This project was carried out to determine the effects of processing and combination of African yam bean and yellow root cassava on the chemical and antinutritional properties of the blends. It also determined the effects of the combination on the sensory properties of the food products.

Yellow root cassava tuber (UMUCASS 37 variety) used for this research was procured from the Teaching and Research Farm of Ladoke Akintola University of Technology, Ogbomoso, Oyo State, Nigeria. Nigeria. The AYB seeds were bought at an indigenous market and identified at the LAUTECH teaching and research farm.

Cassava grits were produced from yellow root cassava using the method of Sanni and Jaji (2003) Grits were produced from freshly harvested yellow root pro-vitamin A cassava by peeling, washing, cutting, soaking (72 h, 28 ±2 °C), dewatering, roasting (120 °C), sieving and milling to obtain yellow root cassava grits while AYB flour was obtained as described by Aniedu and Aniedu (2014) by cleaning, roasting (190 °C, 10 min), dehulling, milling and sieving (425 μm). Simplex lattice design was used to obtain different formulations from blends of yellow root cassava grit and AYB flour. The formulations were done with (60 – 100%) cassava grit and (0 – 40%) AYB flour, while 100% AYB flour and 100% cassava grits were used as controls. The blends were thoroughly mixed for about 20 minutes using a Kenwood mixer (Model: Chef XL KVL4100S, made in China) to achieve uniform blending.

Gruel samples were prepared from different blends of yellow root cassava grit fortified with AYB flour as described by Ngwu, Aburime and, Ani (2014). Four hundred grams (400 g) of each blend was reconstituted with 500 milliliters of water, and 2 liters of water was used to bring it to boil reconstituted flour was progressively added to the hot water while continually whisking to avoid lumps. The mix was left to simmer for around five (5) minutes while being constantly stirred until it was done.

The meal was prepared from different blends of yellow root cassava grit and AYB flour as described by Aniedu and Aniedu (2014). The blends were reconstituted into meals by cooking 100 grams of each of the blends in hundred (100) mL of boiling water while stirring vigorously for 5 minutes.

The proximate composition of the blends was determined as described by the Association of Official Analytical Chemists (AOAC, 2010). Carbohydrate content was determined by difference AOAC (2010). Calorific content was calculated using the values obtained for carbohydrate, fat, and protein values. The β-carotene of the flour mixes was estimated using Rodriguez-Amaya and Kimura (2004) method that uses acetone extraction for carotenoid analysis. Tannin was determined with the method based on the fact that tannin-like substances in an alkaline solution diminish phosphotungstomolybdic acid, resulting in a strongly colored blue solution as devised by Adegunwa, Alamu and Omitogun (2011), Spectrophotometer was used to measure the absorbance at 760 (AA Analyse Perkin Nerma)/ Phytate was determined according to AOAC (2010). Kakade et al. (1974) technique was employed in the determination of trypsin inhibitors. Absorbance reading was taken at 410 nm with a spectrophotometer (AA Analyse Perkin Nerma). The hydrogen cyanide concentration was determined using the method of Alkaline picrate calorimetric while a spectrophotometer was then used to measure the absorbance of elutes from the standard and the sample at 510 nm. (Mburu, Swaleh and Njue, 2013). Raffinose and Stachyose (oligosaccharides) were both determined with HPLC techniques (František et al., 1995). The mobile phase used was demineralized water in a reverse phase HPLC (RP-HPLC) and on a Silica C18 column.

Sensory attributes of the cooked gruel and meal samples were carried out using a 9-point hedonic scale preference test. A total number of 50 panelists were used and to effectively compare the sensory ratings between the panelists, the panelists were semi-trained. Panelists were given coded samples of meal and gruel and asked to assess the items on a 9-point hedonic scale. (where one represents dislike significantly, and (nine) represents like significantly) for sensory attributes such as flavor, color, consistency, mouthfeel, texture, appearance, taste, and overall acceptability. On the panel were staff and students from the Ladoke Akintola University of Technology's Department of Food Science and Engineering in Ogbomoso, Oyo State, Nigeria.

