The protocol for this study was approved by the Regional Ethics Committee for Research in Human Health and signed consent was obtained from the households taking part in the study. A previous study conducted by Mananga et al. [9] revealed that tomatoes, onions, garlic, leeks and refined palm oil were the major common ingredients used in the preparation of stir fried bean. However, the main difference lay in the use of spices. An investigation (using a questionnaire) into food was conducted to determine the most consumed stir fried bean based dishes, the quantity and different types of ingredients used in the preparation of these recipes (Table 1) during July to October 2023. The sample size of the population was estimated using Open Epi 3.01, with the assumption of a 50% frequence of household who cook bean based dishes in the target study site, with a 5% margin of error, 95% confidence level. Adding 10% for incomplete data or biases observed in this study. Therefore, the estimated sample size was 422 households.

Table 1. Description of the spices and ingredients content of the main bean based dishes.

The red bean seeds (DOR-701) were obtained from the Institute of Agricultural Research for Development (IRAD) in Foumbot, Cameroon. Based on data from a food survey, we categorised households into 18 groups according to the spices they used to prepare stir-fried beans. After pre-treating the beans (by soaking them for eight hours and then boiling them for one hour), samples of beans were provided to each household according to their dietary habits. Appointments were scheduled with the households to observe the cooking process, note the cooking times, identify and collect the ingredients used and weigh the quantities.

The three most commonly used methods of cooking stir-fried beans were recorded. Chopped vegetables and fruit were added at the beginning of the cooking process, while spices were incorporated midway through. The cooking time ranged from 22 to 58 minutes depending on the household and the type of fuel used (butane or a wood fire). After cooking, the different recipes based on the spices used were collected from each group of households, and the ingredients used to prepare bean-based dishes were weighed. Nine recipes were collected from households: three using ginger alone as a spice; three using ginger, green aniseed and cloves as spices; and three using ginger and white pepper as spices.

After collecting the bean-based dishes, each meal was cooled to room temperature. Equal proportions of each dish were then homogenised using a Vevor blender. Aliquots were used to determine the moisture content [11]. Samples of the dried meals were packed in polyethylene bags, properly closed, and stored in a deep freezer at −20˚C for further analysis (Figure 1).

Figure 1. Stir-fried beans based dishes collected from households.

2.3.1. Proximate and Mineral Analyses

The moisture, protein, fat, fibre, ashes, carbohydrates and mineral contents of bean dishes were assessed using the standard methods as recommended by the AOAC [11]. The energy value (E) per 100g of dry weight was obtained according to the formula: E = (9 × % fat) + (4 × % protein) + (4 × % carbohydrate) [12].

2.3.2. Determination of β-Carotene Contents

The β-carotene content was determined using the method described by Ranganna [13]. The β-carotene was determined by soaking 1 g of the sample in 5 ml of methanol for 2 h at room temperature under dark conditions in order to get a complete extraction. The β -carotene layer was separated using hexane solvent. The absorbance was read at 436 nm. The beta carotene content was calculated using the following formula: β-carotene (mg/100g) = OD (436 nm) × V × D × 100 × 100/W × Y (with V = Total volume of extract; D = Dilution factor; W = Sample weight; Y = Percentage dry weight content of the sample).

2.3.3. Extraction of Phytochemical Tests and Antioxidant Activities

The extraction of phytochemical molecules was carried out by maceration. A precise mass of 1 g of each sample was placed in an Erlenmeyer flask with 30 ml of hydroalcoholic solution (70% ethanol). The mixture was subjected to constant agitation for 30 minutes, protected from light and at room temperature, and then the supernatant was separated from the residue by filtration. To ensure complete extraction, the residue underwent two additional successive extractions under the same conditions but with reduced solvent volumes (10 ml). The three filtrates obtained were then combined in a 50 ml volumetric flask, and the volume was adjusted to the mark with 70% ethanol.

2.3.4. Determination of Total Phenolic Compounds

The antioxidant capacity has been evaluated by means of the total phenolic and total flavonoid contents (TPC and TFC respectively). The determination of total phenolic compounds (TPC) was done by the Folin-Ciocalteu method using Gallic acid as a standard with slight modifications [14]. Approximately 2 mL of the extract solution of each sample was mixed with 2 mL of Folin Ciocalteu reagent 2 N for 1 min. After reacting for 5 min, 2 mL of 10 % of Na₂CO₃ solution was added and the mixture was vortexed vigorously and kept at room temperature in a dark environment for 15 min. The absorbance was measured at 760 nm. The TPC was calculated using a standard curve of the standard gallic acid (concentrations ranging from 20 to 200 μg/mL) and the result was expressed as mg Gallic acid equivalents (GAE)/100 g dry weight (DW) of the sample (mg GAE/100 g DW).

