Effects of Different Fermentation Periods on the Nutritional and Anti-Nutritional Properties of “Tuwo” Produced from Maize and Bambara Groundnut

Effects of Different Fermentation Periods on the Nutritional and Anti-Nutritional Properties of “Tuwo” Produced from Maize and Bambara Groundnut

Daramola, A. S¹, Dr, Adebayo, T. K², Abdulraheem, I. A³, Ibrahim, M.C⁴

Federal polytechnic Offa, Kwara state, Nigeria 

DOI: https://dx.doi.org/10.47772/IJRISS.2025.90500079

Received: 08 April 2025; Revised: 22 April 2025; Accepted: 25 April 2025; Published: 30 May 2025

ABSTRACT

This study aimed to evaluate the effects of fermentation period on nutritional and anti-nutritional properties of tuwo made from maize and bambara groundnut. The bambara groundnuts were subjected to fermentation at 24 h, 48 h and 72 h prior to pulverizing into flour. Maize flour was composited with the fermented bambara groundnut flour and coded as sample A (100% maize flour), sample B (90% maize flour + 10% fermented bambara groundnut at 24 h), sample C (90% maize flour + 10% fermented bambara groundnut at 48 h) and sample D (90% maize flour + 10% fermented bambara groundnut at 72 h). The tuwo samples were subjected to proximate,  anti-nutritional and sensory analysis using standard analytical methods. The sensory properties of the tuwo samples were assessed using standard 9-point hedonic scale with 9 representing like extremely and 1 representing dislike extremely. The proximate composition of the dumpling samples showed that moisture varied from 48.00 to 55.10%, ash from 0.47 to 1.95%, crude fibre from 4.11 to 6.44%, crude lipid from 1.06 to 3.39%, crude protein from 0.37 to 0.90%, carbohydrate from 88.83 to 93.08% and dry matter from 44.90 to 52.01%. The antinutritional properties result showed that phytate varied from 9.70 to 13.16 mg/100 g, oxalate from 53.13 to 92.50 mg/100 g, tannin from 0.000212 to 0.000274 mg/100 g. The sensory properties of the tuwo samples showed that tuwo from sample A was the most preferred by the sensory assessors; however, other tuwo samples supplemented with bambara groundnut samples had comparable sensory ratings. The tuwo samples were of high moisture contents. Supplementation of fermented bambara groundnut flour at 24 h, 48 h and 72 h improved the total ash, crude fibre, crude lipid and crude protein. However, reduction in carbohydrate and dry matter were observed. Antinutritional properties of the tuwo samples including phytate, oxalate and tannin reduced at varying periods (24 h, 48 h and 72 h) of fermented bambara groundnut flour inclusion.

INTRODUCTION

Maize-based dumplings, commonly referred to as “tuwo” in Nigeria, are staple foods consumed across various regions. However, their nutritional value is limited due to their high carbohydrate and low protein content. This dietary imbalance contributes to widespread protein-energy malnutrition (PEM) in many parts of sub-Saharan Africa. To improve the nutritional profile of maize-based products, supplementation with protein-rich legumes such as Bambara groundnut has been proposed (Elham et al., 2019).

Bambara groundnut (Vigna subterranea) is a nutrient-dense legume known for its high protein, lipid, and mineral content. Despite its rich nutritional properties, Bambara groundnut remains underutilized due to factors such as hard-to-cook characteristics and the presence of antinutritional factors like phytate, tannins, and oxalate. Fermentation is a widely recognized processing method that enhances food quality by increasing protein bioavailability, reducing antinutritional compounds, and improving sensory attributes (Olanipekun et al., 2018).

The objective of this study was to evaluate the effects of different fermentation periods on the proximate, nutritional and sensory characteristics of maize-Bambara groundnut composite tuwo. The study aims to establish the optimal fermentation duration that enhances both the nutritional value and acceptability of these dumplings.