Number of samples analyzed: 1

Number of repeated analyses: 1

Number of experiment replication: 1

Data obtained were analyzed using Analysis of variance (ANOVA) while the means were separated using Duncan's multiple range test (DMRT), a significance level of 5% was considered.

The proximate components of yellow root cassava grits and AYB seed flour blends are indicated in Table 1. The values obtained for the moisture varied between 4.66 to 7.92 percent and a significant (p <0.05) difference was observed in each of the blends except in the blends that had 10-30% of AYB flour substitution. The roasted AYB flour had the least moisture content which was close to 4.88% reported by Ndidi et al. (2014) for roasted AYB flour. All of the formulations had low moisture content which could be enough to have long storage when packaged in moistureproof materials. The fat content of the samples varied significantly 2.20 – 2.82% with the highest fat content in the 100% yellow root cassava grits (2.82%). The values obtained were close to the value reported by Eleazu and Eleazu (2012) for yellow root cassava. The total ash (minerals) ranged from 2.16 to 2.66% and the highest value was recorded with roasted AYB flour which is close to the report of Ndidi et al. (2014). The protein level of the blended samples ranged between 2.72 and 20.43%, with the highest inclusion of roasted AYB flour having the highest protein content. Significant differences (p <0.05) were recorded among the blends, validating the fact that AYB contributed significantly to the protein composition of the blends. This backs up prior research that shows leguminous plants are good sources of nutrients, including a diverse spectrum of minerals and amino acids (Fagbemi, Oshodi and Ipinmoroti, 2004; Maphosa and Jideani, 2017). The crude protein content of the yellow root cassava grits was consistent with previous observations that cassava root food products are low in protein and that its consumption in meals necessitates the addition of adequate amino acids supplement (Burrell, 2003; Esonu, 2006; Olugbemi, Mutayoba and Lekule, 2010; Ngiki, Igwebuike and Moruppa, 2014). The crude fibre of the samples ranged from 1.15 to 1.40%. Higher fibre content was recorded in flour blends with AYB flour substitution and was significant though the values were lower than the values reported. This could be as a result of the processing method used to process African yam beans into flour. The carbohydrate contents of the blended samples were in the range of 68.65 and 83.23%. These samples' high carbohydrate readings are attributable to the carbohydrate content of their basic raw materials, especially the yellow root cassava tubers (El-sahy and Siliha, 2008; Awoyale et al., 2015).

The beta–carotene of the yellow root cassava grits and AYB flour blends is as shown in Fig 3. It ranged between 1.33 and 3.97 μg/g, the hundred percent yellow root cassava grit had the highest amount of beta–carotene due to the variety of the cassava used, which was enriched with beta– carotene. The value falls within the reported range by Eyinla et al. (2019) for food products from yellow root cassava. The blended samples also recorded some amounts of beta-carotene, which is a vitamin A precursor. As the substitution of AYB flour increased, the value of beta– carotene of the blended sample decreased. Consumption of these food products can contribute to the source of vitamin A in the diets of the people where cassava is their major staples. There were significant (p <0.05) differences among the blends.

Saponin levels of the blends ranged between 0.039 to 0.087%. The results are consistent with those obtained by previous researchers for processed African yam beans. (Ajibola and Olapade, 2016: Anya and Ozung, 2019). The least value was observed in 100% yellow cassava grits while the sample with 100% AYB flour had the highest. This is a pointer to the fact that African yam bean contains some anti-nutrients. Saponins bind to iron, zinc, calcium, and vitamins to create insoluble mineral complexes, rendering them inaccessible (Samtiya, Aluko and Dhewa, 2020). There have been reports that processing such as roasting reduced the saponin content in African yam beans (Onyeike and Omubo-Dede, 2002; Ojuederie, Ajiboye and Babalola, 2020). Indicating that the low levels of saponin recorded in the roasted African yam bean were traceable to the effect of heat on the anti-nutrient. It has been found that low quantities of saponins in beans are not harmful to health, but larger concentrations in the diet can be poisonous at about ≥150 mg/kg body weight (Samtiya, Aluko and Dhewa, 2020).

