To enhance the organoleptic properties and nutritional qualities of the locust beans, the seeds are normally processed. Organoleptic properties are the aspects of food, water or other substances that people experience through their senses such as smell, taste, touch and sight. It is worthy to note that its organoleptic properties are enhanced through the fermentation process. Fermentation is the chemical conversion of organic substrate into simpler compounds through the action of enzymes produced by microorganisms such as bacteria, yeasts or moulds. This process helps to augment the taste, micronutrients, minerals and protein constituents of the locust bean seeds.
Processing the African locust bean pods into the final product involves the following steps;
1. The pods are first collected after which they undergo depodding to extract the seeds from the yellowish pulp.
2. The seeds are then collected and selected before cooking for 1 to 2 days to remove the seed coats. While cooking, wood ash can be added to the iru seeds to fasten the boiling process of the cotyledons.
3. The boiled iru seeds are then dehulled, washed and rinsed in clean water.
4. Afterwards, the seeds are cooked further for another 2-3 hours to soften the cotyledons and kuru is normally added at this stage.
5. The seeds are drained with a local sieve and then spread in a fermenting perforated calabash known as nkata or ajere.
6. The seeds are allowed to ferment for 2 to 5 days at room temperature in other to give the desired result.
7. Once the locust beans are fermented, two types of the final product (iru, dawadawa) can be obtained.
The fermented iru can be mashed and moulded into shapes or can be let loose as seeds. It can turn out to be harder (iru woro) or softer (iru pete), but any of these types of iru can be used for seasoning assorted food dishes such as soup and stews. N:B – To accelerate the fermentation process of the seeds, Gmelina arborea (gamhar) or banana leaves are normally used.