Iru, Dawadawa: The Alkaline Fermented Locust Bean Condiment of West Africa

Iru, also widely known as dawadawa or sumbala, is a traditional fermented food condiment made from the seeds of the African locust bean tree (Parkia biglobosa). Originating in West Africa, it is a pungent, alkaline fermented product with a powerful umami flavor that acts as a natural seasoning. Unlike lactic acid fermented foods like yogurt or kanji, iru undergoes an alkaline fermentation dominated by Bacillus species, which break down proteins into amino acids and ammonia, resulting in a significant rise in pH. It is used as a flavor base for soups, stews, and sauces across the region, often compared to miso or a very potent bouillon cube.

Cultural Roots, Local Names, and Regional Variations

Cultural Origins

The use of fermented locust beans dates back centuries in West African foodways. The Parkia biglobosa tree grows in a belt from the Atlantic coast of Senegal through to Sudan and Uganda. Traditional knowledge of fermenting the seeds into a shelf stable condiment spread across ethnic groups, each developing distinct handling techniques. The condiment plays a role in major rituals including births, marriages, and funerals, underscoring its cultural significance beyond mere sustenance .

Local Names Across West Africa

· Nigeria (Yoruba): Iru, classified into Iru Woro (used for stews) and Iru Pete (used for ewedu and egusi soup)

· Nigeria (Hausa): Dawadawa or Daddawa

· Nigeria (Igbo): Ogiri (note: this can also refer to fermented sesame or castor oil seed products)

· Burkina Faso, Niger, Mali: Sumbala or Soumbala

· Ghana: Dawadawa or Kpalgu

· Benin: Netetou or Afitin

· Senegal: Doso mari or Tijon

The versatility of the locust bean tree is notable: the bark is used for tanning, leaves are used in soups or as wraps for steamed puddings like moimoi, and the fruit pulp is eaten raw or made into a sweet drink. Roasted seeds are also used as a coffee substitute known as Sudan coffee .

Microbiology and Probiotic Profile

Dominant Microbial Communities

Iru undergoes a solid state alkaline fermentation. The defining characteristic is the hydrolysis of proteins into amino acids and ammonia by Bacillus species, which drives the pH from near neutral to an alkaline range of 7.0 to 8.2 . A 2025 study on dawadawa from Ghana identified the following predominant genera using 16S rRNA sequencing :

Dominant Genera Identified

Bacillus

The most abundant genus, with Bacillus subtilis being the single most prevalent species

Staphylococcus

Present as a subdominant genus

Streptococcus

Present as a subdominant genus

Lactobacillus

Present as a subdominant genus, primarily in the latter stages

Specific Bacillus species consistently isolated across multiple studies include :

· Bacillus subtilis (the dominant fermenting organism)

· Bacillus licheniformis (contributes to proteolysis)

· Bacillus pumilus

· Bacillus amyloliquefaciens

· Bacillus cereus (detected in some studies, raising safety considerations)

Total Bacterial Counts

During the 72 hour fermentation period for soy daddawa (a similar product using soybean instead of locust bean), bacterial counts increased dramatically from an initial 3.9 log CFU per gram to a peak of 10.61 log CFU per gram, equivalent to approximately 40 billion colony forming units per gram . This places iru among the highest known microbial density fermented foods.

Peak Probiotic Diversity and Count Stage

The peak of probiotic diversity and microbial count occurs at the end of the active fermentation period, approximately 48 to 72 hours after initiation, just before the drying stage. At this point:

· The pH reaches its maximum alkaline level between 8.0 and 8.2

· Bacillus populations are at their highest concentration, exceeding 10¹⁰ CFU per gram

· The full consortium of proteolytic Bacillus species is established

· The condiment has developed its characteristic pungent aroma and sticky texture

Traditional producers recognize this stage by the strong ammonia like smell and the softening of the seeds. After this point, the product is typically sun dried, which reduces viable counts but extends shelf life. Domestic dawadawa has been shown to exhibit higher microbial diversity compared to commercially produced samples, with greater amplicon sequence variant richness .

Gut Microbiome Modulation

Recent metagenomic research in a 2025 mouse model demonstrated that dietary supplementation with Parkia biglobosa (iru) significantly alters gut bacterial community structure. The study revealed a unique microbial shift: Iru increased Firmicutes to 75.00 percent and decreased Bacteroidota to 15.00 percent compared to control groups. Notably, it increased specific phyla including Campilobacterota (23.36 percent) and Desulfobacterota (23.85 percent), which differs from the typical pattern of conventional fermented foods that mainly favor Firmicutes and Bacteroidota. Histopathological analysis showed no significant adverse effects in key organs, suggesting this novel microbiome modulation may be associated with increased short chain fatty acid production and improved gut barrier function .

Preparation Guidelines

Raw Materials

African locust bean seeds (Parkia biglobosa or Parkia filicoidea)

Quantity: 500 grams, dried seeds

Water

Sufficient for boiling and washing

Wood ash or potash (traditional method)

Used to aid in dehulling and soften seeds

Salt (modern variation)

Sometimes added after fermentation

Traditional Preparation Process

Step 1: Seed cleaning and sorting

Remove stones, debris, and damaged seeds. Wash thoroughly with clean water.

