Crafting The Perfect Coffee

The principles of fresh coffee processing are the same worldwide. Over the years the equipment used to perform this, has improved and will continue to evolve as new technologies are developed.


Robert Harris – How We Roast Our Beans


Green Coffee beans arrive in the warehouse in 60kg Hessian sacks. Upon arrival they are tested to ensure they have not suffered in transit, then stored at a constant humidity and temperature. When required the coffee sacks are cut open and the beans are emptied into a receiving hopper.


Green beans are then stored in silos. Each silo holds only one variety (Origin) of Green Bean from one particular region.


There are 3 main stages of roasting:

1. The Drying Phase

The beans enter the roasting chamber and moisture is taken away from the surface of the beans. The moisture content decreased from 9-13% of the bean’s content to about 6%.

2. The Roasting Phase

At 135°C the bean colour changes from green to yellow/cinnamon. Inside the bean carbon dioxide is forming as the acids start to break down. The colour continues to change to brown as simple sugars are caramelised. Between 165°C and 180°C the bean becomes brittle. Built up carbon dioxide and moisture causes the bean’s structure to rupture - called the first crack.

More browning occurs, more acid breaks down, the bean’s natural sourness is reduced and more carbon dioxide is produced.

Second crack occurs between 195°C and 220°C depending on the type of roaster used. The temperature continues to rise and the colour to darken.

The point at which the roast is terminated determined the final flavour of the cup.

3. The Cooling Phase

This is where the beans temperature is brought back to room temperature or below. The faster this is completed the more the volatile aromas and flavours are preserved.


After cooling, the beans are released into a de-stoner, to remove any larger foreign material. Roasted coffee beans are nearly half the weight of green beans so any heavier material can be separated and removed.


Blending is the process of mixing different origins together to create a blend of coffee. Blending can occur either before roasting (pre-blending) or after roasting (post-blending). Post-Blending allows each origin of coffee to be roasted separately to its optimum flavour, rather than roasting the blend of different origins together to one set of parameters.

Separate roasting is especially useful for beans of vastly different sizes and densities, which can roast very differently.

Pre-Blending is more efficient than post-blending and provides a simpler work flow to roast the exact required quantity.


Once roasted, it's very important that coffee is not subjected to moisture, heat or extremes of temperature. Packaging plays an important role in this. Roasted coffee beans release Carbon Dioxide over several weeks and even months. Most roasters now pack beans into packaging with one-way valves. These valves allow the Carbon Dioxide to escape without letting Oxygen or moisture in.


The two most typical grinders used for commercial grinding are rolling mills or blade grinders.

A rolling mill consists of several groups of cylinders placed on top of each other. The beans are fed between two cylinders with grooves, which turn towards each other. Each set of cylinders grinds the beans more finely until the required grind size is reached.

Grinding using blade grinders is achieved by passing the coffee beans through a series of moving blades.


The grinding process increased the surface area of roast and ground coffee and therefore speeds up the release of carbon dioxide (known as degassing).

Ground coffee can therefore be left to degas for 1-5 days and packed into bags without valves. The degassing timeframe depends on bean blend, packaging format and environmental conditions. Alternatively, the ground coffee can be packed immediately in valve packs.