To receive the wrong quality of coffee creates huge
problems for any roaster. If anything this has been reinforced by modern
just-in-time supply chain practices.
Large roasting plants slot incoming containers into
the production line on the basis of the quality, i.e. to be used in blend or
production run number X. The quality is known in the sense that the purchasing
department has previously approved a sample of the coffee and it has been
allocated a purchase or quality code. The plant has received the shipping sample
and has verified its conformity with the purchase code.
It is extremely important to the roaster that the
shipping sample is fully representative of the actual shipment because at the
roasting plant the container is discharged directly into a receiving silo. This
leaves little room for manoeuvre - reversing the operation is both awkward and
time-consuming. Of course someone watches the actual discharge to ensure no
excessive foreign matter or clumps of coffee are present. Clumps suggest water
or condensation damage and a potential risk of mould.
After dumping the coffee passes through a transfer
duct into the electronic weighing silo. During this passage a time switch opens
a valve at regular intervals, permitting a small amount of beans to fall into a
sample receptacle. In this way the entire load is automatically sampled, from
beginning to end. The resulting sample is then thoroughly mixed and checked to
ensure it indeed matches the purchase or quality code. This system is much more
accurate than the old way of using a sampling iron on perhaps 10% of the bags.
After approval and weighing the coffee is then transferred to the final storage
silo pending supply to the roasting process. During this transfer any foreign
matter, dust and chips are removed, again automatically.