An introduction to small scale nib roasting with the Micronizer

There are 5 main problems that can occur when removing and separating the shells from raw cocoa beans:
– Pulp residue, insect fragments and foreign material
– Microbiological contamination of the nibs
– Loss of cocoa butter by diffusion into the shells
– Loss of nibs during breaking and winnowing
– Residual shell particles in nibs

The Micronizer can remove or largely overcome these issues in a single, uncomplicated operation and to avoid the majority of hand sorting which can be very time consuming.

Sort

Sort the raw beans to remove:

Foreign objects such as stones, sticks, burlap, or other items that may have stowed away
Spoiled beans: Discard any beans that are defective or spoiled
Other debris: Remove any broken, flat, or germinated beans

Micronize, Crack & Winnow

Shell removal can be improved by the application of infrared radiation. This rapidly raises the surface temperature of the beans. The cocoa beans are subjected for an interval of 60 – 120 seconds to a mixture of infrared radiation and direct heat. As a result, the organic materials and foreign bodies sticking to the shells are either cremated to dust or cremated onto the surface.

Beans are continuously turned in order to ensure even and equal heat treatment. The shells are quickly heated up, dry out, expand and thereby detach themselves from the nibs. Partial cracking of the shells can also take place at this stage. Additionally, the indirect heating of the nibs by infra-red radiation causes a rise in their natural steam pressure which further aids removal of the shells.

Crack and winnow the beans while they are still warm. Less waste will also occur and the quality of the nibs improves and breaking becomes more efficient. The separation of nibs from shells comes close to a theoretical optimum!

Micronizing means less nib in the shell residue, less shell in the nibs and a significant reduction in cocoa butter migration into the shells duing a conventional roasting stage.

Cool

After the pre roast & separation, let the nibs rest and cool down.

Roast

The roasting process has two phases. A preliminary drying and cooling phase which reduces moisture content followed by a rapid rise in heat

Phase one: Nibs are carefully dried at a temperature below 100 degrees c until the moisture content is reduced
Phase two: Nibs are rapidly heated to the exact roasting temperature required and kept at this temperature until the desired degree of roasting has been achieved as well as maximum aroma development.

Roasting nibs gives a better controllability of the roast as the nibs are smaller and more evenly sized giving a more consistent roast.

Cool Again

After the roasting process is complete, let the nibs rest and cool,

Conclusion

Increase in Nib Yield
The combination of radiation and heat treatment during Micronizing makes it possible to reduce the loss of nib material to below 1%.

The high level of moisture in the nib keeps it elastic and flexible – this makes the nibs less brittle and break only into a few nibs of larger size. The proportion of fines on the other hand is reduced by up to 40%.

Small nibs and fines usually remain attached to the shells and go to waste – a reduction in the amount of fines on therefore automatically leads to a rise in nib yield. This can help keep the amount of dust produced during breaking to a minimum.

Lower Shell Residue in the Nib Material
Micronizing reduces the amount of shell residue below 1%. This reduction diminishes the health hazard accordingly.

The intensive heat to which the beans are subjected for 60 – 120 seconds while passing under the radiators incinerates any organic foreign matter attached, or burns it into the shell surface. In the latter case it can be removed with the shell.

A second advantage of shell residue reductions the removal of detrimental influences exerted by shell particles on taste and aroma.

The average nib size is increased and the total surface is greatly reduced as compared to nib material produced by conventional methods.

For micro-organisms there is much less chance of them being transferred to nib surface provided of course that the contact period is no longer than usual. The combined heat and radiation effects of micronizing destroy about 50% of all micro-organisms on the shell itself, so that the danger of microbe transfer is even further limited. The importance of micronizing in limiting micro-biological contamination is therefore considerable.

Reduced Micro-biological Contamination of the Nib Material
The average nib size is increased and the total surface is greatly reduced as compared to nib material produced by conventional methods.

For micro-organisms there is much less chance of them being transferred to the nib surface provided of course that the contact period is no longer than usual. The combined heat and radiation effects of micronizing destroy about 50% of all micro-organisms on the shell itself, so that the danger of microbe transfer is even further limited. The importance of micronizing in limiting micro-biological contamination is therefore considerable.

Reduction of Fat Loss due to Migration into Shells
Micronization causes only a negligible loss of fat through migration – therefore micronizing has no detrimental effects on the quality of the fat.

Removal of Volatiles from the Nibs and Roasting in a Moist Atmosphere
The natural moisture is the ideal medium for the removal of the steam volatile substances which are detrimental to the aroma. This is known as ‘natural convection’.

The heating causes the nibs to sweat and water from the nib centre migrates to the surface where it evaporates slowly at a low temperature. A humid atmosphere develops from the natural moisture content of the nibs and the relative humidity of the air in the drum is close to 1.

Roasting in a moist atmosphere allows temperatures and moisture distribution in the nib to remain uniform throughout it.

Temperatures according to cocoa-type can range between 104 degrees c and 130 degrees c. A reduction of amino-acids takes place in the course of non-enzymatic browning reactions (Maillard Reaction – a chemical reaction between amino acids and reducing sugars)