MATERIALS AND METHODS

Materials

Maize grains were purchased from Owode Market in Offa Local Government area of Kwara state while bambara groundnut were procured from a local market in Zaria, Kaduna State. Equipment required for the successful conduct of this study was made available for usage by the Food Processing Laboratory of Food Technology Department in Federal Polytechnic Offa, Kwara State.

Methods

Preparation of maize flour

Maize flour was prepared according to the method described by Ezekiel (2022), with modification. The maize grains were sorted to remove stones, damaged kernels and other extraneous materials. The sorted maize grains were then washed in clean water, drained, oven dried at 70 ^oC for 2 h. The dried grains were decorticated on a Grantex decorticating machine to aid the removal of the maize bran and the germ to obtain the grits. Thereafter, the decorticated maize grit was milled using a disc attrition mill (PUC, Germany) to obtain the flour followed by sieving using a sieve with 300-μm aperture and then kept in airtight polythene bags until needed.

Figure 1: Flow chart for the preparation of maize flour

Source: Ezekiel  (2022) (modified

Fermented bambara groundnut flour preparation

Bambara groundnut flour was prepared as described by Ola and Opaleye (2019), with modification. Known weight of bambara nut were cleaned and washed with tap water. It was steeped in water for 24 h and dehulled. The steeped beans were boiled at 100 ^oC in the steeped water for 15 mins, drained and spread out to dry a little at room temperature. Known weight of dehulled bambara nut were poured into the perforated polythene bag, tightly sealed and incubated at 32 ºC for periods of 24 h, 48 h and 72 h respectively. At regular intervals of 12 h, samples were taken out for appropriate analysis. At the end of each fermentation period, samples were washed, drained and oven dried at 55ºC for 24 h, cooled, milled using hammer mill and then sieved with 180 µm sieves to fine particles. The flour was packed in a polythene bags, sealed and kept in a deep freezer until required for analyses.

Figure 2: Flow chart for the preparation of bambara groundnut flour

Source: Ola and Opaleye (2019) (modified)

Production of tuwo

Tuwo was produced from maize-fermented bambara groundnut flour as described by Arise et al. (2022), with modification. The overall ratio of flour to water was 1:3 (w/v). Cold slurry of the flour was first prepared by mixing 40 % of the desired quantity of flour (500 g) with 60 % of the desired quantity of water (3 L). This was followed by bringing it into boiling and the cold slurry initially prepared was added to this boiling water coupled with vigorous stirring, using a wooden flat spoon to form a pap-like consistency. The remaining quantity of the flour (60 % of the desired total) was then added gradually to the boiling pap-like paste with continuous stirring so as to facilitate non-formation of lumps and to ensure a homogenous gel formation. The remaining quantity of water (40 % of the desired total) was finally added to the formed gel and stirred vigorously to ensure smoothness of the gel desired. The final product so obtained is called “tuwo”

Figure 3: Flow chart for the production of tuwo

Source: Arise et al. (2022) (modified)

Table 1: Formulation of blends for production of tuwo from maize-fermented bambara groundnut flour blends

Where

Sample A = control

Source: Ajayi et al. (2019) (modified)

Analytical Methods

• Proximate Composition: Moisture, crude protein, crude lipid, crude fiber, ash, and carbohydrate content were determined using standard AOAC (2019) methods.
• Antinutritional Factors: Phytate, oxalate, tannins, and saponins were analyzed to determine their reduction during fermentation.
• Sensory Evaluation: A 9-point hedonic scale was used, with 1 representing “dislike extremely” and 9 representing “like extremely.”