2.3.5. Determination of Total Flavonoid Contents (TFC)

The total flavonoid content was evaluated using the method described by Dhar et al. [14] with minor modifications. The TFC was determined using a standard curve of quercetin and expressed as mg quercetin equivalents (QE)/100 g dry weight (DW) of the sample (mg QE/100 g DW).

2.3.6. Determination of Total Tannin Contents

The determination of total tannin was carried out using the method described by Burns [15]. About 1 ml aliquot of supernatant was taken and mixed with 5 ml of vanillin-HCl reagent prepared by combining an equal volume of 8% concentrated HCl in methanol and 4% vanillin in methanol. The resulting mixture was incubated at ambient temperature (25˚C) for 20 minutes and D-catechin was used as a standard. The total tannin content was evaluated in mg equivalent of catechin/100 g dry weight (DW) of the sample using the calibration curve.

2.3.7. Determination of Total Alkaloid Contents

Total alkaloid contents were determined by iron chloride and hydrogen chloride methods as described by Singh et al. [16] and the values were expressed as mg quinin equivalents (QuE/100 g dry weight (DW)) of the sample (mg QuE/100 g DW).

2.3.8. Determination of inVitro Antioxidant Activity

1)Total antioxidant capacity

The antioxidant capacity of dishes was assessed using the method of Prieto et al. [17]. In each test tube, it was successively introduced 50 µL of each extract solution and 200 µL of reagent solution (0.6 M sulfuric acid, 28 mM of sodium phosphate and 4 mM of ammonium molybdate). Tubes were capped with beads and heated to 95˚C for 90 min, then cooled. Absorbance of the blue staining mixture was measured at 695 nm. Total antioxidant capacity was expressed as mg gallic acid equivalent/100 g DW sample.

2)Ferric Reducing Antioxidant Power test (FRAP)

The FRAP assay was performed according to the method described by Benzie and Strain [18] with minor modifications. The extract solution of 100 µL was mixed with 3 mL of FRAP reagent and incubated in a dark room for 5 min. The absorbance of the solution was determined at 593 nm. Ferric reducing antioxidant power was expressed as mg of Fe²⁺ equivalent/100 g dry weight (DW) of the sample using the calibration curve of Fe²⁺.

3) Anti free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH)

The 2,2-diphenyl-1-picrylhydrazyl(DPPH) radical capacity of the different extracts was determined following the methods described by Lopes-Lutz et al. [19] with slight modifications. In test tubes, 150 µL of samples were added at different concentrations 1.5% 1.25%; 1%; 0.75% and 0.5%. Then, 3.9 mL of DPPH solution (1.0 mM in 70% aqueous methanol) was added and incubated for 60 min in the dark at room temperature. The inhibition (%) was calculated by the following equation: Inhibition = (absorbance of control − absorbance of sample/absorbance of control) * 100.

The IC50 (mg/ml) is the concentration of the antioxidant that traps 50% of free radicals. It was obtained by performing a nonlinear regression on a graph showing the trapping percentage as a function of concentration.

The obtained data of the sample were presented as mean ± standard deviation (SD) of nine samples with three replicates per dish. Different data were analyzed by one way analysis of variance (ANOVA). IBM SPSS statistics version 25.0 was used for data analysis. Differences between samples were tested according to Tukey’s test at p < 0.05.

Overall, 415 questionnaires were validated for analysis, with 7 being ignored due to incomplete or incoherent information. Figure 2 shows the frequency of consumption of different bean dishes. Of those surveyed, 333 (80.24%) had a preference for ready-to-eat bean dishes. Of these, 271 (65.30%) preferred fried beans, 54 (13.01%) preferred pounded beans, and 14 (3.37%) preferred corn chaff. Of all the people surveyed, 78 (18.79%) had no particular preference for a bean-based dish. Beans can be prepared in various ways, with the addition of several ingredients, which also influences the cooking time. These different preparation methods can significantly affect the final nutritional and functional quality of the food. This finding is consistent with that reported by Rossi [20], who found that bean consumption varies according to cultural identity and ethnic origin, with significant differences between cultural groups.

Figure 2. Frequency of consumption of the different bean based dishes.

Table 2lists the most commonly consumed spices. These spices were collected according to the various preparation methods and combinations used in households. Eighteen (18) techniques for cooking stir-fried beans were identified. The results showed that 138 households (33.25%) used ginger as their only spice; 65 households (15.66%) used ginger combined with white pepper; and 57 households (13.73%) used ginger combined with green aniseed and cloves. The choice of spices by consumers could be justified by their flavour, smell, availability at the time of the study and their very pronounced aroma. These findings are consistent with those of Fritts et al. [21], who demonstrated that moderate additions of dried herbs and spices significantly increased liking and preference for most vegetables compared to oil and salt alone.

