(introduction...)

The following steps are required for the commercialisation of neem products:

· Harvest: hand picking (for best quality) or collecting (sweeping up) fruits and kernels which have been depulped by bats and birds

· Cleaning with water/sand

· De-pulping: by hand or modified coffee depulper

· Drying: controlled exposure to sunlight/drying device

· Disinfection with calcium hypochlorite

· Storage in a dry, shady and well ventilated place, preferably at 20 C

· Extraction:

· alcoholic batch extraction (one-step extraction)

· methods for obtaining an azadirachtin-enriched extract: two-step extraction, supercritical CO₂,

· Formulation: increases stability but emulsifiers often also have synergistic or additive effects (e.g. sesame, soya or castor oil, piperonyl butoxide etc.).

2.2.1 Collection systems

The commercialisation of neem products requires an effective and reliable collection system for neem seeds, which does not exist in most countries. It turns out that reliable collection and preparation of neem kernels of good quality for a reasonable price is one of highest hurdles in setting up neem processing in developing countries. On the one hand, in participatory training communities have to be persuaded to collect neem seeds during the one or two local harvesting seasons and to accept neem as an additional cash crop; on the other hand there has to be a commitment on the part of the entrepreneurs to buy a certain amount of the collected seeds frequently, even if they cannot process them all due to marketing problems. Moreover, the kernels may be of inferior quality in the early stages or due to extraordinary weather conditions, e.g. contaminated with fungi (Aspergillus spp.). The entrepreneurs, however, should keep the collectors motivated by continuing to buy at least some of the seeds. It is helpful to intensify the training and pay a premium for better quality.

2.2.2 Harvesting methods

There exist two ways to obtain neem seeds:

· birds and/or bats feed on the pulp of the ripe neem fruits and drop the seeds underneath or near the trees (which happens in some places in Asia and Africa);

or

· the fruits are picked from the tree (in areas where the neem tree has been introduced only recently such as central and south America). The seeds are then collected from the ground.

In the former case the seeds can be collected (swept up) more cheaply but further cleaning from debris is still required, as is depulping sometimes.

There are different harvesting techniques applied in other regions; the best one was developed in Nicaragua.

Pruning takes place during harvesting time, so a good proportion of the seeds can be picked directly from the chopped branches on the ground. Leupolz (1995) found that the average harvesting capacity is 30 kg fruits during 6 working hours (5 kg fruits/h).

During picking of the neem fruits the workers do not differentiate between ripe and unripe fruits for reasons of efficiency. Unripe fruits are stored in the shade at the processing site.

The average harvest in neem plantations is approx. 5 kg fruits/tree.

2.2.3 Processing technology seeds

Neem fruits can be processed in two different ways:

a) Wet processing on a small scale:

The fruit is depulped by hand, by rubbing and squeezing the pulp in water using sieves or hand-driven modified coffee depulpers. Modified coffee depulpers, however, have turned out to cause too much loss (damaged kernels and subsequent fungal infection).

The unripe fruits can be depulped after being stored for 4 - 5 days in the shade. After depulping, the seeds have to be washed in water, dried for 4 - 5 hours in the sun and then moved to the shade, if the sun is strong enough to risk lowering the azadirachtin content of the kernels. The time required for drying depends on the climatic conditions. The seeds should have a moisture content of less than 7%. A higher moisture content will lead to fungal contamination and subsequently to a reduced azadirachtin content.

b) Wet processing in a depulping plant:

Here the fruits are delivered to a processing plant. The process is more or less the same as on a small scale. The fruits are sorted into ripe and unripe ones. The ripe ones are depulped in depulping rollers (cylinders) with a capacity of 300-500 fruits/hour.

The depulped seeds will be either washed manually or by mill electric washing machines to be eventually dried on drying sieves.

Usually the limiting factor for wet processing units is the lack of sites covered by a roof for ripening the unripe fruits and for drying the seeds. A problem encountered by both small-scale and semi-industrial processing is the lack of adequate drying units for the seeds, to avoid fungal contamination and reduce the moisture content.

In arid areas without water the seeds are cleaned by rubbing them in sand.

For storage, the seeds should be disinfected by some means, e.g. calcium hypochlorite, and dried in the sun or by heating devices to achieve a moisture content lower than 7%. The seeds should be stored in a shady and airy place. This is one of the main problems, especially on village level, due the lack of space in the huts of the poor collectors.

There has been good experience with entrepreneurs sponsoring drying and storing facilities to gain better quality seeds and build a close relationship between the collectors and themselves. This includes receiving credit to process the inferior quality seeds into neem oil for the village.