RESULTS AND DISCUSSION

Proximate composition of tuwo samples from maize and fermented bambara groundnut flour blends

Table 2: Proximate composition of tuwo samples from maize and fermented bambara groundnut flour blends

Values are mean ± standard deviation of duplicate determinations. Data with different superscripts along the same row are significantly different at p < 0.05

Key

Sample A = 100% maize flour

Sample B = 90% maize flour + 10% fermented bambara groundnut at 24 h

Sample C = 90% maize flour + 10% fermented bambara groundnut at 48 h

Sample D = 90% maize flour + 10% fermented bambara groundnut at 72 h

Moisture content of food is indicative of dry matter of foods and has impact on shelf-life and nutritive value; thus, the lower the moisture content, the longer the shelf-life (Onimawo and Akubor, 2012). The moisture contents of the tuwo samples varied significantly (p < .05) from 48.00 to 55.10% with tuwo from sample D (90% maize flour + 10% fermented bambara groundnut at 72 h) having the highest moisture content (55.10%) while the least moisture content (48.00%) was observed in tuwo from sample A (100% maize flour). Varying in fermentation periods may have significantly (p < .05) increased the moisture contents of the dumpling samples. The moisture contents of the tuwo samples are higher than the acceptable level 10 – 14% for moisture contents of foods which assures long shelf stability (Okechukwu-Ezike and Oly-Alawuba, 2019; Chinma et al., 2012); high moisture creates an ideal environment for microorganisms. Also moisture can activate enzymes causing food degradation hence, a pointer to high microbial proliferation in the dumpling samples which could further lead to spoilage. The findings of the current study are lower than 76.22 – 78.72% reported for moisture contents of amala from yam flour fortified with moringa leaf powder studied by Ramota et al. (2013), 70.92 – 73.26% for moisture contents of amala from yam-distiller’s spent grain blends Awoyale et al. (2010) and 76.87 – 79.01% for moisture contents of plantain-soy amala researched by Adekunle and Mayowa (2018).

The ash contents of the dumpling samples varied from 0.47 to 1.95% with dumpling from sample C (90% maize flour + 10% fermented bambara groundnut at 48 h) significantly (p < .05) having the highest ash content (1.95%) while the lowest ash content (0.47%) was observed in dumpling from sample D (90% maize flour + 10% fermented bambara groundnut at 72 h). No significant difference (p > .05) was observed between the ash contents of the dumpling from sample A (100% maize flour) and B (90% maize flour + 10% fermented bambara groundnut at 24 h) while other dumpling samples varied significantly (p < .05). Ash content is an indication of minerals in foods; hence, sample C could contain more minerals than other dumpling samples. The highest ash contents in sample C could be attributed to loss of organic matter and accumulation of inorganic matter caused by the activities of enzymes and microorganism during fermentation (Terefe et al., 2021; Uvere et al., 2010). Similar findings have been reported for fermented maize flour by Terefe et al. (2021). The results obtained in the current study are slightly in line with 1.74 – 2.78% for ash contents of Moringa oleifera fortified amala studied by Ramota et al. (2013), lower than 3.20 – 3.44% reported for ash contents of cocoyam-cowpea flour blends Amala studied by Idowu and Adeola (2013) but higher than 0.30 – 0.37% for ash contents of plantain-soy amala researched by Adekunle and Mayowa (2018).

The crude fibre contents of the dumpling samples ranged from 4.11 to 6.44% with the highest crude fibre content (6.44%) observed in sample D (90% maize flour + 10% fermented bambara groundnut at 72 h) while the least crude fibre content (4.11%) was observed in dumpling from 100% maize flour (sample A). Significantly (p < .05), supplementation of the differently fermented bambara groundnut resulted in increase in crude fibre contents of the dumpling samples. Increase in crude fibre contents of the dumpling samples owing to increase in fermentation periods are not in line with the findings of other literatures; Anasiru et al. (2019) reported decrease in crude fibre contents 2.32 – 3.97% for crude fibre contents of fermented sweet corn flour and Olanipekun et al. (2012) also reported decrease 4.93 – 6.49% in crude fibre contents of bambara groundnut flour. Oboh (2006) contributed that, fermented foods, such as legume has lower fibre contents. The results obtained in the current study are higher than 1.11 – 1.47% reported for fibre contents of unripe plantain-African yam bean flour blends researched by  Salome et al. (2021) and 0.60 – 2.18% for fibre contents of lafun-pigeon pea flour blends studied  by Bolaji et al. (2021) but lower than 9.38 – 13.41% for fibre contents of okara fortified stiff dough (amala) studied by Ilelaboye and Ogunsina (2018). Dietary fibre (DF) describes a number of different substances, such as cellulose, pectin, lignin and guar, all of which are naturally found only in plants and are resistant to digestion in, and absorption by, the human small intestine (Bauer and Turler-Ibderbitzin, 2008).