Tannin content was in the range of 0.14 to 0.15%, and in all of the blends, there were no significant changes in the tannin level. For AYB flour, the results were lower than those reported by Anya and Ozung (2019) for AYB (0.31 – 0.34%). Tannins are high-molecular-weight (>500), water-soluble phenolic chemicals that can precipitate protein, particularly pepsin (Adamczyk et al., 2017). Studies have shown that tannins are concentrated in the seed coat of legume seeds and are heat resistant. Indicating that the dehulling of the seed coat in the processing method reduced the tannin content in African yam bean flour. Tannin consumption of 1.5 – 2.5 g per day in the diet is considered safe (Sharma et al., 2019).

Therefore, the tannin level found in this study should not have any detrimental effects associated with tannins, such as antagonistic competition reducing accessible protein. Trypsin inhibitor content was in the range of 1.24 and 3.15 mg/g. The values are within the range of 2.22 – 3.05 reported by Ajibola and Olapade (2016) for processed AYB seeds.

Phytate concentrations of the flour blends were in the ranges of 0.82 and 2.69 mg/g, and all the blended samples differed significantly (p <0.05). In both animal and human nutrition, phytic acid has been recognized as the most potent antinutritional factor in foods and a source of mineral ion deficit (Grases, Prieto and Costa-Bauza, 2017). The low phytate contents suggest that minerals otherwise chelated by phytate can be much more available. Hydrogen cyanide levels are as shown in Fig 3; they ranged between 0.07 and 4.47 mg/kg. Roasting and fermentation processes involved in the production of cassava grits reduced the hydrogen cyanide to safe levels. As indicated by the Joint FAO/WHO Expert Committee on Food Additives (JECFA), a codex level of 10 mg HCN/kg body weight (10 ppm) in cassava flour does not cause severe toxicity. (WHO, 2004). Indicating that the food products are within the safe level and will pose no hazard to the consumers.

Haemagglutin contents varied from 1.47 to 3.49 mg/100 g. In this investigation, the flour blends containing 100 percent AYB flour had the highest hemagglutin level (3.49 mg/100 g), which is lesser than the 5.30 mg/100 mg reported by Ngwu, Aburime and Ani (2014) for roasted AYB.

Stachyose levels ranged from 1.51 to 1.81%, while raffinose ranged from 0.38 to 0.45%. The reduction of stachyose and raffinose in all the blended samples is of interest. This is because oligosaccharides (raffinose and stachyose) are implicated in flatulence and diarrhea.

The result of the sensory evaluation of gruel samples made with cassava grit and African yam bean flour mixes is as shown in Table 3. All of the samples received good sensory ratings for all of the qualities, as well as overall acceptability. The panelists' ratings for the gruels' taste and flavor were not different significantly (p >0.05) across all samples. In appearance, samples manufactured from 100% AYB flour and 20 – 30% AYB flour substitute did not differ substantially (p <0.05). The sample created with 100 percent AYB flour and the samples manufactured with 10 – 30 percent AYB flour had no discernible variation in general acceptability. but they varied significantly with the samples made from 100% cassava grit and 40% AYB flour substitution. The least score for color, consistency, mouth feels texture, and appearance was observed in the sample with 40% Substitution of AYB flour. The high mean scores observed for flavor, color, consistency, mouthfeel texture, appearance, taste, and overall acceptability indicated that all the gruel samples had acceptable sensory properties. as the percentage of substitution increased up to 30%, the degree of similarity in all of the samples increased for practically all of the criteria. The high mean scores observed for appearance, color, hand feel, mouthfeel, mouldability, and overall acceptability indicated that all the meal samples were of good sensory attributes except the meal prepared from 100% AYB. The highest score for overall acceptability was observed in the sample with 70% yellow root cassava grits and 30% AYB flour.