Table 2.Methods for cooking stir fried beans according to the spices used.

The moisture content of the bean based dishes raised significantly from 63.94 (D9) to 65.57 (D2) g/100 g of fresh weight of bean based dishes. The amount of moisture in the recipes is dependent on the type of dish and also the amount of water used in the preparation. The moisture content was lower compared to the value (71 g/100 g edible portion) found by Ponka et al. [22] in Koki (traditional dish) prepared from crushed cowpea and palm oil and consumed in Cameroon. But higher than the moisture content of 61.5 g/100 g edible portion recorded by Ponka et al. [22] in Ekomba(traditional dish) prepared from maize flour with roasted peanut paste. Fat, total protein, crude fiber, carbohydrate and ash contents of the bean based dishes are shown in Table 3. The total protein values expressed in g/100 g DW varied from 20.41 (D3) to 27.77 (D2). The dishes are good sources of protein, however a significance diffrence (p < 0.05) was observed between the protein contents of all the bean based dishes. This could be due to the fact that beans already contain 20 to 25% protein based on their dry weight content [9]. The protein content of the bean based dishes is higher than those of other beans seed such as Lima bean-benniseed food 8.33%, Lima bean prorridge 8.30% DW [23]. These dishes can be used to improve proteins intake in high risk protein energetic malnutrition in preschool children. Fat ranged in g/100 g DW from 21.99 (M6) to 33.89 (D9). The higher fat content observed in the samples is due to poor knowledge of the recommendations regarding good feeding where population add a big quantity of hot red palm oil. Many studies highlight the fact that, the oil absorption capacity of a plant-based product is defined by a foods component's ability to trap oil, which influences the techno-functional protudiesperties of the final product. Complex carbohydrates primarily cause oil absorption [24]. Additionally, the use of large quantities of cooking oils tends to increase the proportion of fats relative to other macronutrients, such as proteins and carbohydrates. As legumes are an important source of carbohydrates and proteins, they have a high oil absorption capacity [25]. Most dishes with basic protein and carbohydrate content had higher oil intake during cooking. This was the case for D3, D5, D8 and D9, which had the highest cooking oil intake. The high level of oil in the dishes could contribute to increasing the prevalence of metabolic disorders. Crude fiber contents varied in g/100 g DW from 5.10 (D9) to 8.07 (D3). The high rate of crude fiber could be explain by the fact that beans are naturally rich in dietary fiber. In addition, the cell walls of legumes contain polysaccarides, which constitute insoluble and soluble fibre [26]. The increase in fibre content in these dishes is very important for health because the consumption of fiber-rich food is associted with a reduce risk of developing heart diseases, rectal and colon cancer, diabetes [27]. Ash contents ranged in g/100 g DW from 5.10 (D9) to 8.08 (D4). Carbohydrate levels ranged from 23.28 (D3) to 34.36 g/100 g DW (D8). This low carbohydrate contents in bean based dishes make these dishes a good source of meal for people with metabolic disorders (diabetes, hypertension). The carbohydrate contents of the bean based dishes is lower compared to the value (62.05 g/100 g edible portion) found by Kana et al. [28] in cassava stew prepared from cassava, manioc, onion, dried fish, herbs and garlic, and value (39,4 g/100 g edible portion) found by Sharma et al. [29] in Fufu corn. The energy content in the samples ranged from 401.75 for D6 to 523.65 kcal/100 g for D9 and was significantly different (p < 0.05). The energy content of the samples were higher than the value of 87 and 185 Kcal/100 g edible portion of “pomme pilées” and “Etondo salé” respectively found by Kouebou et al. [30] and consumed in Cameroon.

Table 3.Proximate composition of bean based dishes (g/100 g).

Mean values in a line having different superscript are significantly different at (p < 0.05). D1 - D9 = Dish 1 - Dish 9.