Fats are saturated lipids at room temperature which are known to play protective roles in the body system (Olusanya, 2008; Duru et al., 2012). The mean results for the crude lipid samples of the dumpling samples varied significantly at 95% confidence level from 1.06 to 3.39% with dumpling from sample D (90% maize flour + 10% fermented bambara groundnut at 72 h) having the highest crude lipid content (3.39%) while the lowest crude lipid content (1.06%) was observed in dumpling from sample A (100% maize flour). Significant (p < .05) increase in crude lipid contents of the dumpling samples were observed with increased periods of fermentation. This negates the claim of Olanipekun et al. (2012) that fermentation resulted in decrease in fat contents of bambara groundnut 5.11 – 6.52% which is attributed to the utilization of oxidized lipids to generate energy for the growth and cellular activities. The values reported in this study are comparable to 0.72 – 1.76% reported for fat contents of cocoyam-cowpea flour blends amala studied by Idowu and Adeola (2017) but lower than 3.38 – 3.78% for fat contents of Maize-Kidney bean flour blends by Ohini et al. (2019) and 8.00 – 10.89% for fat contents of unripe plantain-African yam bean flour blends Amala by Salome et al. (2021). The low-fat contents of other dumpling samples could be beneficial as they would not be prone to oxidative rancidity; hence, ensuring prolonged shelf stability.

The crude protein contents of the dumpling samples varied from differed significantly (p < .05) from 0.37 to 0.90%. Dumpling from sample D (90% maize flour + 10% fermented bambara groundnut at 72 h) had the highest crude protein content (0.90%) while the least crude protein content (0.37%) was observed in sample A (100% maize flour). The result showed Significantly (p < .05) increase in crude protein contents of the dumpling samples with increase in fermentation periods of the bambara groundnut flour. This is attributed to the logarithmic growth of different strains of microorganisms during fermentation, which produces proteolytic enzymes, increasing the protein content (Ojokoh et al., 2020). Moreover, the increase in protein content of the dumpling samples after fermentation of bambara groundnut could also be attributed to a decrease in carbon ratio in the total mass and an increase in cell biomass and productions of non-protein nitrogen compounds like ammonia, amines, amino acids, and peptides as these all are included in the crude protein content (Onyango et al., 2013). Similar findings have been reported for increase in protein contents of fermented maize by Li et al. (2012). The results are slightly in line with 0.55 – 1.30% reported for amala from plantain-soy flour blends researched by Folorunso and Ayodele (2018) but lower than 2.17 – 2.87% reported for protein contents of unripe plantain flour amala studied by Karim et al. (2020) and 1.86 – 2.45% reported for crude fibre contents of cocoyam-cowpea amala flour blends from Idowu and Adeola (2017).

