Cocoa processing at ADM Cocoa is described in the simplified diagram below. The various production steps and critical control points are then discussed.
On the basis of the analysis of the individual bean lots, an optimal blend is prepared. In this way, fluctuating characteristics can be reduced or evened out before the beans are further processed. An alternate approach is to process specific lots of beans and blend the resulting cocoa liquors.
Cleaning, breaking and winnowing
The actual production process starts with the following three steps: cleaning, breaking, and winnowing. Their objective is to obtain clean, broken, de-shelled kernels (nibs). The beans are sieved, foreign matter is removed and the clean beans are then broken to loosen the shells from the nibs. After the breaking step, the product is sieved into a number of fractions to reach optimal separation during winnowing. These fractions then go to the winnowing cabinets where the “lighter” broken shell is removed by a stream of air. The breaking and winnowing steps separate the essential ingredient of the cocoa bean, the kernel, most often described as the nib, from its shell. Strong magnets remove magnetic foreign matter from the nib. The nib may then be stored, awaiting further processing. The separated shell is often sold to agricultural mulch or fertilizer producers.
Sterilization and alkalization
The microbiologically contaminated nib is sterilized in a batch or a continuous process by wetting and heating with steam. After sterilization, the nib can be roasted directly (natural process) or can be alkalized first (Dutching process). Alkalizing or Dutching consists of treating the cocoa nibs with an alkali solution such as potassium or sodium carbonate. It is practiced primarily to modify the flavor and color of cocoa powder or cocoa liquor.
The roasting process has the objectives of reducing the water content and further developing flavor. Roasting is particularly important to the final flavor because the nib’s flavor is formed from the precursors that developed during fermentation.
The roasted nib is typically ground in a multi-stage process. During grinding, the broken kernels change from a solid to a fluid mass of cocoa particles suspended in cocoa butter. This is due to the high fat content of the bean: About half of the nib is fat. Grinding breaks up the cell structure of the cocoa nibs and releases the cocoa butter.
After the last stage of the grinding process, the mass is passed through sieves and over strong magnets to remove any remaining coarse cocoa or metal particles. This finely ground fluid mass, the cocoa liquor, can either be stored in tanks to await pressing or shipped and used by chocolate manufacturers for further processing into chocolate.
Cocoa butter constitutes about half the weight of the cocoa nib. This fat is partially removed from the cocoa liquor by means of hydraulic presses applying pressures as high as 450 kg/cm2. Depending upon the pressing time and the setting of the press, the resulting cakes may have a fat content of 10 to 24 percent.
After pressing, the cakes are broken into kibbled cake. The pressing operation is microbiologically vulnerable, as this is the only part of the process when the product is not in a closed system and is thus exposed to the surroundings. Hygienic procedures are therefore of particular importance in the pressing department.
Kibbled cake is typically stored by fat content and degree of alkalization and may be blended before pulverization to obtain the desired type of cocoa powder. The cocoa butter is filtered and stored in tanks.
The powder grinding lines pulverize cocoa cake particles into the defined fineness levels. After pulverization, the powder is cooled so that the fat of the cocoa powder crystallizes into its stable form. Next, the free-flowing powder is passed through sieves and over magnets prior to packing in paper bags or in bulk containers.
The cocoa butter from the presses is filtered and stored. Upon request, the butter can be partly or wholly deodorized. Delivery of the various types of cocoa butter can be either in liquid form or in solid form (packed in plastic-lined cardboard boxes).