Coffee Production and Trade

Physical properties of coffee

All food products possess numerous characteristics related to their state, aspect or appearance such as weight, volume, size, shape, colour, solubility, moisture content and texture. From the tree to the cup, the various physical characteristics of coffee in its different forms play an important part in the way it is handled, and in the design of equipment used to process and prepare it.

For example:

• Coffee cherries are harvested when their red colour indicates that the appropriate maturity has been reached. Colour is also a guide to the degree of roast of the beans;
• Floatation or winnowing is used to physically separate defective cherries on the basis of density, and to remove foreign material such as twigs and stones;
• Size, shape and colour are used to grade beans after they have been dried to the correct, even, moisture content suitable for storage.

As coffee is a natural product it is variable, but some typical physical properties of coffee are given in the table below:

Bulk density	(kg/m3)
Red cherry	800
Wet green beans	800
Dry beans / pergamino	400
Light roast beans	368
Dark roast beans	288
Coarse ground coffee	304
Fine ground coffee	400

Weight yields

Wet processed coffee:
250kg fresh cherry = 102kg wet parchment = 54kg dry parchment = 45kg dry polished coffee

Dry processed coffee:
250kg fresh cherry = 91kg dry cherry = 45kg dry polished coffee

Roasting causes on average a 16% loss in weight and a 50-80% increase in bean volume.

Moisture content (m.c.)

Fresh cherry:	≈ 50%
Green bean:	8-13%
Roast coffee:	< 7% (depending on humidity)
Soluble powder:	< 4%