The carbohydrate contents of the dumpling samples were of range 88.83 to 93.08%. Dumpling from sample A (100% maize flour) significantly (p < .05) had the highest carbohydrate content (93.08%) while the least carbohydrate content (88.83%) was observed in dumpling from sample D (90% maize flour + 10% fermented bambara groundnut at 72 h). No significant variation (p > .05) was observed between the carbohydrate contents of dumplings supplemented with bambara groundnut fermented at 24 h and 48 h respectively (sample B and C). However, significant (p < .05) decrease in carbohydrate contents of the fermented bambara groundnut-supplemented dumpling samples B, C and D were observed. During fermentation, microorganisms utilize carbohydrates as an energy source and produce carbon dioxide as a by-product and this causes the nitrogen in the fermented product to be concentrated, and thus, the proportion of protein in the total mass increases (Nasseri et al., 2011); hence, a pointer to the decrease in carbohydrate contents of the fermented-bambara groundnut flour supplemented dumplings in the current study. The findings of the current study are in line with the report of Fetuga et al. (2014) whose study reported 76.90 – 87.68% for carbohydrate contents of sweet potato flour amala, 28.52 – 74.42% for carbohydrate contents of maize tuwo-cirina forda blends by Adeoti et al. (2013) and 70.3 – 77.7% reported for cocoyam-cowpea flour blends amala studied by Idowu and Adeola (2017). Carbohydrate supplies energy to cells such as brains, muscles and blood, contributes to fat mechanism, acts as mild natural laxative, and spares proteins as an energy source (Idowu and Adeola, 2017).

Table 3: Antinutritional properties and fatty acid composition of dumpling samples from maize and fermented bambara groundnut flour blends

The antinutritional properties  of dumpling samples from maize and fermented bambara groundnut flour blends are shown in table 4.2.

The phytate contents of the dumpling samples varied significantly (p < .05) from 9.70 to 13.16 mg/100 g with dumpling from sample B (90% maize flour + 10% fermented bambara groundnut at 24 h) having the highest phytate content (13.16 mg/100 g) while the least phytate content (9.70 mg/100 g) was observed in dumpling from sample A (100% maize flour). Significant (p < .05) reduction in phytate contents of the dumpling samples supplemented with fermented bambara groundnut (sample B, C and D) were observed with increase in fermentation periods. Processing, especially fermentation, has been reported to reduce phytic acid content of cereals, legumes and tubers as a result of the activity of the endogenous phytases from both raw ingredient and inherent microorganisms which hydrolyse phytic acid in many fermented food product preparation inisitol and orthophosphate (Sandberg and Andlid, 2002; Ola and Opaleye, 2019); The results obtained in the current study are lower than 105.52 – 311.35 mg/100 g reported for phytate contents of fermented maize flour by Terefe et al. (2021) but higher than 0.15 – 3.64 mg/100 g for phytate contents of fermented bambara groundnut flour by Ola and Opaleye (2019) and 0.17 – 0.87 mg/100 g for phytate contents maize-bambara nut composite flours by Adejuyitan et al. (2022).

The oxalate contents of the dumpling samples differed significantly at 95% confidence level from 53.13 to 92.50 mg/100 g with dumpling from sample A (100% maize flour) having the highest oxalate content (92.50 mg/100 g) while the least oxalate (53.13 mg/100 g) was observed in dumpling from sample B (90% maize flour + 10% fermented bambara groundnut at 24 h). The study showed significant (p < .05) reduction in oxalate contents of the dumpling samples supplemented with fermented bambara groundnut (sample B, C and D) at varying fermentation periods. Similar decreasing trends in oxalate contents 0.72 – 1.49 mg/100 g of fermented bambara nut flour studied by Ola and Opaleye (2019). Fermentation reduces anti-nutrients through enzymatic activity, microbial metabolism such as lactic acid bacteria that produces enzymes that break down anti-nutrients.   Similar trend also agrees with the findings of Abiodun and Adepeju (2011) and Oke and Bolarinwa (2012) for cocoyam flour and dehulled bambara nut flour, respectively. The results obtained in the current work are higher than 0.15 – 0.26 mg/100 g for oxalate contents of maize-bambara nut composite flour by Adejuyitan et al. (2022).

