Irú is a type of fermented locust beans used as a condiment in cooking. It is similar to ogiri

Ogiri

Ogiri is a flavoring made of fermented oil seeds, such as sesame seeds or egusi seeds. The process and product are similar to iru or douchi. Its smell is like cheese, miso, or stinky tofu.Ogiri is best known in West Africa....

 and douchi

Douchi

Douchi , also called Chinese fermented black beans , is a flavoring most popular in the cuisine of China, and is used to make black bean sauce....

. It is very popular among the Yoruba people

Yoruba people

The Yoruba people are one of the largest ethnic groups in West Africa. The majority of the Yoruba speak the Yoruba language...

 of Nigeria

Nigeria

Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...

. It is used in cooking soup

Soup

Soup is a generally warm food that is made by combining ingredients such as meat and vegetables with stock, juice, water, or another liquid. Hot soups are additionally characterized by boiling solid ingredients in liquids in a pot until the flavors are extracted, forming a broth.Traditionally,...

s like egusi soup and ogbono soup

Ogbono soup

Ogbono soup is a Nigerian dish made with ground ogbono seeds, with considerable local variation. Besides the seeds, water, and oil, it typically contains leaf vegetables, other vegetables, seasonings, and meat. Typical leaf vegetables include bitterleaf and celosia. Typical other vegetables...

.

It can be found fresh or dried. The fresh variety is usually wrapped in moimoi leaves, which are similar in appearance and texture to banana

Banana

Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....

 leaves. It has a pungent smell.

The dried variety is flattened into discs or cakes for sale. Dried iru is weaker in flavor and pungency than fresh (though frying dried iru in cooking oil will restore much of the flavor). The dried variety stores very well in freezers.

In the fermentation, the reducing sugar content increases, and the total free amino acid content decreases initially, however in the end there is a large increase in free amino acid content.