in the roaster.

It is easier to winnow debacterized and roasted cocoa beans as they produce the “puffing effect” between the shell and the nib. After winnowing, the nibs are ground in two stages into a cocoa mass with a narrow particle size distribution.

Due to the high and uniformly distributed energy and density in the bead mill, the finesse of the cocoa liquor could be adapted to the finess of the chocolate mass. This reduces the wearing out of the downstream equipment and fine cocoa liquor could also be added directly in to the conching process while producing high cocoa
content in chocolate.

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