The tannin contents of the dumpling samples varied insignificantly (p > .05) from 0.000212 to 0.000274 mg/100 g with dumpling from sample B (90% maize flour + 10% fermented bambara groundnut at 24 h) having the highest tannin content (0.000274 mg/100 g) while the least tannin content (0.000212 mg/100 g) was observed in dumpling from sample C (90% maize flour + 10% fermented bambara groundnut at 48 h). Reduction in tannin due to fermentation might have been caused by the activity of polyphenol oxidase or fermented microflora on tannins (Abiodun and Adepeju, 2011). The observed decrease in tannin with increase in fermentation time agrees with the report of Onweluzo and Nwabgwu (2009). The results obtained in the current study are lower than 0.02 – 0.03 mg/100 g reported for tannin contents of fermented bambara nut flour by Ola and Opaleye (2019) and 3.84 – 4.80 mg/100 g for tannin contents of maize-kidney beans composite flours by Ohini et al. (2019).

Table 4: Sensory properties of dumpling samples from maize and fermented bambara groundnut flour blends

Key

Sample A = 100% maize flour

Sample B = 90% maize flour + 10% fermented bambara groundnut at 24 h

Sample C = 90% maize flour + 10% fermented bambara groundnut at 48 h

Sample D = 90% maize flour + 10% fermented bambara groundnut at 72 h

The sensory properties of tuwo samples from maize and fermented bambara groundnut flour blends are presented in table 4. Sensory properties, such as flavours, aroma, taste, texture, and mouthfeel, are among the most important attributes of food products in ensuring their acceptability to the consumers. The colour attribute ratings of the dumpling samples varied significantly (p < .05) from 7.95 to 8.50 with dumpling from sample A (100% maize flour) having the highest rating for colour (8.50) while the least value (7.95) was observed in dumpling from sample D (90% maize flour + 10% fermented bambara groundnut at 72 h).

The texture attribute ratings of the dumpling samples ranged from 7.60 to 8.10 with dumpling from 100% maize flour (sample A) having the highest texture attribute rating (8.10) while the lowest value (7.60) was observed in dumpling from sample D (90% maize flour + 10% fermented bambara groundnut at 72 h). Significant variations at 95% confidence level were observed between the texture attribute ratings of the dumpling samples.

The aroma attribute ratings of the dumpling samples ranged from 7.45 to 8.30 with dumpling from sample A (100% maize flour) having the highest value for aroma rating (8.30) while the lowest value (7.45) was observed in dumpling from sample D (90% maize flour + 10% fermented bambara groundnut at 72 h). No significant variation (p > .05) was observed between dumpling from sample B (90% maize flour + 10% fermented bambara groundnut at 24 h) and C (90% maize flour + 10% fermented bambara groundnut at 48 h) while other dumpling samples differed significantly (p < .05).

The overall acceptability ratings of the dumpling samples differed significantly (p < .05) from 8.00 to 8.55 with dumpling from sample C (90% maize flour + 10% fermented bambara groundnut at 48 h) having the most rating for overall acceptability (8.50) while the least overall acceptability rating (8.00) was observed in dumpling from sample D (90% maize flour + 10% fermented bambara groundnut at 72 h).

CONCLUSION AND RECOMMENDATION

Conclusion

The proximate, anti-nutritional and sensory properties of tuwo from maize and fermented bambara groundnut flour blends were studied. The dumpling samples were of high moisture contents. Supplementation of fermented bambara groundnut flour at 24 h, 48 h and 72 h improved the total ash, crude fibre, crude lipid and crude protein. However, reduction in carbohydrate and dry matter were observed. Antinutritional properties of the dumpling samples including phytate, oxalate, tannin and saponin reduced at varying periods (24 h, 48 h and 72 h) of fermented bambara groundnut flour inclusion. Organoleptically, dumpling from 100% maize flour (sample A) was the most acceptable of all the dumpling samples; however, other dumpling samples supplemented with bambara groundnut samples had comparable sensory ratings, thus, indicating that acceptable dumpling could be produced maize and differently fermented bambara groundnut flour.

Recommendation

Further studies are hereby recommended on the functional, pasting, and storage stability of the dumpling samples produced in this study.

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APPENDIX