The results of mineral contents of bean based dishes in mg/100 g DW are presented in Table 4. Calcium, magnesium, phosphorus and zinc contents raised from 89.10 (D7) to 100.17 (D2), from 62.10 (D2) to 91.00 (D3), from 245.00 (D1, D3, D4) to 289.00 (D2) and 1.99 (D4) to 3.25 (D2) respectively. A significant difference was observed between the mineral contents of all the bean based dishes. Calcium and phosphorus appeared to be the majors minerals in samples. Zinc was the least abundant mineral in the samples. Calcium and phosphorus contents were higher compared to those reported by Kouebou et al. [30] in Cameroonian dishes: “Igname Malaxé” and dried fish groundnut soup. Magnesium content in the samples was lower than the magnesium content of 120 mg/100 g edible portion found in groundnut-pudding consumed in Cameroon [30]. Furthermore, the zinc values obtained in the study are similar to those recorded by Kouebou et al. [30] in “Banane Malaxée”. According to FAO-WHO [31], it has been proved that zinc helps to strengthen the immune system which is important to speed up the healing process after cell damage. β-Carotene is a natural pigment belonging to the carotenoid family, it is an organic compounds found in many plant based foods. The levels observed in the bean dishes collected, expressed in mg/100 g DW, ranged from 0.51 (D1 and D7) to 1.11 (D8). A significance diffrence (p < 0.05) was observed between the β-carotene contents of all the bean based dishes. These significant differences could be due to variations in the quantities of ingredients used to make the dishes (tomatoes, red oil). Studies have indeed shown that these ingredients are excellent sources of provitamin A, and using them in ready-to-eat meals could further increase the concentration of β-carotene in these dishes [32].

Table 4.Mineral and β-carotene contents of bean based dishes (mg/100 g DW).

Mean values in a line having different superscript are significantly different at (p < 0.05). D1 - D9 = Dish 1 - Dish 9.

Legumes are a good source of phenolic compounds and anthocyanins that exert an antioxidant effect, they directly neutralize reactive oxygen species and free radicals, reducing oxidative stress [33]. Total phenolic compounds (TPC), total flavonoids, tannins, alcaloids, ferric ion reducing antioxidant power (FRAP) and DPPH (%) inhibition ratio of bean based dishes were determined in water, ethanol 70% extracts (Table 5). Ethanolic extract revealed that the TPC in mg gallic acid /100 g DW was increased from 388.26 (D2) to 592.25 (D9). The TPC of the bean based dishes was lower than that of other studies by Djuikwo et al. [34] (1170.40 mg EAG/100 g edible portion) in functional biscuits made of wheat flour and Diospyros mespiliformis pulp. The significance difference observed (p < 0.05) in the total phenolic compounds could be due to the quantities of the ingredients used to prepare these dishes. However, many authors have demonstrated the thermosensitivity of secondary metabolites, such as phenolic compounds. When exposed to high temperatures for prolonged periods, these compounds undergo biochemical mechanisms that lead their denaturation [27]. Total flavonoids compounds ranged from 46.38 (D7) to 152.29 (D4) mg CE/100 g DW. The flavonoids contents were higher compared to the value 11.87 mg as rutin equivalent (RE)/g of dried plant obtained in the Faba bean (Vicia faba) genotypes cultivated in Tunisia [35]. The TPC and TFC can be used as important indicators of the antioxidant capacity for any product that is intended to be considered as a natural source of antioxidants in functional foods [35]. Tannins are sometimes considered as antinutritional factor but their antioxidant activity at a certain threshold has been proven [36]. The presented tannin contents fluctuated between 308.79 (D5) to 537.50 mg Ca/100 g DW (D9). The lowest values of total alkaloids were observed in D2 (27.44 mgQu/100 g DW) and the highest values were observed in D5 (50.08 mgQu/100 g DW). Total antioxidant capacity varied from 23.06 (D2) to 45.54 mgAG/100 g DW (D4). The IC₅₀ values ranged from 2.49 (D2) to 3.55 mg/mL (D3). This result was higher than 45% of DPPH inhibition ratio of 1 g of dried beetroot pomace determined by Vodnar et al. [37]. FRAP of bean based dishes varied from 7.72 to 12.59 mg FeII/100 g DW for D2 and D4 respectively. These results are lowest compared to the values 61.1% - 66.4% and 69.5% - 74.3% for DPPH and FRAP respectively obtained in the Pinto and Black bean affected by thermal processing [38]. The current finding was in line with the finding of Swati et al. [39] observed the effects of cooking on the antioxidant capacities may differ depending on cooking method, localization of the strutures and conditions (temperature, cooking time, portion, ingredients, presence of oxygen and water). In this study, the bean based dishes’s antioxidant activities (DPPH, FRAP) decreased which was consistent with Silva et al [40]. Optimising various cooking practices (ingredients, cooking time, pre-treatment methods) would improve the antioxidant potential of the stir fried bean based dish and could protect consumers from free radicals attacks.

Table 5.Bioactive components and antioxidant profile of bean based dishes.

Mean values in a line having different superscript are significantly different at (p < 0.05). D1 - D9 = Dish 1 - Dish 9; TPC = Total Phenolic Compounds; TAC = Total Antioxidant Capacity Q = Quercetin; CE = Catechin, Qu = Quinin; GA = Gallic acid; FeII = Iron.