Sumatra is one of the ‘old-school’ coffee growing regions. The two main shipping ports that exported coffee to the world were Moka, in Yemen and Java, in Indonesia. Moka Java is actually a term used for blended coffees from Indonesia and Africa. Sumatra is a very poor part of Indonesia, which means that there has been very little experimentation with processing techniques. There has been lots of interest in the Indonesian coffee from the specialty sector as there is great potential to improve quality and traceability. Often very simple changes can be implemented to see a dramatic change in quality.
The wet-hulled method of processing and the in-bag fermentation are unique methods to Indonesia. These are widely controversial forms of processing. The coffee is milled, removing the fruit layer of the coffee. This leaves coffee which still has its mucilage (sticky flesh) and its parchment layer (husk or shell) attached. The sticky ‘parchment coffee’ is then stored in bags to allow the decomposition of the mucilage. This coffee is then raked across patios to dry. Usually, coffee is dried completely (10-12% moisture content) in its parchment layer, but with the wet-hulled process, it is dried to approximately 30% moisture. The coffee is then hulled (removal of parchment layer). Because the coffee is still wet and soft, the huller often shapes the beans into a crescent shape. There is much debate about whether this changes the flavour attributes of the coffee or not. It certainly changes the way it has to be roasted.
Some producers who are working closely with coffee buyers have done some small experimental lots. Due to Sumatra’s high humidity, the producers are scared that if the coffee sits in parchment for too long, it may go mouldy, thats why they hull it really early, at 30% moisture. Some trials have been done with allowing the parchment coffee to dry to 20% instead of 30%. The results were good as the beans weren’t being deformed by the huller. Honey process is also occurring on a small scale, which removes the need for bag fermentation as the parchment coffee is laid out to dry immediately after milling.
Sumatran coffee often gets a bad wrap due to the commonly found blended coffee that is exported under the brand of ‘Mandheling - Grade 1’. The best coffees we’ve had out of Sumatra have been meticulously hand sorted to remove any foreign material or defective beans from the rest. The coffee we buy is ‘Triple Picked’, which means that it has gone through a process of hand sorting three times.
Traceability is almost non-existent with Sumatran coffee. Very few Estates exist in Sumatra. The reality of their industry is that the majority of the coffee comes from extremely small scale farmers, some of which have only a few coffee trees in their front or back yard. These small-holder farmers sell their coffee to local buyers. The government has made it illegal to sell coffee cherries, as there has been a lot of theft as coffee often grows alongside the road, where it is easily picked straight off the tree. Due to this law, small-holder farmers have been forced to buy small processing machines so that they can sell their coffee.