Step 2: Boiling

Boil the seeds for 12 to 24 hours depending on seed hardness. Traditional preparation uses wood ash or potash in the boiling water to soften the tough seed coats. The seeds are boiled until they become soft and the seed coats begin to loosen.

Step 3: Dehulling

Drain the boiled seeds. Rub between hands or pound lightly to remove the dark brown seed coats. Winnow or wash away the hulls. The remaining cotyledons (the split seeds) are light yellow to cream in color.

Step 4: Second boiling (optional)

Some producers boil the dehulled seeds again briefly to further soften them before fermentation.

Step 5: Fermentation

Drain the cooked cotyledons thoroughly. Wrap them in leaves (banana or Ficus leaves) or place them in a covered basket or calabash lined with cloth. Leave the wrapped package in a warm location. Ferment for 48 to 72 hours. Optimal fermentation temperature is between 30 and 40 degrees Celsius.

Step 6: Checking doneness

Properly fermented iru develops a strong, pungent, ammonia like aroma. The seeds become soft, sticky, and darken to a deep brown or black color. The pH rises to approximately 8.0. A slimy texture indicates successful Bacillus fermentation. The product should have a savory, umami taste.

Step 7: Processing and storage

The fermented seeds can be used fresh (as a paste) or sun dried for longer preservation. Sun drying reduces the moisture content and concentrates the flavor. Dried iru can be stored for several months in airtight containers. Some producers grind the dried seeds into a powder for convenient use as a seasoning.

Medicinal and Nutraceutical Benefits

Iru is recognized as a functional food with multiple health properties derived from both its microbial content and the phytochemicals of the locust bean.

Nutritional Composition

Proximate analysis of dawadawa from Ghana reveals significant nutritional density:

· Protein: 36.12 to 50.00 percent

· Fat: 17.45 to 27.70 percent

· Fiber: 6.39 to 7.32 percent

· Iron: 79.60 to 135.00 mg per kg

· Zinc: 37.75 to 91.77 mg per kg

· Calcium: 0.73 to 1.61 percent

The Sunyani region samples exhibited the highest protein content among locations tested .

Probiotic Attributes of Bacillus Strains

Bacillus strains isolated from daddawa have been evaluated for probiotic attributes. As spore forming bacteria, Bacillus species possess inherent stability and can survive harsh gastrointestinal conditions, including stomach acid and bile salts. This makes them particularly suitable for use as probiotic supplements compared to more fragile lactic acid bacteria . The functional bacterial groups present in dawadawa correlate with enhanced protein and mineral bioavailability .

Bioactive Properties

Traditional medicinal applications include treatment of malaria, diabetes mellitus, infections, and inflammatory diseases . The plant based secondary metabolites contribute to several validated biological activities:

· Anti inflammatory effects

· Antibacterial activity

· Antidiabetic properties

· Diuretic effects

Gut Health Benefits

The consumption of iru has been associated with modulation of the gut microbiome toward increased short chain fatty acid (SCFA) production, particularly butyrate. The increase in Lachnospiraceae (48 percent in Iru fed mice in one study) is significant because this family is known for producing butyrate, a short chain fatty acid that strengthens the gut barrier and reduces inflammation. Unlike many fermented foods that simply add live microbes, iru appears to restructure the existing gut ecosystem .

Bioactive Metabolites

The fermentation process generates a range of bioactive compounds:

· Free amino acids from protein hydrolysis, increasing bioavailability

· Ammonia (responsible for the pungent aroma and pH rise)

· Peptides with potential antimicrobial and antihypertensive activities

· Short chain fatty acids including acetate, propionate, and butyrate

· Polyphenols (approximately 4.3 percent content) that selectively promote beneficial bacteria

Safety Considerations

Microbiological Safety

The detection of Bacillus cereus in some traditional iru samples raises a safety concern, as this species can produce enterotoxins and emetic toxins . Traditional producers have long preferred specific fermentation practices, and modern research suggests that starter culture technology could enhance safety while maintaining desirable organoleptic properties. Studies have emphasized the need for starter culture utilization to ensure consistent and safe production .

Alkaline Fermentation Safety

Unlike acidic ferments (pH below 4.5) which inherently inhibit pathogen growth, alkaline ferments operate at pH levels permissive to some undesirable microorganisms. However, the dominance of Bacillus species and their production of antimicrobial compounds creates a competitive exclusion effect. Traditional knowledge of proper fermentation time and temperature is critical for safety.

Histamine Content

As a protein rich fermented product, iru contains biogenic amines including histamine. Individuals with histamine intolerance, mast cell disorders, or severe small intestinal bacterial overgrowth (SIBO) should introduce it very gradually, starting with very small amounts (less than 1 gram).

Usage Note

Iru has an extremely pungent aroma that some describe as reminiscent of strong cheese or even body odor. First time users should hold their nose while adding it to dishes. A small amount, approximately one teaspoon per pot of soup, goes a long way. The flavor mellows significantly during cooking, leaving a deep umami richness without the raw pungency. Purchase iru from reputable sources preferably from communities with generations of production experience to ensure authentic fermentation practices .

Enjoy iru as a seasoning base for egusi soup, ewedu soup, okro soup, or ogbono soup. It can also be added to stewed beans, rice dishes, or used as a flavor enhancer for plant based meals. The dried powdered form can be sprinkled directly into dishes like a spice.