Iru

Ingredients

Beans

• 1 kgdried African locust beans (Parkia biglobosa seeds)
• water to cover, plus more for boiling
• 2 tbspwood ash or 1 tsp bicarbonate of soda (to soften the hulls)

Fermenting and storing

• banana or Uapaca leaves, wilted over a flame, to line the basket
• 1clean woven basket or colander
• 30 gfine salt, for the dry-salted keeping version

Directions

1. Sort the seeds, discarding stones and split beans, and rinse well.
2. Boil the seeds hard in plenty of water with the ash or bicarbonate for 8–12 hours, topping up with boiling water, until a seed crushes easily between finger and thumb. In Nigeria this is done overnight over a wood fire.
3. Drain and dehull: rub the hot seeds against a rough basket or between the palms and rinse in several changes of water so the black hulls float off, leaving pale yellow cotyledons.
4. Boil the dehulled cotyledons a second time for 45–60 minutes until fully soft, then drain very thoroughly and spread to steam-dry for 20 minutes. Surface water gives you slime, not iru.
5. Line a basket with wilted leaves, pack the warm beans in a layer 5–8 cm deep, cover with more leaves and wrap the whole basket in cloth or jute.
6. Ferment in a warm dark place at 35–40°C (95–105°F) for 48–72 hours. Do not disturb it for the first 24 hours. The natural Bacillus subtilis on the leaves does the work.
7. Check at 48 hours: the beans should be coated in a sticky, pulling thread, smell sharply of ammonia and mushrooms, and have darkened to olive-black. Ferment 24 hours longer for a stronger iru woro.
8. For fresh iru (iru pete), mash lightly and use within 3 days, refrigerated. For keeping iru, mix through the salt, then sun-dry the beans 2–3 days until hard and store airtight for months.

Technique

• The ammonia smell is correct and is the sign of a healthy Bacillus fermentation, exactly as in Japanese natto. Pink, orange or fuzzy green growth, or a sour vinegar smell, means contamination – discard the batch.
• Temperature control matters more than time. Below 30°C (85°F) the ferment stalls and spoilage organisms take over; a warm airing cupboard, a yoghurt maker on low or a box with a heat mat all work.
• Everything must be scrupulously clean but not sterile: the leaves carry the culture, so use fresh leaves, wilted only to make them pliable.

Substitutions

• Cannot find locust beans? Soya beans fermented the same way give iru woro’s cousin, and Japanese natto is a workable stand-in in stews.
• Wilted banana leaf can be replaced by fig or vine leaves; in a pinch, a bamboo steamer basket lined with muslin ferments well.

Variations

• Iru woro, the whole-bean salted and dried version sold in Lagos markets.
• Iru pete, mashed and soft, dissolved into stews for a smoother savour.
• Ogiri, the Igbo relative made from fermented castor or melon seeds.

History

Parkia biglobosa seeds boiled and fermented by Yoruba and Hausa producers; iru is the seasoning that defines efo riro and ewedu.

Frequently asked questions

What is Iru?

Iru is a fermented & pickled from Nigeria: fermented locust beans, black and sticky, dropped into stews for deep savour. Parkia biglobosa seeds boiled and fermented by Yoruba and Hausa producers; iru is the seasoning that defines efo riro and ewedu.

How long does Iru take to make?

Iru takes 1 hr of preparation and 3 days of cooking. The recipe makes about 400 g (enough for 15–20 pots of soup). It is rated hard to make.

What can I substitute in Iru?

Yes, within limits. Cannot find locust beans? Soya beans fermented the same way give iru woro’s cousin, and Japanese natto is a workable stand-in in stews. Wilted banana leaf can be replaced by fig or vine leaves; in a pinch, a bamboo steamer basket lined with muslin ferments well.

What is the most important thing to get right in Iru?

Line a basket with wilted leaves, pack the warm beans in a layer 5–8 cm deep, cover with more leaves and wrap the whole basket in cloth or jute.