Sigri Coffee

One of the highlights of my recent trip to CLTC was the tour of the
Sigri Coffee processing plant. Sigri coffee is the main PNG coffee
that is imported in to New Zealand, and a significant part of most of
the espresso blends I roast. The coffee is well known for it's
acidity particularly if only roasted to a relatively light roast.
This acidity does not suit my palate on it's own, so as a single
origin bean it is not so good, but in a blend it really adds a lot.

The Sigri processing plant is right next door to CLTC and uncle Ross
has a good relationship going with the manager guy there, so we were
able to go there on Saturday afternoon for a coffee cupping session
and a tour of the plant.

First off the coffee cherries get delivered on the back of pickup
trucks or what ever vehicle the growers may have available. Ideally
the cherries would all be red, however this is not always the case as
the pickers get kind of lazy and throw in a bunch of unripe green
cherries too. This is particularly true at the beginning and end of
the season when there are less ripe cherries around.

The cherries are dumped in to a big bin kind of thing and from there
they go through a machine that squeezes the bean out of the cherry.
At this stage the bean is covered in a slimy mucilage that is kind of
sweet.

In PNG most coffee is wet processed, this means that the mucilage is
removed before the bean is dried. In some other coffee growing
countries the beans are dry processed so the beans are just set out
to dry at this stage. For wet processing the beans are put in big
vats and soaked in water for a day before being moved to the next vat
the next day and yet another vat the next day. The number of vats
varies from place to place, but at Sigri they have 3 vats.

After that they are laid out to dry, this is sometimes done on tables
to let air circulate around the beans a bit more, or other times they
are dried on a concrete pad. After the beans are dried (it takes about 7
days I think) they are called parchment, the bean itself is
covered in a layer of silvery coloured stuff that should be removed
prior to roasting.

There can be a variance in the colour of the bean at this stage, as
some were riper than others when they were picked. Ideally they
should be a uniform colour, they fetch a better price that way. So
what they do is put them in some great big conditioning vats. Air is
pumped down to the bottom of the vat then blows back up through the
beans. They are kept in these vats for something like 25 days and
when they come out they are much more uniform in colour, a nice green/
blue colour.

At this stage the beans are sent through a machine that removes all
the sticks and stones that may have made it in to the beans. I can't
remember exactly how that machine worked but it was kind of cool.

Next up they need to remove the parchment from the beans. There are
2 machines that they use to do this, the first one kind of squeezes
the beans to try and get the bean out of the parchment. The second
machine polishes the beans, not too much, you don't want the beans to
be shiny, just enough to clean them up a bit. After they have gone
through those 2 machines they are looking pretty good and are ready
to be sorted and bagged.

The beans are sorted by size, so there are a series of trays with
different sized holes in them and the beans fall through. To stop
the beans from blocking up the holes there are a bunch of balls that
knock any stuck beans back out of the holes. The largest beans are
called AA, followed by A, B, C, maybe D I forget, possibly even some
other low grades, and peaberry. The peaberry are the most rare, they
account for only about 6% or 7% of the crop and are round in shape.
Most coffee cherries have 2 beans, but occasionally they only have 1,
that is when you get the peaberry beans. Peaberry and AA generally
will fetch the best price, and A and B are also reasonably good. In
New Zealand we usually get A and B grades from Sigri.

Once they are sorted in to their sizes there are 2 different ways of
sorting out the good from the bad beans. The first way is usually
used for the cheaper grades like C and D. The beans are put in to
this machine that blows are up from the bottom. The heavier beans
are the better ones and they fall down as the air is not strong
enough to blow them up. They fall in to a sack on the left of the
machine. The lighter beans bounce of the top and are directed to the
right where another jet of stream at a slightly lesser pressure again
blows the lighter beans up and the heavier beans fall in to another
sack. The beans that are still light enough are directed in to a
third sack that is sold to places like Nescafe for their awful
instant coffee stuff.

The better grades of bean are sorted on a rack that vibrates. The
rack is on a slight angle so the heavier beans gradually move to the
one side and the lighter beans to the other.

Once the beans have been sorted they can either be hand sorted to
remove any beans that are black or beans that are deformed, or for
the better grades they are sorted by the coolest machine that they
had there. This machine detected colour differences and when it saw
a black bean it shot a jet of compressed air at the bean, sending it
in to another sack. The beans that made it through the first pass of
this machine were then processed again at a different speed to get
any remaining ones out. Once again the reject beans were bagged up
and sold to Nescafe. After that the beans are all sorted by hand,
mainly to remove any deformed beans and also to catch any black beans
that may have made it through the last step.

If after hand sorting the beans are not up to scratch then they are
resorted by hand again, what a job.

After our tour we went in to the coffee cupping room and sampled 8
different beans. The first 4 had not been processed yet and still
had the parchment on when they were roasted. They all tasted pretty
similar to me, and none of them were all that memorable. Then we had
samples of AA, A, B and Peaberry that had just been processed. The
AA and peaberry were quite different to the A and B beans, they had
noticeably more acidity in them. I actually preferred the A grade
bean, to me it was a bit better balanced so more pleasant by itself
than the other AA and peaberry. In a blend however I think the AA
and peaberry may have more to contribute.

If you have read this far through this posting then I congratulate
you, a lot of people I am sure have stopped long before they get this
far.