Minimizing postharvest losses

The final quality of coffee depends a lot on how well the coffee has been picked, processed, dried, packed and stored. In order to minimize contamination until safe storage, it is therefore important to carefully harvest and safely handle the harvested coffee through primary processing activities.

The quality of the final coffee depends on how and when picking is done from the field. Many farmers mix red ripe berries with shrivelled, black, discoloured and defective beans. The unripe berries produce beans that break easily, are of inferior quality, are small in size and are usually eliminated as part of the husks during milling, resulting in qualitative and quantitative postharvest losses. Furthermore, the immature beans give a bitter taste to the coffee.

• When picking coffee, carefully pick only the mature red beans leaving the green ones on the trees to ripen further. Always pick, do not strip.
• Hessian bags, tarpaulin or propylene bags should be spread out below the coffee trees to avoid harvested beans from falling onto the bare ground. This is done to ensure proper collection of all falling beans during harvesting and to minimize contamination from beans falling on the ground. All beans on the ground should be collected and mixed with composting materials. This ensures that any beans infested with pests, like the coffee berry borer, will be destroyed, hence reducing spread of infections.
• Remove all inferior or green beans, leaves, twigs and foreign matter from harvested beans. Pick regularly, every 2 weeks, to get good yields and better quality.

Coffee farmers in Africa lose on average up to 30 % of their harvest due to poor handling during wet and dry processing. This is mainly due to moulding as a result of slow drying or poor ventilation in the storage units of the dried coffee. Such coffee also develops off-flavours, which eventually affect its cupping quality. Most of these losses are avoidable if the farmer makes an extra effort to carefully handle the harvested produce.

It is better to wet process Arabica coffee so that its superior quality can be maintained. Wet processing begins by removing the skin of the berries before drying. A pulping machine is used to remove the skin from harvested berries soon after picking. Pulped coffee beans should then be fermented for about 12 to 48 hours to remove the slippery mucilage before drying.

Wash with clean water the fermented beans and dispose-off the mucilaginous water in a 3-series ditch. Spread the washed coffee beans to a thin thickness and turn frequently to ensure even drying up to 12 % moisture content before sale. The moisture content can be measured using a moisture meter, where available, or by biting it – a dry bean will snap open easily. Mats, tarpaulins, concrete floor or mesh on raised platforms can be used for drying to maintain good quality. Dry coffee in batches following the fermentation procedure and avoid mixing coffee fermented on different days.

Robusta coffee can be dry processed, but the drying process should start immediately after harvesting to avoid moulding. A lot of losses are normally incurred during the drying stage. Most farmers dry their coffee on the ground. This has several implications in terms of postharvest losses:

• A lot of chaff and dirt is collected with the coffee as it is being removed from the ground resulting in qualitative losses.
• In the event that it rains, farmers find it extremely difficult to collect the coffee beans from the ground resulting in quantitative postharvest losses. In addition, beans get wet resulting in moulding and hence qualitative losses.
• Animals and humans walk through the coffee, destroying some of the beans and/or spreading them, leading to quantitative losses.

Avoid drying coffee on the bare ground, instead use mats, tarpaulins, concrete floors or mesh on raised platforms in order to maintain good quality. In case you do not have any materials available, drying coffee on the ground is possible, but it is recommended that a fence or barrier be constructed around the drying area. This will keep children and farm animals from trampling over the drying coffee. Spread the beans to a thin thickness and turn frequently to ensure even drying. Dry the coffee in batches as it is harvested and avoid mixing coffee harvested on different days. Each batch should be dried properly to 13 % moisture content before selling or delivering to the milling centre.

Most farmers store their coffee in the houses in which they sleep. Coffee that is stored with other crops (and at times with animals), is prone to attack from vermin (such as rats) resulting in qualitative and quantitative losses. In-house stored coffee may also acquire unfavourable odours, thus lowering its quality.

• Pack organic coffee in clean sacks made from natural fibres (sisal/jute) that are free from any form of contamination.
• If possible, construct special rooms for storage of coffee or at a collective store well separated from other products. This avoids introducing other aromas into the coffee.
• Ensure that dried coffee does not get wet again to prevent fermentation, which would otherwise spoil the quality of the coffee.
• Place (standing) coffee sacks on pallets or wooden poles, off the wall, in a leakproof store with good ventilation.